Auger-process-induced charge separation in semiconductor nanocrystals
Auger-process-induced charge separation in semiconductor nanocrystals
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DOI：
10.1103/physrevb.55.13173
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发表时间：
1997-05-15
影响因子：
3.7
通讯作者：
McBranch, DW
中科院分区：
文献类型：
--
作者：
Klimov, VI;McBranch, DW
利用飞秒非线性传输技术研究了CdS纳米晶体的光学非线性和超快载流子动力学机制。获得的数据表明，在高泵浦水平下，主导空穴弛豫通道发生变化，非线性复合效应开始发挥重要作用。这表现为一个明显的差异，在低和高泵浦强度在准平衡，在长时间激发后测量的非线性光学响应。在很宽的泵浦强度范围内的非线性传输的波长和时间依赖性的分析清楚地表明，这种差异是由于在表面/界面相关的状态的空穴的俄歇过程辅助捕获。这种捕获导致有效的电荷分离和直流电场的产生，该直流电场在高泵浦强度下修改NC中的非线性光学响应。
Femtosecond nonlinear transmission techniques are applied to study mechanisms for optical nonlinearities and ultrafast carrier dynamics in CdS nanocrystals (NC's). The obtained data indicate the change in a dominant hole relaxation channel at high pump levels where nonlinear recombination effects start to play a significant role. This is manifested as a distinct difference in nonlinear-optical responses measured at low and high pump intensities in quasiequilibrium at long times after excitation. The analysis of the wavelength and time dependence of the nonlinear transmission over a wide pump-intensity range shows clearly that this difference is due to an Auger-process-assisted trapping of holes at surface/interface-related states. This trapping leads to efficient charge separation and the generation of a dc electric field that modifies the nonlinear optical response in NC's at high pump intensities.