MOCVD Growth of III-V Compounds on Si Using Strained Superlattices

1986 ◽  
Vol 67 ◽  
Author(s):  
Shiro Sakai ◽  
Tetsuo Soga ◽  
Masanari Takeyasu ◽  
Masayoshi Umeno
Keyword(s):  
Electronic Properties ◽  
Intermediate Layer ◽  
Lattice Mismatch ◽  
Gaas Layer ◽  
X Ray Diffraction ◽  
X Ray ◽  
Double Heterostructure ◽  
Si Substrates ◽  
Mocvd Growth ◽  
Structural And Electronic Properties

ABSTRACTGaAs and GaAsP with the entire compositional range are grow on Si using an intermediate layer of GaAsP strained superlattices to relax the lattice mismatch. The orientation of the overgrown GaAs layer is found to be determined by the direction of the off-angle of the Si (100) surface. The grown layers are characterized by photoluminescence, x-ray diffraction, electro reflectance and DLTS. GaAs/GaAlAs double heterostructure lasers and GaAsP visible LED's are fabricated on Si substrates. The structural and electronic properties of the grown layers and the device performances are reported in this paper.

Structural and Electronic Properties of (CdTe)1−x(In2Te3)x Films Grown by Close-spaced vapor Transport Combined with Free Evaporation

2000 ◽  
Vol 15 (8) ◽  
pp. 1811-1815 ◽  
Author(s):  
M. Zapata-Torres ◽  
Y. P. Mascarenhas ◽  
M. A. Santana-Aranda ◽  
J. Luyo-Alvarado ◽  
M. Melé-Lirandez ◽  
...  
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
Single Phase ◽  
Vapor Transport ◽  
X Ray Diffraction ◽  
X Ray ◽  
A Value ◽  
Structural And Electronic Properties ◽  
Direct Band ◽  
Transmission Measurements

The structural and electronic properties of (CdTe)1−x(In2Te3)x thin films as a function of substrate temperature were studied using x-ray diffraction, energy dispersive x-ray analysis, and Raman, transmission, and modulated transmission spectroscopies. The films were grown by the close-spaced vapor transport technique combined with free evaporation; CdTe and In2Te3 were used as sources. From x-ray diffraction the presence of mixed phases and differences in composition were detected, and good correlation with Raman spectroscopy was found. Transmission spectroscopy suggested the possibility of a modulation of the band gap of the alloy from a value as low as 0.5 eV up to 1.5 eV. Single-phase films presented a direct band gap of around 1.15 eV, as obtained from modulated transmission measurements.

Properties of Pure and Sulfided NiMoO4 and CoMoO4 Catalysts: Tpr, Xanes and Time-Resolved XRD Studdzs

1997 ◽  
Vol 497 ◽  
Author(s):  
S. Chaturvedi ◽  
J. A. Rodriguez ◽  
J. C. Hanson ◽  
A. Albornoz ◽  
J. L. Brito
Keyword(s):  
Electronic Properties ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
Direct Transformation ◽  
X Ray ◽  
Β Phase ◽  
Structural And Electronic Properties ◽  
X Ray Absorption ◽  
Kinetics Of ◽  
Cobalt And Nickel

ABSTRACTX-ray absorption near-edge spectroscopy (XANES) was used to characterize the structural and electronic properties of a series of cobalt- and nickel-molybdate catalysts (AMoO4.nH20, α-AMoO4, β-AMoO4; A= Co or Ni). The results of XANES indicate that the Co and Ni atoms are in octahedral sites in all these compounds, while the coordination of Mo varies from octahedral in the a-phases to tetrahedral in the β-phases and hydrate. Time-resolved x-ray diffraction shows a direct transformation of the hydrates into the β-AMoO4 compounds (following a kinetics of first order) at temperatures between 200 and 350 °C. This is facilitated by the similarities that the AMoO4.nH20 and β-AMoO4 compounds have in their structural and electronic properties. The molybdates react with H 2 at temperatures between 400 and 600 °C, forming gaseous water and oxides in which the oxidation state of Co and Ni remains +2 while that of Mo is reduced to +5 or +4. After exposing α-NiMoO4 and P-NiMoO4 to H2S, both metals get sulfided and a NiMoSx phase is formed. For the β phase of NiMoO4 the sulfidation of Mo is more extensive than for the a phase, making the former a better precursor for catalysts of hydrodesulfurization reactions.

scholarly journals Structural and electronic properties of the spinel Li4Ti5O12

2019 ◽  
Vol 20 (46) ◽  
pp. 7-12 ◽  
Author(s):  
Sarantuya Lkhagvajav ◽  
Namsrai Tsogbadrakh ◽  
Enkhjargal Enkhbayar ◽  
Sevjidsuren Galsan ◽  
Pagvajav Altantsog
Keyword(s):  
Electronic Properties ◽  
First Principles ◽  
Density Functional ◽  
Experimental Studies ◽  
First Principles Calculations ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structural And Electronic Properties ◽  
Hubbard U ◽  
Uv Visible

In this study, the structure and electronic properties of the spinel compound Li4Ti5O12 (LTO) are investigated both theoretical and experimental methods. The experimental studies of structural and electronic properties were performed by X-ray diffraction and UV-visible spectroscopy. The first principles calculations allowed to establish the relationship between the structure and electronic properties. The spinel type structure of LTO is refined by the Rietveld analysis using the X-ray diffraction (XRD). The band gap of LTO was determined to be 3.55 eV using the UV-visible absorption spectra. The Density functional theory (DFT) augmented without and with the Hubbard U correction (GGA and GGA +U+J0) is used to elucidate the electronic structure of LTO. We have performed systematic studies of the first principles calculations based on the GGA and GGA+U for the crystal structure and electronic properties of spinel LTO. We propose that a Hubbard U correction improves the DFT results.

