Ar^+轰击SrTiO_3表面的持续光电导现象

Persistent photoconductivity in Ar^+ bombardment SrTiO_3 surfuce

持续光电导现象在光电器件中有着潜在的应用。采用亚禁带光激发手段研究了SrTiO_3表面的持续光电导效应。Ar+轰击后的SrTiO_3单晶可以形成具有光电效应的表面导电层。在温度80 K至300 K范围内,饱和光电导与激光功率强度之间呈现幂律规律,表现出带间陷阱复合的特征。激光辐照中止后,持续光电导的衰减时间达到1000 s以上。光电流的衰减符合扩展指数律,弥散参数β维持在0.2左右,基本不随温度改变,而特征时间τ随温度升高从49.6 s增加到2706 s;在低温区(80~150 K)的载流子复合势垒是7.1 meV,而在室温附近(150~300K)的载流子复合势垒增加到95 meV。这些特征表明Ar^+轰击SrTiO_3表面的光电导在衰减过程符合随机局部势能涨落模型,在低温时由浅能级陷阱的复合占主导,而在室温时则由深能级陷阱的复合占主导。

Persistent photoconductivity(PPC)phenomena has potential applications in optoelectronic devices.The PPC on the surface of SrTiO3 was studied by the means of sub-band gap excitation.A conducting layer which shows optoelectronic effects was formed on the surface of SrTiO3 single crystal by Ar+ion bombardment.In the temperature range from 80 K to 300 K,the saturated photoconductivity exhibits a power law dependency with the power of the illumination laser,indicating the characteristics of the recombination by in-gap trap defects.After the termination of laser,it takes more than 1000 s for the photoconductivity to disappear.The photoconductivity fits well to the stretched exponent decay,with a temperature-independent stretching exponentβabout 0.2.The characteristic timeτincreases from 49.6 s to 2706 s with the increasing temperature.In the lower temperature range(from 80 K to 150 K),the barrier height for the recombination is to be 7.1 meV.However,in the higher temperature range(from 150 K to 300 K),the barrier height for the recombination is increased to 95 meV.From these features,the photoconductivity decay process of SrTiO3 surface layer can be attributed to the random local potential fluctuation due to the Ar+bombardment.Thus shallow traps is dominated at lower temperature,while deep traps is dominated at the higher temperature.