Structural investigation of InAs/InGaAs/InP nanostructures: origin and stability of nanowires.

2004 ◽  
Vol 829 ◽  
Author(s):  
L. Nieto ◽  
H. R. Gutiérrez ◽  
J. R. R. Bortoleto ◽  
R. Magalhães-Paniago ◽  
M. A. Cotta
Keyword(s):  
Buffer Layer ◽  
Strain Relaxation ◽  
Additional Stress ◽  
Chemical Beam Epitaxy ◽  
Compositional Modulation ◽  
Transmission Electron ◽  
Inas Nanowires ◽  
Inp Substrates ◽  
Lattice Matched ◽  
Microscopy Images

ABSTRACTIn this letter we present results on the growth of InAs nanowires (NW's) on InGaAs lattice-matched to (100) InP substrates by Chemical Beam Epitaxy. We observed that the nanostructure stability depends on the thickness of the InGaAs layer. This effect may result from two different conditions: the nanostructure strain field depth and/or compositional modulation in the buffer layer. Our investigation shows that anisotropic strain relaxation for nanowires grown on InGaAs is faster than for those grown on InP but the elastic energy in the nanostructures is no different from the InAs/InP case. These results suggest that the InAs strain relaxation does not depend significantly on the InGaAs buffer layer thickness. Nevertheless, transmission electron microscopy images show an additional stress field superimposed on that usually observed for the InAs nanostructures, which is attributed to compositional modulation in the ternary layer.

Origin of Grown-in Dislocations in III-V Compound Semiconductor Epitaxial Layers

1985 ◽  
Vol 62 ◽  
Author(s):  
S. Nakahara ◽  
S. N. G. Chu
Keyword(s):  
Lattice Mismatch ◽  
Strain Relaxation ◽  
Chemical Compositions ◽  
Misfit Dislocations ◽  
Quaternary Alloys ◽  
Transmission Electron ◽  
Half Loop ◽  
Micro Analysis ◽  
Inp Substrates ◽  
Lattice Matched

ABSTRACTA transmission electron microscope was used to study the origin of grown-in dislocations observed in quaternary InGaAsP layers grown by vapor phase epitaxy on (001) InP substrates. Many of the grown-in dislocations were found to exist as dislocation dipoles and were connected to particles formed at the lnGaAsP/lnP interface. X-ray micro-analysis has indicated that the particles are quaternary alloys having chemical compositions slightly richer in both Ga and P than that of the lattice-matched InGaAsP layer. In some cases, this compositional deviation led to a significant lattice mismatch. As the particle grows larger, a strain relaxation occurs by generating misfit dislocations around the particle in the form of a dislocation half loop. If these dislocation half loops do not develop into a complete loop by totally surrounding the particle, they leave two unclosed dislocation segments (a dislocation dipole), which are replicated by the quaternary overlayer along the substrate normal direction, i.e., [001]. These dislocations eventually become a source for grown-in dislocations.

Anisotropic Surface Roughness in Strain Relaxed In0.40GA0.60As on Gaas with a Step-Graded InxGA1-xAs Buffer Layer

1993 ◽  
Vol 312 ◽  
Author(s):  
J. C. P. Chang ◽  
B. K. Kad ◽  
S. R. Nutt ◽  
K. L. Kavanagh
Keyword(s):  
Electron Microscopy ◽  
Surface Roughness ◽  
Buffer Layer ◽  
Strain Relaxation ◽  
Phase Segregation ◽  
Periodic Variation ◽  
Cross Sectional ◽  
Anisotropic Surface ◽  
Transmission Electron ◽  
Plane Direction

AbstractWe report the structural characterization of the 3-D relaxation morphology of In0.4Ga0.6As grown on a step-graded InxGa1-xAs buffer layer on GaAs. Scanning electron microscopy showed “grooves” spaced on the order of microns running only in the [110] direction. Each groove was observed with cross-sectional transmission electron microscopy to mark the location of a vertical low-angle tilt and/or twist boundary. The veiy rough layer morphology may be the result of island coalescence or severe surface roughness that created the grain boudnaries as the layer grew. Strain relaxation in the In0.4Ga0.6As layer was much reduced in the [101] in-plane direction. The asymmetry in residual in-plane strains in the In0.3Ga0.7AS layer and/or the increased In composition may be responsible for the development of an anisotropic surface roughness. X-ray microanalysis revealed a periodic variation in layer composition which correlated with a fine contrast modulation presumably the result of phase segregation.

