scholarly journals Effect of the Gaseous Atmosphere in GaAs Films Grown by Close-Spaced Vapor Transport Technique

Crystals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 68
Author(s):  
J. Cruz Bueno ◽  
Godofredo García Salgado ◽  
R. Balderas Valadez ◽  
J. Luna López ◽  
F. Nieto Caballero ◽  
...  
Keyword(s):  
Molecular Nitrogen ◽  
Chemical Vapor ◽  
Structural Disorder ◽  
Hydrogen Atmosphere ◽  
Nitrogen Atmosphere ◽  
Vapor Transport ◽  
Gaseous Atmosphere ◽  
Crystallinity Degree ◽  
Significant Difference ◽  
Gaas Films

The effect of the gaseous atmosphere in the growth of gallium arsenide (GaAs) films was studied. The films have been grown by close-spaced vapor transport (CSVT) technique in a home-made hot filament chemical vapor deposition (HFCVD) reactor using molecular hydrogen and molecular nitrogen as the transport agent. An important point about the gaseous atmosphere is the ease in creating volatile compounds when it makes contact with the GaAs source, this favors the transport of material in a CSVT system. Chemical reactions are proposed in order to understand the significant difference produced from the gaseous atmosphere. The films grown with hydrogen are (almost) continuous and have homogeneous layers with preferential orientation (111). The films grown with nitrogen are granular and rough layers with the coexistence of the orientations (111), (220) and (311) in the crystals. The incorporation of impurities in the films was corroborated by energy dispersive spectroscopy (EDS) showing traces of oxygen and nitrogen for the case of the samples obtained with nitrogen. Films grown in a hydrogen atmosphere show a higher band gap than those grown in a nitrogen atmosphere. With the results of XRD and micro-Raman we observe a displacement and broadening of the peaks, characteristic of a structural disorder. The calculations of the FWHM allow us to observe the crystallinity degree and determine an approximate crystallite size using the Scherrer’s equation.

Effect of Annealing in Atomic Hydrogen or Nitrogen Atmospheres on SiOx Nanoclusters Obtained by HFCVD

2009 ◽  
Vol 5 ◽  
pp. 105-111 ◽  
Author(s):  
G. García-Salgado ◽  
T. Díaz-Becerril ◽  
A. Coyopol ◽  
E. Rosendo-Andrés ◽  
H. Juárez ◽  
...  
Keyword(s):  
Atomic Hydrogen ◽  
Silicon Oxide ◽  
Deep Level ◽  
Growth Parameters ◽  
Chemical Vapor ◽  
Hydrogen Atmosphere ◽  
Nitrogen Atmosphere ◽  
Photoluminescence Intensity ◽  
Force Microscopy ◽  
Hot Filament

SiOx nanoclusters were obtained by Hot Filament Chemical Vapor Deposition using a quartz solid source and atomic hydrogen. The nanoclusters were characterized by Photoluminescence, Atomic Force Microscopy, Energy Dispersive Analysis X-ray and Fourier Transform Infrared Spectroscopy. FTIR and EDS characterization clearly show that the material is non stoichiometric silicon oxide with a composition that depends on the growth parameters, such as source-substrate distance and time of growth. Nanoclusters of SiOx presented photoluminescence with two principal peaks at around 859 and 920 nm. Photoluminescence intensity was enhanced when samples were annealed in hydrogen atmosphere and quenched when they were annealed in nitrogen atmosphere. However, it was observed that the same samples annealed once more with the initial atomic hydrogen conditions showed an increase in photoluminescence. From these results we suppose the photoluminescence produced in this material is influenced by deep level transitions associated with dangling bonds passivated with hydrogen on the surface of the Si crystallites embedded within SiOx nanoclusters.

Multiple Donors in Zinc Oxide Substrates

2002 ◽  
Vol 719 ◽  
Author(s):  
K. Thonke ◽  
N. Kerwien ◽  
A. Wysmolek ◽  
M. Potemski ◽  
A. Waag ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Chemical Vapor ◽  
Binding Energies ◽  
Vapor Transport ◽  
Chemical Vapor Transport ◽  
Oxide Substrates ◽  
Multiple Donors ◽  
Major Donors ◽  
Available Zinc ◽  
Transport Technique

AbstractWe investigate by photoluminescence (PL) nominally undoped, commercially available Zinc Oxide substrates (from Eagle Picher) grown by seeded chemical vapor transport technique in order to identify residual donors and acceptors. In low temperature PL spectra the dominant emission comes from the decay of bound exciton lines at around 3.36 eV. Zeeman measurements allow the identification of the two strongest lines and some weaker lines in-between as donorrelated. From the associated two-electron satellite lines binding energies of the major donors of 48 meV and 55 meV, respectively, can be deduced.

scholarly journals Evolution of reduction process from tungsten oxide to ultrafine tungsten powder via hydrogen

2021 ◽  
Vol 40 (1) ◽  
pp. 171-177
Author(s):  
Yue Wang ◽  
Ben Fu Long ◽  
Chun Yu Liu ◽  
Gao An Lin
Keyword(s):  
Surface Morphology ◽  
Tungsten Oxide ◽  
Tungsten Powder ◽  
Reduction Process ◽  
Chemical Vapor ◽  
Transition Process ◽  
Vapor Transport ◽  
Fibrous Structure ◽  
Chemical Vapor Transport ◽  
Oxide Particles

Abstract Herein, the evolution of reduction process of ultrafine tungsten powder in industrial conditions was investigated. The transition process of morphology and composition was examined via SEM, XRD, and calcination experiments. The results show that the reduction sequence of WO2.9 was WO2.9 → WO2.72 → WO2 → W on the surface, but WO2.9 → WO2 → W inside the oxide particles. With the aid of chemical vapor transport of WO x (OH) y , surface morphology transformed into rod-like, star-shaped cracking, floret, irregularly fibrous structure, and finally, spherical tungsten particles.

In situ formation of highly exposed NiPS3 nanosheets on nickel foam as an efficient 3D electrocatalyst for overall water splitting

2021 ◽  
Author(s):  
Liang Fang ◽  
Yanping Xie ◽  
Peiyin Guo ◽  
Jingpei Zhu ◽  
Shuhui Xiao ◽  
...  
Keyword(s):  
Water Splitting ◽  
Nickel Foam ◽  
Chemical Vapor ◽  
Bifunctional Catalyst ◽  
Vapor Transport ◽  
Chemical Vapor Transport ◽  
Overall Water Splitting ◽  
One Step ◽  
Transport Method

Vertical NiPS3 nanosheets in situ grown on conducting nickel foam were fabricated by a facile one-step chemical vapor transport method and used as an efficient bifunctional catalyst for overall water splitting.

Chemical Vapor Transport of Ternary Indium Molybdates.

ChemInform ◽  
2005 ◽  
Vol 36 (44) ◽  
Author(s):  
Udo Steiner ◽  
Werner Reichelt
Keyword(s):  
Chemical Vapor ◽  
Vapor Transport ◽  
Chemical Vapor Transport
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