Di Gennaro Emiliano, Coscia Ubaldo, Ambrosone Giuseppina, Khare Amit, Granozio Fabio Miletto, di Uccio Umberto Scotti
Dipartimento di Fisica, Univ. di Napoli Federico II and CNR-SPIN, Compl. Univ. di Monte S. Angelo, Via Cinthia I-80126 Napoli (Italy).
Dipartimento di Fisica, Univ. di Napoli Federico II and CNISM Unitá di Napoli, Compl. Univ. di Monte S. Angelo, Via Cinthia I-80126 Napoli (Italy).
Sci Rep. 2015 Feb 11;5:8393. doi: 10.1038/srep08393.
The time-resolved photoconductance of amorphous and crystalline LaAlO3/SrTiO3 interfaces, both hosting an interfacial 2-dimensional electron gas, is investigated under irradiation by variable-wavelengths, visible or ultraviolet photons. Unlike bare SrTiO3 single crystals, showing relatively small photoconductance effects, both kinds of interfaces exhibit an intense and highly persistent photoconductance with extraordinarily long characteristic times. The temporal behaviour of the extra photoinduced conductance persisting after light irradiation shows a complex dependence on interface type (whether amorphous or crystalline), sample history and irradiation wavelength. The experimental results indicate that different mechanisms of photoexcitation are responsible for the photoconductance of crystalline and amorphous LaAlO3/SrTiO3 interfaces under visible light. We propose that the response of crystalline samples is mainly due to the promotion of electrons from the valence bands of both SrTiO3 and LaAlO3. This second channel is less relevant in amorphous LaAlO3/SrTiO3, where the higher density of point defects plays instead a major role.
研究了非晶态和晶态的LaAlO₃/SrTiO₃界面（两者都存在界面二维电子气）在可变波长的可见光或紫外光光子照射下的时间分辨光电导。与表现出相对较小光电导效应的裸SrTiO₃单晶不同，这两种界面都表现出强烈且高度持久的光电导，其特征时间极长。光照后持续存在的额外光致电导的时间行为显示出对界面类型（非晶态或晶态）、样品历史和照射波长的复杂依赖性。实验结果表明，在可见光下，晶态和非晶态LaAlO₃/SrTiO₃界面的光电导是由不同的光激发机制引起的。我们提出，晶态样品的响应主要是由于SrTiO₃和LaAlO₃价带中的电子跃迁。在非晶态LaAlO₃/SrTiO₃中，这种第二通道的作用较小，其中较高密度的点缺陷起主要作用。