Step-graded buffer layer study of the strain relaxation by transmission electron microscopy

1994 ◽  
Vol 28 (1-3) ◽  
pp. 497-501 ◽  
Author(s):  
D. González ◽  
D. Araújo ◽  
S.I. Molina ◽  
A. Sacedón ◽  
E. Calleja ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Buffer Layer ◽  
Strain Relaxation ◽  
Transmission Electron

ZnSe Growth on Lattice-Matched InxGa1-xAs Substrates

1998 ◽  
Vol 05 (03n04) ◽  
pp. 693-700 ◽  
Author(s):  
S. Heun ◽  
R. Lantier ◽  
J. J. Paggel ◽  
L. Sorba ◽  
S. Rubini ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Molecular Beam Epitaxy ◽  
Dislocation Density ◽  
Residual Strain ◽  
Molecular Beam ◽  
Strain Relaxation ◽  
Line Emission ◽  
Transmission Electron ◽  
Lattice Matched

The properties of ZnSe epilayers fabricated by molecular beam epitaxy on lattice-matched In x Ga 1-x As buffers grown on GaAs(001) substrates have been investigated by means of photoluminescence spectroscopy and transmission electron microscopy. For suitable values of x and ternary-layer thickness, the partial character of the strain relaxation within the III–V layer can be compensated for, minimizing the residual strain in the ZnSe overlayer. Large reductions in the dislocation density and Y-line emission as compared to conventional ZnSe/GaAs heterostructures can be reproducibly obtained.

Strain Relaxation Via Interface Nucleation of Misfit Dislocations in Intermixing Layers

1992 ◽  
Vol 263 ◽  
Author(s):  
Hyo-Hoon Park ◽  
Jung Kee Lee ◽  
El-Hang Lee ◽  
Jeong Yong Lee ◽  
Soon-Ku Hong
Keyword(s):  
Electron Microscopy ◽  
Homogeneous Nucleation ◽  
Critical Thickness ◽  
Strain Relaxation ◽  
Relaxation Mechanism ◽  
Semiconductor Heterostructures ◽  
Misfit Dislocations ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Lattice Matched

ABSTRACTThe strain relaxation mechanism via the homogeneous nucleation of misfit dislocations from interface during interdiffusion in lattice-matched semiconductor heterostructures has been investigated. Transmission electron microscopy studies in intermixed GaInAsP/InP heterostructures revealed that the critical interdiffusion depth for the nucleation of 90° 1/6<112> partial dislocations from a tensile interface is much shallower than that of 60° 1/2<110> perfect dislocations from a compressive interface. A critical thickness model for the interface nucleation of these dislocations is developed as a modification of the classical surface nucleation'model.

Tem Assessment of Different Mechanisms Contributing to Stress Relaxation in Strained InGaAs/InAlAs Systems

1992 ◽  
Vol 263 ◽  
Author(s):  
F. Peiro ◽  
A. Cornet ◽  
J.R. Morante ◽  
S. A. Clark ◽  
R.H. Williams
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Stress Relaxation ◽  
Lattice Mismatch ◽  
Strain Relaxation ◽  
Lattice Parameter ◽  
Growth Morphology ◽  
Transmission Electron ◽  
Inp Substrates

ABSTRACTA study by Transmission Electron microscopy (TEM) of strained InGaAs/InAlAs systems on InP substrates is presented. The influence of the lattice mismatch, epilayer thickness and modulation of the lattice parameter on the morphology of the system is analyzed. A discussion of the strain relaxation mechanisms occurring for each growth morphology is also presented.

A Transmission Electron Microscopical Investigation of Phase Transformations in TiNi

1980 ◽  
Vol 38 ◽  
pp. 340-341
Author(s):  
P. Moine ◽  
G. M. Michal ◽  
R. Sinclair
Keyword(s):  
Electron Microscopy ◽  
Phase Transformations ◽  
Applied Stress ◽  
Structural Changes ◽  
Microscopical Investigation ◽  
Temperature Range ◽  
Transmission Electron ◽  
Electron Microscopical ◽  
Diffraction Effects ◽  
Microscopy Images

Premartensitic effects in near equiatomic TiNi have been pointed out by several authors(1-5). These include anomalous contrast in electron microscopy images (mottling, striations, etc. ),diffraction effects(diffuse streaks, extra reflections, etc.), a resistivity peak above Ms (temperature at which a perceptible amount of martensite is formed without applied stress). However the structural changes occuring in this temperature range are not well understood. The purpose of this study is to clarify these phenomena.

