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- Thin films (10)
- Annealing (5)
- Materials science (5)
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- Gallium arsenide (4)
- III-V semiconductors (4)
- Semiconductor switches (4)
- Silicon (4)
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- Film growth (3)
- Optical properties (3)
- Pulsed laser deposition (3)
- Pulsed lasers (3)
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- Semiconducting films (3)
- Semiconductor quantum dots (3)
- Activation energy (2)
- Chemical elements (2)
- Copper compounds (2)
- Crystal orientation (2)
- Deposition (2)
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- Irradiation (2)
- Metal oxides (2)
- Metal-organic frameworks (2)
Articles 31 - 51 of 51
Full-Text Articles in Engineering
Nonthermal Laser-Induced Formation Of Crystalline Ge Quantum Dots On Si(100), M. S. Hegazy, H. E. Elsayed-Ali
Nonthermal Laser-Induced Formation Of Crystalline Ge Quantum Dots On Si(100), M. S. Hegazy, H. E. Elsayed-Ali
Electrical & Computer Engineering Faculty Publications
The effects of laser-induced electronic excitations on the self-assembly of Ge quantum dots on Si (100) - (2×1) grown by pulsed laser deposition are studied. Electronic excitations due to laser irradiation of the Si substrate and the Ge film during growth are shown to decrease the roughness of films grown at a substrate temperature of ∼120 °C. At this temperature, the grown films are nonepitaxial. Electronic excitation results in the formation of an epitaxial wetting layer and crystalline Ge quantum dots at ∼260 °C, a temperature at which no crystalline quantum dots form without excitation under the same deposition conditions. …
Activation Energy Of Surface Diffusion And Terrace Width Dynamics During The Growth Of In (4×3) On Si (100) - (2×1) By Femtosecond Pulsed Laser Deposition, M. A. Hafez, H. E. Elsayed-Ali
Activation Energy Of Surface Diffusion And Terrace Width Dynamics During The Growth Of In (4×3) On Si (100) - (2×1) By Femtosecond Pulsed Laser Deposition, M. A. Hafez, H. E. Elsayed-Ali
Electrical & Computer Engineering Faculty Publications
The nucleation and growth of indium on a vicinal Si (100) - (2×1) surface at high temperature by femtosecond pulsed laser deposition was investigated by in situ reflection high energy electron diffraction (RHEED). RHEED intensity relaxation was observed for the first ∼2 ML during the growth of In (4×3) by step flow. From the temperature dependence of the rate of relaxation, an activation energy of 1.4±0.2 eV of surface diffusion was determined. The results indicate that indium small clusters diffused to terrace step edges with a diffusion frequency constant of (1.0±0.1) × 1011 s-1. The RHEED specular …
Formation Of In- (2×1) And In Islands On Si (100) - (2×1) By Femtosecond Pulsed Laser Deposition, M. A. Hafez, H. E. Elsayed-Ali
Formation Of In- (2×1) And In Islands On Si (100) - (2×1) By Femtosecond Pulsed Laser Deposition, M. A. Hafez, H. E. Elsayed-Ali
Electrical & Computer Engineering Faculty Publications
The growth of indium on a vicinal Si (100) - (2×1) surface at room temperature by femtosecond pulsed laser deposition (fsPLD) was investigated by in situ reflection high-energy electron diffraction (RHEED). Recovery of the RHEED intensity was observed between laser pulses and when the growth was terminated. The surface diffusion coefficient of deposited In on initial two-dimensional (2D) In- (2×1) layer was determined. As growth proceeds, three-dimensional In islands grew on the 2D In- (2×1) layer. The RHEED specular profile was analyzed during film growth, while the grown In islands were examined by ex situ atomic force microscopy. The full …
Melting And Solidification Study Of As-Deposited And Recrystallized Bi Thin Films, M. K. Zayed, H. E. Elsayed-Ali
Melting And Solidification Study Of As-Deposited And Recrystallized Bi Thin Films, M. K. Zayed, H. E. Elsayed-Ali
Electrical & Computer Engineering Faculty Publications
Melting and solidification of as-deposited and recrystallized Bi crystallites, deposited on highly oriented 002-graphite at 423 K, were studied using reflection high-energy electron diffraction (RHEED). Films with mean thickness between 1.5 and 33 ML (monolayers) were studied. Ex situ atomic force microscopy was used to study the morphology and the size distribution of the formed nanocrystals. The as-deposited films grew in the form of three-dimensional crystallites with different shapes and sizes, while those recrystallized from the melt were formed in nearly similar shapes but different sizes. The change in the RHEED pattern with temperature was used to probe the melting …
