Journal articles: 'Semiconductors Nanostructured materials Quantum dots'

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Thangaraj, Baskar, Pravin R. Solomon, and Srinivasan Ranganathan. "Synthesis of Carbon Quantum Dots with Special Reference to Biomass as a Source - A Review." Current Pharmaceutical Design 25, no. 13 (August 16, 2019): 1455–76. http://dx.doi.org/10.2174/1381612825666190618154518.

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Quantum dots (QDs) have received much attention due to their extraordinary optical application in medical diagnostics, optoelectronics and in energy storage devices. The most conventional QDs are based on semiconductors that comprise heavy metals whose applications are limited due to toxicity and potential environmental hazard. Of late, researchers are focusing on carbon-based quantum dots, which have recently emerged as a new family of zero-dimensional nanostructured materials. They are spherical in shape with a size below 10 nm and exhibit excitation-wavelength-dependent photoluminescence (PL). Carbon quantum dots (CQDs) have unique optical, photoluminescence and electrochemical properties. They are environment-friendly with low toxicity as compared to toxic heavy metal quantum dots. Generally, CQDs are derived from chemical precursor materials, but recently researchers have focused their attention on the production of CQDs from waste biomass materials due to the economic and environmental exigency. In this review, recent advances in the synthesis of CQDs from waste biomass materials, functionalization and modulation of CQDs and their potential application of biosensing are focused. This review also brings out some challenges and future perspectives for developing smart biosensing gadgets based on CQDs.

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Omr, Hossam A. E., Mark W. Horn, and Hyeonseok Lee. "Low-Dimensional Nanostructured Photocatalysts for Efficient CO2 Conversion into Solar Fuels." Catalysts 11, no. 4 (March 25, 2021): 418. http://dx.doi.org/10.3390/catal11040418.

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The ongoing energy crisis and global warming caused by the massive usage of fossil fuels and emission of CO2 into atmosphere continue to motivate researchers to investigate possible solutions. The conversion of CO2 into value-added solar fuels by photocatalysts has been suggested as an intriguing solution to simultaneously mitigate global warming and provide a source of energy in an environmentally friendly manner. There has been considerable effort for nearly four decades investigating the performance of CO2 conversion by photocatalysts, much of which has focused on structure or materials modification. In particular, the application of low-dimensional structures for photocatalysts is a promising pathway. Depending on the materials and fabrication methods, low-dimensional nanomaterials can be formed in zero dimensional structures such as quantum dots, one-dimensional structures such as nanowires, nanotubes, nanobelts, and nanorods, and two-dimensional structures such as nanosheets and thin films. These nanostructures increase the effective surface area and possess unique electrical and optical properties, including the quantum confinement effect in semiconductors or the localized surface plasmon resonance effect in noble metals at the nanoscale. These unique properties can play a vital role in enhancing the performance of photocatalytic CO2 conversion into solar fuels by engineering the nanostructures. In this review, we provide an overview of photocatalytic CO2 conversion and especially focus on nanostructured photocatalysts. The fundamental mechanism of photocatalytic CO2 conversion is discussed and recent progresses of low-dimensional photocatalysts for efficient conversion of CO2 into solar fuels are presented.

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Nötzel, Richard. "InN/InGaN quantum dot electrochemical devices: new solutions for energy and health." National Science Review 4, no. 2 (January 7, 2017): 184–95. http://dx.doi.org/10.1093/nsr/nww101.

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AbstractA review is given of the exceptional electrochemical performance of epitaxial InN/InGaN quantum dots (QDs) as photoelectrodes for solar hydrogen generation by water splitting, as biosensor transducers and as anion-selective electrodes, and they are also evaluated as supercapacitor electrodes. The performance is benchmarked against the best performances of other reported materials and nanostructures. A model based on the unique interplay of surface and quantum properties is put forward to understand the boost of catalytic activity and anion selectivity interlinking quantum nanostructure physics with electrochemistry and catalysis. Of equal impact is the direct growth on cheap Si substrates without any buffer layers, allowing novel device designs and integration with Si technology. This makes the InN/InGaN QDs viable, opening up new application fields for III-nitride semiconductors.

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KNOLL, WOLFGANG, MING-YONG HAN, XINHENG LI, JOSE-LUIS HERNANDEZ-LOPEZ, ABHIJIT MANNA, KLAUS MÜLLEN, FUMIO NAKAMURA, et al. "NANOSCOPIC BUILDING BLOCKS FROM POLYMERS, METALS, AND SEMICONDUCTORS FOR HYBRID ARCHITECTURES." Journal of Nonlinear Optical Physics & Materials 13, no. 02 (June 2004): 229–41. http://dx.doi.org/10.1142/s0218863504001815.

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This paper describes some of our efforts in the area of nanostructured thin film architectures. The resulting interfacial hybrid assemblies are built from (1) organic/polymeric objects based on dendrimer systems, from (2) surface-functionalized Au nanoparticles, and (3) from a variety of semiconducting quantum dots. Dendrimers as polymeric building blocks with a strictly monodisperse particle size distribution in the nanometer range can be functionalized in the core, the scaffold, or at the periphery, thus offering interesting hybrid materials for a wide range of applications. The combination with Au clusters and their local surface plasmon resonances suggests new strategies for optoelectronic devices or unconventional bio-sensor platforms. The possibility of tuning the luminescent properties of semiconducting nanoparticles by size or compositional bandgap engineering complements the assembly kit with building blocks for supramolecular thin film nanocomposite materials.

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Jin, Ho, Sukyung Choi, Hyo Joong Lee, and Sungjee Kim. "Layer-by-Layer Assemblies of Semiconductor Quantum Dots for Nanostructured Photovoltaic Devices." Journal of Physical Chemistry Letters 4, no. 15 (July 15, 2013): 2461–70. http://dx.doi.org/10.1021/jz400910x.

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Vigil, Elena. "Nanostructured Solar Cells." Key Engineering Materials 444 (July 2010): 229–54. http://dx.doi.org/10.4028/www.scientific.net/kem.444.229.

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Novel types of solar cells based on nanostructured materials are intensively studied because of their prospective applications and interesting new working principle – essentially due to the nanomaterials used They have evolved from dye sensitized solar cells (DSSC) in the quest to improve their behavior and characteristics. Their nanocrystals (ca. 10-50 nm) do not generally show the confinement effect present in quantum dots of size ca. 1-10nm where electron wave functions are strongly confined originating changes in the band structure. Nonetheless, the nanocrystalline character of the semiconductor used determines a different working principle; which is explained, although it is not completely clear so far,. Different solid nanostructured solar cells are briefly reviewed together with research trends. Finally, the influence of the photoelectrode electron-extracting contact is analyzed.

