Rectifying Polarity Switch of Pt/TiO 2-x /Pt
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1174-V06-07
Rectifying Polarity Switch of Pt/TiO2-x/Pt Ni Zhong1,2, Hisashi Shima1,2, and Hiro Akinaga1,2 1
Nanotechnology Research Institute (NRI), National Institute of Advanced Industrial Science and Technology (AIST) 2 CREST, Japan Science and Technology ABSTRACT
Current-voltage (I-V) characteristic of Pt/TiO2-x/Pt has been investigated. The Pt/TiO2-x/Pt devices in the initial state exhibit a rectifying I-V behavior. By applying a pulse voltage, the rectifying polarity could be switched to an opposite direction. The mechanism of the rectifying polarity switch is proposed as the local drift of defects, such as oxygen vacancies (VO), due to applying pulse voltage. It is found that the required pulse voltage height for the polarity switch (Vswitch) exhibits much dependence on the operation temperature and width of applied pulse voltage. With an increase of the pulse voltage width or the measurement temperature (T), Vswitch exhibits a decrease with increase of T. These results suggest that the rectifying polarity switch in the Pt/TiO2-x/Pt is attributed to a thermal and dynamic dependence process, which agree well with the localized migration of VO induced by applied pulse voltage. INTRODUCTION TiO2-x attracted considerable interest in the application of heterogeneous photocatalysts, solar cells, gas sensor, biocompatible materials and nanoscale electronic device. Most recently, current conduction and carrier transport of the TiO2-x/metal interface are considered to be applicable in the semiconductor technology.1,2 In our group, a novel switchable property has been explored on a simple metal/oxide/metal (MOM) structure by carefully controlling the fabricating process.3,4 This switch device could be considered as a simple diode. And the polarity of this diode is switchable by applying pulse voltage even after it is prepared. TiO2-x could be considered as a doped n-type semiconductor because of oxygen vacancy. A direct observation of the field-induced motion of color centers in rutile crystals has been reported.5,6 By applying a field, blue color drifts towards negative terminal, and positive terminal becomes transparent.6 It is attributed to the motion of VO due to the applied field. Moreover, It has been reported that formation of a continuous channel of VO was revealed by X-ray absorption near-edge spectroscopy in SrTiO3.7 It could explain a sudden current jump after a forming process found in SrTiO3 crystal with Pt electrodes, 8 which is also found in rutile crystal.9 Therefore, by applying pulse voltage, motion of VO is expected as a thermal and dynamic dependence process in oxide semiconductor such as TiO2-x and SrTiO3. The mechanism of the switch characteristic in our prepared Pt/TiO2-x/Pt device has been attributed to the shunting and recovery of the metal/oxide interfacial electronic barrier due to the localized drift of VO. Most recently, the Schottky barrier at Pt/TiO2-x interface has also been probed by electric beam induced current (EBIC), which is support for the proposed mechanism. And it will be rep
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