Dissertations / Theses on the topic 'Optical polarizing thin film'

In Chapter 3 a homologous family of dialkyl phthalates is used to investigate the effect of plasticiser/polymer compatibility on the response characteristics of transparent, thin-film optical gas sensors for carbon dioxide. A strong correlation is found between plasticiser/polymer compatibility and sensitivity in phenol red/ethyl cellulose CO<SUB>2</SUB>-sensitive films. This relationship applies to CO<SUB>2</SUB>-sensitive films based on other polymers such as polystyrene and poly(methyl methacrylate). This relationship also extends to optical O<SUB>2</SUB>-sensitive films, implying that the relationship is general for thin film optical sensors. In Chapter 4 an optical sensor is developed for breath-by-breath gaseous carbon dioxide analysis. The detector is based on a general formulation described in previous work where a phase transfer agent, tetraoctylammonium hydroxide (TOAOH), is used to incorporate a hydrophilic pH-sensitive dye into a hydrophobic plastic film to create an effectively solid-state colourimetric sensor. In this work the formulation has been modified to yield a sensor which is capable of responding to clinically important levels of carbon dioxide (0.1-5%) in less than 200ms. This is comparable with the response of commercially available capnometers based on infrared sensing of carbon dioxide, which are currently widely used for clinical analysis. In Chapter 5 the hydrophobic bases, tetraoctylammonium hydroxide (TOAOH), tetrakisdecylammonium hydroxide (TKAOH) and tetradodecylammonium hydroxide (TDAOH), are used to solubilise the anionic form of <I>m</I>-cresol purple in ethyl cellulose to create colourimetric thin-film sensors for monitoring carbon dioxide in the gas phase and dissolved in solution. When used for making dissolved carbon dioxide measurements both TKAOH and TDAOH appear significantly more resistant toward interference by protons or other ions at high concentration when compared to TOAOH, the hydrophobic base which has been used for such work in previous studies. In Chapter 6 the preparation and characterisation of three different plastic thin-film colourimetric sensors for gaseous ammonia are described. Each of these film optrodes gives a reproducible and reversible response towards gaseous ammonia. The sensitivity of the film sensors was found to be dependent upon the pK<SUB>a</SUB> of the encapsulated dye. The sensitivity of the plastic film sensor decreases markedly with increasing operation temperature and the 90% response and recovery times are slow and activation-controlled.

This thesis consists of a study of several thin film semiconductor structures of practical technological use either presently or in the near future. The first system studied is an ultra thin film single crystal gallium arsenide layer. The absorption spectra of these layers are measured and transitions at both the F- point and L-point of the Brillouin Zone are observed, the latter are not normally measurable in thicker layers. The observed shift in the F-point absorption edge is attributed to contributions from the Franz-Keldysh Effect and the Moss-Burstein Effect. The temperature dependence of the L-point energy gap is measured and compared with previous data. The next system investigated is an n-type porous silicon layer coated with p-type polyaniline. Both photoluminescence and electroluminescence spectra and the electrical characteristics have been measured for this system. The interface between the two layers is found to be a rectifying junction consistent with a potential barrier formed at the interface. In forward bias, it is possible to generate electroluminescence in the visible and near infra red regions. The final structure studied is a thin film cadmium sulphide-cadmium telluride solar cell structure. The cells are found to have a low efficiency of around 1% as grown, but a process of treatment with cadmium chloride and annealing in air improves this by a factor of approximately ten. Photoluminescence measurements on the back surface of the cadmium telluride revealed three major emission bands at 1.59 eV, 1.55 eV and 1.45 eV. By varying temperature and incident laser power, attempts at assigning the bands to specific impurity centres in the cadmium telluride is made Using a novel bevelling etch technique to prepare samples, depth dependent measurement of the photoluminescence is possible. This reveals that the major changes associated with the improvement in efficiencies occurs at the interface between the CdS and the CdTe.

Since the recent discovery of a new class of high critical temperature superconductors (HTS), much interest has been shown in their potential use as optical detectors. The purpose of this research was to test thin film samples of the HTS Y1Ba2Cu3O7-delta as detectors and investigate any response to optical radiation. A laboratory test facility was designed and built for this purpose. The experimental results exhibit a variety of optical responses that are dependent upon the physical characteristics of each HTS thin film. Polycrystalline films exhibited a different detection mode than did epitaxial films. This research demonstrates that HTS thin films are viable optical detectors and have the potential to become competitive high-performance detectors as the new technology continues to emerge.

Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2007.<br>Committee Chair: A. Rahman Zaghloul ; Committee Members: W. Russell Callen and Doug Yoder. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Passive intrinsic bistability is of great interest. Our Fabry-Perot interference filters exhibit bistability due to a temperature dependent refractive index. Operating across the entire viable spectrum permits wide application to the demonstration and development of concepts for optical computing. Thermal evaporation of zinc sulfide and chiolite is used to produce Fabry-Perot interference filters. The effect of the thickness of the spacer, and reflectivities of the mirrors, on the nonlinear characteristics of these devices is investigated. The mathematic description of these etalon's linear, as well as their nonlinear, behavior is presented. The experimental apparatus is described. Measured values of the minimum critical detuning and minimum observed power are presented.

The development of a simple, semi-reversible, colorimetric oxygen sensor based on the redox chemistry of 2,6-dichloroindophenol in the presence of fructose and tetrabutylammonium hydroxide is described. The sensor is colourless in the absence of oxygen, but gives a strong blue coloration in oxygen at >30 Torr and quantitative analyses are possible between 0 and 50 Torr. The second type of sensor examined is based on the oxygen quenching of luminescence emitted from polymer encapsulated: platinum octaethylporphyrin, palladium octaethylporphyrin or tris(4,7-diphenyl-1,10-phenanthroline) ruthenium (II). Several means of collecting data from such sensors are evaluated. Gated fluorimeters can give erroneous data unless the natural and quenched lifetimes of the lumophores lie in the range 200 μs - 4ms. Several factors affect the oxygen sensitivity of these films including humidity, which depresses the sensitivity by 42% when using ethyl cellulose as the encapsulating matrix and by 14% when using cellulose acetate butyrate. No significant humidity effect is observed when using silicones, polyvinylchloride or polystyrene. The non-linear relationship between quenching efficiency (I<SUB>0</SUB>/I or τ<SUB>0</SUB>/τ) and partial pressure of oxygen observed in these films was examined and a simple Freuchlich power law shown to fit response data from six sensors which show a 600 fold variation in oxygen sensitivity. The non-linearity is a result of a site distribution in the sensor film and this has been further investigated using initial rate studies and distribution modelling. Such studies indicate that simulated data from a simple uniform distribution in the quenching rate constant (and/or oxygen solubility) gives good fits to experimental decay curves from the six different sensing systems examined. The required model parameters are easily accessible from experimental data and consistent with those calculated for diffusion controlled quenching by oxygen.

A method was developed to access the interior of light-guiding structures in order to exploit the enhanced sensing potential of the highly confined electromagnetic field distributions, located within the core of a waveguide. The work presented in this thesis explores therefore the possibilities of optical waveguide spectroscopy utilising transparent mesoporous thin-film waveguides deposited on top of athin gold layer. These multi-layer assemblies are employed in a prism-coupling attenuated total internal reflection (ATR) configuration. The angular read-out of the reflected light intensity allows label-free detection schemes with high sensitivity to changes of the dielectric environment in the case of the presence of analyte molecules within the probing region. This optical waveguide spectroscopy technique has been used to study the real-timediffusion of Ruthenium 535-bisTBA (N-719) dye into mesoporous nanocrystalline titaniumdioxide films. The porous films were prepared on top of gold substrates and prism coupling was used to create a guided wave in the nanocrystalline film. Dying was carried out by bring the film into contact with a 3 x 10-4 moldm-3 dye solution and using optical waveguide spectroscopy to monitor the change in both the refractive index and theextinction coefficient of the nanoporous layer as dye diffused into the porous network. Dyeuptake in a 1.27 μm film was slow with the refractive index of the film still increasing after 22 hours.

