Cathodoluminescence of Ingaas-GaAs Single Heterostructures

1986 ◽  
Vol 82 ◽  
Author(s):  
E.A. Fitzgerald ◽  
K.L. Kavanagh ◽  
D.G Ast ◽  
P.D. Kirchner ◽  
G.D. Pettit ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Dislocation Density ◽  
Major Effect ◽  
Misfit Dislocations ◽  
Interface Morphology ◽  
Sem Images ◽  
Transmission Electron ◽  
Gaas Buffer Layer ◽  
Order Of Magnitude ◽  
Recombination Centers

ABSTRACTMismatched InGaAs-GaAs epitaxial layers were grown by molecular beam epitaxy (MBE) on substrates containing 9800 or <100 dislocations/cm2. Cathodoluminescence (CL), transmission electron microscopy (TEM), Rutherford backscattering spectroscopy (RBS), and energy dispersive x-ray analysis (EDX) were used to analyze the effect of mismatch and substrate dislocation density on interface morphology. Surface ridges in scanning electron microscopy (SEM) images were found to correlate with areas of high recombination in CL. The spacing of dark recombination lines seen in CL was found to be an order of magnitude larger than the spacing of misfit dislocations seen in TEM. CL/IEM correlation reveals that some areas of the misfit array act more strongly as recombination centers than others. CL of step etched samples show that interface defects propagate into the GaAs buffer layer to depths of 4000 Å below the interface. The substrate dislocation density does not have a major effect on the number or spacing of the dark recombination lines.

TEM investigation of defect reduction and etch pit formation in GaN

2003 ◽  
Vol 798 ◽  
Author(s):  
Angelika Vennemann ◽  
Jens Dennemarck ◽  
Roland Kröger ◽  
Tim Böttcher ◽  
Detlef Hommel ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Dislocation Density ◽  
Line Tension ◽  
Threading Dislocations ◽  
Dislocation Loops ◽  
Etch Pits ◽  
Defect Reduction ◽  
Transmission Electron ◽  
Order Of Magnitude ◽  
Edge Dislocations

ABSTRACTGaN samples of this study were chemically wet etched to gain easier access to the dislocation sturcture. The scanning electron microscopy and transmission electron microscopy investigations revealed four different types of etch pits. After brief etching, several dislocations with screw component showed large etch pits, which may be correlated with the core of the screw dislocation. By means of SiNx micromasking the dislocation density could be reduced by more than one order of magnitude. The reduction of threading dislocations in the SiNx region in GaN grown on 〈0001〉 sapphire is due to bending of the threading dislocations into the {0001} plane, such that they form dislocation loops if they meet dislocations with opposite Burgers vectors. Accordingly, the achievable reduction of the dislocation density is limited by the probability that these dislocations interact. Edge dislocations bend more easily on account of their low line tension. This results in a preferential bending and reduction of dislocations with edge character.

Hacroscopic Defects in Epitaxial Silicon on Simox and in Annealed SIMOX

1987 ◽  
Vol 107 ◽  
Author(s):  
A. Mogro-Campero ◽  
N. Lewis ◽  
S.A. Al-Marayati
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Temperature ◽  
Dislocation Density ◽  
Silicon Surface ◽  
Epitaxial Silicon ◽  
Buried Oxide ◽  
Transmission Electron ◽  
Annealing Step ◽  
Order Of Magnitude

AbstractEpitaxial silicon layers of 5¼m were grown on SIMOX wafers. The dislocation density decreases by more than an order of magnitude as a function of distance away from the buried oxide. Shallow pits (about 0.5 urn deep and several um wide) are observed on the epitaxial layer with a density of 1-2 mm2. Their density did not change with various processing variations. A search for the origin of the pits by transmission electron microscopy reveals that they may be associated with regions of irregularly thin and sometimes missing buried oxide, which appear after the usual high temperature SIMOX annealing step. These defective regions in the buried oxide appear to initiate twinned growth in the epitaxial silicon, and are associated with pits at the top epitaxial silicon surface.

