Study of photo-induced electron transport phenomena on oxide semiconductor surfaces

我们研究了氧化物半导体表面的电子结构和载流子动力学，这在光催化应用化学和强关联电子系统物理中具有重要意义。利用高分辨角度分辨光电子能谱和新发展的时间分辨光电子能谱在BL07LSU上进行了实验研究。通过吸附氢原子和引入表面缺陷，使钛酸锶和氧化锌晶体表面金属化，具有很强的电子相关性。通过实时跟踪表面光电压的弛豫来研究载流子动力学。对于纳米TiO2光催化剂，锐钛矿型晶体的化学反应活性要好于金红石型晶体。光激发载流子在锐钛矿型上的寿命比在金红石型上的寿命长10倍，这是根据实验测定的两个晶体表面的时间常数来估算的。

We studied electronic structure and carrier dynamics of oxide semiconductor surfaces that are significant in applied chemistry of photocatalysis and in physics of strongly correlated electronic system. Experiments were carried out with high-resolution angle-resolved photoemission spectroscopy and newly developed time-resolved photoemission spectroscopy at SPring-8 BL07LSU.Surfaces of SrTiO3 and ZnO crystals are metalized with quite strong electron correlation by adsorbing hydrogen atoms and introducing surface defects.The carrier dynamics was studied by tracking relaxation of the surface photovoltage in real time. For the photocatalysts of TiO2 nanoparticles, chemical reactivity has been reported better on the anatase-type crystal than on the rutile-type. The photo-excited carriers were found to have 10 times longer lifetime on the anatase-type than on the rutile type, as evaluated from the experimentally determined time constants from the two crystal surfaces.