This thesis presents optical characterization of the static and dynamic magnetic interactions in ferromagnetic and multiferroic heterostructures with time-resolved and interface-specific optical techniques. The focus of the thesis is on elucidating the underlying physics of key physical parameters and novel approaches, crucial to the performance of magnetic recording and spintronic devices.;First, time-resolved magneto-optical Kerr effect (TRMOKE) is applied to investigate the spin dynamics in L10 ordered FePt thin films, where perpendicular magnetic anisotropy Ku and intrinsic Gilbert damping alpha0 are determined. Furthermore, the quadratic dependence of Ku and alpha0 on spin-orbit coupling strength xi is demonstrated, where xi is continuously controlled through chemical substitution of Pt with Pd element. In addition, a linear correlation between alpha0 and electron scattering rate 1/T e is experimentally observed through modulating the anti-site disorder c in the L10 ordered structure. The results elucidate the basic physics of magnetic anisotropy and Gilbert damping, and facilitate the design and fabrication of new magnetic alloys with large perpendicular magnetic anisotropy and tailored damping properties.;Second, ultrafast excitation of coherent spin precession is demonstrated in Fe/CoO heterostructures and La0.67Ca0.33MnO 3 thin films using TRMOKE technique. In the Fe/CoO thin films, Instant non-thermal ferromagnet (FM) -- antiferromagnet (AFM) exchange torque on Fe magnetization through ultrafast photo-excited charge transfer possesses in the CoO layer is experimentally demonstrated at room temperature. The efficiency of spin precession excitation is significantly higher and the recovery is notably faster than the demagnetization procedure. In the La0.67Ca 0.33MnO3 thin films, pronounced spin precessions are observed in a geometry with negligible canting of the magnetization, indicating that the transient exchange field is generated by the emergent AFM interactions due to charge transfer and modification of the kinetic energy of eg electrons under optical excitation. The results will help promoting the development of novel device concepts for ultrafast spin manipulation.;Last, the interfacial spin state of the multiferroic heterostructure PbZr0.52Ti0.4803/La0.67Sr0.33MnO 3 and its dependence on ferroelectric polarization is investigated with interface specific magnetization induced second harmonic generation (MSHG). The spin alignment of Mn ions in the first unit cell layer at the heterointerface can be tuned from FM to AFM exchange coupled, while the bulk magnetization remains unchanged as probed with MOKE. The discovery provides new insights into the basic physics of interfacial magneto-electric (ME) coupling.

This dissertation describes the fabrication and integration of a thin film edge emitting laser (EEL) whose optical output is coupled into a polymer waveguide integrated onto the same electrical interconnection substrate. This embedded laser/waveguide structure is a fundamental building block toward the realization of planar lightwave circuits using embedded optical interconnections. The demonstration of a thin film laser integrated with a planar waveguide eliminates the need for either an external optical source coupled to the waveguide or a bump bonded optical source with a beam turning element to turn an optical beam into the waveguide. In this work, the wedge-induced facet cleaving (WFC) method is adapted to fabricate the thin film EELs. Bisbenzocyclobutene (BCB) polymers are used to fabricate channel waveguides, and thin film lasers are integrated with the polymer waveguides. The coupling efficiency from the laser to the polymer waveguide is estimated through measurement and theoretically calculated. In the theoretical calculation, the thin film transfer matrix method is used to analyze the optical modes in the semiconductor cavity. The coupling efficiency from the laser to the polymer waveguide is analyzed using a finite element method (FEM), and are then compared to the experimental results. The experimentally estimated coupling efficiency is in good agreement with that of the theoretical calculation. In addition, the relationship between threshold current, output power, and facet reflectivity of the thin film laser is analyzed using FEM.

Electro-optical properties of thin film are of great interest owing to the perpetual demand for miniaturization and higher speed devices for communication, electronic, and biomedical applications. The thickness of polymer films developed for these applications has decreased dramatically making interfacial effects significant. It is well documented that, in submicron thickness range, both film/substrate & film/air interface are critical. In this study, we probe the dynamics of electro-optical polymer thin films in the sub-micron thickness regime to understand interfacial effects. The polymer chain dynamics of Polypropylene oxide (PPO) under electric field are investigated in this study. The effects of electric field strength, frequency, and polymer molecular weight on the polymer chain dynamics under electric field are studied. Experimental results show that PPO exhibits both piezoelectric and electrorestrictive effects at significantly high frequencies (101kHz range). Conventional organic materials are responsive only at frequencies in <1kHz range. A high signal-to-noise ratio differential interferometry is designed to quantitatively study the effects of film thickness, electric field frequency and amplitude on the dynamic properties of PPO thin films ranging from 30 nm to 400 nm. The interferometer can concurrently monitor the index of refraction, thickness change of polymer films, and birefringence due to the applied electrical field.<br>Master of Science

Evaluation of the wet etching properties of several different thin film oxidesgrown by physical vapour deposition was performed in this work. MgO, Al2O3,SiO2, TiO2, HfO2 ZrO2 and Y2O3 were coated on two types of substrates; Si andborosilicate glass and etching tests were performed in different etchingsolutions. MgF2 thin films have also been evaluated. Important aspects of the choice of the thin films was taken into account in orderto match to good optical properties such as refractive index (n), extinction coefficient (k) and optical thickness (TP) as well as good chemical properties in the wet etching process. A description is made of the physics of optical filters and how a combination of different oxides stacked onto each other can create interference filters. A description of the manufacturing process of the thin films where physical vapour deposition (PVD) was used is presented. Thermal shift of the optical spectra caused by porous coatings was investigated and analyses of the thin films by ellipsometry, surface profilometry and transmission spectrophotometry have been performed. The wet etching properties were evaluated by monitoring the transmission insituon transparent borosilicate glass substrates. A method of how to measure the wet etching rate for different thin films is described. A computer software was used to calculate the Pourbaix diagrams in order to understand the chemical behaviour of the etching solutions. The pH can have a significant impact on the etching behaviour. In case of TiO2, it can be dissolved in an alkaline solution of H2O2. The catalytically process behind this is evaluated. Etching rate for both Y2O3 andSiO2 were matched by adjusting the etchant concentration as a case example. The group IVB oxides are difficult to etch. The catalytic etching of TiO2 with peroxide is slow but detectable. Al2O3, Y2O3 and MgO are reasonably easy to etch but have too low refractive indices to be useful in multilayer optical filters. The In-situ etching instrument was found to be very useful for measuring etching rates.<br>Utvärdering av våtkemiska egenskaper för flera olika oxidtunnfilmer utfördes idetta arbete på tunnfilmer av MgO, Al2O3, SiO2, TiO2, HfO2 ZrO2 and Y2O3 vakuumdeponerade på både kiselwafers och borosilikatglas. Etstester gjordes med ett flertal etslösningar. Även MgF2-tunnfilmer utvärderades. Både optiska och kemiska egenskaper togs i beaktande vid utvärderingen av tunnfilmerna. De optiska lagar som gäller för tunnfilmer redovisas, bl a hur kombinationer av olika oxider kan skapa interferrensfilter. En beskrivning av tillverkningsprocessen varvid PVD användes presenteras. Termiskt skift av det optiska transmissionsspektrat orsakat av porositet undersöktes. Analyser av tunnfilmerna med ellipsometri, profilometri och transmissions spektroskopi utfördes. Våtetsningsegenskaperna utvärderades genom att mäta in-situ vid etsprocessen på transparenta borosilikatglassubstrat. Metoden för att mäta etshastigheten för olika oxider är beskriven. Datorberäkningar av pourbaixdiagram användes för att skapa en förståelse av de kemiska egenskaperna för etslösningarna. Etsegenskaperna påverkas till stordel av lösningens pH. TiO2 kan etsas i basisk lösning av peroxid. Denna process utvärderades, likaså utvärderades etshasigheten för Y2O3 och SiO2 för att erhålla matchande par avoxider som en fallstudie. Grupp IVB oxiderna är mycket svåra att etsa. Katalytisk etsning av TiO2 med peroxid är detekterbar men långsam. Al2O3, Y2O3 och MgO är förhållandevis enkla att etsa men har för låga brytningsindex för att var praktiskt använbara i optiska multilagerfilter. In-situ etsinstrumentet befanns vara ett utmärkt verktyg för att mäta etshastigheten för tunnfilmer.