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Kim, M. J., L. C. Liu, S. H. Risbud, and R. W. Carpenter. "Nanostructure of semiconductor quantum dots in a borosilicate glass matrix by complementary use of HREM and AEM." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 4 (August 1990): 728–29. http://dx.doi.org/10.1017/s0424820100176770.

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When the size of a semiconductor is reduced by an appropriate materials processing technique to a dimension less than about twice the radius of an exciton in the bulk crystal, the band like structure of the semiconductor gives way to discrete molecular orbital electronic states. Clusters of semiconductors in a size regime lower than 2R {where R is the exciton Bohr radius; e.g. 3 nm for CdS and 7.3 nm for CdTe) are called Quantum Dots (QD) because they confine optically excited electron- hole pairs (excitons) in all three spatial dimensions. Structures based on QD are of great interest because of fast response times and non-linearity in optical switching applications.In this paper we report the first HREM analysis of the size and structure of CdTe and CdS QD formed by precipitation from a modified borosilicate glass matrix. The glass melts were quenched by pouring on brass plates, and then annealed to relieve internal stresses. QD precipitate particles were formed during subsequent "striking" heat treatments above the glass crystallization temperature, which was determined by differential thermal analysis.

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Chen, G., and A. Shakouri. "Heat Transfer in Nanostructures for Solid-State Energy Conversion." Journal of Heat Transfer 124, no. 2 (November 20, 2001): 242–52. http://dx.doi.org/10.1115/1.1448331.

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Solid-state energy conversion technologies such as thermoelectric and thermionic refrigeration and power generation require materials with low thermal conductivity but good electrical conductivity and Seebeck coefficient, which are difficult to realize in bulk semiconductors. Nanostructures such as superlattices, quantum wires, and quantum dots provide alternative approaches to improve the solid-state energy conversion efficiency through size and interface effects on the electron and phonon transport. In this review, we discuss recent research and progress using nanostructures for solid-state energy conversion. The emphasis is placed on fundamental issues that distinguish energy transport and conversion between nanoscale and macroscale, as well as heat transfer issues related to device development and property characterization.

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Prokes, S. M., and Kang L. Wang. "Novel Methods of Nanoscale Wire Formation." MRS Bulletin 24, no. 8 (August 1999): 13–19. http://dx.doi.org/10.1557/s0883769400052842.

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In recent years, tremendous interest has been generated in the fabrication and characterization of nanoscale structures such as quantum dots and wires. For example, there is interest in the electronic, magnetic, mechanical, and chemical properties of materials with reduced dimensions. In the case of nanoscale semiconductors, quantum effects are expected to play an increasingly prominent role in the physics of nanostructures, and a new class of electronic and optoelectronic devices may be possible. In addition to new and interesting physics, the formation and characterization of nanoscale magnetic structures could result in higher-density storage capacity in hard disks and optical-recording media. Likewise, phonon confinement leads to a drastic reduction of thermal conductivity and can be used to improve the performance of thermoelectric devices.In 1980, H. Sakaki predicted theoretically that quantum wires may have applications in high-performance transport devices, due to their sawtoothlike density of states (E1/2), where E is the electron energy. Since then, most quantum wires have been made by fabricating a gratinglike gate on top of a two-dimensional (2D) electron gas contained in a semiconductor heterojunction or in metal-oxide-semiconductor structures. By applying a negative gate voltage to the system, its structure can be changed from a 2D to a one-dimensional (1D) regime, where electron confinement is achieved by an electrostatic confining potential. It was not until recently that “physical” semiconductor quantum wires with the demonstrated 1D confinement by physical boundaries began to be fabricated.

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OSTRIKOV, KEN, and SHUYAN XU. "PLASMA-AIDED NANOFABRICATION: "PLASMA-BUILDING BLOCK" APPROACH." International Journal of Nanoscience 05, no. 04n05 (August 2006): 439–44. http://dx.doi.org/10.1142/s0219581x06004607.

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Unique features and benefits of the plasma-aided nanofabrication are considered by using the "plasma-building block" approach, which is based on plasma diagnostics and nanofilm characterization, cross-referenced by numerical simulation of generation and dynamics of building blocks in the gas phase, their interaction with nanostructured surfaces, and ab initio simulation of chemical structure of relevant nanoassemblies. The examples include carbon nanotip microemitter structures, semiconductor quantum dots and nanowires synthesized in the integrated plasma-aided nanofabrication facility.

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Резник, И. А., А. С. Златов, П. О. Ильин, Р. A. Заколдаев, С. A. Мошкалёв, and A. O. Орлова. "Люминесцентные и фотоэлектрические свойства гибридных структур на основе многослойного графена и 0D и 2D полупроводниковых квантовых нанокристаллов." Журнал технической физики 128, no. 6 (2020): 726. http://dx.doi.org/10.21883/os.2020.06.49403.66-20.

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Establishing the laws of the mechanisms underlying the interaction of nanostructured materials is one of the most important tasks on the way to creating a new generation of efficient photovoltaic devices. In this paper, we study the luminescent and photoelectric properties of hybrid structures formed on the basis of multilayer graphene nanobelts and semiconductor quantum nanocrystals: 0D-: core-shell CdSe / ZnS quantum dots, and 2D-: CdSe nanoplatelets. It was shown that the multiexponential decay of the excitonic luminescence of CdSe nanoplates at room temperature originates from the delayed luminescence due to the presence of trap states on the surface of the nanoplates. It has been established that in the dry layers of nanoplatelets on a dielectric substrate and in the composition of hybrid structures with graphene nanoribbons, the efficiency of delayed excitonic luminescence of nanoplates increases. It has been demonstrated that the rate of increase in photoconductivity in hybrid structures based on CdSe nanoplatelets is an order of magnitude higher than the rate of this process in similar structures based on CdSe / ZnS quantum dots, which indicates the formation of an effective energy / charge transfer channel from nanoplatelets to graphene nanoribbons.

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del-Castillo, J., A. C. Yanes, J. Méndez-Ramos, and V. D. Rodríguez. "Luminescence of Nanostructured SnO2-SiO2 Glass-Ceramics Prepared Sol–Gel Method." Journal of Nanoscience and Nanotechnology 8, no. 4 (April 1, 2008): 2143–46. http://dx.doi.org/10.1166/jnn.2008.068.