Structural and Electronic Properties Study of Colombian Aurifer Soils by Mössbauer Spectroscopy and X-ray Diffraction

LACAME 2004 ◽  
2006 ◽  
pp. 61-68
Author(s):  
H. Bustos Rodríguez ◽  
Y. Rojas Martínez ◽  
D. Oyola Lozano ◽  
G. A. Pérez Alcázar ◽  
M. Fajardo ◽  
...  
Keyword(s):  
Mössbauer Spectroscopy ◽  
Electronic Properties ◽  
Mossbauer Spectroscopy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mößbauer Spectroscopy ◽  
Structural And Electronic Properties

Structural and electronic properties of indium-doped YBa2Cu3Oσ

1991 ◽  
Vol 6 (3) ◽  
pp. 446-449 ◽  
Author(s):  
Georg Weidlich ◽  
Michael Goelz ◽  
Ruiping Wang ◽  
William E. Evenson ◽  
John A. Gardner ◽  
...  
Keyword(s):  
Magnetic Flux ◽  
Electronic Properties ◽  
Solubility Limit ◽  
Formula Unit ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structural And Electronic Properties ◽  
Oxide Phases ◽  
Diffraction Patterns

We have measured x-ray diffraction patterns and Meissner flux exclusion of YBa2Cu3Oσ containing indium. All samples were synthesized at temperatures near 940 °C, and the data indicate the indium atomic solubility to be approximately 3% per formula unit. At the solubility limit Tc is reduced from 92.7 K to 91.3 K relative to undoped samples, and the total magnetic flux excluded is reduced from approximately 40% to about 10%. For samples of formula InxY1−xBa2Cu3Oσ concentrations of other Y–Ba–Cu oxide phases are low and do not depend systematically on x. These results indicate that indium substitutes predominantly for yttrium when x is small.

Strain Evaluation of GaAs Layers Grown on Ultrahigh-Pressure-Annealed Strain-Free GaAs-On-Si Structures

1997 ◽  
Vol 486 ◽  
Author(s):  
Takehito Jimbo ◽  
Hiroshi Ishiwara
Keyword(s):  
Chemical Vapor ◽  
Xrd Analysis ◽  
Gaas Layer ◽  
Ultrahigh Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Si Substrates ◽  
Gaas On Si ◽  
Gaas Films ◽  
Regeneration Effect

AbstractIn order to form strain-free GaAs films on Si substrates, GaAs-on-Si structures have been formed by molecular beam epitaxy (MBE) or metalorganic chemical vapor deposition (MOCVD) and subsequently annealed under ultrahigh pressure at 2 GPa. The samples were then reannealed at atmospheric pressure in order to investigate the regeneration effect of strain in the GaAs films. It was found from X-ray diffraction (XRD) analysis and photoluminescence (PL) measurement that in the reannealed samples the strain near the surface of GaAs film was smaller than that near the interface with Si. Finally, additional GaAs layers were grown using MBE on both as-grown and strain-free GaAs-on-Si structures and it was found that the residual strain in the GaAs layer on strain-free GaAs-on-Si structure was smaller than in the as-grown case.

TEMPERATURE EFFECT ON STRUCTURAL AND ELECTRONIC PROPERTIES OF ZINC OXIDE NANOWIRES SYNTHESIZED BY CARBOTHERMAL EVAPORATION METHOD

2012 ◽  
Vol 11 (05) ◽  
pp. 1250032 ◽  
Author(s):  
MOHAMMAD ORVATINIA ◽  
ROGHAYEH IMANI
Keyword(s):  
Zinc Oxide ◽  
Grain Boundary ◽  
Elevated Temperatures ◽  
Synthesis Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Si Substrates ◽  
Structural And Electronic Properties ◽  
Different Temperatures ◽  
Sem Micrograph

Zinc Oxide ( ZnO ) nanowires were synthesized on the Si substrates by carbothermal evaporation of ZnO + C at elevated temperatures. The syntheses were carried out at different temperatures from 750°C to 950°C. Characterizations of layers were performed to study the effect of synthesis temperature on morphology, crystal structure and electrical behavior of fabricated nanowires. The physical characterization was performed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray (EDAX) methods. SEM micrograph of layers revealed that the samples grown at the lower temperatures have better quality. However, below 800°C the growth of nanowires was stopped. So the 800°C was concluded to be the optimum temperature for growth of high quality nanowires by proposed system. By recording the conductivity variations as a function of inverse temperature, 1/T, the semiconductor property of the samples was verified. It is demonstrated that two distinct factors affect the electrical conductivity of layers, which are due to the bulk and grain boundary. We experimentally proved that the activation energy corresponding to grain boundary is higher than that of the bulk. As another result we have established for the first time that by increasing synthesis temperatures, both activation energies shift to higher values.

