超薄极限下的高效率单晶碱锑光电阴极
A single-crystal alkali antimonide photocathode: high efficiency in the ultra-thin limit
摘要：
光致发射电子源的特性决定了许多电子加速器和光子探测器的性能。迄今为止，所有的高效可见光光阴极材料要么是多晶的，要么表现出内在的表面无序，这两者都限制了发射的电子束亮度。在这封信中，我们演示了Cs $_3$ Sb外延薄膜的合成在3C-SiC（001）使用分子束外延。在532 nm处，薄膜的量子效率超过2%，厚度为4 nm。我们还发现，外延膜在650 nm处的量子效率比Si上的多晶膜大一个数量级。此外，这些薄膜允许角分辨光电子能谱测量的电子结构，这被发现是在良好的协议与理论。外延薄膜通过提高阈值附近的效率、减少表面无序以及在单原子层水平上设计新的光电发射功能的可能性，打开了戏剧性亮度增强的大门。
英文摘要：
The properties of photoemission electron sources determine the ultimate performance of a wide class of electron accelerators and photon detectors. To date, all high-efficiency visible-light photocathode materials are either polycrystalline or exhibit intrinsic surface disorder, both of which limit emitted electron beam brightness. In this letter we demonstrate the synthesis of epitaxial thin films of Cs$_3$Sb on 3C-SiC (001) using molecular-beam epitaxy. Films as thin as 4 nm have quantum efficiencies exceeding 2\% at 532 nm. We also find that epitaxial films have an order of magnitude larger quantum efficiency at 650 nm than comparable polycrystalline films on Si. Additionally, these films permit angle-resolved photoemission spectroscopy measurements of the electronic structure, which are found to be in good agreement with theory. Epitaxial films open the door to dramatic brightness enhancements via increased efficiency near threshold, reduced surface disorder, and the possibility of engineering new photoemission functionality at the level of single atomic layers.
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