Cushing Scott K, Molesky Ilana J P, de Roulet Bethany R, Lee Angela, Marsh Brett M, Szoke Szilard, Vaida Mihai E, Leone Stephen R
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA.
Sci Adv. 2020 Apr 3;6(14):eaay6650. doi: 10.1126/sciadv.aay6650. eCollection 2020 Apr.
Metal oxide semiconductor junctions are central to most electronic and optoelectronic devices, but ultrafast measurements of carrier transport have been limited to device-average measurements. Here, charge transport and recombination kinetics in each layer of a Ni-TiO-Si junction is measured using the element specificity of broadband extreme ultraviolet (XUV) ultrafast pulses. After silicon photoexcitation, holes are inferred to transport from Si to Ni ballistically in ~100 fs, resulting in characteristic spectral shifts in the XUV edges. Meanwhile, the electrons remain on Si. After picoseconds, the transient hole population on Ni is observed to back-diffuse through the TiO, shifting the Ti spectrum to a higher oxidation state, followed by electron-hole recombination at the Si-TiO interface and in the Si bulk. Electrical properties, such as the hole diffusion constant in TiO and the initial hole mobility in Si, are fit from these transient spectra and match well with values reported previously.
金属氧化物半导体结是大多数电子和光电器件的核心，但载流子输运的超快测量一直局限于器件平均测量。在此，利用宽带极紫外（XUV）超快脉冲的元素特异性，测量了Ni-TiO-Si结各层中的电荷输运和复合动力学。硅光激发后，推断空穴在约100飞秒内从硅弹道式传输到镍，导致XUV边缘出现特征光谱位移。同时，电子留在硅上。皮秒后，观察到镍上的瞬态空穴群体通过TiO反向扩散，将钛光谱转移到更高的氧化态，随后在Si-TiO界面和硅体中发生电子-空穴复合。这些瞬态光谱拟合了诸如TiO中空穴扩散常数和Si中初始空穴迁移率等电学性质，且与先前报道的值匹配良好。
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