Misfit dislocations in heteroepitaxial systems with low dislocation density

1978 ◽  
Vol 36 (1) ◽  
pp. 132-133
Author(s):  
W. Hagen ◽  
H. Strunk
Keyword(s):  
Electron Microscopy ◽  
Dislocation Density ◽  
Misfit Dislocations ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
Transmission Electron ◽  
Low Dislocation Density ◽  
Heteroepitaxial Layers ◽  
Transparent Area ◽  
Electron Transparent Area

The growth of heteroepitaxial layers causes stress across the interface which in a certain range of layer thickness may he relaxed by the formation of misfit dislocations at the interface. Systematic investigations of such misfit structures by transmission electron microscopy (TEM) have previously heen conducted only on systems with a relatively large misfit parameter f, i.e. with a high dislocation density. However, this case presents difficulties in the analysis because of the complexity of the dense structures.Interfaces containing a low density of misfit dislocations, e.g. heteroepitaxial systems with low misfit, should consequently be investigated. High voltage electron microscopy (HVEM) enables us to study specimens of several μm in thickness and offers decisive advantages over 100 kV TEM: i) generally, specimens can he prepared by thinning the substrate only, ii) thick foils are mechanically stable, which allows the preparation of specimens with an electron transparent area of several mm2.We report here new results on the initial formation of misfit dislocation structures in the heteroepitaxial system Ge on GaAs (f = 0.074%).

scholarly journals Study of Strain Relaxation in InAs/GaAs Strained-layer Superlattices by Raman Spectroscopy and Electron Microscopy

2000 ◽  
Vol 53 (5) ◽  
pp. 697
Author(s):  
A. K. Gutakovsky ◽  
S. M. Pintus ◽  
A. I . Toropov ◽  
N. T. Moshegov ◽  
V. A. Haisler ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Raman Spectroscopy ◽  
Elastic Strain ◽  
Strain Relaxation ◽  
Misfit Dislocations ◽  
Strained Layer ◽  
Transmission Electron ◽  
Dimensional Network ◽  
Order Of Magnitude ◽  
Strained Layer Superlattices

InAs/GaAs strained-layer superlattices (SLS) grown on a GaAs(100) substrate were studied by both Raman spectroscopy (RS) and transmission electron microscopy (TEM). It was shown that the interfaces inside the superlattice are coherent, but the superlattice–substrate interface contain an orthogonal two-dimensional network of 60° misfit dislocations. Using these experimental data values of elastic strain in individual layers and the average values of the residual elastic strain in SLS were determined. The latter are approximately one order of magnitude higher than theoretically predicted data, which suggests that the relaxation of elastic strains was not fully complete. Subsequent annealing of these structures led to the generation of more misfit dislocations, consistent with further relaxation of elastic strain.

scholarly journals Antitumor Potential of Green Synthesized ZnONPs Using Root Extract of Withania somnifera against Human Breast Cancer Cell Line

Separations ◽  
2021 ◽  
Vol 8 (1) ◽  
pp. 8
Author(s):  
Kollur Shiva Prasad ◽  
Shashanka K Prasad ◽  
Ravindra Veerapur ◽  
Ghada Lamraoui ◽  
Ashwini Prasad ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Cell Line ◽  
Withania Somnifera ◽  
Root Extract ◽  
Dependent Manner ◽  
Sem Images ◽  
Xrd Pattern ◽  
Transmission Electron

Herein we report the synthesis of zinc oxide nanoparticles (ZnONPs) using Withania somnifera root extract (WSE) as an effective chelating agent. The microscopic techniques viz., X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) were employed to analyze the as-obtained ZnONPs. The crystalline planes observed from the XRD pattern agrees with the hexagonal wurtzite structure of the as-prepared ZnONPs. The aggregations and agglomerations observed in the SEM images indicated that the size of the as-prepared ZnONPs was between 30 and 43 nm. The interplanar distance between the lattice fringes observed in the HRTEM image was found to be 0.253 nm, which is in good agreement with the (100) plane obtained in the XRD pattern. Furthermore, the anti-breast cancer cytotoxic evaluation was carried out using the MCF-7 cell line, and the results showed significant cytotoxic effects in a dose-dependent manner.

