Dissertations / Theses on the topic 'Silicon foils'

Thesis (M.S.)--Materials Science and Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Tummala Rao; Committee Member: Pulugurtha Raj; Committee Member: Wong C P. Part of the SMARTech Electronic Thesis and Dissertation Collection.

A proposed design of the variable energy positron annihilation spectroscopy (VEPALS) system based on secondary electron (SE) emission from a thin carbon foil has been investigated practically. The SE yield and the positron transmission coefficient were investigated as a function of the positron beam energy, the annular electrode potentials, and the column lengths of the annular electrode. The positron lifetime spectra of single crystal p-type silicon(Si) sample under different annular electrode potentials were analyzed. The result gives a supposed annular electrode potential of 1.5 kV. In view of this, the positron lifetime spectra were measured under different positron beam energy by fixing the annular electrode potential. It can be seen that all the spectra have the main p-type Si bulk lifetime component of 234 ps occupying more than 60% intensities. The intensity of the 234 ps component reaches up to 84.5 ±1.3 % when the positron beam energy is 15 keV. Further, the origin of the satellite peaks in the positron lifetime spectra are also investigated. It has been shown that the satellite peaks is attributed to the overflowing positrons on the MCP detector. The single crystal strontium titanate (STO) substrates after vacuum annealing treatment have been investigated in detail by several experimental techniques. The crystallization changes induced by the vacuum annealing were investigated by X-ray diffraction(XRD). Secondary phases were occurred after annealing treatment. The measured X-ray photoelectron spectroscopy (XPS) at O1s and C1s core levels were analyzed. The additional peaks after annealing are attributed to hydroxyl species, C-OH compounds, and carbonates. The variable energy Doppler broadening spectroscopy (VEDBS) and the traditional coincidence positron annihilation lifetime spectroscopy (PALS) were used to probe defects in STO samples. For long annealing time samples, the S parameters decrease below the reference level. The S-Wplot suggests that almost the same type of vacancy defects were induced during the annealing treatment. The positron lifetime results suggest that the main defects in annealed samples are oxygen monovacancies or divacancies and Sr-O vacancy complexes. The sample with annealing time of 110h has minimum positron effective diffusion length and maximum average lifetime, which is attributed to the increase of the vacancy-type defects during the long annealing treatment.
published_or_final_version
Physics
Master
Master of Philosophy

Analyse du spectre de rayons X émis après la traversée d'une feuille de C par un faisceau d'ions de Si de 44mev. Identification des raies satellites observées à partir de résultats théoriques par la méthode de Dirac-fock multiconfigurationnelle; mise en évidence de plusieurs configurations ayant un électron m. Par analyse des spectres à partir des valeurs calculées des rapports de branchement, confirmation d'un processus de population statistique des états excités initiaux associés à une même configuration électronique. Effet de la réponse du gaz d'électrons libres de la cible sur l'énergie de la raie de résonnance.

The focus of this thesis is on the optimization and fabrication of p-i-n amorphous silicon (a-Si:H) solar cells both on glass and transparent plastic substrates. These solar cells are specifically fabricated on transparent substrates to facilitate the integration of thin film batteries with these solar cells. To comply with plastic substrates, different silicon layers are optimized at the low processing temperature of 135 C. In the first part of the optimization process, the structural, electronic, and optical properties of boron- and phosphorous-doped, hydrogenated nanocrystalline silicon (nc-Si:H) thin films deposited by plasma-enhanced chemical vapor deposition (PECVD) at the substrate temperature of 135 C are elaborated. Additionally, in this part, the deposition of protocrystalline silicon (pc-Si) films on glass substrates are investigated. In the device integration and fabrication part of this thesis, the optimization process is continued by fabricating single junction devices with different hydrogen dilution ratios for the cell absorber layer. The optimum device performance is achieved with an absorber layer right at the transition from amorphous to microcrystalline silicon. To further improve the performance of the fabricated solar cells, amorphous silicon carbide buffer layers are introduced between the nc-Si p-layer and the undoped pc-Si absorber layer. Single junction p-p'-i-n solar cells are fabricated and characterized both on glass and plastic substrates. Our measurements show conversion efficiencies of 7.0% and 6.07% for the cells fabricated on glass and plastic substrates, respectively. In the last part of this research, the light trapping enhancement in amorphous silicon solar cells using Distributed Bragg Reflectors (DBRs) are experimentally demonstrated. Reflectance characteristics of DBR test structures, consisting of amorphous silicon (a-Si) / amorphous silicon nitride (SiN) film stacks are analysed and compared with those of conventional ZnO/Al back reflectors. DBR optical measurements show that the average total reflectance over the wavelength region of 600-800 nm is improved by 28% for DBR back structures. Accordingly, single junction amorphous silicon solar cells with DBR and Al back reflectors are fabricated both on glass and plastic substrates. Our results show that the short-circuit current density and consequently the conversion efficiency is enhanced by 10% for the cells fabricated on textured transparent conductive oxide substrates. In addition, these DBR back structures are designed and employed to improve the efficiency of semi-transparent solar cells. In this application, the optimized DBR structures are designed to be optically transparent for the part of the visible range and highly reflective for the red and infra-red part of the spectrum. Using these DBR structures, the efficiency of the optimum semi-transparent solar cell is enhanced by 5%.