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Nanostructured silica based glass-ceramics samples of composition (100 – x)SiO2-xSnO2, with x from 1 to 10, have been synthesized by thermal treatment of precursor sol–gel glasses. The average size of the obtained SnO2 nanocrystals, calculated by using the X-ray diffraction, can be predetermined by using well-controlled concentration of tin precursor. The mean radius ranging from 1.6 to 5.5 nm, is comparable to the exciton Bohr radius, corresponding to wide band-gap semiconductor quantum-dots in an insulator SiO2 glass. A spectroscopy study in terms of optical absorption and photoluminescence spectra has been carried out as a function of SnO2 concentration. Size-dependent red-shifts of excitation and emission bands, with increasing of tin precursor concentration, point to the quantum confinement effect. The nanocrystal sizes have been obtained and compared by using the Brus and Scherrer equations. The band gap increase is in agreement with results, based on the effective mass model. The recombination of conduction band electron with oxygen vacancies is proposed to explain the luminescence red-shift.

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KNOLL, WOLFGANG, XINHUA ZHONG, FERNANDO STEFANI, RUDOLF ROBELEK, LIFANG NIU, HEIKO ROCHHOLZ, JENNIFER SHUMAKER-PARRY, and MAX KREITER. "OPTICS WITH NANO-SIZED STRUCTURES MADE FROM SEMICONDUCTORS AND (NOBLE) METALS." Journal of Nonlinear Optical Physics & Materials 15, no. 03 (September 2006): 355–67. http://dx.doi.org/10.1142/s0218863506003359.

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We summarize some of our efforts in synthesizing and characterizing nanoscopic objects fabricated from semiconducting materials and noble metals. The optical properties of colloidal semiconductors (quantum dots) are analyzed, in particular, with respect to their spectral photoluminescence properties (bandgap engineering) and the characteristic emission blinking. The statistical evaluation of the on- and off-states seen in the time-dependent recordings of the photoluminescence emitted from a single nanoparticle confirmed the reported power-law probability distribution, however, with a superimposed decay of the on-state density (which is illumination intensity dependent). This results in a loss of fluorescence intensity upon extended illumination when these particles are used in biosensor assays. Next, a colloid particle-based template protocol for the fabrication of non-trivial Au nanostructures is described. The resulting nano-crescents can be varied in terms of their size and shape. It is demonstrated how their plasmonic resonance characteristics can thus be tuned with respect to the spectral position of their (multipole) absorbance peaks, and their polarization properties.

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Ünlü, Hilmi. "A thermoelastic model for strain effects on bandgaps and band offsets in heterostructure core/shell quantum dots." European Physical Journal Applied Physics 86, no. 3 (June 2019): 30401. http://dx.doi.org/10.1051/epjap/2019180350.

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A thermoelastic model is proposed to determine elastic strain effects on electronic properties of spherical Type I and Type II heterostructure core/shell quantum dots (QDs) as a function of dimensions of constituent semiconductors at any temperature. Proposed model takes into account the difference between lattice constants, linear expansion coefficients and anisotropy of elastic moduli (Young's modulus and Poisson's ratio) of constituent semiconductors, respectively. In analogous to lattice mismatch, we introduce so called the elastic anisotropy mismatch in heterostructures. Compressive strain acting on core (shell) side of heterointerfaces in CdSe/CdS, CdSe/ZnS, and ZnSe/ZnS QDs increases (decreases) as shell diameter is increased, which causes increase (decrease) in core bandgap as sell (core) diameter is increased in these nanostructures. Furthermore, there is a parabolic increase in conduction band offsets and core bandgaps in CdSe/CdS, CdSe/ZnS, and ZnSe/ZnS QDs and decrease in conduction band offset and core bandgap of ZnSe/CdS QD as core (shell) diameter increases for fixed shell (core) diameter. Comparison shows that using isotropic elastic moduli in determining band offsets and core band gaps gives better agreement with experiment than anisotropic elastic moduli for core bandgaps of CdSe/CdS, CdSe/ZnS, ZnSe/ZnS, and ZnSe/CdS core/shell QDs. Furthermore, we also show that the strain-modified two band effective mass approximation can be used to determine band offsets by using measured core band gaps in core/shell heterostructure QDs with Type II interface band alignment. Excellent agreement between predicted and measured core bandgaps in CdSe and ZnSe based core/shell QDs suggests that proposed model can be a good design tool for process simulation of core/shell heterostructure QDs.

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Zhou, W. L., J. Lin, and C. J. O'Connor. "One, Two, and Three Demisional Gold Nanoparticle Arrays from Reverse Micelles." Microscopy and Microanalysis 6, S2 (August 2000): 58–59. http://dx.doi.org/10.1017/s1431927600032785.

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Nanoparticles (1-100 nm) of semiconductors and metals have shown some unique optical, electric and magnetic and catalytic properties which are greatly different from their bulk materials. Recently the use of these nanoparticles as quantum dots in nanoelectronics requires their arrangement in one, two, and three dimensions (1D, 2D and 3D). Therefore more attention has been paid to the organization of these nanoparticles into ordered arrays in order to achieve novel collective properties. Gold colloids have been well studied for its self-organization in several systems. Here we present 1D, 2D and 3D gold self-organization nanostructure generated from reverse micelles (microemulsion system).Gold nanoparticles were prepared by the reduction of HAuCU in CTAB (cetyltrimethylammonium bromide)/Octane+l-Butanol/H2O microemusion system using NaBH4 as the reducing agent. Typically, 0.3g of CTAB, 0.148ml of 0.056M HAuCl4 aqueous solution, l.Og octane (surfactant) and 0.25g 1-butanol (cosurfactant) were mixed together and stirred vigorously for 10 min until a homogenous phase was obtained.

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Prokhorov, Alexei, and Valentyn Volkov. "Coherent optical effects in two-dimensional nanostructures with semiconductor quantum dots." EPJ Web of Conferences 220 (2019): 02010. http://dx.doi.org/10.1051/epjconf/201922002010.

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The effects of quantum coherence arising in an ensemble of semiconductor quantum dots located near the surface of two-dimensional optical materials are considered. The conditions for the realization of strong coupling between surface plasmon-polaritons and quantum dot in proximity to graphene are studied.

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García de Arquer, F. Pelayo, Dmitri V. Talapin, Victor I. Klimov, Yasuhiko Arakawa, Manfred Bayer, and Edward H. Sargent. "Semiconductor quantum dots: Technological progress and future challenges." Science 373, no. 6555 (August 5, 2021): eaaz8541. http://dx.doi.org/10.1126/science.aaz8541.

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In quantum-confined semiconductor nanostructures, electrons exhibit distinctive behavior compared with that in bulk solids. This enables the design of materials with tunable chemical, physical, electrical, and optical properties. Zero-dimensional semiconductor quantum dots (QDs) offer strong light absorption and bright narrowband emission across the visible and infrared wavelengths and have been engineered to exhibit optical gain and lasing. These properties are of interest for imaging, solar energy harvesting, displays, and communications. Here, we offer an overview of advances in the synthesis and understanding of QD nanomaterials, with a focus on colloidal QDs, and discuss their prospects in technologies such as displays and lighting, lasers, sensing, electronics, solar energy conversion, photocatalysis, and quantum information.