Microstructural study of GaAs epitaxial layers on Ge(100) substrates

1995 ◽  
Vol 10 (4) ◽  
pp. 843-852 ◽  
Author(s):  
N. Guelton ◽  
R.G. Saint-Jacques ◽  
G. Lalande ◽  
J-P. Dodelet
Keyword(s):  
Electron Microscopy ◽  
Surface Preparation ◽  
Growth Conditions ◽  
Vapor Transport ◽  
Threading Dislocations ◽  
Misfit Dislocations ◽  
Antiphase Boundaries ◽  
Microstructural Study ◽  
Mismatch Strain ◽  
Transmission Electron

GaAs layers grown by close-spaced vapor transport on (100) Ge substrates have been investigated as a function of the experimental growth conditions. The effects on the microstructure of the surface preparation, substrate misorientation, and annealing were studied using optical microscopy and transmission electron microscopy. Microtwins and threading dislocations are suppressed by oxide desorption before deposition. Single domain GaAs layers have been obtained using a 50 nm thick double domain buffer layer on an annealed Ge substrate misoriented 3°toward [011]. The mismatch strain is mainly accommodated by dissociated 60°dislocations. These misfit dislocations extend along the interface by the glide of the threading dislocations inherited from the substrate, but strong interaction with antiphase boundaries (APB's) prevents them from reaching the interface. These results are discussed and compared with previous reports of GaAs growth on Ge(100).

Defect-Engineered Graded GexSi1-x Buffers on Si (001) with Extreme Low Threading Dislocation Density

1995 ◽  
Vol 378 ◽  
Author(s):  
G. Kissinger ◽  
T. Morgenstern ◽  
G. Morgenstern ◽  
H. B. Erzgräber ◽  
H. Richter
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Atomic Force Microscopy ◽  
Dislocation Density ◽  
Threading Dislocation ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Dislocation Densities ◽  
Threading Dislocation Density

AbstractStepwise equilibrated graded GexSii-x (x≤0.2) buffers with threading dislocation densities between 102 and 103 cm−2 on the whole area of 4 inch silicon wafers were grown and studied by transmission electron microscopy, defect etching, atomic force microscopy and photoluminescence spectroscopy.

Structure of vacuum-deposited Zn3P2 films

1986 ◽  
Vol 64 (10) ◽  
pp. 1369-1373 ◽  
Author(s):  
U. von Sacken ◽  
D. E. Brodie
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Film Thickness ◽  
Substrate Temperature ◽  
Columnar Structure ◽  
Major Effect ◽  
Film Structure ◽  
Electron Bombardment ◽  
Initial Growth ◽  
Transmission Electron

The structure of polycrystalline Zn3P2 films has been studied for 1- to 2-μm-thick vacuum-deposited films on glass substrates. Transmission electron microscopy and X-ray diffraction techniques have been used to obtain a detailed, quantitative analysis of the film structure. The initial growth consists of small (≤ 10 nm), randomly oriented grains. As the film thickness increases, the growth of crystallites with the {220} planes oriented approximately parallel to the substrate is favoured, and a columnar structure develops along with a highly preferred orientation. This structure has been observed directly by transmission electron microscopy of thin cross sections of the films. The size of the grains at the free surface increases with the film thickness, reaching approximately 200–300 nm when the film is 1 μm thick. The effects of substrate temperature and low-energy (0.5–2 keV) electron bombardment of the film during growth have also been studied. Neither substrate temperature nor electron bombardment appear to have a major effect on the film structure. The primary effect of electron bombardment appears to be the creation of preferred nucleation sites on the substrate.

A method of precise misorientation determination

2003 ◽  
Vol 36 (6) ◽  
pp. 1319-1323 ◽  
Author(s):  
A. Morawiec
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Spatial Resolution ◽  
Standard Procedure ◽  
Good Spatial Resolution ◽  
Transmission Electron ◽  
Order Of Magnitude ◽  
Achievable Accuracy ◽  
Better Than

A method that improves the accuracy of misorientations determined from Kikuchi patterns is described. It is based on the fact that some parameters of a misorientation calculated from two orientations are more accurate than other parameters. A procedure which eliminates inaccurate elements is devised. It requires at least two foil inclinations. The quality of the approach relies on the possibility to set large sample-to-detector distances and the availability of good spatial resolution of transmission electron microscopy. Achievable accuracy is one order of magnitude better than the accuracy of the standard procedure.

Sign in / Sign up

Export Citation Format

Share Document