A Study of Defects in Ordered Ternary Semiconductor Epilayers

1988 ◽  
Vol 130 ◽  
Author(s):  
S. McKernan ◽  
C. B. Carter ◽  
D. P. Bour ◽  
J. R. Shealy
Keyword(s):  
Electron Microscope ◽  
Stacking Faults ◽  
Dark Field ◽  
Growth Surface ◽  
Ordered Structure ◽  
Planar Defects ◽  
Gaas Substrates ◽  
Surface Models ◽  
Ternary Semiconductor ◽  
Very High

AbstractOrdered GaxIn1-xP epilayers grown on GaAs substrates have been studied in the electron microscope. Dark-field images and high-resolution micrographs have directly revealed the presence of an ordering of the Ga and In (111) planes. Several different planar defects have been identified in the ordered structure. There is a very high density of faults parallel to the (001) growth surface. Models for these faults have been constructed in terms of stacking faults and twin boundaries in the ordered structure. Other flat planar defects which occur approximately parallel to (111) and (111) planes can also be described in these terms.

Direct observation of ordering in (GaIn) P

1988 ◽  
Vol 3 (3) ◽  
pp. 406-409 ◽  
Author(s):  
S. McKernan ◽  
B. C. De Cooman ◽  
C. B. Carter ◽  
D. P. Bour ◽  
J. R. Shealy
Keyword(s):  
Electron Microscope ◽  
Direct Observation ◽  
Vapor Phase ◽  
Growth Conditions ◽  
Dark Field ◽  
Growth Surface ◽  
Organometallic Vapor Phase Epitaxy ◽  
Planar Defects ◽  
Group Iii ◽  
Gaas Substrates

Gax In1 − x Pepilayers grown under a range of growth conditions by organometallic vapor phase epitaxy (OMVPE) on GaAs substrates have been studied in the electron microscope. The results show the presence of an ordering of the group III sublattice parallel to some of the {111} planes. Dark-field images directly reveal ordered domains of different orientations that appear not to be perfect, but contain many planar defects parallel to the growth surface.

Overlapping Shockley/Frank Faults in 4H-SiC PiN Diodes

2006 ◽  
Vol 527-529 ◽  
pp. 383-386 ◽  
Author(s):  
Mark E. Twigg ◽  
Robert E. Stahlbush ◽  
Peter A. Losee ◽  
Can Hua Li ◽  
I. Bhat ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Light Emission ◽  
Stacking Faults ◽  
Dark Field ◽  
Pin Diodes ◽  
Plan View ◽  
Planar Defects ◽  
Burgers Vector ◽  
Partial Dislocations ◽  
Transmission Electron

Using light emission imaging (LEI), we have determined that not all planar defects in 4H-SiC PiN diodes expand in response to bias. Accordingly, plan-view transmission electron microscopy (TEM) observations of these diodes indicate that these static planar defects are different in structure from the mobile stacking faults (SFs) that have been previously observed in 4H-SiC PiN diodes. Bright and dark field TEM observations reveal that such planar defects are bounded by partial dislocations, and that the SFs associated with these partials display both Frank and Shockley character. That is, the Burgers vector of such partial dislocations is 1/12<4-403>. For sessile Frank partial dislocations, glide is severely constrained by the need to inject either atoms or vacancies into the expanding faulted layer. Furthermore, these overlapping SFs are seen to be fundamentally different from other planar defects found in 4H-SiC.

TEM Studies of Ordering in MOCVD-Grown (GaIn)P on GaAs

1987 ◽  
Vol 104 ◽  
Author(s):  
S. McKernan ◽  
B. C. De Cooman ◽  
C. B. Carter ◽  
D. P. Bour ◽  
J. R. Shealy
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Dark Field ◽  
Growth Surface ◽  
Gaas Substrates ◽  
High Resolution Images

ABSTRACTGaxIn(1−x)P epilayers grown on GaAs substrates by MOVPE, for different growth temperatures and values of x∼0.5, have been studied by electron microscopy. The results indicate that under certain conditions the ternary epilayer is ordered parallel to the (111) plane. Dark-field images obtained using the superlattice reflections reveal ordered domains of different orientations. High-resolution images have been obtained from the ordered domains. The structure of these domains is not perfect but contains many planar faults parallel to the growth surface.