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Gélvez, Adriana Lucia, Willian Gutierrez, and Fredy Rodríguez Prada. "Efecto Aharonov-Bohm en puntos cuánticos no uniformes." Innovaciencia Facultad de Ciencias Exactas, Físicas y Naturales 3, no. 1 (December 15, 2015): 9–17. http://dx.doi.org/10.15649/2346075x.361.

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Introducción: Recientemente, las investigaciones en el campo de la materia condensada se han venido enfocando en el estudio de estructuras fabricadas mediante diferentes técnicas de crecimiento de cristales, en especial de materiales semiconductores y esto ha despertado un gran interés en el estudio teórico y aprovechamiento tecnológico de las importantes propiedades que despliegan los sistemas de partículas confinadas en puntos cuánticos con diferentes morfologías (nano-estructuras semiconductoras cero-dimesionales). Un atractivo especial en el área de los sistemas de baja dimensionalidad es el estudio de las propiedades opto-electrónicas de puntos cuánticos en forma de irregulares. Los Anillos Cuánticos, especialmente, son estructuras que poseen simetría axial y presentan una cavidad semiconductora en la región comprendida entre su radio interno y externo. Debido al confinamiento periódico el comportamiento de los portadores de carga en esta estructura deben tener un carácter diferente en presencia de un campo magnético externo, como sucede con el denominado Efecto Oscilatorio Aharonov-Bohm (AB). Este fenómeno se observa generalmente cuando una partícula cargada confinada en un sistema de baja dimensionalidad está afectada por un campo electromagnético externo. Materiales y Métodos: Se analiza el efecto de la irregularidad morfológica en puntos cuánticos lenticulares y de anillos cuánticos tipo cráter, que se encuentran sometidos a un campo magnético en la dirección de crecimiento, sobre el espectro energético de un electrón confinado en cada uno de ellos. Resultados y discusión: Los defectos estructurales son modelados mediante funciones en coordenadas cilíndricas, las cuales presentan soluciones analíticas para los casos isotrópicos. Posteriormente, los resultados de los estados energéticos del electrón en las estructuras simétricas permiten obtener el comportamiento de la energía para problemas completos y complejos mediante el uso de métodos numéricos, como diagonalización exacta y expansión en series. Conclusiones: Se presentan en este trabajo los niveles energéticos de un electrón en función de intensidad del campo magnético y se reportan comportamientos diferentes para ambos tipos de QDs considerados, principalmente porque en los de tipo cráter se presentan oscilanes AB, característico de anillos cuánticos unidimensionales. En este estudio el surgimiento de oscilaciones AB, en puntos cuántico tipo cráter se debe a la mayor probabilidad de ubicar al electrón en el borde de la estructura, ya que esta zona es la de menor confinamiento cuántico. Introduction: Recently, research in the field of condensed matter have been focusing on the study of structures fabricated by different techniques of crystal growth, especially semiconductor materials this has aroused great interest in the theoretical study and technological performance of the important properties that display particle systems confined in quantum dots with differentmorphologies (semiconductor nanostructures zero - dimensional). A special interest in the field of low - dimensional systems is the study of opto - electronic properties of quantum dots with irregular shapes. Quantum Rings, especially, are semiconductor structures having axial symmetry and have a cavity in the region between the inner and outer radius. Due to the periodic confinement the behavior of charge carriers in such structures should have a different character in the presence of an external magnetic field, as with the so-called Aharonov-Bohm Effect (AB). This phenomenon is usually observed when a charged particle confined in a low dimensional system is affected by an external electromagnetic field. Materials and methods: We analyzes the effect of morphological irregularity of lenticular- like and crater-like quantum dots, and the effect of a magnetic field applied in the growth direction on the energy spectrum of an electron confined in these structures. Results and discussion: Structural defects are modeled by functions in cylindrical coordinates, which presented analytical solutions for the isotropic case. Subsequently, the results of energy states of the electron in symmetrical structures allow obtain the energy to complete and complex problems by using numerical methods, as exact diagonalization and series expansion. Conclusions: We present the energy levels of an electron as a function of magnetic field intensity and shown different behaviors for both types of QDs considered, mainly AB oscillations in crater-like quantum dots, characteristic phenomena of one-dimensional quantum rings. This effect is due to the higher probability of finding the electron in the outer border of the structure, because this region has the lowest quantum confinement.

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Žurauskienė, N., S. Ašmontas, A. Dargys, J. Kundrotas, G. Janssen, E. Goovaerts, Stanislovas Marcinkevičius, Paul M. Koenraad, J. H. Wolter, and R. P. Leon. "Semiconductor Nanostructures for Infrared Applications." Solid State Phenomena 99-100 (July 2004): 99–108. http://dx.doi.org/10.4028/www.scientific.net/ssp.99-100.99.

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We present the results of time-resolved photoluminescence (TRPL) and optically detected microwave resonance (ODMR) spectroscopy investigations of semiconductor quantum dots and quantum wells. The ODMR spectra of InAs/GaAs QDs were detected via modulation of the total intensity of the QDs emission induced by 95 GHz microwave excitation and exciton fine structure was studied. Very long life times (up to 10 ns) of photoexcited carriers were observed in this system using TRPL at low temperatures and excitation intensities promising higher responsitivity of such QDs for quantum dot infrared photodetector development. The effects of proton and alpha particles irradiation on carrier dynamics were investigated on different InGaAs/GaAs, InAlAs/AlGaAs and GaAs/AlGaAs QD and QW systems. The obtained results demonstrated that carrier lifetimes in the QDs are much less affected by proton irradiation than that in QWs. A strong influence of irradiation on the PL intensity was observed in multiple QWs after high-energy alpha particles irradiation.

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Chen, Yeechi, Keiko Munechika, and David S. Ginger. "Bioenabled Nanophotonics." MRS Bulletin 33, no. 5 (May 2008): 536–42. http://dx.doi.org/10.1557/mrs2008.107.

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AbstractBiological molecules such as oligonucleotides, proteins, or peptides can be used for the synthesis, recognition, and assembly of materials with nanoscale dimensions. Of particular interest are the fields of near-field optics and plasmonics. Many potential optical applications depend on the ability to control the relative positioning of organic dyes, plasmon-resonant metal nanoparticles, and semiconductor quantum dots with nanoscale precision. In this article, we describe some recent achievements in biological assembly and nanophotonics, and discuss potential uses of biological materials for assembling optically functional nanostructures. We emphasize the use of biological materials to build well-defined nanostructures for near-field plasmon-enhanced fluorescence.