The effect of the configuration of the confining magnetic field on the operating characteristics of a planar magnetron has been observed. In particular, the heat load and charged particle bombardment of the substrate were measured. A circular planar magnetron was constructed with a magnetic field which could be controlled by the adjustment of the current flowing through coils placed around the circumference and with a separate supply feeding a coil around the centre pole. This allowed the magnetic field configuration to be unbalanced and caused the negative glow plasma to be incident on the substrate. It was found that the "unbalanced" electrically-controlled model could give six times the heat load to a substrate in comparison with a balanced permanent magnet structure. Such a load resulted from the bombardment of the substrate with the plasma (revealed by the measurement of the I-V characteristics), and gave a 30 volt negative bias as well as saturated electron and ion currents of around 90 and 1 mA respectively (a magnetron operating current: 0.8A). The heat load was lkWm⁻². This compared to a 1 volt positive bias with current of 1.4 and 0.5 mA for the balanced case. This bombardment was used as a neutralised ion beam to enhance film growth during sputtering. The effect of the magnetic field configuration has been observed on the operating characteristics of a planar magnetron. In particular, the deposition rate, the currents to a probe and heat load, as a function of the outer pole solenoid current, were measured. The deposition rate/input power was constant at 19 mÅ/s/W, independent of the outer pole solenoid current. In the region from 20 to 40 A of the outer pole solenoid current, the configuration of the magnetic field seemed to be concentric and the electrons were confined by it. But from 40 to 80 A, the magnetic field became dispersed outwards along the direction to the magnetron and the electrons followed it. Consequently, following bombardment of the surface by electrons and neutralising ions, the currents to a probe and the heat load, gave a behaviour. The effect of the pressure has been observed on probe current, floating potential and heat load. With the pressure increasing, they decreased. It seems that the mean free path of particles becomes shorter and then scattering of them increases. The influence of the magnetic field strength on the plasma, created at the rear of a substrate, has been observed. In particular, the floating potential and the charged particle bombardment of the substrate were measured. Permanent magnets at the rear of the substrate, outside of the chamber, could make the configuration of the magnetic field change and control the floating potential from -3 to -59 V. At the same time, they influenced the current-voltage characteristics of a probe and made it change following the direction of the field. Ti0₂ is a very important thin film material in optics because the refractive index is high and it can also satisfy the requirements of a hard, dense and chemically stable coating. In our study, the effect of the floating potential, and the resulting ion beam bombardment on the properties of Ti0₂ thin films deposited by reactive planar magnetron sputtering, has been observed. In reactive magnetron sputtering of Ti0₂, as the partial pressure of oxygen is increased, reaction products form on the target (it is poisoned) which lead to an unstable situation with the cathode switching from metal to oxide uncontrollably. More sophisticated control techniques are required in order to get a stoichiometric Ti0₂, film. The oxygen flow was controlled by observation of the light emission of the Ti spectral line. This was measured using a band pass filter and a photomultiplier. It maintained the oxygen flow by regulating a piezovalve. The optical emission controller gave a complete range of Ti to oxygen ratios. As a result, we obtained samples with a high refractive index of 2.52 at 633 nm and a high deposition rate of 4 Å/s. The properties measured were the refractive index, the surface composition and morphology, and the crystallinity. The relationship between the refractive index and the proportions of 'anatase' and 'rutile' crystal structures of the Ti0₂ films was especially considered and the dependence on the floating potential was assessed. Also, Al₂0₃, Cuo, ZnO have been sputtered and the effect of pressure instability assessed. Their properties were measured.

The aim of this PhD was to undertake a study of combustion chemical vapour deposition (combustion CVD or CCVD) for the optical thin film materials synthesis. The most common variables for thin film formation were investigated, e.g. precursor volatility/availability and the result was the development of an innovative process using low-impact velocity aerosol generation in combination with a premixed propane flame. To perform coating studies, new equipment was developed that was, in concept, compatible with the flat glass coating manufacturing process giving the process industrial compatibility. Deposition of silicon oxide; d and p-block metal oxides and noble metals were achieved during this work opening opportunities for new routes to thin film optical materials. Precursor delivery/availability was significantly extended, demonstrating the possibility of using cheap, commercially available inorganic salts dissolved in water (ammonium salts, nitrate salts,...). The mechanisms involved in the transport/decomposition/thin film formation are discussed in detail providing alternative explanations to the traditional CVD mechanism reported in the literature. The materials deposited were characterised using XPS, XRD, SEM and AFM and their properties highlighted the flexibility and the novelty of the new system.

The purpose of the thesis was to develop a sensitive oxygen optical sensor, which, when coupled with an enzymatic reaction would lead to the creation of useful optical biosensors for the biochemical analytes hydrogen peroxide and glucose. Chapter 3 is an account of work in which a [Ru(dpp)<SUB>3</SUB> <SUP>2+</SUP>(Ph<SUB>4</SUB>B<SUP>-</SUP>)<SUB>2</SUB>]-based oxygen optical sensor, immobilized in silicone rubber, was developed and fully characterised. The sensor was extremely sensitive and stable towards oxygen compared with previous literature findings. The sensitivity of the oxygen sensors was temperature independent, but the response and recovery times decreased with increasing temperature. Chapter 4 gives results from an investigation into some of the factors controlling the sensitivity of a series of [Ru(L)<SUB>3</SUB> <SUP>2+</SUP>(Ph<SUB>4</SUB>B<SUP>-</SUP>)<SUB>2</SUB>]-based oxygen optical sensors immobilized in cellulose acetate. The sensitivity was found to vary according to the lumophore's lifetime and the amount of plasticizer used in the formulation. The sensitivity of the oxygen sensor increased with longer lumophore lifetime and with plasticizer volume. Chapter 5 provides results from a study of an analogous, highly sensitive optical sensor, i.e. [Ru(dpp)<SUB>3</SUB> <SUP>2+</SUP>(Ph<SUB>4</SUB>B<SUP>-</SUP>)<SUB>2</SUB>] immobilized in cellulose acetate butyrate and plasticized by tributyl phosphate which was coupled with an enzymatic reaction to produce a hydrogen peroxide optical biosensor. This biosensor was found to be more sensitive than those previously reported in the literature, due to the increased activity of the catalase enzyme as measured by Michaelis kinetics. Chapter 6 gives an account of the development and characterisation of a glucose biosensor. The biosensor sensitivity could be tuned for different applications by varying the amount of glucose oxidise used in the formulation. The activity, as measured by Michaelis kinetics was largely independent of temperature.

The polarization properties of embedded centro-symmetric and periodic multilayer stacks under conditions of frustrated total internal reflection (FTIR) are considered. The centro-symmetric multilayer stack consists of a high-index center layer sandwiched between two identical low-index films and high-index – low-index bilayers repeated on both sides of the central trilayer maintaining the symmetry of the entire stack. The periodic multilayer consists of periodically repeated low-index – high-index bilayers. Each multilayer stack is embedded in a high-index prism. Embedded centro-symmetric multilayer stacks are designed to function as efficient polarizers or polarizing beam splitters (PBSs) under conditions of FTIR over an extended range of incidence angles. For a given set of refractive indices, all possible solutions for the thicknesses of the layers that suppress the reflection of p-polarized light at a specified angle, and the associated reflectance of the system for the orthogonal s polarization, are determined. The angular and spectral sensitivities of polarizing multilayer stacks employing 3, 7, 11, 15 and 19 layers of BaF2 and PbTe thin films embedded in a ZnS prism, operating at ë = 10.6 ìm, are presented. Embedded centro-symmetric multilayer stacks are also designed to function as complete-transmission quarter-wave or half-wave retardation (QWR or HWR) devices under conditions of FTIR. QWR and HWR designs at ë =1.55 mì are presented that employ 11 and 7 layers of Si and SiO2 thin films embedded in GaP and Si cube prisms, respectively. The angular and spectral sensitivities of these devices are also considered. Embedded centro-symmetric multilayer stacks under FTIR conditions are also designed to produce various 50%-50% beam splitters. Embedded periodic multilayer stacks are designed to function as polarizers and PBSs at discrete multiple angles of incidence and wavelengths under condition of FTIR. For a given set of refractive indices, all possible solutions for the thicknesses of the layers that suppress the reflection of p-polarized light at a specified angle, and the associated reflectance of the system for the orthogonal s polarization, are determined. The angular and spectral sensitivities of polarizing multilayer stacks employing 4, 6, 8, 10, 12, 14, 16 and 18 layers of BaF2 and PbTe thin films embedded in a ZnS prism, operating at ë= 10.6 ìm, are presented.

The work contained within this thesis considers the applicability of wavefront sensing to the problem of laminate and thin film metrology and considers whether such technology can be applied to the problem of in-situ thickness measurement. Some initial investigations were carried out to develop new applications based on current technology. The main body of the work investigated the development of a thickness monitor based on measuring the separation of surface reflections and the further development required to incorporate a wavefront sensor into the system to allow the reflected wavefronts to be analysed. The initial system was developed theoretically using a mathematical model and tested experimentally giving a high dynamic range (lOJlm - 8mm) and good accuracy (50nm) for this application. Analysis of higher order aberration modes introduced by the film structure have been carried out in simulation and a robust algorithm fonnulated to measure film thickness and surface tilt simultaneously using a single measurement. The most prominent aberrations introduced by laminate layers were identified as tilt, defocus, astigmatism and coma and monitoring of these modes allowed thickness variation to be measured. Experiments and simulations were shown to agree and further development of a sensor based on analysis of the interference between wavefronts allowed much thinner laminates to be measured. This work will allow further development of an industrial thickness monitor capable of measuring film thickness and surface fonn in multiple laminates simultaneously and suitable for in-line in-situ real time measurements.

