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-TiO₂-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 TiO₂, shifting the Ti spectrum to a higher oxidation state, followed by electron-hole recombination at the Si-TiO₂ interface and in the Si bulk. Electrical properties, such as the hole diffusion constant in TiO₂ 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，但载流子传输的超快测量仅限于器件平均测量。此处，使用宽带极紫外 (XUV) 超快脉冲的元素特异性来测量 Ni-TiO ₂ -Si 结各层中的电荷传输和复合动力学。硅光激发后，推断空穴在约 100 fs 内从 Si 弹道传输到 Ni，导致 XUV 边缘出现特征光谱偏移。与此同时，电子保留在硅上。皮秒后，观察到 Ni 上的瞬态空穴群通过 TiO ₂反向扩散，将 Ti 光谱移动到更高的氧化态，然后在 Si-TiO ₂界面和 Si 体中发生电子-空穴复合。电学性质，例如 TiO ₂中的空穴扩散常数和 Si 中的初始空穴迁移率，由这些瞬态光谱拟合，并且与之前报道的值很好地匹配。