Atomic Structures and Chemical States of Active and Inactive Dopant Sites in Si-Doped GaN

Poisonous Vapor Adsorption on Pure and Modified Aluminum Nitride Nanosheet for Environmental Safety: A DFT Exploration

Sustainability ◽

10.3390/su122310097 ◽

2020 ◽

Vol 12 (23) ◽

pp. 10097

Author(s):

Hongni Zhang ◽

Wenzheng Du ◽

Tong Zhao ◽

Rajeev Ahuja ◽

Zhao Qian

Keyword(s):

Band Gap ◽

Adsorption Energy ◽

Density Functional ◽

Theoretical Work ◽

Environmental Safety ◽

Atomic Scale ◽

Atomic Structures ◽

Vapor Sensing ◽

Two Dimensional Materials ◽

Si Doped

Through Density Functional Theory (DFT), we have unveiled the atomic structures, adsorption characteristics and electronic structures of the poisonous and explosive vapor, m-dinitrobenzene (m-DNB), on pure, defective and various doped AlN nanosheets from a physical perspective. It is found that the adsorption energy, band gap change and sensitivity to the vapor are significantly increased through atomic-scale modification of the nanosheet. The AlN monolayer with Al-N divacancy has the largest adsorption energy and has potential to be utilized as adsorption or filtration materials for m-DNB vapor. The Si-doped AlN nanosheet possesses a much larger band gap change (−0.691 eV) than the pure nanosheet (−0.092 eV) after adsorption and has a moderate adsorption energy, which could be candidate material for explosive vapor sensing. This theoretical work is proposed to provide guidance and clue for experimentalists to develop more effective two-dimensional materials for environmental safety and sustainability.

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Atomic Structures of Planar Defects in Si and GaAs

MRS Proceedings ◽

10.1557/proc-262-209 ◽

1992 ◽

Vol 262 ◽

Cited By ~ 1

Author(s):

S. Takeda ◽

S. Muto ◽

M. Hirata

Keyword(s):

Experimental Evidence ◽

Diffuse Scattering ◽

Planar Defect ◽

Dangling Bond ◽

Hrem Image ◽

Planar Defects ◽

Atomic Structures ◽

Gaas Matrix ◽

Si Doped ◽

Diffraction Patterns

ABSTRACTAtomic structures of planar defects in Si and GaAs have been studied by TEM. An HREM image of the edge of {113} planar defect has been obtained with <110> incidence. An analysis of the image has showed diat the edge consists of 5-, 6- and 7-membered rings without dangling bond. Anisotropie morphology of the defect could be understood from the model proposed in this report. Weak diffuse scattering and an extinction rule in diffraction patterns from the defect have been found. The experimental evidence has supported the model of the {113} defect.A planar defect on {111} in a heavily Si doped GaAs has been studied. The result has indicated that Si precipitates on the two {111} net planes inserted in the GaAs matrix.

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The study of interfacial reactions of nickel thin films on GaAs

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100074616 ◽

1983 ◽

Vol 41 ◽

pp. 156-157

Author(s):

L.J. Chen ◽

Y.F. Hsieh

Keyword(s):

Thin Films ◽

Integrated Circuits ◽

Interfacial Reactions ◽

Metal Contacts ◽

Nickel Thin Films ◽

Thin Foils ◽

The Status ◽

Si Doped ◽

Electron Microscopes

One measure of the maturity of a device technology is the ease and reliability of applying contact metallurgy. Compared to metal contact of silicon, the status of GaAs metallization is still at its primitive stage. With the advent of GaAs MESFET and integrated circuits, very stringent requirements were placed on their metal contacts. During the past few years, extensive researches have been conducted in the area of Au-Ge-Ni in order to lower contact resistances and improve uniformity. In this paper, we report the results of TEM study of interfacial reactions between Ni and GaAs as part of the attempt to understand the role of nickel in Au-Ge-Ni contact of GaAs.N-type, Si-doped, (001) oriented GaAs wafers, 15 mil in thickness, were grown by gradient-freeze method. Nickel thin films, 300Å in thickness, were e-gun deposited on GaAs wafers. The samples were then annealed in dry N2 in a 3-zone diffusion furnace at temperatures 200°C - 600°C for 5-180 minutes. Thin foils for TEM examinations were prepared by chemical polishing from the GaA.s side. TEM investigations were performed with JE0L- 100B and JE0L-200CX electron microscopes.

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Finding the Right Problems: Some HREM Applications to Interfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100111938 ◽

1984 ◽

Vol 42 ◽

pp. 376-379

Author(s):

D. Cherns

Keyword(s):

Grain Boundaries ◽

High Resolution Electron Microscopy ◽

Boundary Structure ◽

Atomic Structures ◽

Grain Boundary Structure ◽

Resolution Electron ◽

Point To Point ◽

The Right ◽

New Generation ◽

Better Than

The use of high resolution electron microscopy (HREM) to determine the atomic structure of grain boundaries and interfaces is a topic of great current interest. Grain boundary structure has been considered for many years as central to an understanding of the mechanical and transport properties of materials. Some more recent attention has focussed on the atomic structures of metalsemiconductor interfaces which are believed to control electrical properties of contacts. The atomic structures of interfaces in semiconductor or metal multilayers is an area of growing interest for understanding the unusual electrical or mechanical properties which these new materials possess. However, although the point-to-point resolutions of currently available HREMs, ∼2-3Å, appear sufficient to solve many of these problems, few atomic models of grain boundaries and interfaces have been derived. Moreover, with a new generation of 300-400kV instruments promising resolutions in the 1.6-2.0 Å range, and resolutions better than 1.5Å expected from specialist instruments, it is an appropriate time to consider the usefulness of HREM for interface studies.

