TEM study of epitactically grown GaAs/ScxEr1−xAs/GaAs heterostructures

1990 ◽  
Vol 48 (4) ◽  
pp. 586-587
Author(s):  
Jane G. Zhu
Keyword(s):  
Crystal Structure ◽  
Lattice Mismatch ◽  
New Physics ◽  
Dark Field ◽  
Salt Crystal ◽  
Plan View ◽  
Weak Beam ◽  
Transmission Electron ◽  
Potential Applications ◽  
The Difference

The incorporation of metal layers into semiconductors is attracting growing attention due to potential applications in novel electronic devices and new physics of very thin metal films in semiconductors. This paper reports the growth of GaAs/ScxEr1−xAs/GaAs (x=0 and ∼0.3) on (100) GaAs substrates by molecular beam epitaxy (MBE) and the characterization of these heterostructures by transmission electron microscopy (TEM). ErAs, ScAs and many other rare-earth arsenides have the rock-salt crystal structure, which is different from the zinc-blende structure of GaAs. The difference in the crystal structure substantially affects the heteroepitactic growth. The lattice mismatch between ErAs (ScAs) and GaAs is 1.6% (-3.3%). Lattice-matched growth of ScxEr1−xAs/GaAs can be obtained at x=0.32. TEM has been used in this study extensively to characterize the microstructure and the growth-related defects. Both cross-section and plan-view samples have been studied using strong-beam, weak-beam dark-field and high-resolution imaging, as well as selected-area diffraction.

Dissociation of Misfit Dislocations in GeSi/{111}Si Interfaces

1993 ◽  
Vol 319 ◽  
Author(s):  
Frank Ernst
Keyword(s):  
Lattice Mismatch ◽  
Stacking Faults ◽  
Chemical Vapor ◽  
Interfacial Area ◽  
Dark Field ◽  
Dislocation Network ◽  
Misfit Dislocations ◽  
Si Substrates ◽  
Weak Beam ◽  
Transmission Electron

AbstractThe accommodation of lattice mismatch is studied in Ge0.15Si0.85 layers grown epitaxially on {111}-oriented Si substrates by chemical vapor deposition (CVD) at 1100°C. Weak beam dark field microscopy reveals a regular misfit dislocation network, which resembles the honeycomb network of edge-type dislocations anticipated by the O-lattice theory. In contrast to the latter, however, the real network exhibits extended nodes where the misfit dislocations dissociate into misfit partial dislocations. Between the partials, high resolution transmission electron microscopy (HRTEM) reveals intrinsic and extrinsic stacking faults. Owing to the presence of these stacking faults, three different atomistic structures of the GeSi/Si interface coexist and compete for the interfacial area according to their energy. The observed configuration is shown to minimize the total energy of the interface.

Transmission Electron Microscopy studies of the vacancy ordering in YSI2-X thin films

1991 ◽  
Vol 49 ◽  
pp. 562-563
Author(s):  
F.-R. Chen ◽  
T. L. Lee ◽  
L. J. Chen
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
Thin Films ◽  
Diffraction Pattern ◽  
Annealing Temperature ◽  
Lattice Mismatch ◽  
Si Substrate ◽  
Metal Thin Films ◽  
Transmission Electron ◽  
Vacancy Ordering

YSi2-x thin films were grown by depositing the yttrium metal thin films on (111)Si substrate followed by a rapid thermal annealing (RTA) at 450 to 1100°C. The x value of the YSi2-x films ranges from 0 to 0.3. The (0001) plane of the YSi2-x films have an ideal zero lattice mismatch relative to (111)Si surface lattice. The YSi2 has the hexagonal AlB2 crystal structure. The orientation relationship with Si was determined from the diffraction pattern shown in figure 1(a) to be and . The diffraction pattern in figure 1(a) was taken from a specimen annealed at 500°C for 15 second. As the annealing temperature was increased to 600°C, superlattice diffraction spots appear at position as seen in figure 1(b) which may be due to vacancy ordering in the YSi2-x films. The ordered vacancies in YSi2-x form a mesh in Si plane suggested by a LEED experiment.

