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Title: Reflection High-Energy Electron Diffraction Beam-Induced Structural and Property Changes on WO3 Thin Films

Abstract

Reduction of transition metal oxides can greatly change their physical and chemical properties. Using deposition of WO3 as a case study, we demonstrate that reflection high-energy electron diffraction (RHEED), a surface-sensitive tool widely used to monitor thin-film deposition processes, can significantly affect the cation valence and physical properties of the films through electron-beam induced sample reduction. The RHEED beam is found to increase film smoothness during epitaxial growth of WO3, as well as change the electronic properties of the film through preferential removal of surface oxygen.

Authors:
; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1170457
Report Number(s):
PNNL-SA-103911
47621; 47862; KP1704020
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters, 105(5):051606
Country of Publication:
United States
Language:
English
Subject:
Environmental Molecular Sciences Laboratory

Citation Formats

Du, Yingge, Zhang, Hongliang, Varga, Tamas, and Chambers, Scott A. Reflection High-Energy Electron Diffraction Beam-Induced Structural and Property Changes on WO3 Thin Films. United States: N. p., 2014. Web. doi:10.1063/1.4892810.
Du, Yingge, Zhang, Hongliang, Varga, Tamas, & Chambers, Scott A. Reflection High-Energy Electron Diffraction Beam-Induced Structural and Property Changes on WO3 Thin Films. United States. doi:10.1063/1.4892810.
Du, Yingge, Zhang, Hongliang, Varga, Tamas, and Chambers, Scott A. Fri . "Reflection High-Energy Electron Diffraction Beam-Induced Structural and Property Changes on WO3 Thin Films". United States. doi:10.1063/1.4892810.
@article{osti_1170457,
title = {Reflection High-Energy Electron Diffraction Beam-Induced Structural and Property Changes on WO3 Thin Films},
author = {Du, Yingge and Zhang, Hongliang and Varga, Tamas and Chambers, Scott A.},
abstractNote = {Reduction of transition metal oxides can greatly change their physical and chemical properties. Using deposition of WO3 as a case study, we demonstrate that reflection high-energy electron diffraction (RHEED), a surface-sensitive tool widely used to monitor thin-film deposition processes, can significantly affect the cation valence and physical properties of the films through electron-beam induced sample reduction. The RHEED beam is found to increase film smoothness during epitaxial growth of WO3, as well as change the electronic properties of the film through preferential removal of surface oxygen.},
doi = {10.1063/1.4892810},
journal = {Applied Physics Letters, 105(5):051606},
number = ,
volume = ,
place = {United States},
year = {Fri Aug 08 00:00:00 EDT 2014},
month = {Fri Aug 08 00:00:00 EDT 2014}
}
  • Reduction of transition metal oxides can greatly change their physical and chemical properties. Using deposition of WO{sub 3} as a case study, we demonstrate that reflection high-energy electron diffraction (RHEED), a surface-sensitive tool widely used to monitor thin-film deposition processes, can significantly affect the cation valence and physical properties of the films through electron-beam induced sample reduction. The RHEED beam is found to increase film smoothness during epitaxial growth of WO{sub 3}, as well as change the electronic properties of the film through preferential removal of surface oxygen.
  • Nitrogen doped tungsten oxide (WO3) films were grown by reactive magnetron sputter-deposition by varying the nitrogen content in the reactive gas mixture keeping the deposition temperature fixed at 400 C. The crystal structure, surface morphology, chemical composition, and electrical resistivity of nitrogen doped WO3 films were evaluated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and electrical conductivity measurements. The results indicate that the nitrogen-doping induced changes in the microstructure and electrical properties of WO3 films are significant. XRD measurements coupled with SEM analysis indicates that the increasing nitrogen content decreases the grain size and crystalmore » quality. The nitrogen concentration increases from 0 at.% to 1.35 at.% with increasing nitrogen flow rate from 0 to 20 sccm. The corresponding dc electrical conductivity of the films had shown a decreasing trend with increasing nitrogen content.« less
  • Reflection high-energy electron diffraction (RHEED) was used to monitor the strain of GaN/AlN quantum dots (QDs) grown by molecular beam epitaxy. Quantitative and absolute values of the in- and out-of-plane strains of the QDs were determined and compared to reference values, obtained by x-ray diffraction measurements. A very good agreement was found between RHEED and x-ray measurements. The growth and thermal ripening of the dots were analyzed. A progressive strain relaxation was observed during the ripening stage, suggesting a morphology evolution of the dots.
  • Reflection high-energy electron diffraction (RHEED) rocking curves have been studied for the Si(111)-((3){sup 1/2}{times}(3){sup 1/2}) {ital R}30{degree}--Ag structure as a function of varying degrees of surface roughness as generated by Ar{sup +} ion bombardment. Under increased surface roughness, most peaks in the rocking curves showed a characteristic change represented by splitting, shifting, and variation in intensity. This characteristic change in the rocking curves is identified as a result of surface step generation accompanied by modulation of the surface potential barrier. This surface roughness effect well explains the behavior of RHEED intensity oscillations during epitaxial growth and identifies the origin ofmore » phase differences of different beams.« less
  • Reflection high-energy electron diffraction (RHEED) intensity oscillations have been used for controlled, layer-by-layer growth of thin film heterostructures of the infinite-layer end-member compounds SrCuO{sub 2} and CaCuO{sub 2}. These artificially structured films are grown on (100) SrTiO{sub 3} substrates by pulsed laser deposition under a low-pressure oxygen ambient, using a combination of atomic oxygen and pulsed molecular oxygen, at a relatively low temperature of 500{degrees}C. X-ray diffraction and transmission electron microscopy are used for the structural characterization of the epitaxial heterostructures. Systematic variations in the electrical properties of the multilayers have been observed as a function of the thickness ofmore » the SrCuO{sub 2} and CaCuO{sub 2} layers for unit-cell-level modulation periods.« less