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Gordillo, H., I. Suárez, R. Abargues, P. Rodríguez-Cantó, S. Albert, and J. P. Martínez-Pastor. "Polymer/QDs Nanocomposites for Waveguiding Applications." Journal of Nanomaterials 2012 (2012): 1–9. http://dx.doi.org/10.1155/2012/960201.

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In this paper we review our recent progress in a still young type of active waveguides based on hybrid organic (polymer)—inorganic (semiconductor quantum dots) materials. They can be useful for the implementation of new photonic devices, because combining the properties of the semiconductor nanostructures (quantum size carrier confinement and temperature independent emission) with the technological capabilities of polymers. These optical waveguides can be easily fabricated by spin-coating and UV photolithography on many substrates (SiO2/Si, in the present work). We demonstrate that it is possible to control the active wavelength in a broad range (400–1100 nm), just by changing the base quantum dot material (CdS, CdSe, CdTe and PbS, but other are possible), without the necessity of changing fabrication conditions. Particularly, we have determined the optimum conditions to produce multi-color photoluminescence waveguiding by embedding CdS, CdSe and CdTe quantum dots into Poly(methyl methacrylate). Finally, we show new results regarding the incorporation of CdSe nanocrystals into a SU-8 resist, in order to extrapolate the study to a photolithographic and technologically more important polymer. In this case ridge waveguides are able to confine in 2D the light emitted by the quantum dots.

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Islam, Md Mahfujul. "Photoluminescence in Analysis of Surface and Interfaces of Semiconductor Nanostructures." International Letters of Chemistry, Physics and Astronomy 57 (August 2015): 102–13. http://dx.doi.org/10.18052/www.scipress.com/ilcpa.57.102.

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The intensity and excitation energy is chosen for different materials to probe different regions and excitations concentrations in the sample. The intensity of the PL signal provides information on the quality of surfaces and interfaces. Also, information on the electronic bands structure and the SC Energy gap can be obtained, as well as thermodynamics quantities such as temperature. For this experiment we just compared the photoluminescence (PL) spectra of AlGaAs/GaAs quantum wells (QWs) with different well widths (100 Å and 85 Å) and InAs/GaAs quantum dots (QD) structures as well as the theoretical aspects were covered. The sample are held in a cryostat and excited by a Helium-Neon laser. The emitted light is then captured by an optical fiber plugged to a spectrometer The optical fibre is plugged to a spectrometer equipped with a CCD detector, driven by a computer allowing us to acquire data. And this was used to avoid interaction between charge carriers and thermally excited phonons, it was used cryogenic temperature around 2k to cool the sample. simply with the theoretical models this experiement allows to collect numerous information about the lowest band to band transition in semiconductor materials.and for quantum dots which was the last sample in this study couldn’t be resolved individually.

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Schreder, B., C. Dem, M. Schmitt, A. Materny, W. Kiefer, U. Winkler, and E. Umbach. "Raman spectroscopy of II-VI semiconductor nanostructures: CdS quantum dots." Journal of Raman Spectroscopy 34, no. 2 (2003): 100–103. http://dx.doi.org/10.1002/jrs.959.

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RAMADURAI, DINAKAR, TAKAYUKI YAMANAKA, MILANA VASUDEV, YANG LI, VISWANATH SANKAR, MITRA DUTTA, MICHAEL A. STROSCIO, TIJANA RAJH, ZORAN SAPONJIC, and SONG XU. "ENVIRONMENTAL EFFECTS INFLUENCING THE VIBRATIONAL MODES OF DNA: NANOSTRUCTURES COUPLED TO BIOMOLECULES." International Journal of High Speed Electronics and Systems 18, no. 01 (March 2008): 47–61. http://dx.doi.org/10.1142/s0129156408005126.

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The interactions of charges in DNA with the vibrational modes in DNA depend on the spectra of these vibrational modes. Using (a) the Su-Schrieffer-Heeger (SSH) Hamiltonian approach, (b) integrated structures of DNA and manmade nanostructures, and (c) gel electrophoresis techniques,1 the interaction between charges in DNA and the vibrational modes of DNA are investigated. As is well-known, DNA has a rich spectrum of modes in the THz spectral regime. The use of manmade nanostructures integrated with DNA facilitates the engineering of nanoscale systems useful in studying the role of environmental effects on the vibrational modes of DNA as well as the interaction of these modes with charge carriers in DNA. Among the DNA-based structures considered in this account are: B-DNA and Z-DNA strands related by a conformational change; and DNA molecules bound on one terminal to indirect bandgap semiconductor quantum dots. Gel electrophoresis is used as a tool for the analysis of carrier interactions in novel integrated DNA-manmade-nanostructure complexes, and models based on the SSH Hamiltonian2 are employed as a means of analyzing the interactions between the vibrational modes of DNA and charge carriers in DNA.3-4

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25

Deodanes, O., J. C. Molina, C. Violantes, D. Pleitez, J. Cuadra, H. Ponce, and C. Rudamas. "White Light Emitting CdS Quantum Dot Devices Coated with Layers of Graphene Carbon Quantum Dots." MRS Advances 5, no. 63 (2020): 3337–43. http://dx.doi.org/10.1557/adv.2020.436.

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AbstractCadmium sulfide quantum dots (CdS QDs) are semiconductor nanoparticles having sizes in the order of nanometers. They are materials that have outstanding properties for down conversion applications. These nanostructures have been used in the fabrication of white light emitting diodes (WLEDs) in the last years. However, inhomogeneous deposition of CdS QD conversion materials allows unwanted UV light escape. In addition, low efficiency due to strong self-quenching effect, incompatibility between CdS QD solution/crystal polyester resin matrix and reabsorption are common problems that need to be solved. In this work, we try to address the incompatibility between the CdS QD solution/crystal polyester resin matrix by using a solvent exchange procedure. To block the unwanted UV-light escape, we coated our devices with a mixture of graphene carbon quantum dot (GCQD) solution/crystal polyester resin matrix. The QDs and the WLED prototypes were characterized by absorption and photoluminescence (PL) spectroscopy. The QDs embedded in the matrix shown a good homogeneous dispersion. On the other hand, the mixture shown a rapid solidification. These facts indicate a good compatibility between the CdS QDs and the crystal polyester resin. We also observed a considerable reduction of unwanted near UV-light. White light emission from WLED devices with common crystal polyester resin and low-cost materials has been achieved.