TEM evaluation of graded SixGe1-x heterolayers

1991 ◽  
Vol 49 ◽  
pp. 894-895
Author(s):  
N. David Theodore ◽  
Mamoru Tomozane ◽  
Ming Liaw
Keyword(s):  
Heterojunction Bipolar Transistors ◽  
Gas Flow ◽  
Field Effect Transistors ◽  
Chemical Vapor ◽  
Dark Field ◽  
Bipolar Transistors ◽  
Structural Quality ◽  
Weak Beam ◽  
Transmission Electron ◽  
And Behavior

There is extensive interest in SiGe for use in heterojunction bipolar transistors. SiGe/Si superlattices are also of interest because of their potential for use in infrared detectors and field-effect transistors. The processing required for these materials is quite compatible with existing silicon technology. However, before SiGe can be used extensively for devices, there is a need to understand and then control the origin and behavior of defects in the materials. The present study was aimed at investigating the structural quality of, and the behavior of defects in, graded SiGe layers grown by chemical vapor deposition (CVD).The structures investigated in this study consisted of Si1-xGex[x=0.16]/Si1-xGex[x= 0.14, 0.13, 0.12, 0.10, 0.09, 0.07, 0.05, 0.04, 0.005, 0]/epi-Si/substrate heterolayers grown by CVD. The Si1-xGex layers were isochronally grown [t = 0.4 minutes per layer], with gas-flow rates being adjusted to control composition. Cross-section TEM specimens were prepared in the 110 geometry. These were then analyzed using two-beam bright-field, dark-field and weak-beam images. A JEOL JEM 200CX transmission electron microscope was used, operating at 200 kV.

scholarly journals Characterization Microstructural and Electrochemical of AgPd Alloy Bimetallic Nanoparticles

MRS Advances ◽  
2017 ◽  
Vol 2 (50) ◽  
pp. 2857-2863 ◽  
Author(s):  
A. Santoveña ◽  
C. Rodriguez-Proenza ◽  
J.A. Maya-Cornejo ◽  
A. Ruiz-Baltazar ◽  
D. Bahena ◽  
...  
Keyword(s):  
Bimetallic Nanoparticles ◽  
Electrochemical Characterizations ◽  
Dark Field ◽  
High Catalytic Activity ◽  
X Ray Diffraction ◽  
Bimetallic Systems ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Potential Applications

ABSTRACTBimetallic nanoparticles are of special interest for their potential applications to fuel cells, among the bimetallic systems, AuPd bimetallic nanoparticles have received great interest as they can be widely used as effective catalysts for various electrochemical reactions. Monodisperse AgPd alloy nanoparticles were synthesized by polyol method using silver nitrate and potassium tetrachloropalladate(II) in ethylene glycol as the reducing agent at 160 °C. Structural, compositional and electrochemical characterizations of synthesized bimetallic nanoparticles were investigated. High-angle annular dark field scanning/transmission electron microscopy (HAADF-STEM) images and parallel beam X-ray diffraction (XRD) of the bimetallic nanoparticles were obtained. XRD and the contrast of the HAADF-STEM images show that the bimetallic nanoparticles have an alloy structure. Cyclic voltammetry was carried out in order to confirm the electrochemical responses of the AgPd/C electrocatalysts for methanol oxidation. Thanks to the narrow size distribution of the AgPd alloy bimetallic nanoparticles (9.15 nm) the supported AgPd/C electrocatalysts have high catalytic activity toward methanol electro-oxidation.

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.