Flexible electronics has attracted significant attention in the recent past due to the booming wearables market in addition to the ever-increasing interest for faster, thinner and foldable mobile phones. Ultra-thin bare silicon ICs fabricated by thinning down standard ICs to thickness below 50 μm are flexible and therefore they can be integrated on or in polymer foils to create flexible hybrid electronic (FHE) components that could be used to replace rigid standard surface mount device (SMD) components. The fabricated FHE components referred as chip foil packages (CFPs) in this work are ideal candidates for FHE system integration owing to their ability to deliver high performance at low power consumption while being mechanically flexible. However, very limited information is available in the literature regarding the reliability of CFPs under static and dynamic bending. The lack of such vital information is a major obstacle impeding their commercialization. With the aim of addressing this issue, this thesis investigates the static and dynamic bending reliability of CFPs. In this scope, the static bending reliability of CFPs has been investigated in this thesis using flexural bending tests by measuring their fracture strength. Then, Finite Element Method (FEM) simulations have been implemented to calculate the fracture stress of ultra-thin flexible silicon chips where analytical formulas may not be applied. After calculating the fracture stress from FEM simulations, the enhancement in robustness of ultra-thin chips (UTCs) against external load has also been proved and quantified with further experimental investigations. Besides, FEM simulations have also been used to analyse the effect of Young’s Modulus of embedding materials on the robustness of the embedded UTCs. Furthermore, embedding the UTCs in polymer layers has also been experimentally proven to be an effective solution to reduce the influence of thinning and dicing induced damages on the robustness of the embedded UTCs. Traditional interconnection techniques such as wire bonding may not be implemented to interconnect ultra-thin silicon ICs owing to the high mechanical forces involved in the processes that would crack the chips. Therefore, two novel interconnection methods namely (i) flip-chip bonding with Anisotropic Conductive Adhesive (ACA) and (ii) face-up direct metal interconnection have been implemented in this thesis to interconnect ultra-thin silicon ICs to the corresponding interposer patterns on foil substrates. The CFP samples thus fabricated were then used for the dynamic bending reliability investigations. A custom-built test equipment was developed to facilitate the dynamic bending reliability investigations of CFPs. Experimental investigations revealed that the failure of CFPs under dynamic bending was caused mainly by the cracking of the redistribution layer (RDL) interconnecting the chip and the foil. Furthermore, it has also been shown that the CFPs are more vulnerable to repeated compressive bending than to repeated tensile bending. Then, the influence of dimensional factors such as the thickness of the chip as well as the RDL on the dynamic bending reliability of CFPs have also been studied. Upon identifying the plausible cause behind the cracking of the RDL leading to the failure of the CFPs, two methods to improve the dynamic bending reliability of the RDL have been suggested and demonstrated with experimental investigations. The experimental investigations presented in this thesis adds some essential information to the state-of-the-art concerning the static and the dynamic bending reliability of UTCs integrated in polymer foils that are not yet available in the literature and aids to establish in-depth knowledge of mechanical reliability of the components required for manufacturing future FHE systems. The strategies devised to enhance the robustness of UTCs and CFPs could serve as guidelines for fabricating reliable FHE components and systems.

