Growth and Characterization of Thermal Oxides on Gallium Nitride

1997 ◽  
Vol 468 ◽  
Author(s):  
Scott D. Wolter ◽  
Suzanne E. Mohney ◽  
Hari Venugopalan ◽  
Debra L. Waltemyer ◽  
Brian P. Luther
Keyword(s):  
Photoelectron Spectroscopy ◽  
Oxide Surface ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dry Air ◽  
High Temperature Electronics ◽  
Rate Limiting Step ◽  
Thermal Oxide ◽  
Device Applications ◽  
The Stability

ABSTRACTLittle information is available about the thermal oxidation of GaN. Since GaN is of interest for high temperature electronics, knowledge of the stability of GaN in potentially oxidizing environments would be useful. Furthermore, evaluation of the characteristics of the thermal oxide will provide information needed for assessing the potential of this oxide in processing or device applications.In this study, thick GaN epilayers and GaN powders were exposed to dry air at 450°C, 750°C, 900°C, 925°C, 950°C, and 1000°C for periods of 1 to 25 hours. Following oxidation, the epilayers were analyzed by x-ray photoelectron spectroscopy and glancing incidence x-ray diffraction, and the powders were analyzed by conventional x-ray diffraction. For both the GaN films and powders, significant oxidation was observed at 900°C, and the oxide was identified as monoclinic β-Ga2O3. Oxidation in dry air resulted in roughening of the oxide/GaN interface and oxide surface. In the temperature range 900°C to 1000°C, linear kinetics were observed for times up to 10 hours indicating an interfacial reaction mechanism as the rate limiting step for oxidation. An apparent activation energy of ∼72 kcal/mole was determined for this process.

Preparation of Pd/GO/Cu Electrode and Its Electrochemical Degradation for 2,4-Dichlorophenol

2020 ◽  
Vol 20 (6) ◽  
pp. 3604-3609
Author(s):  
Jian Zhang ◽  
Yuting Jiang ◽  
Bing Wang ◽  
Lanhe Zhang ◽  
Zheng Li ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Water Environment ◽  
Constant Current ◽  
Surface Element ◽  
Impregnation Method ◽  
Electrochemical Degradation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Preparation Conditions ◽  
The Stability

Chlorinated aromatic compounds (CACs) are a class of persistent organic pollutants, which have serious damage to water environment due to their own stable structure. But a good many of CACs were abandoned because of their tremendous yields and wide applications, so it is urgent to find the effective degradation methods for CACs. The electrochemical method is supposed to be a simple, environmentally friendly and effective pathway to degrade CACs. In this paper, a Pd/GO/Cu composite electrode was prepared by a combination of impregnation method and constant current electrodeposition method, which showed good electrochemical degradation efficiency for the 2,4-dichlorophenol. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the surface structure, functional group composition, crystal structure and surface element valence of the electrode. Moreover, the stability of the electrode was investigated, and the preparation conditions of the electrode were optimized.

X-ray photoelectron spectroscopy and x-ray diffraction study of the thermal oxide on gallium nitride

1997 ◽  
Vol 70 (16) ◽  
pp. 2156-2158 ◽  
Author(s):  
S. D. Wolter ◽  
B. P. Luther ◽  
D. L. Waltemyer ◽  
C. Önneby ◽  
S. E. Mohney ◽  
...  
Keyword(s):  
Gallium Nitride ◽  
Diffraction Study ◽  
Photoelectron Spectroscopy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Thermal Oxide

scholarly journals FeCrAlloy Monoliths Coated with Ni/Al2O3 Applied to the Low-Temperature Production of Ethylene

Catalysts ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 291 ◽  
Author(s):  
Paula Brussino ◽  
Juan Bortolozzi ◽  
Oihane Sanz ◽  
Mario Montes ◽  
María Ulla ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Catalyst Layer ◽  
X Ray Diffraction ◽  
Ethane Conversion ◽  
X Ray ◽  
Structured Catalyst ◽  
Temperature Programmed ◽  
Ni Species ◽  
The Stability ◽  
Geometric Surface