Trace-element remobilisation from W–Sn–U–Pb zoned hematite: Nanoscale insights into a mineral geochronometer behaviour during interaction with fluids

2020 ◽  
Vol 84 (4) ◽  
pp. 502-516 ◽  
Author(s):  
Max R. Verdugo-Ihl ◽  
Cristiana L. Ciobanu ◽  
Nigel J. Cook ◽  
Kathy Ehrig ◽  
Ashley Slattery ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Dark Field ◽  
Pb Isotope ◽  
Transmission Electron ◽  
Low Concentrations ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Inclusion Trails ◽  
Isotope Systematics

AbstractPreferential removal of W relative to other trace elements from zoned, W–Sn–U–Pb-bearing hematite coupled with disturbance of U–Pb isotope systematics is attributed to pseudomorphic replacement via coupled dissolution reprecipitation reaction (CDRR). This hematite has been studied down to the nanoscale to understand the mechanisms leading to compositional and U/Pb isotope heterogeneity at the grain scale. High-Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF STEM) imaging of foils extracted in situ from three locations across the W-rich to W-depleted domains show lattice-scale defects and crystal structure modifications adjacent to twin planes. Secondary sets of twins and associated splays are common, but wider (up to ~100 nm) inclusion trails occur only at the boundary between the W-rich and W-depleted domains. STEM energy-dispersive X-ray mapping reveals W- and Pb-enrichment along 2–3 nm-wide features defining the twin planes; W-bearing nanoparticles occur along the splays. Tungsten and Pb are both present, albeit at low concentrations, within Na–K–Cl-bearing inclusions along the trails. HAADF STEM imaging of hematite reveals modifications relative to ideal crystal structure. A two-fold hematite superstructure (a = b = c = 10.85 Å; α = β = γ = 55.28°) involving oxygen vacancies was constructed and assessed by STEM simulations with a good match to data. This model can account for significant W release during interaction with fluids percolating through twin planes and secondary structures as CDRR progresses from the zoned domain, otherwise apparently undisturbed at the micrometre scale. Lead remobilisation is confirmed here at the nanoscale and is responsible for a disturbance of U/Pb ratios in hematite affected by CDRR. Twin planes can provide pathways for fluid percolation and metal entrapment during post-crystallisation overprinting. The presence of complex twinning can therefore predict potential disturbances of isotope systems in hematite that will affect its performance as a robust geochronometer.

A Weak-Beam Dark-Field Study of Stacking Faults in a Co-Cr-Mo-C Alloy

1976 ◽  
Vol 34 ◽  
pp. 378-379
Author(s):  
Ernest L. Hall
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Field Study ◽  
Previous Investigation ◽  
Stacking Faults ◽  
Aging Treatment ◽  
Dark Field ◽  
Bright Field ◽  
Weak Beam ◽  
Transmission Electron

In a previous investigation (1) of the mechanisms of strengthening in a Co-28 wt% Cr-6 wt% Mo-0.29 wt% C alloy (H.S. 21), it was observed that the fee regions of this alloy were generally heavily faulted, and the density of stacking faults was seen to be dependent upon the time and temperature of the aging treatment after solutionizing. In the present study, weak-beam darkfield transmission electron microscopy was used to examine the interaction of stacking faults on intersecting {111} planes. The alloy was solutionized at 1230°C for 4 hours, quenched in water, and aged at 650°C for 8 hours in order to produce a suitable density of faults. Figure 1 shows a bright-field (BF), weak-beam dark-field (WB DF) pair of micrographs illustrating both the successful and unsuccessful intersection of faults which exist in different ﹛111﹜ planes.