碩士
國立交通大學
光電工程系所
96
In recent years, flexible display technology has been investigated significantly. They have characteristic of light、thin、bendy and portable! Much of recent flexible research on thin-film electronics has been focused on amorphous silicon TFT. But poly silicon thin film transistor technology provides a better alternative since it offers higher current and faster switching speed. And TFT based on metal foil has the advantage of cheap and softly. For application of flexible display, display panels are required to sustain a certain degree of bending. Bending would induce strain in the electronic circuits and may affect TFT device characteristics. So we investigate the effects of different radius of bending parallel the channel length on p-type poly silicon TFT on metal foil base. First, we investigate the trends after hundreds of bending parallel the channel length on p-type poly silicon TFT on metal foil base to make sure the electronic characteristics stable or not. Then extraction the parasitic resistance 、 flat band voltage and trap density 、threshold voltage、subthreshold slope and mobility. That’s help discuss the reasons of mobility and current changing under bending condition. Another consideration we also study the reliability of p-type polycrystalline silicon thin film transistors on metal foil fabricated by the ELC method under bending condition. We utilize DC stress to simulate the operation of P-type poly-Si TFTs and observe the degradation degree under bending condition. The result indicates that threshold voltage shift more worse in bending situation no matter under compressive or tensile condition than in plan situation. It also indicates that mobility under compressive bending drain bias DC stress better than tensile bending drain bias DC stress.

碩士
國立虎尾科技大學
光電與材料科技研究所
99
In this study, taking the very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) to develop a flexible Aluminum foil substrate a-Si:H thin film solar cells (N-I-P), we research the effect of The different device structures and process technologies for amorphous silicon solar cells. In the beginning, we fabricate deposition thin film solar cell under 250 degrees Celsius on the amorphous silicon solar cells. However we research the vary parameters that influence to the a-Si:H solar cell and thin film solar cell specific and optical properties. Here we research the deposition rate, optical properties, and electrical properties to find the optimal performance by adjusting the varying hydrogen dilution ratio, pressure, VHF power, electrode separations, and total gas flow, therefore we put the optimal performance to use flexible a-Si:H solar cell. In the next research, we analyze the flexible a-Si:H solar cells by Fourier transform infrared (FTIR), UV-VIS, Hall effect, Photo conductivity (σph) and dark conductivity(σd), Atomic Force Microscpoic (AFM), Field-Emission Scanning Electron Microscope (FE-SEM), and J-V measure. In the study, we found a adhesion problem between the mental and the thin film. However that problem we have solved it by adding ITO layer, therefore that way increase the conversion efficiency of the current density and fill factor. By adding ITO layer that made the current density increased from 3.24 mA/cm2 to 3.64 mA/cm2, fill factor increased from the 31.23 % to 47.95 %.In addition to the conversion efficiency enhanced from 0.72 % to 1.24 %. We achieved the conclusion of the best device by adjusted the electrode distance, VHF-power, and hydrogen dilution ratio to optimize the thickness of intrinsic layer. The best device characteristics: open circuit voltage of 0.83 V, short circuit current density of 4.45 mA/cm2, fill-factor of 58.93 %, and conversion efficiency of 2.17 %.