Formation of Luminescent Si Nanocrystals by High-Temperature Annealing of Ion-Beam-Sputtered Si/SiO2 Multilayers

2003 ◽  
Vol 775 ◽  
Author(s):  
Suk-Ho Choi ◽  
Jun Sung Bae ◽  
Kyung Jung Kim ◽  
Dae Won Moon
Keyword(s):  
Quantum Confinement ◽  
Radiative Recombination ◽  
Ion Beam ◽  
Quantum Confinement Effect ◽  
Visible Range ◽  
Ion Beam Sputtering ◽  
Transmission Electron ◽  
Si Nanocrystals ◽  
Beam Sputtering ◽  
Microscopy Images

AbstractSi/SiO2 multilayers (MLs) have been prepared under different deposition temperatures (TS) by ion beam sputtering. The annealing at 1200°C leads to the formation of Si nanocrystals in the Si layer of MLs. The high resolution transmission electron microscopy images clearly demonstrate the existence of Si nanocrystals, which exhibit photoluminescence (PL) in the visible range when TS is ≥ 300°C. This is attributed to well-separation of nanocrystals in the higher-TS samples, which is thought to be a major cause for reducing non-radiative recombination in the interface between Si nanocrystal and surface oxide. The visible PL spectra are enhanced in its intensity and are shifted to higher energy by increasing TS. These PL behaviours are consistent with the quantum confinement effect of Si nanocrystals.

scholarly journals Improved Performance of GaN-Based Light-Emitting Diodes Grown on Si (111) Substrates with NH3 Growth Interruption

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 399
Author(s):  
Sang-Jo Kim ◽  
Semi Oh ◽  
Kwang-Jae Lee ◽  
Sohyeon Kim ◽  
Kyoung-Kook Kim
Keyword(s):  
Buffer Layer ◽  
Light Emitting Diodes ◽  
Defect Density ◽  
Strain Relaxation ◽  
Multiple Quantum Well ◽  
Light Output ◽  
Multiple Quantum ◽  
Light Emitting ◽  
Growth Interruption ◽  
Aln Buffer

We demonstrate the highly efficient, GaN-based, multiple-quantum-well light-emitting diodes (LEDs) grown on Si (111) substrates embedded with the AlN buffer layer using NH3 growth interruption. Analysis of the materials by the X-ray diffraction omega scan and transmission electron microscopy revealed a remarkable improvement in the crystalline quality of the GaN layer with the AlN buffer layer using NH3 growth interruption. This improvement originated from the decreased dislocation densities and coalescence-related defects of the GaN layer that arose from the increased Al migration time. The photoluminescence peak positions and Raman spectra indicate that the internal tensile strain of the GaN layer is effectively relaxed without generating cracks. The LEDs embedded with an AlN buffer layer using NH3 growth interruption at 300 mA exhibited 40.9% higher light output power than that of the reference LED embedded with the AlN buffer layer without NH3 growth interruption. These high performances are attributed to an increased radiative recombination rate owing to the low defect density and strain relaxation in the GaN epilayer.

scholarly journals Green Synthesis of Feather-Shaped MoS2/CdS Photocatalyst for Effective Hydrogen Production

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
Yang Liu ◽  
Hongtao Yu ◽  
Xie Quan ◽  
Shuo Chen
Keyword(s):  
Electron Microscopy ◽  
Hydrogen Production ◽  
Photoelectron Spectroscopy ◽  
Diffuse Reflectance ◽  
Sulfur Source ◽  
X Ray ◽  
Transmission Electron ◽  
Microscopy Images ◽  
Effective Hydrogen ◽  
Better Than

MoS2/CdS photocatalyst was fabricated by a hydrothermal method for H2production under visible light. This method used low toxic thiourea as a sulfur source and was carried out at 200°C. Thus, it was better than the traditional methods, which are based on an annealing process at relatively high temperature (above 400°C) using toxic H2S as reducing agent. Scanning electron microscopy and transmission electron microscopy images showed that the morphologies of MoS2/CdS samples were feather shaped and MoS2layer was on the surface of CdS. The X-ray photoelectron spectroscopy testified that the sample was composed of stoichiometric MoS2and CdS. The UV-vis diffuse reflectance spectra displayed that the loading of MoS2can enhance the optical absorption of MoS2/CdS. The photocatalytic activity of MoS2/CdS was evaluated by producing hydrogen. The hydrogen production rate on MoS2/CdS reached 192 μmol·h−1. This performance was stable during three repeated photocatalytic processes.

Sign in / Sign up

Export Citation Format

Share Document