Growth Of Ge Quantum Dots On Si(100)-(2×1) By Pulsed Laser Deposition, M. S. Hegazy, H. E. Elsayed-Ali
Growth Of Ge Quantum Dots On Si(100)-(2×1) By Pulsed Laser Deposition, M. S. Hegazy, H. E. Elsayed-Ali
Electrical & Computer Engineering Faculty Publications
Self-assembled germanium quantum dots (QDs) were grown on Si(100)-(2×1) by pulsed laser deposition. In situ reflection-high energy electron diffraction (RHEED) and postdeposition atomic force microscopy are used to study the growth of the QDs. Several films of different thicknesses were grown at a substrate temperature of 400 °C using a Q-switched Nd:yttrium aluminum garnet laser (λ= 1064 nm, 40 ns pulse width, 23 J/cm 2 fluence, and 10 Hz repetition rate). At low film thicknesses, hut clusters that are faceted by different planes, depending on their height, are observed after the completion of the wetting layer. With increasing film thickness, …
Self-Assembly Of Ge Quantum Dots On Si(100)- 2×1 By Pulsed Laser Deposition, M. S. Hegazy, H. E. Elsayed-Ali
Self-Assembly Of Ge Quantum Dots On Si(100)- 2×1 By Pulsed Laser Deposition, M. S. Hegazy, H. E. Elsayed-Ali
Electrical & Computer Engineering Faculty Publications
Self-assembled Ge quantum dots are grown on Si(100)- 2×1 by pulsed laser deposition. The growth is studied by in situ reflection high-energy electron diffraction and postdeposition atomic force microscopy. After the completion of the wetting layer, transient hut clusters, faceted by different planes, are observed. When the height of these clusters exceeded a certain value, the facets developed into {305} planes. Some of these huts become {305}-faceted pyramids as the film mean thickness was increased. With further thickness increase, dome clusters developed on the expense of these pyramids. © 2005 American Institute of Physics. [DOI: 10.1063/1.1949285]
High-Efficiency Solar Cells Based On Cu(Inal)Se[Sub 2] Thin Films, S. Marsillac, P. D. Paulson, M. W. Haimbodi, R. W. Birkmire, W. N. Shafarman
High-Efficiency Solar Cells Based On Cu(Inal)Se[Sub 2] Thin Films, S. Marsillac, P. D. Paulson, M. W. Haimbodi, R. W. Birkmire, W. N. Shafarman
Electrical & Computer Engineering Faculty Publications
A Cu(InAl)Se2solar cell with 16.9% efficiency is demonstrated using a Cu(InAl)Se2thin film deposited by four-source elemental evaporation and a device structure of glass/Mo/Cu(InAl)Se2/CdS/ZnO/indium tin oxide/(Ni/Algrid)/MgF2. A key to high efficiency is improved adhesion between the Cu(InAl)Se2 and the Mo back contact layer, provided by a 5-nm-thick Ga interlayer, which enabled the Cu(InAl)Se2 to be deposited at a 530 °C substrate temperature. Film and device properties are compared to Cu(InGa)Se2 with the same band gap of 1.16 eV. The solar cells have similar behavior, with performance limited by recombination through …
Atomic Hydrogen Cleaning Of Inp(100): Electron Yield And Surface Morphology Of Negative Electron Affinity Activated Surfaces, M. A. Hafez, H. E. Elsayed-Ali
Atomic Hydrogen Cleaning Of Inp(100): Electron Yield And Surface Morphology Of Negative Electron Affinity Activated Surfaces, M. A. Hafez, H. E. Elsayed-Ali
Electrical & Computer Engineering Faculty Publications
Atomic hydrogen cleaning of the InP(100) surface has been investigated using quantitative reflection high-energy electron diffraction. The quantum efficiency of the surface when activated to negative electron affinity was correlated with surface morphology. The electron diffraction patterns showed that hydrogen cleaning is effective in removing surface contaminants, leaving a clean, ordered, and (2×4)-reconstructed surface. After activation to negative electron affinity, a quantum efficiency of ∼6% was produced in response to photoactivation at 632 nm. Secondary electron emission from the hydrogen-cleaned InP(100)-(2×4) surface was measured and correlated to the quantum efficiency. The morphology of the vicinal InP(100) surface was investigated using …
Optical Properties Of Wide Band Gap Indium Sulphide Thin Films Obtained By Physical Vapor Deposition, N. Barreau, S. Marsillac, J. C. Bernède, T. Ben Nasrallah, S. Belgacem
Optical Properties Of Wide Band Gap Indium Sulphide Thin Films Obtained By Physical Vapor Deposition, N. Barreau, S. Marsillac, J. C. Bernède, T. Ben Nasrallah, S. Belgacem
