적외선 분광에 의한 TiO2박막의 전기저항 바뀜 연구

초록

Oxide thin films such as SrZrO3, TiO2, NiO, and (Pr,Ca)MnO3, which show resistive switching behavior, have attracted attentions due to their applications to non-volatile storage device, called resistive random access memory (RRAM). By applying short voltage pulses, a low-resistance state (LRS) can be switched into a high-resistance state (HRS) and vice versa, and the corresponding resistance states have a good retention property. Recently the RRAM materials have been intensively studied, however the mechanism of the switching behavior is still unclear. Here we present results of infrared (IR) spectroscopic investigations of TiO2 thin films. Reflectance of the two states, i.e. the LRS and the HRS which show resistance ratio >> 102, is measured by micro-Fourier transform-IR spectrometer in the region of 600-12000 cm-1. The reflectance of the LRS is higher than that of the HRS, which is consistent with the metallic nature of the LRS. In order to extract the dielectric functions of the LRS and HRS of the TiO2 thin film, the overall reflectance spectra are fitted by the simulations based on the Fresnel equation. The obtained dielectric functions are discussed in the scheme of the effective medium theory by assuming vertical conducting paths.