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Title: Microstructural evolution of thin film vanadium oxide prepared by pulsed-direct current magnetron sputtering

Abstract

Vanadium oxide (VO{sub x}) thin films have been deposited by pulsed-DC magnetron sputtering using a metallic vanadium target in a reactive argon and oxygen environment. While the process parameters (power, total pressure, oxygen-to-argon ratio) remained constant, the deposition time was varied to produce films between 75 {+-} 6 and 2901 {+-} 30 A thick, which were then optically and electrically characterized. The complex dielectric function spectra ({epsilon} = {epsilon}{sub 1} + i{epsilon}{sub 2}) of the films from 0.75 to 5.15 eV were extracted by ex situ, multiple-angle spectroscopic ellipsometry (SE) measurements for the series of varied thickness VO{sub x} samples. Significant changes in {epsilon} and resistivity occur as a function of thickness, indicating the correlations exist between the electrical and the optical properties over this spectral range. In addition, in situ measurements via real time SE (RTSE) were made on the film grown to the largest thickness to track optical property and structural variations during growth. RTSE was also used to characterize changes in the film occurring after growth was completed, namely during post sputtering in the presence of argon and oxygen while the sample is shielded, and atmospheric exposure. RTSE indicates that the exposure of the film to themore » argon and oxygen environment, regardless of the shutter isolating the target, causes up to 200 A of the top surface of the deposited film to become more electrically resistive as evidenced by variations in {epsilon}. Exposure of the VO{sub x} thin film to atmospheric conditions introduces a similar change in {epsilon}, but this change occurs throughout the bulk of the film. A combination of these observations with RTSE results indicates that thinner, less ordered VO{sub x} films are more susceptible to drastic changes due to atmospheric exposure and that microstructural variations in this material ultimately control its environmental stability.« less

Authors:
;  [1];  [2];  [3];  [4]
  1. Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)
  2. Sandia National Laboratories, P.O. Box 5800-1411, Albuquerque, New Mexico 87185-1411 (United States)
  3. Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27606 (United States)
  4. Department of Physics and Astronomy, University of Toledo, Toledo, Ohio 43606 (United States)
Publication Date:
OSTI Identifier:
22089561
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 112; Journal Issue: 9; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-8979
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ARGON; CORRELATIONS; DEPOSITION; DIELECTRIC MATERIALS; DIRECT CURRENT; ELECTRIC CONDUCTIVITY; ELLIPSOMETRY; EV RANGE; EVOLUTION; MAGNETRONS; MICROSTRUCTURE; OPTICAL PROPERTIES; OXYGEN; SPECTRA; SPUTTERING; STABILITY; SURFACES; THICKNESS; THIN FILMS; VANADIUM OXIDES

Citation Formats

Motyka, M. A., Horn, M. W., Gauntt, B. D., Dickey, E. C., and Podraza, N. J. Microstructural evolution of thin film vanadium oxide prepared by pulsed-direct current magnetron sputtering. United States: N. p., 2012. Web. doi:10.1063/1.4759255.
Motyka, M. A., Horn, M. W., Gauntt, B. D., Dickey, E. C., & Podraza, N. J. Microstructural evolution of thin film vanadium oxide prepared by pulsed-direct current magnetron sputtering. United States. doi:10.1063/1.4759255.
Motyka, M. A., Horn, M. W., Gauntt, B. D., Dickey, E. C., and Podraza, N. J. Thu . "Microstructural evolution of thin film vanadium oxide prepared by pulsed-direct current magnetron sputtering". United States. doi:10.1063/1.4759255.
@article{osti_22089561,
title = {Microstructural evolution of thin film vanadium oxide prepared by pulsed-direct current magnetron sputtering},
author = {Motyka, M. A. and Horn, M. W. and Gauntt, B. D. and Dickey, E. C. and Podraza, N. J.},
abstractNote = {Vanadium oxide (VO{sub x}) thin films have been deposited by pulsed-DC magnetron sputtering using a metallic vanadium target in a reactive argon and oxygen environment. While the process parameters (power, total pressure, oxygen-to-argon ratio) remained constant, the deposition time was varied to produce films between 75 {+-} 6 and 2901 {+-} 30 A thick, which were then optically and electrically characterized. The complex dielectric function spectra ({epsilon} = {epsilon}{sub 1} + i{epsilon}{sub 2}) of the films from 0.75 to 5.15 eV were extracted by ex situ, multiple-angle spectroscopic ellipsometry (SE) measurements for the series of varied thickness VO{sub x} samples. Significant changes in {epsilon} and resistivity occur as a function of thickness, indicating the correlations exist between the electrical and the optical properties over this spectral range. In addition, in situ measurements via real time SE (RTSE) were made on the film grown to the largest thickness to track optical property and structural variations during growth. RTSE was also used to characterize changes in the film occurring after growth was completed, namely during post sputtering in the presence of argon and oxygen while the sample is shielded, and atmospheric exposure. RTSE indicates that the exposure of the film to the argon and oxygen environment, regardless of the shutter isolating the target, causes up to 200 A of the top surface of the deposited film to become more electrically resistive as evidenced by variations in {epsilon}. Exposure of the VO{sub x} thin film to atmospheric conditions introduces a similar change in {epsilon}, but this change occurs throughout the bulk of the film. A combination of these observations with RTSE results indicates that thinner, less ordered VO{sub x} films are more susceptible to drastic changes due to atmospheric exposure and that microstructural variations in this material ultimately control its environmental stability.},
doi = {10.1063/1.4759255},
journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 9,
volume = 112,
place = {United States},
year = {2012},
month = {11}
}