This paper investigates the oxidative dehydrogenation of ethane to produce ethylene at low temperatures (500 °C) in metallic structured substrates. To check this point, the FeCrAlloy® monoliths with different channel sizes (289–2360 cpsi) were prepared. The monoliths were coated with a Ni/Al2O3 catalyst (by washcoating of alumina and the latter nickel impregnation) and characterized by Scanning Electron Microscopy and Energy-Dispersive X-ray analysis (SEM-EDX), Temperature-Programmed Reduction (TPR), X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). The catalytic results showed that all monoliths coated with ~300 mg of catalyst presented similar ethane conversion (15%) at 450 °C. However, the lowest selectivity to ethylene was found for the monolith with the lower channel size and the higher geometric surface area, where a heterogeneous catalyst layer with Ni enriched islands was generated. Therefore, it can be said that the selectivity to ethylene is linked to the distribution of Ni species on the support (alumina). Nevertheless, in all cases the selectivity was high (above 70%). On the other hand, the stability in reaction tests of one of the coated monoliths was done. This structured catalyst proved to be more stable under reaction conditions than the powder catalyst, with an initial slight drop in the first 8 h but after that, constant activity for the 152 h left.

scholarly journals MnO2-loaded activated carbon and its adsorption of formaldehyde

BioResources ◽  
2019 ◽  
Vol 14 (3) ◽  
pp. 7193-7212 ◽  
Author(s):  
Liangcai Wang ◽  
Yishuang Wu ◽  
Shasha Liu ◽  
Yimeng Zhang ◽  
Yu Chen ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Photoelectron Spectroscopy ◽  
Infrared Spectrometry ◽  
Adsorption Efficiency ◽  
X Ray Diffraction ◽  
Isothermal Model ◽  
X Ray ◽  
Preparation Conditions ◽  
The Stability ◽  
Coconut Shell Activated Carbon

Coconut shell activated carbon (AC) loaded with MnO2 was tested as an adsorbent for formaldehyde. Preparation conditions of MnO2-loaded AC (MnO2-AC) were optimized. The resulting AC and MnO2-AC were characterized by scanning electron microscopy, Brunauer-Emmet-Teller analysis, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometry, and X-ray diffraction. The results showed that the adsorption efficiency of formaldehyde (3.5 mg/L) by MnO2-AC (concentration of manganese nitrate/sodium carbonate was 0.3 mol/L, impregnation oscillation time of 4 h, calcination temperature and time of 350 C and 4 h, respectively) was 93.1%, which increased by 251% compared to that of the AC. The adsorption equilibrium of MnO2-AC was achieved after 4 h. With increasing dosage of MnO2-AC, the rate of increasing of the adsorption efficiency became more gradual. The adsorption process of the formaldehyde solution with a low concentration fit the Langmuir adsorption isothermal model, where the adsorption capacity was 9.22 mg/g. The stability and regenerability of MnO2-AC were good.

scholarly journals Microwave heating oxidative stabilization of KMnO4 modified polyacrylonitrile-based carbon fiber precursor

2021 ◽  
Author(s):  
Cheng Zhang ◽  
Jianhua Liu
Keyword(s):  
Mechanical Properties ◽  
Bulk Density ◽  
Photoelectron Spectroscopy ◽  
Tensile Modulus ◽  
Fiber Surface ◽  
Thermal Stabilization ◽  
Oxidation Reactions ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Stability

