Properties Of Epitaxial Cdte On Si(lll) With a (Ca,Ba)F2 Buffer Layer

1987 ◽  
Vol 91 ◽  
Author(s):  
H. Zogg ◽  
S. Blunier
Keyword(s):  
Thermal Expansion ◽  
Buffer Layer ◽  
Room Temperature ◽  
Band Edge ◽  
Structural Quality ◽  
Near Band Edge ◽  
Thermal Expansion Mismatch ◽  
X Ray ◽  
Device Applications ◽  
Near Band Edge Peak

ABSTRACTEpitaxial CdTe has been grown onto Si(lll) wafers by MBE with the aid of a composition graded (Ca,Ba)F2 buffer layer to surmount the large misfit of 19%. Untwinned CdTe layers with smooth surfaces, narrow X-ray lines and strong photoluminescence with a narrow near band edge peak were obtained. The results indicate a comparable structural quality to well known CdTe layers on sapphire, InSb or GaAs used as buffers to grow (Hg, Cd)Te for IR-device applications. In addition, the CdTe layers are near strain free despite a large thermal expansion mismatch. This is most probably due to dislocations which are able to move along the fluoride/Si interface even after growth and down to near room temperature.

Structural Properties of InAs/AlSb Superlattices

1995 ◽  
Vol 379 ◽  
Author(s):  
B. Jenichen ◽  
H. Neuroth ◽  
B. Brar ◽  
H. Kroemer
Keyword(s):  
Buffer Layer ◽  
Peak Shift ◽  
Lattice Parameter ◽  
Structural Quality ◽  
Inhomogeneous Deformation ◽  
X Ray ◽  
Peak Broadening ◽  
Short Period ◽  
Intensity Ratios ◽  
Highly Correlated

ABSTRACTShort-period (InAs)6/(AlSb)6 superlattices (SL) with AlAs-like and InSb-like interfaces (IF) grown on a relaxed AlSb buffer layer are studied by X-ray reflectivity and diffractometry measurements. Reflectivity measurements reveal average IF roughnesses between 0.6 and 1.0 nm. Measurements of the diffuse scattering show that the roughness is highly correlated from layer to layer. Triple crystal area scans illustrate that the inhomogeneous deformation of the buffer layer leads to a certain symmetric peak broadening. In the case of AlAs-like IFs an additional broadening of the SL peaks reveals lattice parameter gradients over the superlattice. This asymmetric peak broadening may be attributed to a further relaxation of the superlattice, which is inhomogeneous with depth. The diffusion of As into the AlSb layers leads to a peak shift and modifies the intensity ratios of the different satellite reflections. The best structural quality is achieved for superlattices with InSb-like IFs.

Phase Transitions in Hoalga

1983 ◽  
Vol 21 ◽  
Author(s):  
M. Doukoure ◽  
D. Gignoux ◽  
F. Sayetat
Keyword(s):  
Thermal Expansion ◽  
Room Temperature ◽  
Magnetic Order ◽  
Magnetocrystalline Anisotropy ◽  
Exchange Interactions ◽  
Thermal Anomaly ◽  
Antiferromagnetic State ◽  
Hexagonal Symmetry ◽  
X Ray ◽  
Magnetic Structures

ABSTRACTHoAlGa is hexagonal at room temperature. It undergoes two magnetic transitions succesively at TN = 32 K from a paramagnetic to a triangular antiferromagnetic state where the Ho moments lie in the basal plane and at Tt = 18 K in the course of which the moments rotate toward c giving rise to a colinear antiferromagnetic arrangement. X-ray experiments performed between 5 and 300 K allow to determine the crystal evolution through the two transitions. The hexagonal symmetry is not lowered through the transitions; this result is compatible with the observed magnetic groups. The thermal expansion curves show a very anisotropic behaviour of the lattice parameters. The “c” parameter shrinks below TN and this anomaly is to be related to the magnetic order. Along a, a positive thermal anomaly appears below 70 K and this can be interpreted by crystal field effects. Stability of magnetic structures is discussed with regard to exchange interactions and magnetocrystalline anisotropy.

Effects of Vacancies on the Thermal Expansion of Mercury Indium Telluride Crystals

2010 ◽  
Vol 663-665 ◽  
pp. 1008-1011
Author(s):  
Ling Hang Wang
Keyword(s):  
Thermal Expansion ◽  
Room Temperature ◽  
Linear Expansion ◽  
Semiconductor Material ◽  
X Ray ◽  
Temperature Range ◽  
Vertical Bridgman ◽  
Indium Telluride

The thermal expansion of a novel semiconductor material, mercury indium telluride (MIT) grown by vertical Bridgman (VB) method, was measured from room temperature till 573K by two methods, i.e. Macroscopic dilatometric and X-ray measurements. It is found that the macroscopic expansion is quite different from the expansion of the lattice (micro-expansion). The macroscopic expansion is lower than micro-expansion in the temperature range of 303-425.5K and has a minimum of -0.14% linear expansion, while the macro-expansion becomes larger than micro-expansion in the temperature higher than 425.5K. The former may be due to the effects of the existing neutral vacancies. The latter may result from the influence of thermal-activated vacancies on the lattice.