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26

Gangadhar, Lekshmi, Anusha Kannan, and P. K. Praseetha. "Quantum Dot-Sensitized Solar Cells via Integrated Experimental and Modeling Study." Journal of Computational and Theoretical Nanoscience 16, no. 2 (February 1, 2019): 436–40. http://dx.doi.org/10.1166/jctn.2019.7746.

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The solar energy is one of the potential renewable green energy source considering the availability of sunlight in abundance and the need for clean and renewable source of energy. Quantum dots are semiconductor nanocrystals having considerable interest in photovoltaic research areas. Cadmium sulfide-sensitized solar cells are synthesized by Chemical bath deposition and titanium nanowires were fabricated by hydrothermal method. The synthesized CdS quantum dots are sensitized to nanoporous TiO2 films to form quantum dots-sensitized solar cell applications. The introduction of TNWs enables the electrolyte to penetrate easily inside the film which increases the interfacial contact between the nanowires, the quantum dots and the electrolyte results in improvement in efficiency of solar cell. The goal of our research is to understand the fundamental physics and performance of quantum dot-sensitized solar cells with improved photoconversion efficiency at the low cost based on selection of TiO2 nanostructures, sensitizers and electrodes through an integrated experimental and modeling study.

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27

Biolatti, Eliana, Irene D’Amico, Radu Ionicioiu, Paolo Zanardi, and Fausto Rossi. "Ultrafast quantum information processing in nanostructured semiconductors." Superlattices and Microstructures 31, no. 2-4 (February 2002): 107–16. http://dx.doi.org/10.1006/spmi.2002.1032.

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28

Comas, F., and A. Odriazola. "SO phonons in spherical nanostructured quantum dots." physica status solidi (b) 242, no. 6 (May 2005): 1267–78. http://dx.doi.org/10.1002/pssb.200440005.

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29

Nozik, Arthur J., and Olga I. Mićić. "Colloidal Quantum Dots of III-V Semiconductors." MRS Bulletin 23, no. 2 (February 1998): 24–30. http://dx.doi.org/10.1557/s0883769400031237.

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Quantization effects in semiconductor structures were first demonstrated in the early 1970s in III-V quantum wells; these structures consisted of a thin epitaxial film of a smaller bandgap (Eg) semiconductor (e.g., GaAs, Eg = 1.42 eV) sandwiched between two epitaxial films of a larger bandgap semiconductor (e.g., Al0.3Ga0.7As, Eg = 2.0 eV). The conduction- and valence-band offsets of the two semiconductor materials produce potential barriers for electrons and holes, respectively. The smaller bandgap semiconductor constitutes the quantum-well region and the larger bandgap material the potential barrier region. If the film of the smaller bandgap material is sufficiently thin (thickness less than the de-Broglie wavelength of the charge carriers, which typically requires thicknesses less than about 300 Å for III-V semiconductors), then the charge carriers are confined in one dimension by the potential barriers, and quantization of the energy levels for both electrons and holes can occur (Figure 1).

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30

Xu, Yuanqing, Weibiao Wang, Zhexue Chen, Xinyu Sui, Aocheng Wang, Cheng Liang, Jinquan Chang, et al. "A general strategy for semiconductor quantum dot production." Nanoscale 13, no. 17 (2021): 8004–11. http://dx.doi.org/10.1039/d0nr09067k.

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31

Abbarchi, Marco, Takaaki Mano, Takashi Kuroda, Akihiro Ohtake, and Kazuaki Sakoda. "Polarization Anisotropies in Strain-Free, Asymmetric, and Symmetric Quantum Dots Grown by Droplet Epitaxy." Nanomaterials 11, no. 2 (February 10, 2021): 443. http://dx.doi.org/10.3390/nano11020443.

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We provide an extensive and systematic investigation of exciton dynamics in droplet epitaxial quantum dots comparing the cases of (311)A, (001), and (111)A surfaces. Despite a similar s-shell exciton structure common to the three cases, the absence of a wetting layer for (311)A and (111)A samples leads to a larger carrier confinement compared to (001), where a wetting layer is present. This leads to a more pronounced dependence of the binding energies of s-shell excitons on the quantum dot size and to the strong anti-binding character of the positive-charged exciton for smaller quantum dots. In-plane geometrical anisotropies of (311)A and (001) quantum dots lead to a large electron-hole fine interaction (fine structure splitting (FSS) ∼100 μeV), whereas for the three-fold symmetric (111)A counterpart, this figure of merit is reduced by about one order of magnitude. In all these cases, we do not observe any size dependence of the fine structure splitting. Heavy-hole/light-hole mixing is present in all the studied cases, leading to a broad spread of linear polarization anisotropy (from 0 up to about 50%) irrespective of surface orientation (symmetry of the confinement), fine structure splitting, and nanostructure size. These results are important for the further development of ideal single and entangled photon sources based on semiconductor quantum dots.

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32

Scherbakov, A. V., A. V. Akimov, D. R. Yakovlev, W. Ossau, L. W. Molenkamp, Y. Terai, S. Kuroda, K. Takita, I. Souma, and Y. Oka. "Dynamics of localized Mn spins in diluted-magnetic-semiconductor nanostructures with quantum dots." physica status solidi (b) 241, no. 2 (February 2004): 361–69. http://dx.doi.org/10.1002/pssb.200301916.

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33

Asahi, Hajime. "Self-Organized Quantum Wires and Dots in III - V semiconductors." Advanced Materials 9, no. 13 (1997): 1019–26. http://dx.doi.org/10.1002/adma.19970091305.

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34

Babiker, S. "Simulation of Single-Electron Transport in Nanostructured Quantum Dots." IEEE Transactions on Electron Devices 52, no. 3 (March 2005): 392–96. http://dx.doi.org/10.1109/ted.2005.843879.

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35

Peng, Hui, Lijuan Zhang, Paul A. Kilmartin, Zoran Zujovic, Christian Soeller, and Jadranka Travas Sejdic. "Quantum dots and nanostructured conducting polymers for biosensing applications." International Journal of Nanotechnology 6, no. 3/4 (2009): 418. http://dx.doi.org/10.1504/ijnt.2009.022930.

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36

Ivanov, S. V., A. G. Gladyshev, A. V. Kamanin, A. G. Kolmakov, N. V. Kryzhanovskaya, Yu G. Musikhin, E. E. Baranov, et al. "Surface control of cooperative phenomena in nanostructured materials with quantum dots." physica status solidi (c) 2, no. 6 (April 2005): 1912–16. http://dx.doi.org/10.1002/pssc.200460524.

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37

Bakanov, A. G., N. A. Toropov, and T. A. Vartanyan. "Optical Properties of Planar Nanostructures Based on Semiconductor Quantum Dots and Plasmonic Metal Nanoparticles." Optics and Spectroscopy 120, no. 3 (March 2016): 477–81. http://dx.doi.org/10.1134/s0030400x16030048.