Abstract Dielectric property, bulk density, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), wide angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and mechanical properties were analyzed. PAN fibers (PFs) are polar materials, and the dielectric constant of KMnO4 modification fibers (Mn-PFs) is reduced. The bulk density of Mn-PFs under microwave stabilization (Mn-MSFs) is 0.04 g/cm3 higher than that of the microwave stabilized fibers (MSFs), shortening the value in one temperature zone. Compared with MSFs5, the stability of Mn-MSFs5 is improved by 10%, and the surface O content and O-containing functional groups are improved. The (002) crystal plane diffraction peak of Mn-MSFs5 is higher than that of MSFs5, and it has a higher stabilized structure. Moreover, after stabilization, the Mn element does not exist on the fiber surface and does not affect the structure of the stabilized fiber. The fineness of Mn-MSFs5 is 1.07 dtex, tensile strength is 1.52 cN/dtex, tensile modulus is 59.3 cN/dtex and elongation at break is 13.5%. It has excellent mechanical properties. In addition, a structural transformation of the thermal stabilization process is proposed, that is, the cyclization reaction first occurs, and then the dehydrogenation and oxidation reactions are performed.

Stability of Indium Tin Oxide/Polymer Interfaces

2002 ◽  
Vol 747 ◽  
Author(s):  
X. Crispin ◽  
A. Crispin ◽  
M. P. de ◽  
S. Marciniak ◽  
W. Osikowicz ◽  
...  
Keyword(s):  
Tin Oxide ◽  
Indium Tin Oxide ◽  
Photoelectron Spectroscopy ◽  
Rutherford Backscattering Spectrometry ◽  
Oxide Surface ◽  
Polymer Interfaces ◽  
Interfacial Chemistry ◽  
Light Emitting ◽  
X Ray ◽  
The Stability

ABSTRACTInterfacial chemistry at indium tin oxide/polymer interfaces is of fundamental importance for the performance of polymer-based light emitting diodes. X-ray photoelectron spectroscopy and Rutherford backscattering spectrometry are used to investigate the stability of the interface formed between indium tin oxide and (i) the light emitting polymer poly(p-phenylenevinylene), and (ii) the hole injecting layer poly(3,4-ethylenedioxythiophene) polystyrenesulfonate. The formed interfaces are not stable and indium-containing species diffuse from the metal oxide surface into the polymer layers.

Fractionation of polymethylene chains: An electron crystallographic investigation

1986 ◽  
Vol 44 ◽  
pp. 794-795
Author(s):  
Douglas L. Dorset
Keyword(s):  
Cross Section ◽  
Binary Systems ◽  
Linear Chain ◽  
Pure Component ◽  
Organic Substrates ◽  
Crystallographic Investigation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Molecular Sizes ◽  
The Stability

A variety of linear chain materials exist as polydisperse systems which are difficultly purified. The stability of continuous binary solid solutions assume that the Gibbs free energy of the solution is lower than that of either crystal component, a condition which includes such factors as relative molecular sizes and shapes and perhaps the symmetry of the pure component crystal structures.Although extensive studies of n-alkane miscibility have been carried out via powder X-ray diffraction of bulk samples we have begun to examine binary systems as single crystals, taking advantage of the well-known enhanced scattering cross section of matter for electrons and also the favorable projection of a paraffin crystal structure posited by epitaxial crystallization of such samples on organic substrates such as benzoic acid.

Investigation of the Effect of Uv-Assisted Oxidation and Nitridation of Hafnium Metal Films

2003 ◽  
Vol 780 ◽  
Author(s):  
C. Essary ◽  
V. Craciun ◽  
J. M. Howard ◽  
R. K. Singh
Keyword(s):  
Uv Radiation ◽  
Photoelectron Spectroscopy ◽  
Grazing Angle ◽  
X Ray Diffraction ◽  
Metal Thin Films ◽  
X Ray ◽  
Force Microscopy ◽  
Si Substrates ◽  
Atomic Force ◽  
Silicon Interface

AbstractHf metal thin films were deposited on Si substrates using a pulsed laser deposition technique in vacuum and in ammonia ambients. The films were then oxidized at 400 °C in 300 Torr of O2. Half the samples were oxidized in the presence of ultraviolet (UV) radiation from a Hg lamp array. X-ray photoelectron spectroscopy, atomic force microscopy, and grazing angle X-ray diffraction were used to compare the crystallinity, roughness, and composition of the films. It has been found that UV radiation causes roughening of the films and also promotes crystallization at lower temperatures.Furthermore, increased silicon oxidation at the interface was noted with the UVirradiated samples and was shown to be in the form of a mixed layer using angle-resolved X-ray photoelectron spectroscopy. Incorporation of nitrogen into the film reduces the oxidation of the silicon interface.