Electrical & Computer Engineering Faculty Publications
Thin films of indium sulphide containing oxygen have been synthesized following a dry physical process. The constituents are deposited by thermal evaporation on glass substrates and then annealed under argon flow. Polycrystalline β-In2S3 containing oxygen thin films are obtained as soon as the temperature of annealing is between 623 and 723 K. In this paper, these β-In2S3 thin films have optically been studied. The optical band gap is direct. Its value is not dependent on the temperature of annealing. It is about 2.8 eV, which is higher than that of β-In2S3 …
Textured Mos 2 Thin Films Obtained On Tungsten: Electrical Properties Of The W/Mos 2 Contact, E. Gourmelon, J. C. Bernède, J. Pouzet, S. Marsillac
Textured Mos 2 Thin Films Obtained On Tungsten: Electrical Properties Of The W/Mos 2 Contact, E. Gourmelon, J. C. Bernède, J. Pouzet, S. Marsillac
Electrical & Computer Engineering Faculty Publications
Textured films of molybdenum disulfide have been obtained by solid state reaction between the constituents in thin films form when a (200) oriented tungsten sheet is used as substrate. The crystallites have their c axis perpendicular to the plane of the substrate. The annealing conditions are T=1073K and t=30 min. The films are stoichoimetric and p type. Such highly textured films are achieved without foreign atom addition (Ni, Co...). It appears, as shown by x-ray photoelectron spectroscopy, that a thin WS2 layer is present at the interface W/MoS2. The crystallization process is discussed by a …
Cualse² Thin Films Obtained By Chalcogenization, S. Marsillac, K. Benchouk, C. El Moctar, J. C. Bernède, J. Pouzet, A Khellil, M. Jamali
Cualse² Thin Films Obtained By Chalcogenization, S. Marsillac, K. Benchouk, C. El Moctar, J. C. Bernède, J. Pouzet, A Khellil, M. Jamali
Electrical & Computer Engineering Faculty Publications
CuAlSe2 thin films have been synthesized by chalcogenization of thin Cu and Al layers sequentially deposited by evaporation under vacuum. It is shown that CuAlSe2 films are obtained with some Cu2-δSe and Se phases present at the surface. These surface phases are suppressed by annealing under vacuum and by chemical etching in a KCN solution. At the end of the process, the XRD spectrum demonstrates that textured CuAlSe2 films have been obtained with preferential orientation of the crystallites along the (112) direction. The gap of the films is 2.7 eV as expected. The …
Optical And Electrical Properties Of Cualse² Thin Films Obtained By Selenization Of Cu/Al/Cu... Al/Cu Layers Sequentially Deposited, J. C. Bernède, S. Marsillac, C. El Moctar, A. Conan
Optical And Electrical Properties Of Cualse² Thin Films Obtained By Selenization Of Cu/Al/Cu... Al/Cu Layers Sequentially Deposited, J. C. Bernède, S. Marsillac, C. El Moctar, A. Conan
Electrical & Computer Engineering Faculty Publications
Optical and electrical properties of CuAlSe2 thin films obtained by selenization of Cu/Al/Cu...Al/Cu layers sequentially deposited have been investigated. It is shown that the expected energy gap (2.67 eV) is measured for well crystallized films, whereas a slightly higher value is measured for films not so well crystallized. Raman diffusion also shows differences between well and poorly crystallized films with peaks corresponding to the reference powder for the former samples. A p-type conductivity is found whatever the crystalline quality of the samples. The conductivity of the films depends also strongly on their crystalline properties. When the films are badly …
Influence Of Copper Doping On The Performance Of Optically Controlled Gaas Switches, St. T. Ko, V. K. Lakdawala, K. H. Schoenbach, M. S. Mazzola
Influence Of Copper Doping On The Performance Of Optically Controlled Gaas Switches, St. T. Ko, V. K. Lakdawala, K. H. Schoenbach, M. S. Mazzola
Electrical & Computer Engineering Faculty Publications
The influence of the copper concentration in silicon-doped gallium arsenide on the photoionization and photoquenching of charge carriers was studied both experimentally and theoretically. The studies indicate that the compensation ratio (NCu/NSi) is an important parameter for the GaAs:Si:Cu switch systems with regard to the turn-on and turn-off performance. The optimum copper concentration for the use of GaAs:Si:Cu as an optically controlled closing and opening switch is determined.
