科研之友
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摘要
A metallic surface is realized on stoichiometric and insulating (100) SrTiO3 by Ar+-ion irradiation. The sheet carrier density and Hall mobility of the layer are similar to 4.0 x 10(14) cm(-2) and similar to 2 x 10(3) cm(2)/Vs, respectively, at 15 K for the irradiation dose of similar to 4.2 x 10(18) ions/cm(2). These samples display ultraviolet light sensitive photoconductivity (PC) which is enhanced abruptly below the temperature (approximate to 100 K) where SrTiO3 crystal undergoes an antiferrodistortive cubic-to-tetragonal (O-h(1) -> D-4h(18)) structural phase transition. This behavior of PC maps well with the temperature dependence of dielectric function and electric field induced conductivity. The longevity of the PC state also shows a distinct change below approximate to 100 K. AtT > 100 K its decay is thermally activated with an energy barrier of approximate to 36 meV, whereas at T < 100 K it becomes independent of temperature. We have examined the effect of electrostatic gating on the lifetime of the PC state. One nontrivial result is the ambient temperature quenching of the photoconducting state by the negative gate field. This observation opens avenues for designing a solid state photoelectric switch. The origin and lifetime of the PC state are understood in the light of field effect induced band bending, defect dynamics, and thermal relaxation processes.
- 出版日期2015-5-18