Thin film optical sensors in which a halide sensitive fluorophore is immobilised in a thin (~ 50 micron) polymer film have been developed and characterised. The sensor films use rhodamine, 6-methoxyquinoline or harmane dyes which have been functionalised and bound to a hydrophilic copolymer. The selection, synthesis, functionalisation, and polymer-binding of the dyes is described, as is the synthesis and physical characterisation of the polymer supports. Two hydrophilic copolymers have been synthesised and characterised and twenty novel halide sensitive compositions have been synthesised, or formulated, and studied. Steady-state luminescence spectroscopy and single photon counting time resolved emission spectroscopy have been used to characterise the luminescence spectra and emission decay kinetics of the lumophores, both in free solution and bound and unbound in polymer films. For all dye/polymer formulations studied the emission decay kinetics are complex. Fitting to discrete exponential analysis gives at least two, and often three decay components, while distribution analysis often gives either a very broad distribution or even groups of distributions. As a consequence the steady state response gives non linear Stern-Volmer analysis when examined over a wide dynamic range. Even so, a reasonable linear Stern-Volmer response is observed for halide over physiologically and technologically important concentration ranges. The sensor films described in this work are reversibly capable of determining aqueous iodide and halide with ~ 4% accuracy at concentrations of around 0.001 mol dm<SUP>-3</SUP>. The 90% response time to molar halide is ~ 30 s. A combination of sensor films allows the simultaneous and rapid determination of both I<SUP>-</SUP> and Br<SUP>-</SUP> in a mixed halide solution. These sensors are potentially useful for the online determination of aqueous halide in a variety of technological applications.

Thisworkillustratesapplicationofthe uniquefiber-optic instrumentationforin situmonitoringofseveral technologicalprocessescommonlyusedinfabricationof semiconducting thin-film nanostructures. This instrumentation is basedonprinciplesoflowcoherenttandeminterferometry, whichdetermineshighsensitivityandprecision in measuring basic technological parameters, such as thickness of forming layers, temperature and bending of the substrate.The probing wavelength 􀈜 = 1.55 􀈝m allows carrying out the measurements on majority of substrates for semiconductor technology: Si, SOI, GaAs, InP, GaP, Al2O3, diamond, ZrO2:Y. Monitoring of such processes as MOVPE, MBEandplasmaetchingin various set-ups was realized. The absolute resolution achieved in these experiments was limited only by calibration accuracy and corresponds to 1􀉨 􀉋at sensitivity of 0.01􀉨 􀉋. The accuracy limit in estimating the thickness of layers during their growth is 2 nm. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/20681

The exploitation of the soft x-ray/extreme ultra-violet (EUV) region of the electromagnetic spectrum is possible mainly due to the development of multilayer (ML) mirrors. This region of the electromagnetic spectrum offers great opportunities in both science and technology. The shorter wavelength allows one to see smaller features in microscopy and write finer features in lithography. High reflectivity with moderate spectral bandwidth at normal/near-normal incidence can be achieved in soft x-ray/ EUV spectral range using these ML mirrors, where natural crystals with the required large periodicity are not available. These MLs are generally artificial Bragg’s reflectors, which consist of alternative high and low density materials with periodicity in the nanometer range. The main advantages of ML optics stem from the tunability of layer thickness, composition, lateral gradient, and the gradient along the normal to the substrate; these can be tailored according to the desired wavelength regime. They have the great advantage of being adaptable to figured surfaces, enabling their use as reflective optics in these spectral regions, for focusing and imaging applications. Broadband reflectivity and wavelength tunability are also possible by using MLs with normal and lateral gradient, respectively. However, fabrication of these ML mirrors requires the capability to deposit uniform, ultra-thin (a few angstroms-thick) films of different materials with thickness control on the atomic scale. Thus, one requires a proper understanding of substrate surfaces, individual layers, chemical reactivity at interfaces and, finally, of the ML structures required for particular applications. The performance of these MLs is limited by (the lack of) contrast in optical constants of the two materials, interfacial roughness, the chemical reactivity of two materials and, finally, errors in the thickness of individual layers. Soft x-ray/extreme ultra-violet ML mirrors have found a wide range of applications in synchrotron radiation beam lines, materials science, astronomy, x-ray microscopy, x-ray laser, x-ray lithography, polarizers, and plasma diagnostics. The Indus–1 synchrotron radiation (SR) source is an operational 450 MeV machine, which produces radiation up to soft x-rays. Indus-2 is a 2.5 GeV machine, which has been commissioned recently to produce hard x-rays (E > 25 keV). The combination of Indus-1 and Indus-2 will cover a broad energy spectrum from IR to hard x-rays. Therefore, there is a significant need and opportunity to study MLs of different pairs of materials, with different parameters such as periodicity and optimum thickness of individual layers. The goal of the present thesis is to fabricate MLs for soft x-ray optics and to study their physics for application as polarizers in the wavelength range from 67 Å to 160 Å on the Indus-1 synchrotron source. To accomplish this task, a UHV electron beam evaporation system has been developed indigenously for the fabrication of MLs. Three different ML systems viz., Mo/Si, Fe/B4C and Mo/Y have been fabricated, and their surfaces and interfaces were investigated thoroughly for the polarizer application. X-ray reflectivity (XRR) has been used extensively in the investigations of these MLs. This is because XRR is a highly sensitive non-destructive technique for the characterization of buried interfaces, and gives microscopic information (at atomic resolution) over a macroscopic length scale (a few microns). Numerical analysis of XRR data has been carried out using computer programs. Depth-graded x-ray photoelectron spectroscopy (XPS) has been used for compositional analysis at interfaces for some of the ML structures, as a technique complementary to XRR. The performance of some of these MLs has been tested in the soft x-ray region, using the Indus-1 synchrotron radiation (SR) source. Prior to studying the MLs, a detailed study of the surfaces and interfaces of thin films, bi-layers, and tri-layers was carried out using XRR and the glancing incidence fluorescence technique. The discontinuous-to-continuous transition and the mode of film growth, which are vital to the optimization of layer thickness (basically for the high-atomic number or high-Z layer) in the ML structures, were also investigated using in situ sheet resistance measurement method. Indus-1 is a soft x-ray SR source that covers atomic absorption edges of many low-Z materials. The present work demonstrates the possibilities of characterizing low-Z thin films and multilayers using soft x-ray resonant reflectivity. In one case, we have shown for first time that soft x-ray resonant reflectivity can be employed as a non-destructive technique for the determination of interlayer composition. In a second study using the Indus-1 SR source, we have shown, by observing the effect of the anomalous optical constant on reflectivity pattern when photon energy is tuned across the atomic absorption edge of the constituent low-Z element, that soft x-ray resonant reflectivity is an element-specific technique. This thesis is organized into 7 chapters. A brief summary of individual