Ebihara Makoto, Sohn Woon Yong, Katayama Kenji
Department of Applied Chemistry, Chuo University, Tokyo 112-8551, Japan.
Rev Sci Instrum. 2019 Jul;90(7):073905. doi: 10.1063/1.5111418.
The transient grating (TG) imaging technique has been developed, where the refractive index change due to the photoexcited charge carriers excited with a stripe patterned light can be visualized. The spatiotemporal imaging of photoexcited charge carriers was demonstrated for a nanoparticulate TiO film. In the analytical procedures to map out the time constant distribution, the averaged response of photoexcited carriers in each image was obtained from the Fourier transform of the TG images since the image has a spatial modulation with a stripe pattern of light. The oscillation response due to the acoustic grating, the decay of the surface trapped electrons (until 1 μs), and thermal diffusion (until 100 µs) were observed. In order to obtain the lifetime imaging of the photoexcited electrons, the target time region (0-1 µs) for the response was selected and fitted with an exponential function, and the time constants were mapped out. We found that the time constants showed a wide range of distribution (68-920 ns), dependent on the sample positions.
瞬态光栅（TG）成像技术已被开发出来，利用这种技术可以观察到由条纹图案光激发的光生电荷载流子引起的折射率变化。已证明可对纳米颗粒TiO薄膜进行光生电荷载流子的时空成像。在绘制时间常数分布图的分析过程中，由于图像具有光条纹图案的空间调制，因此从TG图像的傅里叶变换中获得每个图像中光生载流子的平均响应。观察到了由声光栅引起的振荡响应、表面俘获电子的衰减（直到1 μs）以及热扩散（直到100 μs）。为了获得光生电子的寿命成像，选择了响应的目标时间区域（0 - 1 μs）并用指数函数进行拟合，从而绘制出时间常数分布图。我们发现，时间常数呈现出广泛的分布范围（68 - 920 ns），这取决于样品位置。
