Generation of superconductivity by using FET with extremely thin dielectric SrTiO_3

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Field-effect transistor (FET) has attracted much interest for its ability of career injection into insulating materials such as organic molecules and transition-metal oxides. The purpose of this research is to create a new FET structure consisting of oxides substrates as dielectric layer with high dielectric constants and examine the electric field induced transport and magnetic properties. It is necessary to increase the electric capacitance of a dielectric layer to generate a lot of carrier in the channel layer in FET. SrTiO3 (STO) is a well known dielectric material with a large dielectric constant (10^2-10^4). We have developed extremely thin STO substrate about tens of μm to achieve a large capacitance.FET characteristics were examined for C_<60>(n-type), pentacene and La_2CuO_4(p-type). Typical gate voltage dependence of source-drain I-V characteristics were observed, however, there was no sign of the superconductivity, indicating that the doped carrier is not sufficient to produce superconductivity in the channel layers. It is necessary to increase the carrier density by one order of magnitude to give rise to a detectable change in the resistivity of the channel layers. Thinning of the STO located under the source-drain electrode to a few μm by using the FIB would be effective.