Low temperature metallic state induced by electrostatic carrier doping   of SrTiO$_3$
  Transport properties of SrTiO$_3$-channel field-effect transistors with parylene organic gate insulator have been investigated. By applying gate voltage, the sheet resistance falls below $R_{\Box}$ $\sim$ 10 k$\Omega$ at low temperatures, with carrier mobility exceeding 1000 cm$^2$/Vs. The temperature dependence of the sheet resistance taken under constant gate voltage exhibits metallic behavior ($dR$/$dT$ $>$ 0). Our results demonstrate an insulator to metal transition in SrTiO$_3$ driven by electrostatic carrier density control. 
H. Nakamura, I. H. Inoue, Y. Takahashi, T. Hasegawa, Y. Tokura, H.   Takagi