Crystal Defects In Gan On (0001) Sapphire

1997 ◽  
Vol 482 ◽  
Author(s):  
Matthew T. Johnson ◽  
Zhigang Mao ◽  
C. Barry Carter
Keyword(s):  
Dark Field ◽  
Crystal Defects ◽  
Growth Surface ◽  
Threading Dislocation ◽  
Defect Structures ◽  
Plan View ◽  
Planar Defects ◽  
Dark Field Imaging ◽  
Inversion Domain ◽  
Different Types

AbstractDefect structures in GaN thin films grown on (0001) sapphire have been studied using a combination of different transmission electron microscopy (TEM) techniques. Two fundamentally different types of defects are found in these films. Planar defects which lie on planes perpendicular to the growth surface are common. In some regions of the films, other planar defects are present which run parallel to the surface of the substrate. The terminology used to describe these different defects varies quite widely in the literature and includes combinations of antiphase (inversion) domain boundaries and stacking faults. The second type of defect is generally referred to as a threading dislocation since many thread through the whole thickness of the film. Dislocations with different Burgers vectors have been identified in this work and in previous studies; these dislocations usually have a component of their Burgers vector lying normal to the (0001) plane. The overall defect structures in these films have been characterized using conventional bright-field and dark-field imaging. The detailed structure of the individual defects have been examined using weak-beam microscopy both in plan view and in cross section. This paper illustrates the different types of defects, both planar and linear, compares them to defects which have been characterized more thoroughly in related materials, and discuss the nomenclature of the different defect configurations.

Struktur und thermisches Verhalten von Wachstumszwillingen in dünnen kubisch flächenzentrierten Metallschichten

1965 ◽  
Vol 20 (9) ◽  
pp. 1201-1207 ◽  
Author(s):  
H. Schlötterer
Keyword(s):  
Electron Microscope ◽  
Electron Diffraction ◽  
Hexagonal Phase ◽  
Stacking Faults ◽  
Dark Field Image ◽  
Dark Field ◽  
Periodic Lattice ◽  
Double Diffraction ◽  
Polycrystalline Films ◽  
Matrix Orientation

Single crystal films prepared by evaporation of silver, gold, copper, and nickel on heated cleaved rocksalt crystals and polycrystalline films of silver, gold, copper, platinum, aluminum, and nickel have been studied by transmission electron microscopy and electron diffraction. By means of electron microscope dark-field image and selected area diffraction technique the existence of small growth twins in the films is shown. Extra spots observed in the electron diffraction diagram can be explained partly as spots of the four twin orientations, partly as arising from double diffraction of the (100) matrix orientation and of a twin orientation. In the case of polycrystalline films the double diffraction mechanism results in additional diffraction rings seeming not to belong to the normal face-centred cubic lattice. The assumption of an hexagonal phase or of stacking faults or of periodic lattice defects cannot explain all the extra spots and additional rings.The changing diffraction contrast of thick and thin microtwins obviously depends on the different reflection conditions in the electron microscope. It is shown that it is very complicated to distinguish stacking faults from microtwins, but some criteria of distinction are given.By means of a heating stage the single crystals have been heated in the electron microscope up to more than 1000 °C. The thermal behaviour of the twins has been studied in detail. It can be observed that up to 95% of the twins become invisible by transformation from the twin orientation to the (100) matrix orientation. It is concluded from the experiments that the transformation nucleates at the top or bottom of the thin films. Nevertheless more than 1013 twins and stacking faults per cm3 remain unchanged inspite of heating to temperatures near the melting point of the bulk metal.

ADF-STEM Imaging of Strained GaN0.045As0.955 Epitaxial Layers on (100) GaAs Substrates

2006 ◽  
Vol 982 ◽  
Author(s):  
X. Wu ◽  
M.D. Robertson ◽  
J.A. Gupta ◽  
J.-M. Baribeau ◽  
J.C. Bennett ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Gaas Substrate ◽  
Misfit Strain ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Gaas Substrates ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field

ABSTRACTThe annular dark field (ADF) image contrast of a 0.92% tensile strained GaN0.045As0.955 layer on GaAs substrate was studied with a scanning transmission electron microscope (STEM) as a function of ADF detector inner semi-angles ranging from 28 mrad to 90 mrad. The GaN0.045As0.955 layers were brighter than the surrounding GaAs for the values of ADF detector semiangle up to 65 mrad, and the measured contrast decreased with increasing ADF detector inner semi-angle. For a 37 nm thick specimen, the GaN0.045As0.955 intensity is about 13% higher than that of GaAs in the 28 mrad ADF detector inner semi-angle. Multislice simulations show that the displacement around substitutional N atoms plays an important role in the observed ADF-STEM contrast, while the contribution to the contrast due to misfit strain between GaN0.045As0.955 and GaAs is small.