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38

Kolesova, E. P., A. O. Orlova, V. G. Maslov, Yu K. Gun’ko, O. Cleary, A. V. Baranov, and A. V. Fedorov. "Photocatalytic Properties of Hybrid Nanostructures Based on Nanoparticles of TiO2 and Semiconductor Quantum Dots." Optics and Spectroscopy 125, no. 1 (July 2018): 99–103. http://dx.doi.org/10.1134/s0030400x18070160.

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39

Isaev, Leonid S., Arkady M. Satanin, and Yong S. Joe. "Optical properties of quantum dots produced from inverted-gap semiconductors." Semiconductor Science and Technology 22, no. 5 (March 28, 2007): 471–74. http://dx.doi.org/10.1088/0268-1242/22/5/003.

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40

Morris, Gareth, Ioritz Sorzabal-Bellido, Matthew Bilton, Karl Dawson, Fiona McBride, Rasmita Raval, Frank Jäckel, and Yuri A. Diaz Fernandez. "A Novel Self-Assembly Strategy for the Fabrication of Nano-Hybrid Satellite Materials with Plasmonically Enhanced Catalytic Activity." Nanomaterials 11, no. 6 (June 16, 2021): 1580. http://dx.doi.org/10.3390/nano11061580.

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The generation of hydrogen from water using light is currently one of the most promising alternative energy sources for humankind but faces significant barriers for large-scale applications due to the low efficiency of existing photo-catalysts. In this work we propose a new route to fabricate nano-hybrid materials able to deliver enhanced photo-catalytic hydrogen evolution, combining within the same nanostructure, a plasmonic antenna nanoparticle and semiconductor quantum dots (QDs). For each stage of our fabrication process we probed the chemical composition of the materials with nanometric spatial resolution, allowing us to demonstrate that the final product is composed of a silver nanoparticle (AgNP) plasmonic core, surrounded by satellite Pt decorated CdS QDs (CdS@Pt), separated by a spacer layer of SiO2 with well-controlled thickness. This new type of photoactive nanomaterial is capable of generating hydrogen when irradiated with visible light, displaying efficiencies 300% higher than the constituting photo-active components. This work may open new avenues for the development of cleaner and more efficient energy sources based on photo-activated hydrogen generation.

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41

Robinson, J. T., and O. D. Dubon. "Ge Island Assembly on Metal-Patterned Si: Truncated Pyramids, Nanorods, and Beyond." Journal of Nanoscience and Nanotechnology 8, no. 1 (January 1, 2008): 56–68. http://dx.doi.org/10.1166/jnn.2008.n17.

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The organization of semiconductor nanostructures into functional macroassemblies remains a fundamental challenge in nanoscience and nanotechnology. In the context of semiconductor epitaxial growth, efforts have focused on the application of advanced substrate patterning strategies for the directed assembly quantum-dot islands. We present a comprehensive investigation on the use of simple metal patterns to control the nucleation and growth of heteroepitaxial islands. In the Ge on Si model system, a square array of metal dots induces the assembly of Ge islands into an extensive two-dimensional lattice. The islands grow at sites between the metal dots and are characterized by unique shapes including truncated pyramids and nanorods, which are programmed prior to growth by the choices of metal species and substrate orientation. Our results indicate that ordering arises from the metal-induced oxidation of the Si surface; the oxide around each metal dot forms an array of periodic diffusion barriers that induce island ordering. The metals decorate the island surfaces and enhanced the growth of particular facets that are able to grow as a result of significant intermixing between deposited Ge and Si substrate atoms.

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42

Gammon, Daniel. "High-Resolution Spectroscopy of Individual Quantum Dots in Wells." MRS Bulletin 23, no. 2 (February 1998): 44–48. http://dx.doi.org/10.1557/s0883769400031262.

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Currently spectroscopists are studying many semiconductor quantum-dot (QD) systems in great detail because of their scientific and technological importance. However as in all nanostructure systems in which significant confinement energies exist, size fluctuations lead to inhomogeneous broadening of the spectral lines. This blurring of the spectra severely reduces the amount of information obtainable from spectroscopy. The finding has initiated an effort to isolate optically and study spectroscopically individual QDs. Studies involving individual QDs in most QD systems have been published. Here the results of a series of experiments are reviewed on GaAs QDs defined by interface fluctuations in narrow GaAs quantum wells. These experiments demonstrate the elegance and potential of single-QD spectroscopy.An example of single-QD photoluminescence (PL) spectroscopy appears in Figure 1. The spectra shown were obtained at a temperature of 6 K by successively reducing the size of the laser spot on a GaAs quantum-well sample through the use of small apertures in a metal mask. The bottom trace is a PL spectrum obtained with a macroscopic laser spot diameter of 25μm. The spectrum shows two broad peaks corresponding to the recombination of excitons in parts of the quantum well that are either 10 or 11 monolayers wide (2.8 or 3.1 nm). The spectrum is strongly inhomogeneously broadened as shown most directly by a reduction in the aperture size. The relatively broad lines break up into a decreasing number of extraordinarily narrow PL spikes as the aperture is reduced to submicroscopic dimensions. These PL spikes arise from excitons localized in individual QD potentials. Remarkably the linewidth decreases from several meV in the ensemble-averaged spectrum (25-μm aperture) to 10s of μeV in the single QD spectra, corresponding to an effective improvement in resolution of two orders in magnitude. By probing individual QDs, it becomes possible to resolve directly a number of phenomena that previously were hidden in the inhomogeneous linewidth.

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43

Dugaev, V. K., V. I. Litvinov, P. P. Petrov, O. A. Mironov, and M. Oszwaldowski. "Energy spectrum in quantum dots of IV-VI narrow-gap semiconductors." Semiconductor Science and Technology 8, no. 1S (January 1, 1993): S252—S254. http://dx.doi.org/10.1088/0268-1242/8/1s/055.

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44

Primus, Jean-Louis, Kang-Hoon Choi, Achim Trampert, Andrei M. Yakunin, Jacques Ferré, Joachim H. Wolter, Willem Van Roy, and Jo De Boeck. "Growth and characterization of In1−xMnxAs diluted magnetic semiconductors quantum dots." Journal of Crystal Growth 280, no. 1-2 (June 2005): 32–43. http://dx.doi.org/10.1016/j.jcrysgro.2005.03.027.

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45

Strassburg, M., A. Hoffmann, I. L. Krestnikov, and N. N. Ledentsov. "Optical and Structural Properties of Quantum Dots in Wide-Bandgap Semiconductors." physica status solidi (a) 183, no. 1 (January 2001): 99–104. http://dx.doi.org/10.1002/1521-396x(200101)183:1<99::aid-pssa99>3.0.co;2-a.