chapters is presented below. Chapter 1 gives a brief general introduction to x-ray ML optics. This is followed by a discussion of the importance of the soft x-ray region of electromagnetic radiation. The optical properties of x-rays are reviewed and optical constants are calculated for some of the important materials used for x-ray MLs. The refractive index in the x-ray region being less than unity (except absorption edges), the consequent limitation of conventional transmission lenses is discussed. The limitation of glancing angle incidence optics is presented, motivating the need for ML optics, which is discussed along with a theoretically calculated reflectivity profile. The procedure for materials for the MLs for application in different spectral regions is discussed, along with a survey of literature related to the present thesis. The importance of the quality of surfaces and interfaces on the performance of ML structures has been shown through simulations. The applications of soft x-ray MLs are discussed with emphasis on polarization. This is followed by a review of different modes of growth of thin films. Finally, the scope of the present work is highlighted. Chapter 2 provides brief descriptions of the experimental techniques used in the present investigations and of the numerical methods employed for quantitative data analysis. The XRR technique is discussed elaborately because it has been used extensively. Detailed calculations of x-ray reflectivity from single surfaces, thin films and bi-layers are presented, along with simulated values. The effect of critical angle and Brewster’s angle is also discussed. Data analysis methods for computing x-ray reflectivity from multilayer structures, based on dynamical and kinematical models, have been discussed. The effect of roughness on XRR has been discussed based on the recursion formalism of dynamical theory. Simulations of XRR and experimental XRR data fitting are carried out using computer programs. The XRR experimental set up is also outlined. A theoretical background is given for the electrical measurements on thin films. This is followed by a brief overview of x-ray photoelectron spectroscopy (XPS) and interpretation of spectra. Finally, the glancing incidence x-ray fluorescence (GIXRF) technique is outlined. Chapter 3 describes in detail the ultra-high vacuum electron beam evaporation system developed in house especially for the fabrication of thin films and x-ray multilayer optics. At the outset, a brief overview of different deposition techniques commonly used for the fabrication of x-ray optical elements is presented. Design, fabrication, and assembly of different accessories are discussed. The control of thickness and uniformity of the films deposited has been checked through the experiments, whose results are provided. The results obtained for ML test structures are presented to show the capability of system in carrying out fabrication of high quality x-ray ML structures. Finally, the versatility of evaporation system incorporating in situ characterization facilities such as -situ electrical measurements for different substrate temperatures is illustrated. Chapter 4 presents a study of the growth of ultra-thin Mo films at different substrate temperatures using in situ sheet resistance measurements. First, a theoretical background is given on the different stages of island growth and on factors affecting thin film growth, followed by a discussion of the possible electrical conduction phenomena in continuous and discontinuous metal films. The nature of thin film growth and a detailed microscopic picture at different growth stages are derived from a modeling of sheet resistance data obtained in situ. The various conduction mechanisms have been identified in different stages of growth. In the island growth stage, the isotropic and anisotropic growth of Mo islands is identified from the model. In the insulator-metal transition region, experimentally determined values of critical exponent of conductivity agrees well with theoretically predicted values for a two-dimensional (2D) percolating system, revealing that Mo films on float glass substrate is predominantly a 2D structure. The minimum thickness for which Mo films becomes continuous is obtained as 1.8 nm and 2.2 nm for Mo deposited at substrate temperatures 300 K and 100 K, respectively. An amorphous-to- crystalline transition is also observed, and discussed. Chapter 5 covers the detailed study of the surfaces and interfaces studies in three different ML structures viz., Mo/Si, Fe/B4C and Mo/Y, meant for the polarizer application in the wavelength range of 67 Å to 160 Å. Multilayers with varying periodicity, varying number of layer pairs, and different ratios of high-Z layer thickness to the period, were fabricated using the electron beam system. Initially, a brief overview of the design aspects of ML structures is given, along with the theoretically calculated reflectivity at Brewster’s angle from the best material combinations. In Mo/Si MLs, the interlayer formed at the interfaces due to interdiffusion of the two elements is asymmetric in thickness, i.e., Mo-on-Si interlayer is thicker than the Si-on-Mo interlayer. To take account of these interlayers in XRR data fitting, a four layer model is considered. The effect of interlayers on reflectivity pattern was studied using simulations, and differences with respect to roughness are also discussed. The mechanism of formation of asymmetric interlayers is also discussed. The interlayer composition has determined using depth-graded XPS. The results reveal the formation of the MoSi2 composition at both the interfaces. The experimental results agree well with theoretical calculations based on solid-state amorphization reaction, which is a result of large heat of mixing. The effective heat of formation model reveals the formation of MoSi2 as the first phase. The soft x-ray reflectivity performance of the Mo/Si ML structure at Brewster’s angle is tested using Indus-1 synchrotron radiation (SR). Using XRR and GIXFR, a study of the surfaces and interfaces of bilayers of B4C-on-Fe and Fe-on- B4C, and tri-layers of Fe-B4C-Fe was carried out, with a systematic variation of Fe and B4C layer thicknesses. A sharp interface was observed in Fe-on-B4C, whereas a low density (w.r.t. Fe) interlayer is observed at the B4C-on-Fe interface. The interlayer properties fluctuates w.r.t. the bottom Fe layer thickness and is independent of the top B4C layer thickness. The nature of fluctuations has been discussed in detail. A study of the surfaces and interfaces of Fe/B4C MLs is described. Finally, a study of the surfaces and interfaces of bilayers, tri-layers, and MLs of the Mo/Y system is discussed in detail. Chapter 6 describes the application of soft x-ray resonant reflectivity for the characterization of low-Z thin films and interfaces in multilayer structures. Initially, a discussion of the energy dependence of atomic scattering factors and hence of optical constants is provided with simulations, with emphasis on the atomic absorption edge. Then, a brief overview of synchrotron radiation, with particular emphasis on the parameters of the Indus-1 synchrotron source is given. The possibilities of determining the composition of the buried interlayer with sub-nanometer scale sensitivity using soft x-ray resonant reflectivity are discussed. The methodology has been applied to study the Mo/Si interface both by simulations and by experiments on the Indus-1 SR, by tuning the photon energy to the Si L-absorption edge. Finally, direct evidence of elemental specificity of soft x-ray resonant reflectivity through the observation of the effect of anomalous optical constants on the reflectivity pattern is discussed. We demonstrate the method through simulations and experiments on the B4C material in B4C thin films and Fe/ B4C bi-layers, using Indus-1 SR tuned to the boron Kedge. Chapter 7 summarizes the main findings of the present work, and provides an outlook for further investigations in the field.

