利用氮氧化钛薄膜优化平面金属-半导体界面处的热电子捕获
Optimizing hot electron harvesting at planar metal-semiconductor interfaces with titanium oxynitride thin films
摘要：
了解金属-半导体界面对于半导体和亚带隙太阳能收集的进步至关重要，其中亚带隙光子可以被激发并提取到半导体中。在这项工作中，我们比较了Au/TiO 2和氮氧化钛/TiO 2-x界面的电子提取效率，在后一种情况下，自发形成的氧化物层（TiO 2-x）产生金属-半导体接触。时间分辨泵浦-探测光谱被用来研究在这两种情况下的电子复合率。与Au/TiO 2中的纳秒复合寿命不同，我们发现TiON系统中的电子弛豫存在瓶颈，我们使用陷阱介导的复合模型对此进行了解释。使用这个模型，我们调查的可调谐性的弛豫动力学与氧含量的母膜。优化的薄膜（TiO 0.5N0.5）表现出最高的载流子提取效率，最慢的捕获和可观的热电子人口达到表面氧化物。我们的研究结果表明，氧可以发挥生产作用，在提高电子捕获和延长电子寿命，提供一个优化的金属-半导体界面，只使用原生氧化物的氮氧化钛。
英文摘要：
Understanding metal-semiconductor interfaces is critical to the advancement of photocatalysis and sub-bandgap solar energy harvesting where sub-bandgap photons can be excited and extracted into the semiconductor. In this work, we compare the electron extraction efficiency across Au/TiO2 and titanium oxynitride/TiO2-x interfaces, where in the latter case the spontaneously forming oxide layer (TiO2-x) creates a metal-semiconductor contact. Time-resolved pump-probe spectroscopy is used to study the electron recombination rates in both cases. Unlike the nanosecond recombination lifetimes in Au/TiO2, we find a bottleneck in the electron relaxation in the TiON system, which we explain using a trap-mediated recombination model. Using this model, we investigate the tunability of the relaxation dynamics with oxygen content in the parent film. The optimized film (TiO0.5N0.5) exhibits the highest carrier extraction efficiency, slowest trapping and an appreciable hot electron population reaching the surface oxide. Our results demonstrate the productive role oxygen can play in enhancing electron harvesting and elongating electron lifetimes providing an optimized metal-semiconductor interface using only the native oxide of titanium oxynitride.
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