Alloying of metals provides a vast parameter space for tuning of material, chemical, and mechanical properties, impacting disciplines ranging from photonics and catalysis to aerospace. From an optical point-of-view, pure thin metal films yield enhanced light absorption due to their cavity effects. However, an ideal metal–semiconductor photodetector requires not only high absorption, but also long hot carrier attenuation lengths in order to efficiently collect excited carriers. Here we demonstrate that Ag-Au alloys provide an ideal model system for controlling the optical and electrical responses in nanoscale thin metal films for hot carrier photodetectors with improved performance. While pure Ag and Au have long hot carrier attenuation lengths >20 nm, their optical absorption is insufficient for high efficiency devices. Instead, we find that alloying Ag and Au enhances the absorption by ∼50% while maintaining attenuation lengths >15 nm, currently limited by grain boundary scattering, although the electron attenuation length of pure Au outperforms pure Ag as well as all of the alloys investigated here. Further, our density functional theory analysis shows that the addition of small amounts of Au to the Ag lattice significantly enhances the hot hole generation rate. Combined, these findings suggest a route to high efficiency hot carrier devices based on metallic alloying with potential applications ranging from photodetectors and sensors to improved catalytic materials.

中文翻译：

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纳米级Ag-Au合金膜增强的近红外光响应

金属合金化为调节材料，化学和机械性能提供了广阔的参数空间，从而影响了从光子学，催化到航空航天等学科。从光学角度来看，纯金属薄膜由于其腔效应而产生增强的光吸收。然而，理想的金属-半导体光电探测器不仅需要高吸收，而且还需要较长的热载流子衰减长度，以便有效地收集激发的载流子。在这里，我们证明了Ag-Au合金提供了一种理想的模型系统，用于控制具有改进性能的热载光探测器的纳米级金属薄膜中的光学和电响应。尽管纯银和金具有大于20 nm的长热载流子衰减长度，但它们的光吸收不足以用于高效器件。代替，我们发现，虽然纯Au的电子衰减长度优于纯Ag以及本文研究的所有合金，但将Ag和Au合金化可将吸收率提高约50％，同时保持衰减长度> 15 nm（当前受晶界散射限制）。此外，我们的密度泛函理论分析表明，向Ag晶格中添加少量Au可以显着提高热孔的发生率。综上所述，这些发现暗示了一种基于金属合金的高效热载体设备的途径，其潜在应用范围从光电探测器和传感器到改良的催化材料。尽管纯金的电子衰减长度优于纯银以及此处研究的所有合金。此外，我们的密度泛函理论分析表明，向Ag晶格中添加少量Au可以显着提高热孔的发生率。综上所述，这些发现暗示了一种基于金属合金的高效热载体设备的途径，其潜在应用范围从光电探测器和传感器到改良的催化材料。尽管纯金的电子衰减长度优于纯银以及此处研究的所有合金。此外，我们的密度泛函理论分析表明，向Ag晶格中添加少量Au可以显着提高热孔的发生率。综上所述，这些发现暗示了一种基于金属合金的高效热载体设备的途径，其潜在应用范围从光电探测器和传感器到改良的催化材料。