The exploitation of the soft x-ray/extreme ultra-violet (EUV) region of the electromagnetic spectrum is possible mainly due to the development of multilayer (ML) mirrors. This region of the electromagnetic spectrum offers great opportunities in both science and technology. The shorter wavelength allows one to see smaller features in microscopy and write finer features in lithography. High reflectivity with moderate spectral bandwidth at normal/near-normal incidence can be achieved in soft x-ray/ EUV spectral range using these ML mirrors, where natural crystals with the required large periodicity are not available. These MLs are generally artificial Bragg’s reflectors, which consist of alternative high and low density materials with periodicity in the nanometer range. The main advantages of ML optics stem from the tunability of layer thickness, composition, lateral gradient, and the gradient along the normal to the substrate; these can be tailored according to the desired wavelength regime. They have the great advantage of being adaptable to figured surfaces, enabling their use as reflective optics in these spectral regions, for focusing and imaging applications. Broadband reflectivity and wavelength tunability are also possible by using MLs with normal and lateral gradient, respectively. However, fabrication of these ML mirrors requires the capability to deposit uniform, ultra-thin (a few angstroms-thick) films of different materials with thickness control on the atomic scale. Thus, one requires a proper understanding of substrate surfaces, individual layers, chemical reactivity at interfaces and, finally, of the ML structures required for particular applications. The performance of these MLs is limited by (the lack of) contrast in optical constants of the two materials, interfacial roughness, the chemical reactivity of two materials and, finally, errors in the thickness of individual layers. Soft x-ray/extreme ultra-violet ML mirrors have found a wide range of applications in synchrotron radiation beam lines, materials science, astronomy, x-ray microscopy, x-ray laser, x-ray lithography, polarizers, and plasma diagnostics. The Indus–1 synchrotron radiation (SR) source is an operational 450 MeV machine, which produces radiation up to soft x-rays. Indus-2 is a 2.5 GeV machine, which has been commissioned recently to produce hard x-rays (E > 25 keV). The combination of Indus-1 and Indus-2 will cover a broad energy spectrum from IR to hard x-rays. Therefore, there is a significant need and opportunity to study MLs of different pairs of materials, with different parameters such as periodicity and optimum thickness of individual layers. The goal of the present thesis is to fabricate MLs for soft x-ray optics and to study their physics for application as polarizers in the wavelength range from 67 Å to 160 Å on the Indus-1 synchrotron source. To accomplish this task, a UHV electron beam evaporation system has been developed indigenously for the fabrication of MLs. Three different ML systems viz., Mo/Si, Fe/B4C and Mo/Y have been fabricated, and their surfaces and interfaces were investigated thoroughly for the polarizer application. X-ray reflectivity (XRR) has been used extensively in the investigations of these MLs. This is because XRR is a highly sensitive non-destructive technique for the characterization of buried interfaces, and gives microscopic information (at atomic resolution) over a macroscopic length scale (a few microns). Numerical analysis of XRR data has been carried out using computer programs. Depth-graded x-ray photoelectron spectroscopy (XPS) has been used for compositional analysis at interfaces for some of the ML structures, as a technique complementary to XRR. The performance of some of these MLs has been tested in the soft x-ray region, using the Indus-1 synchrotron radiation (SR) source. Prior to studying the MLs, a detailed study of the surfaces and interfaces of thin films, bi-layers, and tri-layers was carried out using XRR and the glancing incidence fluorescence technique. The discontinuous-to-continuous transition and the mode of film growth, which are vital to the optimization of layer thickness (basically for the high-atomic number or high-Z layer) in the ML structures, were also investigated using in situ sheet resistance measurement method. Indus-1 is a soft x-ray SR source that covers atomic absorption edges of many low-Z materials. The present work demonstrates the possibilities of characterizing low-Z thin films and multilayers using soft x-ray resonant reflectivity. In one case, we have shown for first time that soft x-ray resonant reflectivity can be employed as a non-destructive technique for the determination of interlayer composition. In a second study using the Indus-1 SR source, we have shown, by observing the effect of the anomalous optical constant on reflectivity pattern when photon energy is tuned across the atomic absorption edge of the constituent low-Z element, that soft x-ray resonant reflectivity is an element-specific technique. This thesis is organized into 7 chapters. A brief summary of individual chapters is presented below. Chapter 1 gives a brief general introduction to x-ray ML optics. This is followed by a discussion of the importance of the soft x-ray region of electromagnetic radiation. The optical properties of x-rays are reviewed and optical constants are calculated for some of the important materials used for x-ray MLs. The refractive index in the x-ray region being less than unity (except absorption edges), the consequent limitation of conventional transmission lenses is discussed. The limitation of glancing angle incidence optics is presented, motivating the need for ML optics, which is discussed along with a theoretically calculated reflectivity profile. The procedure for materials for the MLs for application in different spectral regions is discussed, along with a survey of literature related to the present thesis. The importance of the quality of surfaces and interfaces on the performance of ML structures has been shown through simulations. The applications of soft x-ray MLs are discussed with emphasis on polarization. This is followed by a review of different modes of growth of thin films. Finally, the scope of the present work is highlighted. Chapter 2 provides brief descriptions of the experimental techniques used in the present investigations and of the numerical methods employed for quantitative data analysis. The XRR technique is discussed elaborately because it has been used extensively. Detailed calculations of x-ray reflectivity from single surfaces, thin films and bi-layers are presented, along with simulated values. The effect of critical angle and Brewster’s angle is also discussed. Data analysis methods for computing x-ray reflectivity from multilayer structures, based on dynamical and kinematical models, have been discussed. The effect of roughness on XRR has been discussed based on the recursion formalism of dynamical theory. Simulations of XRR and experimental XRR data fitting are carried out using computer programs. The XRR experimental set up is also outlined. A theoretical background is given for the electrical measurements on thin films. This is followed by a brief overview of x-ray photoelectron spectroscopy (XPS) and interpretation of spectra. Finally, the glancing incidence x-ray fluorescence (GIXRF) technique is outlined. Chapter 3 describes in detail the ultra-high vacuum electron beam evaporation system developed in house especially for the fabrication of thin films and x-ray multilayer optics. At the outset, a brief overview of different deposition techniques commonly used for the fabrication of x-ray optical elements is presented. Design, fabrication, and assembly of different accessories are discussed. The control of thickness and uniformity of the films deposited has been checked through the experiments, whose results are provided. The results obtained for ML test structures are presented to show the capability of system in carrying out fabrication of high quality x-ray ML structures. Finally, the versatility of evaporation system incorporating in situ characterization facilities such as -situ electrical measurements for different substrate temperatures is illustrated. Chapter 4 presents a study of the growth of ultra-thin Mo films at different substrate temperatures using in situ sheet resistance measurements. First, a theoretical background is given on the different stages of island growth and on factors affecting thin film growth, followed by a discussion of the possible electrical conduction phenomena in continuous and discontinuous metal films. The nature of thin film growth and a detailed microscopic picture at different growth stages are derived from a modeling of sheet resistance data obtained in situ. The various conduction mechanisms have been identified in different stages of growth. In the island growth stage, the isotropic and anisotropic growth of Mo islands is identified from the model. In the insulator-metal transition region, experimentally determined values of critical exponent of conductivity agrees well with theoretically predicted values for a two-dimensional (2D) percolating system, revealing that Mo films on float glass substrate is predominantly a 2D structure. The minimum thickness for which Mo films becomes continuous is obtained as 1.8 nm and 2.2 nm for Mo deposited at substrate temperatures 300 K and 100 K, respectively. An amorphous-to- crystalline transition is also observed, and discussed. Chapter 5 covers the detailed study of the surfaces and interfaces studies in three different ML structures viz., Mo/Si, Fe/B4C and Mo/Y, meant for the polarizer application in the wavelength range of 67 Å to 160 Å. Multilayers with varying periodicity, varying number of layer pairs, and different ratios of high-Z layer thickness to the period, were fabricated using the electron beam system. Initially, a brief overview of the design aspects of ML structures is given, along with the theoretically calculated reflectivity at Brewster’s angle from the best material combinations. In Mo/Si MLs, the interlayer formed at the interfaces due to interdiffusion of the two elements is asymmetric in thickness, i.e., Mo-on-Si interlayer is thicker than the Si-on-Mo interlayer. To take account of these interlayers in XRR data fitting, a four layer model is considered. The effect of interlayers on reflectivity pattern was studied using simulations, and differences with respect to roughness are also discussed. The mechanism of formation of asymmetric interlayers is also discussed. The interlayer composition has determined using depth-graded XPS. The results reveal the formation of the MoSi2 composition at both the interfaces. The experimental results agree well with theoretical calculations based on solid-state amorphization reaction, which is a result of large heat of mixing. The effective heat of formation model reveals the formation of MoSi2 as the first phase. The soft x-ray reflectivity performance of the Mo/Si ML structure at Brewster’s angle is tested using Indus-1 synchrotron radiation (SR). Using XRR and GIXFR, a study of the surfaces and interfaces of bilayers of B4C-on-Fe and Fe-on- B4C, and tri-layers of Fe-B4C-Fe was carried out, with a systematic variation of Fe and B4C layer thicknesses. A sharp interface was observed in Fe-on-B4C, whereas a low density (w.r.t. Fe) interlayer is observed at the B4C-on-Fe interface. The interlayer properties fluctuates w.r.t. the bottom Fe layer thickness and is independent of the top B4C layer thickness. The nature of fluctuations has been discussed in detail. A study of the surfaces and interfaces of Fe/B4C MLs is described. Finally, a study of the surfaces and interfaces of bilayers, tri-layers, and MLs of the Mo/Y system is discussed in detail. Chapter 6 describes the application of soft x-ray resonant reflectivity for the characterization of low-Z thin films and interfaces in multilayer structures. Initially, a discussion of the energy dependence of atomic scattering factors and hence of optical constants is provided with simulations, with emphasis on the atomic absorption edge. Then, a brief overview of synchrotron radiation, with particular emphasis on the parameters of the Indus-1 synchrotron source is given. The possibilities of determining the composition of the buried interlayer with sub-nanometer scale sensitivity using soft x-ray resonant reflectivity are discussed. The methodology has been applied to study the Mo/Si interface both by simulations and by experiments on the Indus-1 SR, by tuning the photon energy to the Si L-absorption edge. Finally, direct evidence of elemental specificity of soft x-ray resonant reflectivity through the observation of the effect of anomalous optical constants on the reflectivity pattern is discussed. We demonstrate the method through simulations and experiments on the B4C material in B4C thin films and Fe/ B4C bi-layers, using Indus-1 SR tuned to the boron Kedge. Chapter 7 summarizes the main findings of the present work, and provides an outlook for further investigations in the field.

