TY - JOUR
T1 - Stoichiometry and microstructural effects on electrical conduction in pulsed dc sputtered vanadium oxide thin films
AU - Gauntt, Bryan D.
AU - Dickey, Elizabeth C.
AU - Horn, Mark W.
N1 - Funding Information:
This research was sponsored by the United States Army Research Office and United States Army Research Laboratory under Cooperative Agreement No. W911NF-0-2-0026. This publication was also supported by the Pennsylvania State University Materials Research Institute Nano Fabrication Network and the National Science Foundation Cooperative Agreement No. 0335765, National Nanotechnology Infrastructure Network. The authors would like to thank Dr. Nik Podraza for useful suggestions to the manuscript.
PY - 2009/4
Y1 - 2009/4
N2 - Vanadium oxide thin films were deposited using pulsed direct current (dc) magnetron sputtering in an atmosphere containing argon and oxygen. The total pressure was varied from 2.5 to 15 mTorr, and the oxygen-to-argon ratio was varied from 2.5 to 30%. The resulting films were characterized using Rutherford backscattering spectroscopy (RBS), transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), and glancing incidence x-ray diffraction (GIXRD). Electrical resistivity was calculated from 1-V curves acquired from two-point-probe measurements and thicknesses measured from bright-field TEM images of cross-sectioned samples. TEM and GIXRD were used to characterize the crystallinity of each film. A transition from nanocrystalline to amorphous growth was observed with increasing partial pressure of oxygen. In all samples, the only crystalline phase observed was cubic vanadium oxide with the sodium chloride structure. Though the cubic VO x equilibrium phase field is limited to a maximum of x = 1.3, the cubic phase was observed with a value of x up to 2 in the present work. It was apparent from electron diffraction data that increased oxygen content correlated with an increase in the film disorder. The increase in oxygen content also corresponded with an increase in the film resistivity, which varied over 7 orders of magnitude from 1.18 × 10 -3 to 2.98 × 10 4 Ω.cm. The temperature coefficient of resistance was found to increase with increasing oxygen content from -0.1 to -3.5%/°C. A direct correlation between film disorder and temperature coefficient of resistivity (TCR) was observed and could be exploited to engineer materials with the desired TCR.
AB - Vanadium oxide thin films were deposited using pulsed direct current (dc) magnetron sputtering in an atmosphere containing argon and oxygen. The total pressure was varied from 2.5 to 15 mTorr, and the oxygen-to-argon ratio was varied from 2.5 to 30%. The resulting films were characterized using Rutherford backscattering spectroscopy (RBS), transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), and glancing incidence x-ray diffraction (GIXRD). Electrical resistivity was calculated from 1-V curves acquired from two-point-probe measurements and thicknesses measured from bright-field TEM images of cross-sectioned samples. TEM and GIXRD were used to characterize the crystallinity of each film. A transition from nanocrystalline to amorphous growth was observed with increasing partial pressure of oxygen. In all samples, the only crystalline phase observed was cubic vanadium oxide with the sodium chloride structure. Though the cubic VO x equilibrium phase field is limited to a maximum of x = 1.3, the cubic phase was observed with a value of x up to 2 in the present work. It was apparent from electron diffraction data that increased oxygen content correlated with an increase in the film disorder. The increase in oxygen content also corresponded with an increase in the film resistivity, which varied over 7 orders of magnitude from 1.18 × 10 -3 to 2.98 × 10 4 Ω.cm. The temperature coefficient of resistance was found to increase with increasing oxygen content from -0.1 to -3.5%/°C. A direct correlation between film disorder and temperature coefficient of resistivity (TCR) was observed and could be exploited to engineer materials with the desired TCR.
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U2 - 10.1557/jmr.2009.0183
DO - 10.1557/jmr.2009.0183
M3 - Article
AN - SCOPUS:65349098875
SN - 0884-2914
VL - 24
SP - 1590
EP - 1599
JO - Journal of Materials Research
JF - Journal of Materials Research
IS - 4
ER -