Apart from being a support, the three substrates had their own roles in the growth of CNTs. Bamboo charcoal also acted as a catalyst provider. Au-coated silicon wafer participated in the formation of the silica/CNT composite nanowires. Copper foil itself was a catalyst. The silicate, the Au/Si droplet, and the copper particles were the catalysts for the growth of CNTs in these three substrates, respectively. The formation of the CNTs followed the vapor-liquid-solid (VLS) route which involved the decomposition of ethanol vapor into carbon, carbon dissolution inside the liquid catalyst and precipitation to form CNTs.
CNTs could be grown in a very wide temperature range (700-1400°C), but specific substrate for a particular temperature range was needed. The structures of the CNTs varied with the CVD processing conditions. The forms and the amount of catalytic material entering the interior of the CNTs depended on the characteristics of the catalyst for that process
The products formed on different substrates had their own characteristic features . Hollow or silicate filled CNTs with silicate droplet tips were formed on the surface of bamboo charcoal. Their diameter was in hundreds of nanometers and the length was about several microns. CNT-coated silica core-shell structures were obtained on Au-coated silicon wafer. The graphitic carbon shell was formed in thickness about 145 nm for the sample prepared at 1185°C, but amorphous carbon shell was produced in thickness more than 300 nm for the sample prepared at 1236°e. Lastly, CNTs with bamboo-like structure were synthesized on the copper foil substrate. The CNTs were getting thicker from 70 nm to 170 nm when temperature was increased from 700°C to 1000°C. The yield increased with temperature and annealing time if the sample was annealed for less than 30 min.
We report the growth of carbon nanotubes (CNTs) on different types of substrates with or without catalytic materials by using different approaches. The roles of the substrates and the catalysts in the formation of the CNTs are studied . We also characterized and identified the structural properties of the CNTs products. In this work, three types of substrates had been used, namely biomorphic bamboo charcoal , Au-coated silicon wafer, and copper foil. The CNTs were grown on different substrates by chemical vapor deposition (CVD) method at temperature range between 700°C and 1400°C. Ethanol vapor was used as the carbon source, while tetraethyl orthosilicate (TEOS) vapor was also applied to the process for bamboo charcoal.
Zhu, Jiangtao = 碳納米管在不同類型基底上的生長 / 朱江濤.
Adviser: D. H. L. Ng.
Source: Dissertation Abstracts International, Volume: 72-11, Section: B, page: .
Thesis (Ph.D.)--Chinese University of Hong Kong, 2009.
Includes bibliographical references.
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstract also in Chinese.
Zhu, Jiangtao = Tan na mi guan zai bu tong lei xing ji di shang de sheng chang / Zhu Jiangtao.

碩士
大同大學
光電工程研究所
93
The purpose of this paper is to develop a new crystallization method named as energy-assisted agent (EAA) to make smooth and high quality polycrystalline silicon (poly-Si) film through of infrared ray illumination. In this technique, an amorphous silicon (a-Si) film integrates with metal material subjected too a low thermal budget treatment, a high quality poly-Si can be obtained through an efficient energy transfer. As we studied, the average size of grain was 0.4μm, its surface roughness was about 0.34nm. For Raman spectrum, there is a peak value corresponding to Si-Si bond in crystalline silicon and the result of XRD shows preferential crystal orientation of (111). On the other hand, we conducted ESCA depth analysis on the crystallized film to realize the issue of resided metal atom.

Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Metallization and contacting processes have a significant impact on the total manufacturing cost of the high-efficiency solar cells. The metallization of silicon crystalline back-contact solar cells is difficult and still a major issue from the industrial point of view. The core of the current thesis introduces the development of a device, designed to realize and evaluate the potential of a new rear side metallization concept for backcontact cells. Here, the formation of the electrode pattern is based on contacting and structuring a metal foil through a laser processing scheme. In order to ensure a good metallic contact, the developed device shall first assure a safe foil fixing and later an appropriate handling for structuring the metal foil in order to make selective metallic contacts. Meanwhile, the major technological challenges faced during the device development are identified and assessed. Finally this device has been developed and tested at the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg, Germany An overall conclusion of the experimental findings has been made and an outlook for further investigations required in this field has been proposed at the end of this document.
Os processos de fabrico referentes à metalização em células solares de alta eficiência têm um elevado impacto no seu custo global de manufatura. Em particular a metalização de células em silício cristalino do tipo Back-Contact mostra-se ser difícil e, desta forma, um problema do ponto de vista industrial. Este trabalho de tese trata do desenvolvimento de um dispositivo projetado para realizar e avaliar o potencial de um novo conceito de metalização destinado à face traseira de células do tipo Back-Contact. Aqui, a formação dos eletródios em padrão, baseia-se em contactar e estruturar uma folha de alumínio através de aplicação a laser. De forma a garantir um bom contacto metálico, o dispositivo desenvolvido deverá primeiramente assegurar uma boa fixação da folha de alumínio com o substrato, assim como um bom desempenho para a posterior estruturação da folha. Desta forma serão criados os contactos metálicos seletivos. Entretanto, os principais desafios tecnológicos enfrentados durante o desenvolvimento do dispositivo serão identificados e corrigidos. Este aparelho foi desenvolvido e testado no Fraunhofer Instituto de Sistema Energéticos Solares ISE em Friburgo, Alemanha. Por fim, foram ainda efetuados ensaios com o dispositivo, tirando-se as primeiras conclusões acerca do desempenho deste novo conceito de metalização. Serão apresentadas algumas sugestões para futuras investigações nesta área.