碩士<br>國立中央大學<br>物理研究所<br>98<br>In this thesis, we have studied the optical characteristics of ZnSe1-xOx thin film (0≦x≦0.097) by using Photoluminescence (PL)spectroscopy and Photoreflectance (PR) spectroscopy. We observe the band gap decreases dramatically with increasing oxygen concentration by PL at room temperature, which can be explained by the band anticrossing model. We observe the S-shaped PL peaks (0＜x≦0.070) evolve with temperature, we have considered this phenomenon which transits from localized exciton to free exciton. We have used PR to obtain the band gap of these samples. We have used the band anticrossing model to analyze these signals from PL and PR.

碩士<br>國立中央大學<br>物理學系<br>101<br>By using photoluminescence(PL) and Raman spectroscopy, we have studied the optical properties and crystal structure of Zn1-xCdxO (0%≦x≦20%) alloys. The localized states in Zn1-xCdxO were observed via the PL spectra that there will be an S-shaped shift in its temperature dependent PL peak. The line-width of Zn1-xCdxO in Raman signal has been broadened by the disorder of lattice vibration. The signal is asymmetric line shaped. This is described that there exists the confinement effect which leads to a relaxation of the q=0 selection rule. The temperature dependence of phonon line-width and peak position of LO modes are analyzed to be in terms of anharmonic effect induced by thermal expansion and compositional disorders. The lifetime of the phonons can be calculated according to the LO line-width and the energy-time uncertainty relation. It is composed of decay lifetime and intrinsic lifetime . The former lifetime is related to anharmonic effect, it decreases with the increment of the Cd content. The latter lifetime corresponds to the impurity, defects and isotopic fluctuation in the crystal quality. The experimented result indicates that high concentration of Cd in Zn1-xCdxO has better crystal quality and longer , we came up the same results in low-temperature PL line-width.

碩士<br>國立成功大學<br>機械工程學系<br>88<br>Mechanical property in thin film structures has attracted great interest issues. The primary concern is the deleterious effects induced by stress in films. Therefore, to minimize and control the stress it is important to understand the type, magnitude and origin of various stress. The second important concern is to enhance the mechanical properties of hardness and wear resistance. The topic of stress in film is the major interest in this thesis. Essentially all films are in a state of stress after vacuum deposition. Stress of most sputtered film is compressive. In many cases, the stress is high enough that it can cause the film to fail mechanically. For example, peeling, generation of crystalline defects and formation of film surface growths such as hillocks whiskers are the typically consequence of excessive stress. Normally, the total stress of a thin film may be composed of intrinsic stress, thermal stress and water absorption induced stress. For single thin film, residual stress can be measured with a X-ray diffraction or mechanical “bending plate method”. But for multilayer, it is very important to establish a model to calculate the residual stress. In this thesis, a mathematics model is used to evaluate the distribution of stress in multilayer.

碩士<br>國立臺灣科技大學<br>應用科技研究所<br>101<br>NiO thin-film nanostructures were grown by hot filament chemical vapor deposition method on different substrates. X-ray diffraction and Raman spectroscopy confirmed cubic structure for the nickel oxide nanostructures. Field emission scanning electron microscope (FESEM) images revealed different structural morphology for different substrate samples owing to different substrate orientations (i.e. nanowires for Si and nanocubes for sapphire substrate) . Optical properties of near-band-edge emissions of NiO film deposited on sapphire are characterized using photoluminescence (PL) measurements in the temperature range between 10 and 300 K. Free exciton (FX) and bound exciton complexes (BECs) have been observed at low temperatures. Emission features originated from donor-acceptor pair (DAP) have also been determined using power dependent PL spectroscopy at 10 K. The near-band-edge transitions of NiO were characterized experimentally by thermoreflectance (TR) and transmission measurements. The experimental results showed that NiO is a direct semiconductor with band-edge transitions of A=3.27 eV and B=3.55 eV at 300 K, respectively. In comparison with the PL and TR measurements, the transition of A=3.27 eV is inferred to be an excitonic transition near band edge. On the basis of experimental results, the optical properties of NiO nanostructures have thus been realized.

博士<br>國立中央大學<br>光電科學研究所<br>98<br>This thesis focus on the mid-infrared optical thin films including germanium (Ge), silicon monoxide (SiO) and silicon nitride (SiN) thin films. The difference from the conventional thermal evaporation process, these films were prepared by ion beam assisted deposition (IAD) process and expected to obtain the desirable properties at lower temperature. These films were analyzed using the infrared variable angle spectroscopic ellipsometry, Fourier transform infrared spectrometry, UV–NIR spectrophotometer, X-ray photoelectron spectrometry, scanning electron microscopy, atomic force microscopy, X-ray diffraction transmission electron microscopy and nano indenter. The influences of ion bombardment on the structural properties, such as composition, crystalline, and microstructure, and on the mid-infrared optical properties of these films were investigated. The results showed that compared the conventional thermal evaporation process, the mid-infrared optical and structural properties of Ge and SiO thin films could be effectively improved by using the selective conditions of the ion beam voltage and current density in the IAD process. In addition, the SiN thin film with good optical property could be obtained using the IAD technique. Furthermore, the mid-infrared edge filter and anti-reflection coating, which were prepared by using the IAD process, also exhibited the desirable optical performance. These results presented in this work indicated that the IAD technique would have a positive effect on the optical and structural properties of the infrared thin films.

碩士<br>明新科技大學<br>光電系統工程系碩士班<br>107<br>Effects of optical coating combinations, a prism film and a phosphor layer on the short current of the solar cell in the optical solar concentrator and the illuminance of the sunlight passing through the samples were investigated in this study. The optical solar concentrator was a 50 mm x 50 mm x 5 mm B270 thick glass with its sides connected by a solar cell. The prismatic structure of the prism film had a period of 50 μm. A phosphor Y560 having an absorption band of 390 nm to 500 nm and emitting from 490 nm to 700 nm was prepared. This research is mainly divided into two stages. In the first stage, in order to find the best effect of a new structure for optical solar concentrators, seven coating combinations applied and analyzed in this study were composed of optical filters and glass. The optical filters included infrared cut-off, magenta, red, green and blue filters. In the second stage, in order to enable the new structure optical solar concentrators to widely apply in architectural glass with white penetrated light, the optical filters with 80%, 50% and 20% transmittance in the visible range were fabricated by electron beam evaporation. The deflection angle was between 31 and 33 degrees and the spectral curve shifted to a short wavelength of 27 nm when the incident sunlight passed through the prism film. The short current and conversion efficiency of the solar cell in the new optical solar concentrator with the prism film and the coating combination were greatly improved. Experimental results show that the optical coating is more suitable for enhancing the short current than the phosphor layer in the new optical solar concentrator with the prism film. It is completely feasible to replace the phosphor layer with the optical coating in the new optical solar concentrator with the prism film.

碩士<br>國立中央大學<br>光電科學研究所<br>92<br>Optical monitoring is the main method for determinating film thickness. Unlike monitoring by runsheet diagram, we raise a new method by admittance diagram. Runsheet has some popular defects such as diffcult to determinate the extreme point and ineffectiveness of observing film growth. Admittance diagram not only overcome these defects, but can oberve the variation of phase thickness. In this thesis, we vertify these qualities mathematically and by experiment. And real-time compensating by the property observing phase

碩士<br>國立臺灣大學<br>光電工程學研究所<br>93<br>In this research, we compare three series samples of Zinc Oxide. For series one, we got three ZnO sample in the same epitaxy structure but with different annealing temperature. And the series two are the ZnO film which grown on different substrate. The last series are p-type and n-type ZnO thin film grown on Al2O3 with different thickness. All series were grown by metalorganic chemical vapor deposition (MOCVD). For series one (with different annealing temperature), the surface morphology was determined by scanning electron microscopy (SEM), it showed that difference of the grain size with different thermal annealing temperature. From XRD data we knew that the crystallinity quality of samples did not monotonously improve with annealing temperature. Using Raman scattering we could observe the annealed samples showed a decrease of the intensity and linewidth of E1 (LO) mode peak with increasing annealing temperature. From PL spectra, two emission bands were observed. One is the ultraviolet (UV) band with peak position at about 380 nm caused by the transition of excitons, and the other was the green band commonly referred to as a deep-level or trap-state emission caused by the defects of the crystal. So we compared the green band of this series samples to determine which one have the best quality that we know in what kind of the condition will get a high quality material. For series two (pair of ZnO grown on Si and sapphire), used the XRD we could find that the lattice constant of materials grown on different substrate. Comparing with the lattice constant and the UV peak shift, we could find the relationship between the stress and the PL peak positions. From Raman scattering spectra, we could find the more exactly relationship between stress and spectrum theoretically, but our XRD experiment results could not fitted the value of theory. Therefore, our research could not find the relation equation about Raman shift and stress. But the Raman shift was still observed. For last series, we were experimented with XRD, reflectance, PL and Raman scattering. The XRD would determine the sample quality and reflectance could find the thickness of film. PL showed the lighting efficiency and intensity of defect, and Raman spectrum represented the symmetry of material. Those experiment results were found the best quality of sample and to find the best fabricated condition of ZnO thin film materials.