TEM and PL characterisation of MBE-grown epitaxial GaN/GaAs

1996 ◽  
Vol 423 ◽  
Author(s):  
Yan Xin ◽  
P. D. Brown ◽  
C. B. Boothroyd ◽  
A. R. Preston ◽  
C. J. Humphreys ◽  
...  
Keyword(s):  
Single Crystal ◽  
Growth Conditions ◽  
Convergent Beam Electron Diffraction ◽  
Growth Surface ◽  
Gaas Substrates ◽  
Transmission Electron ◽  
Columnar Grains ◽  
Convergent Beam ◽  
Threading Defects ◽  
Very High

AbstractMBE-grown epitaxial GaN deposited at 700°C on {001}, {111}A and B GaAs has been characterised using the combined techniques of transmission electron microscopy (TEM) and photoluminescence (PL). On both { 111 } A and 111 B GaAs substrates, single crystal wurtzite GaN was formed, but with very high densities of threading defects. Best epitaxy occurred on 111B GaAs in accordance with PL measurements. An amorphous phase was identified at the GaN/{ 111 }A GaAs interface and the GaN epilayer evolved in this instance with the same Nterminated growth surface as for the case of growth on 111 B GaAs, as determined by convergent beam electron diffraction (CBED). Growth on {001} GaAs produced highly faulted columnar grains of zincblende GaN. Conversely, growth on {001} GaAs under an additional arsenic flux at 700°C resulted in the deposition of single crystal zincblende GaN with a high density of stacking faults and microtwins. Thus, the microstructure of epitaxial GaN depends very much on the detailed growth conditions and substrate orientations used.

Utilizing Dark Field Electron Microscopy to Produce Lantern Slides

1974 ◽  
Vol 32 ◽  
pp. 116-117
Author(s):  
J. N. Meador ◽  
C. N. Sun ◽  
H. J. White
Keyword(s):  
Electron Microscope ◽  
Electron Micrographs ◽  
Dark Field ◽  
Limiting Factor ◽  
Clinical Laboratories ◽  
Field Electron ◽  
Time Element ◽  
Field Electron Microscopy ◽  
Dark Field Electron ◽  
Dark Field Micrographs

The electron microscope is being utilized more and more in clinical laboratories for pathologic diagnosis. One of the major problems in the utilization of the electron microscope for diagnostic purposes is the time element involved. Recent experimentation with rapid embedding has shown that this long phase of the process can be greatly shortened. In rush cases the making of projection slides can be eliminated by taking dark field electron micrographs which show up as a positive ready for use. The major limiting factor for use of dark field micrographs is resolution. However, for conference purposes electron micrographs are usually taken at 2.500X to 8.000X. At these low magnifications the resolution obtained is quite acceptable.

Direct Observation of the Diffusionless β → β + ω Transformation in Titanium Alloys

1971 ◽  
Vol 29 ◽  
pp. 122-123
Author(s):  
N. E. Paton ◽  
D. de Fontaine ◽  
J. C. Williams
Keyword(s):  
Electron Microscope ◽  
Titanium Alloys ◽  
Direct Observation ◽  
Dark Field ◽  
X Ray Diffraction ◽  
Resistivity Measurements ◽  
Selected Area Electron Diffraction ◽  
Ti Alloys ◽  
Thin Foils ◽  
Field Device

The electron microscope has been used to study the diffusionless β → β + ω transformation occurring in certain titanium alloys at low temperatures. Evidence for such a transformation was obtained by Cometto et al by means of x-ray diffraction and resistivity measurements on a Ti-Nb alloy. The present work shows that this type of transformation can occur in several Ti alloys of suitable composition, and some of the details of the transformation are elucidated by means of direct observation in the electron microscope.Thin foils were examined in a Philips EM-300 electron microscope equipped with a uniaxial tilt, liquid nitrogen cooled, cold stage and a high resolution dark field device. Selected area electron diffraction was used to identify the phases present and the ω-phase was imaged in dark field by using a (101)ω reflection. Alloys were water quenched from 950°C, thinned, and mounted between copper grids to minimize temperature gradients in the foil.

Resolution in the Scanning Transmission Electron Microscope

1972 ◽  
Vol 30 ◽  
pp. 454-455
Author(s):  
M. G. R. Thomson
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Spherical Aberration ◽  
Signal To Noise Ratio ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Objective Lens ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

The variation of contrast and signal to noise ratio with change in detector solid angle in the high resolution scanning transmission electron microscope was discussed in an earlier paper. In that paper the conclusions were that the most favourable conditions for the imaging of isolated single heavy atoms were, using the notation in figure 1, either bright field phase contrast with β0⋍0.5 α0, or dark field with an annular detector subtending an angle between ao and effectively π/2.The microscope is represented simply by the model illustrated in figure 1, and the objective lens is characterised by its coefficient of spherical aberration Cs. All the results for the Scanning Transmission Electron Microscope (STEM) may with care be applied to the Conventional Electron Microscope (CEM). The object atom is represented as detailed in reference 2, except that ϕ(θ) is taken to be the constant ϕ(0) to simplify the integration. This is reasonable for θ ≤ 0.1 θ0, where 60 is the screening angle.

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