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Quasiperiodic interfaces: HREM observations of grain and phase boundaries

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100174795 ◽

1990 ◽

Vol 48 (4) ◽

pp. 332-333

Author(s):

K. L. Merkle

Keyword(s):

Atomic Structure ◽

Direct Determination ◽

Lattice Parameter ◽

Atomic Scale ◽

Misfit Dislocations ◽

Oxide Systems ◽

Atomic Structures ◽

Periodic Arrays ◽

Parameter Ratio ◽

Metal Metal

The atomic structures of internal interfaces have recently received considerable attention, not only because of their importance in determining many materials properties, but also because the atomic structure of many interfaces has become accessible to direct atomic-scale observation by modem HREM instruments. In this communication, several interface structures are examined by HREM in terms of their structural periodicities along the interface.It is well known that heterophase boundaries are generally formed by two low-index planes. Often, as is the case in many fcc metal/metal and metal/metal-oxide systems, low energy boundaries form in the cube-on-cube orientation on (111). Since the lattice parameter ratio between the two materials generally is not a rational number, such boundaries are incommensurate. Therefore, even though periodic arrays of misfit dislocations have been observed by TEM techniques for numerous heterophase systems, such interfaces are quasiperiodic on an atomic scale. Interfaces with misfit dislocations are semicoherent, where atomically well-matched regions alternate with regions of misfit. When the misfit is large, misfit localization is often difficult to detect, and direct determination of the atomic structure of the interface from HREM alone, may not be possible.

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Flux-pinning-related defect structures in melt-processed YBa2Cu3O7-x

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100150514 ◽

1993 ◽

Vol 51 ◽

pp. 936-937

Author(s):

Z. L. Wang ◽

R. Kontra ◽

A. Goyal ◽

D. M. Kroeger ◽

L.F. Allard

Keyword(s):

Volume Fraction ◽

Local Density ◽

Stacking Faults ◽

Image Resolution ◽

Defect Structures ◽

Atomic Structures ◽

Transmission Electron ◽

Point Image ◽

Related Defect ◽

Point To Point

Previous studies of Y2BaCuO5/YBa2Cu3O7-δ(Y211/Y123) interfaces in melt-processed and quench-melt-growth processed YBa2Cu3O7-δ using high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS) have revealed a high local density of stacking faults in Y123, near the Y211/Y123 interfaces. Calculations made using simple energy considerations suggested that these stacking faults may act as effective flux-pinners and may explain the observations of increased Jc with increasing volume fraction of Y211. The present paper is intended to determine the atomic structures of the observed defects. HRTEM imaging was performed using a Philips CM30 (300 kV) TEM with a point-to-point image resolution of 2.3 Å. Nano-probe EDS analysis was performed using a Philips EM400 TEM/STEM (100 kV) equipped with a field emission gun (FEG), which generated an electron probe of less than 20 Å in diameter.Stacking faults produced by excess single Cu-O layers: Figure 1 shows a HRTEM image of a Y123 film viewed along [100] (or [010]).

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High-Resolution Image Simulation of a Tilted Crystal

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100179099 ◽

1990 ◽

Vol 48 (1) ◽

pp. 68-69

Author(s):

C. J. D. Hetherington

Keyword(s):

High Resolution ◽

Crystal Thickness ◽

Thin Specimen ◽

Atomic Structures ◽

Kikuchi Lines ◽

High Resolution Images ◽

Final Estimate ◽

Simulated Images ◽

Habit Planes

Most high resolution images are not directly interpretable but must be compared with simulations based on model atomic structures and appropriate imaging conditions. Typically, the only parameters that are adjusted, in addition to the structure models, are crystal thickness and microscope defocus. Small tilts of the crystal away from the exact zone axis have only rarely been considered. It is shown here that, in the analysis of an image of a silicon twin intersection, the crystal tilt could be accurately estimated and satisfactorily included in the simulations.The micrograph shown in figure 1 was taken as part of an HREM study of indentation-induced hexagonal silicon. In this instance, the intersection of two twins on different habit planes has driven the silicon into hexagonal stacking. However, in order to confirm this observation, and in order to investigate other defects in the region, it has been necessary to simulate the image taking into account the very apparent crystal tilt. The inability to orientate the specimen at the exact [110] zone was influenced by i) the buckling of the specimen caused by strains at twin intersections, ii) the absence of Kikuchi lines or a clearly visible Laue circle in the diffraction pattern of the thin specimen and iii) the avoidance of radiation damage (which had marked effects on images taken a few minutes later following attempts to realign the crystal.) The direction of the crystal tilt was estimated by observing which of the {111} planes remained close to edge-on to the beam and hence strongly imaged. Further refinement of the direction and magnitude of the tilt was done by comparing simulated images to experimental images in a through-focal series. The presence of three different orientations of the silicon lattice aided the unambiguous determination of the tilt. The final estimate of a 0.8° tilt in the 200Å thick specimen gives atomic columns a projected width of about 3Å.

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