Nanosecond Optical Quenching Of Photoconductivity In A Bulk Gaas Switch, M. S. Mazzola, K. H. Schoenbach, V. K. Lakdawala, S. T. Ko
Nanosecond Optical Quenching Of Photoconductivity In A Bulk Gaas Switch, M. S. Mazzola, K. H. Schoenbach, V. K. Lakdawala, S. T. Ko
Electrical & Computer Engineering Faculty Publications
Persistent photoconductivity in copper-compensated, silicon-doped semi-insulating gallium arsenide with a time constant as large as 30 µs has been excited by sub-band-gap laser radiation of photon energy greater than 1 eV. This photoconductivity has been quenched on a nanosecond time scale by laser radiation of photon energy less than 1 eV. The proven ability to turn the switch conductance on and off on command, and to scale the switch to high power could make this semiconductor material the basis of an optically controlled pulsed-power closing and opening switch.
Optical Recording Aspects Of Rf Magnetron Sputtered Iron-Garnet Films, J.P. Krumme, V. Doormann, P. Hansen, H. Baumgart, J. Petruzzello, M.P.A. Viegers
Optical Recording Aspects Of Rf Magnetron Sputtered Iron-Garnet Films, J.P. Krumme, V. Doormann, P. Hansen, H. Baumgart, J. Petruzzello, M.P.A. Viegers
Electrical & Computer Engineering Faculty Publications
The intrinsic magneto-optical readout performance in reflection is calculated for bismuth and cobalt-substituted iron-garnet films on a multilayer interference mirror at 800-, 633-, 488-, and 420-nm wavelengths and is compared with that of a trilayer medium composed of an antireflection layer, a rare-earth transition-metal film, and a metallic mirror. It is found, when disregarding inhomogeneities, like irregular domain shape, ripple of the magnetic anisotropy, and surface roughness, that iron garnets are superior to rare-earth transition-metal films at blue to near-ultraviolet wavelengths if operated at thicknesses where optical interference occurs in the magnetic layer. Optical transmittance at these thicknesses is sufficiently …
Gaas Photoconductive Closing Switches With High Dark Resistance And Microsecond Conductivity Decay, M. S. Mazzola, K. H. Schoenbach, V. K. Lakdawala, R. Germer, G. M. Loubriel, F. J. Zutavern
Gaas Photoconductive Closing Switches With High Dark Resistance And Microsecond Conductivity Decay, M. S. Mazzola, K. H. Schoenbach, V. K. Lakdawala, R. Germer, G. M. Loubriel, F. J. Zutavern
Electrical & Computer Engineering Faculty Publications
Silicon-doped n-type gallium arsenide crystals, compensated with diffused copper, were studied with respect to their application as photoconductive, high-power closing switches. The attractive features of GaAs:Cu switches are their high dark resistivity, their efficient activation with Nd:YAG laser radiation, and their microsecond conductivity decay time constant. In the authors' experiment, electric fields are high as 19 kV/cm were switched, and current densities of up to 10 kA/cm2 were conducted through a closely compensated crystal. At field strengths greater than approximately 10 kV/cm, a voltage `lock-on' effect was observed.
