Institute of Physics, Montanuniversität Leoben, Austria.
Beilstein J Nanotechnol. 2013 Mar 21;4:208-17. doi: 10.3762/bjnano.4.21. Print 2013.
ZnO nanostructures are promising candidates for the development of novel electronic devices due to their unique electrical and optical properties. Here, photoconductive atomic force microscopy (PC-AFM) has been applied to investigate transient photoconductivity and photocurrent spectra of upright-standing ZnO nanorods (NRs). With a view to evaluate the electronic properties of the NRs and to get information on recombination kinetics, we have also performed time-resolved photoluminescence measurements macroscopically.
Persistent photoconductivity from single ZnO NRs was observed for about 1800 s and was studied with the help of photocurrent spectroscopy, which was recorded locally. The photocurrent spectra recorded from single ZnO NRs revealed that the minimum photon energy sufficient for photocurrent excitation is 3.1 eV. This value is at least 100 meV lower than the band-gap energy determined from the photoluminescence experiments.
The obtained results suggest that the photoresponse in ZnO NRs under ambient conditions originates preferentially from photoexcitation of charge carriers localized at defect states and dominates over the oxygen photodesorption mechanism. Our findings are in agreement with previous theoretical predictions based on density functional theory calculations as well as with earlier experiments carried out at variable oxygen pressure.
由于独特的电学和光学性质，氧化锌纳米结构有望成为新型电子器件的候选材料。在此，我们应用光电导原子力显微镜（PC-AFM）来研究直立氧化锌纳米棒（NRs）的瞬态光电导率和光电流谱。为了评估 NRs 的电子性质并获取有关复合动力学的信息，我们还进行了宏观的时间分辨光致发光测量。
我们观察到单个 ZnO NRs 的持续光电导率约为 1800 s，并借助局部记录的光电流光谱对其进行了研究。从单个 ZnO NRs 记录的光电流谱表明，用于光电流激发的最小光子能量为 3.1 eV。该值至少比光致发光实验确定的能带隙能量低 100 meV。
所得结果表明，在环境条件下 ZnO NRs 的光响应主要源自于缺陷态局域化载流子的光激发，而不是氧光脱附机制。我们的发现与基于密度泛函理论计算的先前理论预测以及在可变氧压下进行的早期实验一致。