Epitaxy of Single Crystal Phase Change Materials on Si(111)

2011 ◽  
Vol 1338 ◽  
Author(s):  
P. Rodenbach ◽  
K. Perumal ◽  
F. Katmis ◽  
W. Braun ◽  
R. Calarco ◽  
...  
Keyword(s):  
Phase Change ◽  
Molecular Beam ◽  
Phase Change Materials ◽  
Lattice Mismatch ◽  
X Ray Diffraction ◽  
Quadrupole Mass ◽  
Cubic Symmetry ◽  
X Ray ◽  
Si Substrates

ABSTRACTPhase change materials along the GeTe-Sb2Te3 pseudobinary line (GST) are grown by molecular beam epitaxy (MBE) on Si(111). The growth on (111) oriented substrates leads to greatly increased crystal quality compared to (001) oriented substrates, even for a high lattice mismatch. This holds true even for Si substrates which have a lattice mismatch of around 10% with respect to GST. The growth is controlled in situ via line of sight quadrupole mass spectrometer (QMS). Structural characterization is performed in situ by X-ray diffraction (XRD), which reveals a clear cubic symmetry of the film and a lattice slightly rhombohedrally distorted along the [111] direction.

MOCVD Growth of GaAs on Si with Low Temperature Preheating Process

1992 ◽  
Vol 259 ◽  
Author(s):  
N. Takagi ◽  
T. Eshita ◽  
S. Miyagaki ◽  
M. Kimura ◽  
K. Takasaki
Keyword(s):  
Low Temperature ◽  
Chemical Vapor ◽  
X Ray Diffraction ◽  
X Ray ◽  
Si Substrates ◽  
Mocvd Growth ◽  
Atomic Force ◽  
Preheating Temperature ◽  
Wet Chemical ◽  
Better Than

ABSTRACTA low temperature preheating process is developed for metalorganic chemical vapor deposition (MOCVD) growth of GaAs on wet chemical pretreated Si substrates. NH4 OH/H2 O2 is found to be most effective in decreasing the preheating temperature among the chemicals we tried: NH4 OH/H2 O2, H2SO4 /H2O2, or hot HNO3. By using NH4OH/H2 O2, the preheating temperature is reduced from 1000°C to 875°C. X-ray diffraction measurements and surface observations with an atomic force microscope (AFM) show that the GaAs film quality obtained with the 875 °C preheating process is better than that obtained with 1000°C preheating.

scholarly journals Investigation of Structural and Electronic Properties of CH3NH3PbI3 Stabilized by Varying Concentrations of Poly(Methyl Methacrylate) (PMMA)

Coatings ◽  
2017 ◽  
Vol 7 (8) ◽  
pp. 115 ◽  
Author(s):  
Celline Awino ◽  
Victor Odari ◽  
Thomas Dittrich ◽  
Pongthep Prajongtat ◽  
Thomas Sakwa ◽  
...  
Keyword(s):  
Electronic Properties ◽  
Storage Time ◽  
Impurity Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structural And Electronic Properties ◽  
The Stability ◽  
Xrd Patterns ◽  
Silicon Based ◽  
Pl Quenching

Studies have shown that perovskites have a high potential of outdoing silicon based solar cells in terms of solar energy conversion, but their rate of degradation is also high. This study reports on improvement on the stability of CH3NH3PbI3 by passivating it with polymethylmethacrylate (PMMA). Structural and electronic properties of CH3NH3PbI3 stabilized by polymethylmethacrylate (PMMA) were investigated by varying concentrations of PMMA in the polymer solutions. Stability tests were performed over a period of time using modulated surface photovoltage (SPV) spectroscopy, X-ray diffraction (XRD), and photoluminescence (PL) measurements. The XRD patterns confirm the tetragonal structure of the deposited CH3NH3PbI3 for every concentration of PMMA. Furthermore, CH3NH3PbI3 coated with 40 mg/mL of PMMA did not show any impurity phase even after storage in air for 43 days. The Tauc gap (ETauc) determined on the basis of the in-phase SPV spectra was found in the range from 1.585 to 1.62 eV for the samples stored during initial days, but shifted towards lower energies as the storage time increased. This can be proposed to be due to different chemical reactions between CH3NH3PbI3/PMMA interfaces and air. PL intensity increased with increasing concentration of PMMA except for the perovskite coated with 40 mg/mL of PMMA. PL quenching in the perovskite coated with 40 mg/mL of PMMA can be interpreted as fast electron transfer towards the substrate in the sample. This study shows that, with an optimum concentration of PMMA coating on CH3NH3PbI3, the lifetime and hence stability on electrical and structural behavior of CH3NH3PbI3 is improved.

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