Correlation of the Stress-Temperature History with Microstructure in A1-0.5Cu and A1-0.15Pd Thin Films

1994 ◽  
Vol 356 ◽  
Author(s):  
D. D. Knorr ◽  
K.P. Rodbell
Keyword(s):  
Thin Films ◽  
Thermal Expansion ◽  
Substrate Temperature ◽  
Grain Growth ◽  
Room Temperature ◽  
Temperature History ◽  
Thermal Expansion Mismatch ◽  
Grain Sizes ◽  
Substrate Temperatures ◽  
Precipitate Structure

AbstractBlanket films (1 μm thick) of both A1-0.5Cu and A1-0.15Pd were deposited at room temperature, 150°C, and 300°C. Stress in the as-deposited wafers increased with substrate temperature, as expected from the thermal expansion mismatch on cooling. All conditions were tiicrmally cycled to 450°C three times while continuously monitoring stress. The shapes of the curves were different for the two alloys because precipitates dissolve and reprecipitate in AlCu, but are present over the entire temperature range in AlPd. Lesser differences were evident comparing the stress-temperature behavior for the various substrate temperatures within a single alloy. The precipitate structure also influences the grain growth during thermal cycling, where substantially larger median grain sizes are found in AlCu compared to AlPd.

CRYSTAL STRUCTURE, ELECTRICAL CONDUCTIVITY AND THERMAL EXPANSION OF Pr1-xSrxFeO3-δ(0 ≤ x ≤ 0.6)

2012 ◽  
Vol 26 (32) ◽  
pp. 1250174 ◽  
Author(s):  
V. PRASHANTH KUMAR ◽  
Y. S. REDDY ◽  
P. KISTAIAH ◽  
C. VISHNUVARDHAN REDDY
Keyword(s):  
Crystal Structure ◽  
Electrical Conductivity ◽  
Thermal Expansion ◽  
Room Temperature ◽  
Small Polaron ◽  
Linear Thermal Expansion ◽  
Lattice Parameter ◽  
Polaron Hopping ◽  
X Ray ◽  
Perovskite Type

The crystal structure at room temperature (RT), thermal expansion from RT to 1000°C and electrical conductivity, from RT to 600°C, of the perovskite-type oxides in the system Pr 1-x Sr x FeO 3(x = 0, 0.2, 0.4, 0.6) were studied. All the compounds have the orthorhombic perovskite GdFeO 3-type structure with space group Pbnm. The lattice parameters were determined by X-ray powder diffraction. The Pseudo cubic lattice parameter decreases with an increase in x, while the coefficient of linear thermal expansion increases. The thermal expansion is almost linear for x = 0 and 0.2. The electrical conductivity increases with increasing x while the activation energy decreases. The electrical conductivity can be described by the small polaron hopping conductivity model.

Al2O3 as a Transition Layer for GaN and InGaN Growth on ZnO by MOCVD

2009 ◽  
Vol 1201 ◽  
Author(s):  
Nola Li ◽  
Shen-Jie Wang ◽  
William E. Fenwick ◽  
Andrew Melton ◽  
Chung-Lung Huang ◽  
...  
Keyword(s):  
Room Temperature ◽  
Chemical Vapor ◽  
Shallow Donor ◽  
Near Band Edge ◽  
Band Edge Emission ◽  
X Ray Diffraction ◽  
Edge Emission ◽  
X Ray ◽  
20 Nm ◽  
Related Level

AbstractGaN and InGaN layers were grown on annealed 20 and 50nm Al2O3/ZnO substrates by metalorganic chemical vapor deposition (MOCVD). GaN was only observed by high resolution x-ray diffraction (HRXRD) on 20 nm Al2O3/ZnO substrates. Room temperature photoluminescence (RT-PL) showed the red shift of the GaN near band-edge emission, which might be from oxygen incorporation forming a shallow donor-related level in GaN. HRXRD measurements revealed that (0002) InGaN layers were also successfully grown on 20nm Al2O3/ZnO substrates. In addition, thick InGaN layers (∼200-300nm) were successfully grown on Al2O3/ZnO and bare ZnO substrates. These results are significant as previous studies showed decomposition of the layer at InGaN thicknesses of 100nm or less.

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