Deposition and anneal behavior of Al-1.5%Cu films: TEM characterization

1991 ◽  
Vol 49 ◽  
pp. 884-885
Author(s):  
N. David Theodore ◽  
Mike Dreyer ◽  
Charles Varker
Keyword(s):  
Integrated Circuits ◽  
Imaging Techniques ◽  
Dark Field ◽  
Time To Failure ◽  
Plan View ◽  
Cu Films ◽  
Transmission Electron ◽  
Grain Size Distributions ◽  
The Mean ◽  
Mean Time

Al-1.5%Cu materials are of interest for interconnect-metallization in semiconductor integrated-circuits. It is known from the literature that the mean-time-to-failure (MTF) due to electromigration of the Al-1.5%Cu interconnects depends on the microstructure of the materials. A correlation is seen for instance between grain-size distributions in the material and the MTF. Uniform large-grained distributions improve lifetime. The present study evaluated the microstructure of Al-1.5%Cu films deposited and annealed under different conditions.Al-1.5%Cu films had been deposited at 25°C and at 300°C; the layers had then been annealed at 300°C for 17 hours, prior to TEM investigation. Plan-view TEM specimens were prepared in the 100 substrategeometry, and cross-section TEM specimens were prepared in the 110 substrate-geometry. These were then analyzed using bright-field and dark-field TEM imaging techniques. A JEOL JEM 200CX transmission electron microscope was used for the investigation, operating at 200 kV.

A correlative study of microstructure and surface topography in Al-1.5%Cu films

1992 ◽  
Vol 50 (2) ◽  
pp. 1418-1419
Author(s):  
N. David Theodore ◽  
Bea Cao ◽  
Juan Carrejo ◽  
Peter A. Crozier
Keyword(s):  
Integrated Circuits ◽  
Surface Topography ◽  
Imaging Techniques ◽  
Dark Field ◽  
Material Surface ◽  
Silicon Dioxide Layer ◽  
Plan View ◽  
Cu Films ◽  
Transmission Electron ◽  
Multi Level

Al(Cu) is currently being used for interconnects in semiconductor integrated-circuits. Problems that arise with use of the material are electromigration, stress-migration, and corrosion. Electromigration and stress-migration behaviors of the films are known to depend on grain-sizes and distributions in the material. Surface topography of the films could possibly affect stress-migration as well as use of the material in multi-level metallization schemes. The present study investigates the extent of correlation between microstructure and surface topography in Al-1.5%Cu films.Substrates used for this study consisted of (100) silicon wafers with a 200 nm silicon-dioxide layer on top. Al(1.5%Cu) was sputtered onto the substrates; substrates were held at a temperature of 450°C during sputtering. Layer thicknesses were ∼740 nm. Scanning electron-microscopy was performed using a Cambridge 250-MK III SEM equipped with a heating stage. Plan-view TEM specimens were prepared in the 100 substrate-geometry. These were then analyzed using bright-field and dark-field TEM imaging techniques. A JEOL JEM 200CX transmission electron microscope was used for the investigation, operating at 200 kV.

Diffusion-Induced Recrystallization in Nickel/Palladium Multilayers

2011 ◽  
Vol 309-310 ◽  
pp. 195-202 ◽  
Author(s):  
Guido Schmitz ◽  
M. Kasprzak ◽  
D. Baither
Keyword(s):  
Thin Film ◽  
Driving Force ◽  
Lattice Mismatch ◽  
Ideal Strength ◽  
Diffusion Couples ◽  
X Ray ◽  
Transmission Electron ◽  
The Difference ◽  
Sputter Deposited ◽  
The Ideal

Diffusion-Induced Recrystallization (DIR) is investigated in size mismatched thin film interdiffusion couples. New grains formed in the diffusion zone are characterized by distinctive composition levels which seem to be characteristic to the interdiffusing materials. In this paper, we analyzed sputter-deposited Ni/Pd films. The lattice mismatch and the driving force are varied by pre-alloying one side of the diffusion couples. Recrystallization was detected after heat treatment by transmission electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffractometry. We determined characteristic concentrations from XRD data. Remarkably, the difference between the concentration inside newly formed grains and that of the parent layers remains practically constant, when initial layer concentration is varied. Also, the characteristic compositions are nearly independent of temperature. A thermo-mechanic model has been derived, which demonstrates that the observed concentration differences are such that the stress in front of the moving grain boundary reaches a maximum close to the ideal strength of the host material.

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