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DESCRIPTION:Salinporn Kittiwatanakul\, University of Virginia\n\nVanadium d
ioxide (VO2) exhibits a metal semiconductor transition (MST) at
340 K. This transition is accompanied by the abrupt change in the electri
cal conductivity\, optical transmittance and reflectance in infrared regio
n\, which can be used in the electronic devices such as temperature sensor
s and electric switches. In this study\, Reactive Bias Target Ion Beam Dep
osition was used for epitaxial VO2 growth on TiO2 (1
00) substrates with fixed O2 flow rate at 5.0 sccm to study tra
nsport anisotropy\, and for highly textured VO2 growth on c-pla
ne Al2O3 substrates to study the effect of different
O2 flow rates (4.5-6.0 sccm). The conductivity anisotropy rati
o σ\;c/σ\;b of VO2/TiO2 film was found to be
~41.5 at 300 K\, much larger than that of single crystal VO2 a
nd it is the largest among those previously reported. The temperature depe
ndent anisotropy of the carrier concentration and the mobility is to be di
scussed. With XPS and XAS\, the valence state of vanadium on different VO<
sub>2/c-Al2O3 films was investigated. As the O
2 flow rate increases\, the XRD results show decreasing lattice
parameter\, hence increasing compressive strain along b-axis of monoclini
c VO2\; the transport measurements also show the increasing tra
nsition temperature (TMST) and the increasing change in resisti
vity associated with the strain. The correlation among the valence state\,
the strain and MST in VO2 will be discussed.
DTSTART:20120419T193000Z
LOCATION:Physics Building\, Room 204
SUMMARY:Transport Properties of VO2 Films near the Metal-Semicon
ductor Transition
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