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46

Jang, Youngjin, Arthur Shapiro, Faris Horani, Yaron Kauffmann, and Efrat Lifshitz. "Towards Low-Toxic Colloidal Quantum Dots." Zeitschrift für Physikalische Chemie 232, no. 9-11 (August 28, 2018): 1443–55. http://dx.doi.org/10.1515/zpch-2018-1148.

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Abstract Colloidal quantum dots (CQDs) are of enormous interest in the scientific and engineering fields. During the past few decades, significant efforts have been conducted in investigating Cd- and Pb-based CQDs, resulting in excellent photoluminescence (PL) properties and impressive performance in various applications. But the high toxicity of Cd and Pb elements pushed the scientific community to explore low-toxic CQDs excluding poisonous heavy metals. Several semiconductor materials with lower toxicity than Cd and Pb species have been proposed. This article presents a short overview of recent efforts involving low-toxic CQDs, focusing especially on IV–VI and III–V semiconductors which are active in the near- and short-wave-infrared (IR) regimes. Recent achievements pertinent to Sn- and In-based CQDs are highlighted as representative examples. Finally, limitations and future challenges are discussed in the review.

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47

Huang, She Song, Zhi Chuan Niu, and Jian Bai Xia. "Self-Assembled GaAs Quantum Rings by MBE Droplet Epitaxy." Solid State Phenomena 121-123 (March 2007): 541–44. http://dx.doi.org/10.4028/www.scientific.net/ssp.121-123.541.

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Fabrication of semiconductor nanostructures such as quantum dots (QDs), quantum rings (QRs) has been considered as the important step for realization of solid state quantum information devices, including QDs single photon emission source, QRs single electron memory unit, etc. To fabricate GaAs quantum rings, we use Molecular Beam Epitaxy (MBE) droplet technique in this report. In this droplet technique, Gallium (Ga) molecular beams are supplied initially without Arsenic (As) ambience, forming droplet-like nano-clusters of Ga atoms on the substrate, then the Arsenic beams are supplied to crystallize the Ga droplets into GaAs crystals. Because the morphologies and dimensions of the GaAs crystal are governed by the interplay between the surface migration of Ga and As adatoms and their crystallization, the shape of the GaAs crystals can be modified into rings, and the size and density can be controlled by varying the growth temperatures and As/Ga flux beam equivalent pressures(BEPs). It has been shown by Atomic force microscope (AFM) measurements that GaAs single rings, concentric double rings and coupled double rings are grown successfully at typical growth temperatures of 200°C to 300°C under As flux (BEP) of about 1.0×10-6 Torr. The diameter of GaAs rings is about 30-50 nm and thickness several nm.

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48

Ray, Shariqsrijon Sinha, and Jayita Bandyopadhyay. "Nanotechnology-enabled biomedical engineering: Current trends, future scopes, and perspectives." Nanotechnology Reviews 10, no. 1 (January 1, 2021): 728–43. http://dx.doi.org/10.1515/ntrev-2021-0052.

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Abstract Applications of nanotechnology in biomedical engineering are vast and span several interdisciplinary areas of nanomedicine, diagnostics, and nanotheranostics. Herein, we provide a brief perspective on nanotechnology as an enabling tool for the design of new functional materials and devices for medical applications. Semiconductor nanocrystals, also known as quantum dots, are commonly used in optical imaging to diagnose diseases such as cancer. Varieties of metal and metal oxide nanoparticles, and two-dimensional carbon-based nanostructures, are prospective therapeutics and may also be used in protective antiviral/antibacterial applications. Similarly, a number of nanomaterials have shown the potential to overcome the drawbacks of conventional antiviral drugs. However, assessing the adverse effects and toxicities of nanoparticles in medicine and therapeutics is becoming more critical. This article discusses the latest developments of nanomaterials in diagnosis, nanotheranostics, and nanomedicines, with particular emphasis on the importance of nanomaterials in fighting against coronavirus disease. Further, we considered the safety and toxicity of nanomaterials in the context of biomedical applications. Finally, we provided our perspective on the future of nanotechnology in emerging biomedical engineering fields.

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RUFO, SALVADOR, MITRA DUTTA, and MICHAEL A. STROSCIO. "THE INFLUENCE OF ENVIRONMENTAL EFFECTS ON THE ACOUSTIC PHONON SPECTRA IN QUANTUM-DOT HETEROSTRUCTURES." International Journal of High Speed Electronics and Systems 12, no. 04 (December 2002): 1147–58. http://dx.doi.org/10.1142/s0129156402001964.

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We present calculations of the acoustic phonon spectra for a variety of quantum dots and consider the cases where the quantum dots are both free-standing and embedded in a selection of different matrix materials — including semiconductors, plastic, and water. These results go beyond previous calculations for free-standing quantum dots and demonstrate that the matrix material can have a large effect on the acoustic phonon spectrum and consequently on a variety of phonon-assisted transitions in quantum-dot heterostructures.

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Seraphin, A. A., E. Werwa, and K. D. Kolenbrander. "Influence of nanostructure size on the luminescence behavior of silicon nanoparticle thin films." Journal of Materials Research 12, no. 12 (December 1997): 3386–92. http://dx.doi.org/10.1557/jmr.1997.0445.

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We demonstrate the effect of particle size and quantum confinement on the luminescence properties of nanoscale silicon thin films. Thin films of agglomerated silicon nanoparticles are synthesized using pulsed laser ablation supersonic expansion. Following deposition, standard semiconductor processing techniques are employed to reduce the nanoparticle size. Films are oxidized both in air and chemically to reduce the silicon core dimensions, resulting in a shift of the luminescence emission peak to shorter wavelengths. Removal of the oxide using hydrofluoric acid (HF) results in further blueshifting of the luminescence, as does subsequent reoxidation in air and using nitric acid. The luminescence properties of samples are also studied as a function of excitation intensity. For room temperature excitation with a pulsed 355 nm source, a saturation of the photoluminescence intensity at high excitation intensity is observed, along with a blueshift of the peak PL wavelength. This behavior is found to persist at reduced temperature. A saturation of PL intensity, but no blueshift, is observed for high excitation intensity using a cw 488 nm source at room temperature. At reduced temperatures, no saturation of emission intensity occurs for high intensity 488 nm cw excitation. Both the irreversible shifting of the peak PL wavelength with size reducing treatments and the PL behavior at high excitation intensities indicate that quantum confinement determines the luminescence wavelength.

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Journal articles on the topic 'Semiconductors Nanostructured materials Quantum dots'

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