Interactions of Ge Atoms with High- ê Oxide Dielectric Surfaces

2005 ◽  
Vol 879 ◽  
Author(s):  
Scott K. Stanley ◽  
John G. Ekerdt
Keyword(s):  
Oxide Layer ◽  
Photoelectron Spectroscopy ◽  
Chemical Vapor ◽  
Temperature Programmed Desorption ◽  
Tungsten Filament ◽  
X Ray ◽  
Dielectric Surfaces ◽  
Temperature Programmed ◽  
The Stability ◽  
Ge Nanocrystals

AbstractGe is deposited on HfO2 surfaces by chemical vapor deposition (CVD) with GeH4. 0.7-1.0 ML GeHx (x = 0-3) is deposited by thermally cracking GeH4 on a hot tungsten filament. Ge oxidation and bonding are studied at 300-1000 K with X-ray photoelectron spectroscopy (XPS). Ge, GeH, GeO, and GeO2 desorption are measured with temperature programmed desorption (TPD) at 400-1000 K. Ge initially reacts with the dielectric forming an oxide layer followed by Ge deposition and formation of nanocrystals in CVD at 870 K. 0.7-1.0 ML GeHx deposited by cracking rapidly forms a contacting oxide layer on HfO2 that is stable from 300-800 K. Ge is fully removed from the HfO2 surface after annealing to 1000 K. These results help explain the stability of Ge nanocrystals in contact with HfO2.

scholarly journals α-Cellulose Fibers of Paper-Waste Origin Surface-Modified with Fe3O4 and Thiolated-Chitosan for Efficacious Immobilization of Laccase

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 581
Author(s):  
Gajanan S. Ghodake ◽  
Surendra K. Shinde ◽  
Ganesh D. Saratale ◽  
Rijuta G. Saratale ◽  
Min Kim ◽  
...  
Keyword(s):  
Enzyme Immobilization ◽  
Photoelectron Spectroscopy ◽  
Cellulose Fibers ◽  
Relative Activity ◽  
Significant Activity ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Laccase Immobilization ◽  
Surface Modified

The utilization of waste-paper-biomass for extraction of important α-cellulose biopolymer, and modification of extracted α-cellulose for application in enzyme immobilization can be extremely vital for green circular bio-economy. Thus, in this study, α-cellulose fibers were super-magnetized (Fe3O4), grafted with chitosan (CTNs), and thiol (-SH) modified for laccase immobilization. The developed material was characterized by high-resolution transmission electron microscopy (HR-TEM), HR-TEM energy dispersive X-ray spectroscopy (HR-TEM-EDS), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR) analyses. Laccase immobilized on α-Cellulose-Fe3O4-CTNs (α-Cellulose-Fe3O4-CTNs-Laccase) gave significant activity recovery (99.16%) and laccase loading potential (169.36 mg/g). The α-Cellulose-Fe3O4-CTNs-Laccase displayed excellent stabilities for temperature, pH, and storage time. The α-Cellulose-Fe3O4-CTNs-Laccase applied in repeated cycles shown remarkable consistency of activity retention for 10 cycles. After the 10th cycle, α-Cellulose-Fe3O4-CTNs possessed 80.65% relative activity. Furthermore, α-Cellulose-Fe3O4-CTNs-Laccase shown excellent degradation of pharmaceutical contaminant sulfamethoxazole (SMX). The SMX degradation by α-Cellulose-Fe3O4-CTNs-Laccase was found optimum at incubation time (20 h), pH (3), temperatures (30 °C), and shaking conditions (200 rpm). Finally, α-Cellulose-Fe3O4-CTNs-Laccase gave repeated degradation of SMX. Thus, this study presents a novel, waste-derived, highly capable, and super-magnetic nanocomposite for enzyme immobilization applications.

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