碩士<br>崑山科技大學<br>光電工程研究所<br>105<br>This thesis aims to design the optimal structure of optical thin film for low-emissivity glass based on the software, Essential Macleod. The wavelength range (280 nm ~ 2500 nm) is mainly focused on decreasing the transmittance of infrared region. The six-layered single silver structure of the optical thin film is arranged as follows: Air /SiO2 (82nm) /Si(57nm) /SiO2(150nm) /Si(8nm) /Ag(29nm) /Si(12nm) /Glass, with the average transmittance of ultraviolet region, visible region, infrared region to reach 0.01%, 50.45%, and 1.66%, respectively, which is our best design for single silver structure. The six-layered double silver structure of the optimal optical thin film is arranged as follows: Air /SiO2(46nm) /Si(8nm) /Ag(22nm) /Si(24nm) /Ag(22.4nm) /Si(10nm) /Glass, with the average transmittance of ultraviolet region, visible region, infrared region to reach 0.04%, 51.49%, and 0.85%, which is superior to single silver structure. Therefore, the design of the double silver structure should be considered as the optimal candidate for low-emissivity glass. The eight-layered triple silver structure of the optimal optical thin film is arranged as follows: Air /SiO2(49nm) /Si(8nm) /Ag(19nm) /Si(22nm) /Ag(12nm) /Si(22nm) /Ag(18nm) /Si(10nm) /Glass with the average transmittance of ultraviolet region, visible region, infrared region to reach 0.01%, 57.08%, and 0.68%. The ten-layered quadruple silver structure of the optimal optical thin film is arranged as follows: Air /SiO2(55nm) /Si(7nm) /Ag(16nm) /Si(16nm) /Ag(9nm) /Si(17nm) /Ag(10nm) /Si(19nm) /Ag(17nm) /Si(10nm) /Glass with the average transmittance of ultraviolet region, visible region, infrared region to reach 0.02%, 56.83%, and 0.53%. Using ten-layered triple silver structure for the design of multi-functional anti-blue lighted low-emissivity glass results in adjustable transmittance of central wavelength ranging from 22.67% to 33.35%, which definitely accords to the multifunctional composite characteristics. When applying photochromism, the ten-layered double silver structure of the optical thin film for low-emissivity glass is arranged as follows: Air /SiO2(237.69nm) /WO3(10nm) /Si(10nm) /Ag(25nm) /Si(10nm) /WO3( 55.72nm) /Si(10nm) /Ag(24.87nm) /Si(10nm) /WO3(10nm) /Glass. If WO3 is in the bleached state, the average transmittance of ultraviolet region Tav (280nm~380nm), visible region Tav (381nm~780nm), infrared region Tav (781nm~2500nm) reaches 0.01%, 55.93%, and 0.41%, respectively. If WO3 is in the colored state, the average transmittance of ultraviolet region Tav (280nm~380nm), visible region Tav (381nm~780nm), infrared region Tav (781nm~2500nm) reaches 0.01%, 33.12%, and 0.29%, respectively. Among them, the variation of average transmittance of visible region is 22.81%. Therefore, the design of the ten-layered double silver structure should be considered as a candidate of optical thin film for low-emissivity glass with high functions.

碩士<br>國立中山大學<br>物理研究所<br>84<br>The critical temperature Tco and the surface mophologies of Y1 Ba2Cu3O7-d high temperature superconducting films that are deposited by different targets in the same growth condition are studies. Different total growth pressures(25~120mtorr) result in diffeerent deposition rates. Acorrding to the mean free path theory, the higher the pressure is, the lower the deposition rate . We successfully grow a free-pricipatate film with extremely smooth surface when the growth pressure is fixed at 120 mtorr and the substrate temperature at 780℃. Different partial pressure of O2 also significantly effect the characteristics of films. In the present study, all films are grown in a total pressureof 120mtorr and the substrate temperature is fixed at 750℃. The patial pressure ratio of Ar and O2 is about 1:0.875~1:0.02.It is found that the Tco is reciprocally proportional to the partial pressure of O2. When Ar:O2 is set at 1:0.042, a free-precipitate film whose Tco is 84.17K is grown. We also found that films with Tco around 90K can be grown in a high growth pressure (175mtorr) condition. In optical applications, we have fabricated YBCO films with different surface morphologies, whose surface precipitates coverage distribute from 0 to 100%. Each film is made into a microbridge-type photodetecter by photolithographic method and the dimention of detecter is of 25×650(mm)2. The photoresponse signals decrease exponentially due to the precipitation coverage increasing. A He-Ne laser was userd as a light source. It has a power density of 0.08J/cm2-sec which is stronger than the other sources. All incident lights are chopped into 2Hz. The largest responsivity of the free- precipitate device can attain to 2.3× 103V/W. This device also has a low noise equivalent power(NEP)≦ 5×10-12W‧Hz-0.5 and a large detectitivity (D*) ≧109cm‧Hz0.5‧ W-1。

碩士<br>國立臺灣科技大學<br>電子工程技術研究所<br>86<br>The purpose of this thesis is to analyze numerically the characteristics of about optical thin film components in Matlab language. We can use the simplest way to get accurately results. This thesis is mainly divided into 2 parts. First of all, we began with Maxwell equations and optical admittance theorem to infer optical matrix formula. And then, we design some programs to simulate optical thin film experimental results based on this theorem. We make the further analysis and research of thin film optical components : anti-reflection coatings, high-reflectance coatings, neutral beam splitters, bandpass filter, highpass filter and lowpass filter. The characteristics include reflection Secondly, we also investigate an new analytic method for calculating optical constants of weakly absorbing film, which in developed by Yanfei Zheng and Kazuo Kikuchi in 1997 . We check its accuracy by using the former programs and make a disscussion about this way, and compare the results of this analytic method with those obtained from matrix method.

碩士<br>國立臺北科技大學<br>光電工程系研究所<br>96<br>In this study, the anisotropic TiO2 films were evaporated using an electron-beam. The optical properties of the film with the decreasing pitch period have been investigated. Two kinds of fabrications are presented below: 1. The zigzag thin films are fabricated using glancing angle bideposition technique. As the period of the structure sweep is reduced to below a critical value, the zigzag structures would be restricted to pillar along the substrate normal direction. The bideposited film have birefringence and the optical path for a ray normal incident on the film is linear polarization dependent. Arranging the bideposited film in the Fabry-Perot configuration would help us in observation of phase retardation caused by the anisotropic optical property of the film. 2. The helical thin films are fabricated using glancing angle deposition technique and the substrate rotation. As the velocity of the structure rotate is increased to below a critical value, the helical structures would be restricted to pillar structures. The helical film have Bragg reflection and the optical path for a ray normal incident on the film is circular polarization dependent.

This thesis investigates two methods of optical excitation of alternating-current thin-film electroluminescent (ACTFEL) devices. The two experimental methods investigated in this thesis are the photo-induced charge (PIQ) and luminescence (PIL), and the subthreshold-voltage induced transferred charge (VIQ) techniques. PIQ/PIL experiments utilize an above-bandgap laser pulse to investigate the transport properties of photo-injected electrons and holes within the phosphor layer of the ACTFEL device. VIQ experiments use a broadband xenon lamp pulse to optically reset traps which are ionized by subthreshold bipolar voltage pulses. Both experiments characterize traps within the phosphor layer. PIQ/PIL experiments are performed on evaporated ZnS:Mn ACTFEL devices possessing phosphor layers with thicknesses of 950, 700, and 300 nm. From the PIQ/PIL experiment, an impact excitation threshold electric field for evaporated ZnS:Mn is found to be ~1 MV/cm. Evidence of hole-trapping is also obtained from the PIQ experiment. The holes in evaporated ZnS:Mn ACTFEL devices are found to possess a drift length of ~180 �� 70 nm, a hole lifetime of ~2 ps, and a capture cross-section of ~7 x 10������� cm��. It is speculated that the trap responsible for hole capture is a zinc vacancy or zinc vacancy complex. VIQ experiments are performed on evaporated, atomic layer epitaxy [ALE] (Cl), and ALE (DEZ) ZnS:Mn ACTFEL devices. Data obtained via VIQ experiments yield evidence for the generation of space charge below the EL conduction threshold, as well as providing a means of estimating the physical location, energy depth, density, and capture cross-section of traps responsible for VIQ. The depth of the traps responsible for VIQ in evaporated, ALE (C1), and ALE (DEZ) ZnS:Mn are estimated to be ~1.1, ~0.3, and ~0.8 eV, respectively. It is speculated that the traps responsible for VIQ are due to sulfur vacancies, chlorine, and oxygen, for evaporated, ALE (Cl), and ALE (DEZ), respectively.<br>Graduation date: 1999