Strains In Si-Onsio2 Structures Formed By Oxygen Implantation: Raman Scattering Characterization, D.J. Olego, H. Baumgart, G.K. Celler
Strains In Si-Onsio2 Structures Formed By Oxygen Implantation: Raman Scattering Characterization, D.J. Olego, H. Baumgart, G.K. Celler
Electrical & Computer Engineering Faculty Publications
Low-temperature Raman scattering measurements were carried out to characterize Si-on-SiO2 structures formed by oxygen implantation and subsequent furnace or lamp annealing. The experiments were conducted with 413.1 nm laser light to probe only the thin Si layers at the top of the structures. The Raman spectra of the furnace-annealed samples are red shifted and broadened when compared with a virgin Si surface. The shifts and broadenings decrease with increasing annealing temperatures but they are still present in samples annealed above 1250°C for 3 h. No shifts or broadenings affect the Raman peaks of the layers, which were lamp annealed …
An Optically Controlled Closing And Opening Semiconductor Switch, K. H. Schoenbach, V. K. Lakdawala, R. Germer, S. T. Ko
An Optically Controlled Closing And Opening Semiconductor Switch, K. H. Schoenbach, V. K. Lakdawala, R. Germer, S. T. Ko
Electrical & Computer Engineering Faculty Publications
A concept for a bulk semiconductor switch is presented, where the conductivity is increased and reduced, respectively, through illumination with light of different wavelengths. The increase in conductivity is accomplished by electron ionization from deep centers and generation of bound holes. The reduction of conductivity is obtained by hole ionization from the excited centers and subsequent recombination of free electrons and holes. The transient behavior of electron and hole density in a high power semiconductor (GaAs:Cu) switch is computed by means of a rate equation model. Changes in conductivity by five orders of magnitude can be obtained.
Silicon-On-Insulator Technology By Crystallization On Quartz Substrates, Helmut Baumgart
Silicon-On-Insulator Technology By Crystallization On Quartz Substrates, Helmut Baumgart
Electrical & Computer Engineering Faculty Publications
The purpose of the novel zone-melting recrystallization process (ZMR) is to produce single crystalline Si films on Si02 of high crystalline perfection, which are suitable for device fabrication and subsequent industrial applications. However, silicon films grown on amorphous insulating substrates without seeding contain regularly spaced subgrain boundaries as their predominant growth defect and to a lesser degree twin boundaries and some grain boundaries. Detailed materials studies have revealed the core structure of these extended defects and the fundamental mechanisms responsible for subgrain boundary formation. The nature and origin of subgrain boundaries is reviewed and a model for polygonization of the …
Seeded Oscillatory Growth Of Si Over Sio² By Cw Laser Irradiation, G.K. Celler, L. E. Trimble, K.K. Ng, H.J. Leamy, H. Baumgart
Seeded Oscillatory Growth Of Si Over Sio² By Cw Laser Irradiation, G.K. Celler, L. E. Trimble, K.K. Ng, H.J. Leamy, H. Baumgart
Electrical & Computer Engineering Faculty Publications
Extensive seeded epitaxial growth of crystalline Si over SiO2 was achieved by an oscillatory regrowth method applied to rectangular Si pads recessed into a thick SiO2 film. Narrow (≃5 μm) via holes linked the pads with the bulk (100) Si substrate. Oriented single crystals propagated as far as 500 μm from the seeding area, following the long term advance of a scanned focused laser beam.
Slip Dislocation Formation During Continuous Wave Laser Annealing Of Silicon, Helmut Baumgart
Slip Dislocation Formation During Continuous Wave Laser Annealing Of Silicon, Helmut Baumgart
Electrical & Computer Engineering Faculty Publications
High-voltage electron microscopy (HVEM) has been used for the investigation of the defect structure in cw laser-annealed silicon. We report for the first time a (HVEM) analysis of the formation processes involved in the nucleation and glide of slip dislocations during epitaxial regrowth by cw laser annealing of ion-implantation damaged silicon layers. Based on the combined optical and HVEM observations a model of the dislocation generation and glide processes is presented.