Physically and chemically smooth cesium-antimonide photocathodes on single crystal strontium titanate substrates
Physically and chemically smooth cesium-antimonide photocathodes on single crystal strontium titanate substrates
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单晶钛酸锶基底上物理和化学光滑的铯锑光电阴极
DOI：
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发表时间：
2022
影响因子：
4
通讯作者：
S. Karkare
中科院分区：
文献类型：
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作者：
Pallavi Saha;O. Chubenko;G. Gevorkyan;A. Kachwala;C. Knill;Carlos Sarabia;E. Montgomery;S. Poddar;J. Paul;R. Hennig;H. Padmore;S. Karkare
X射线自由电子激光和超快电子衍射实验的性能在很大程度上取决于来自光注入器的电子源的亮度。在特定的加速梯度下，来自光电注入器的最大亮度受光电阴极发射的电子的平均横向能量(MTE)的限制。对于像碱-锑薄膜这样的高量子效率(QE)阴极来说，对于减轻非线性光电发射对MTE的影响是必不可少的，最小的MTE以及因此可能的最高亮度受到纳米级表面粗糙度和化学不均匀性的限制。在这项工作中，我们证明了在晶格匹配的钛酸锶(STO)衬底上生长的高QE Cs3Sb薄膜与传统的在无序硅表面上生长的Cs3Sb薄膜相比，具有更光滑、化学均匀的4倍表面。我们根据在STO上生长的Cs3Sb薄膜上测量的地形和表面电势的变化来模拟计算粗糙度诱导的MTE，结果表明这些变化足够小，不会对MTE产生相应的影响，从而对亮度也没有影响。
The performance of x-ray free electron lasers and ultrafast electron diffraction experiments is largely dependent on the brightness of electron sources from photoinjectors. The maximum brightness from photoinjectors at a particular accelerating gradient is limited by the mean transverse energy (MTE) of electrons emitted from photocathodes. For high quantum efficiency (QE) cathodes like alkali-antimonide thin films, which are essential to mitigate the effects of non-linear photoemission on MTE, the smallest possible MTE and, hence, the highest possible brightness are limited by the nanoscale surface roughness and chemical inhomogeneity. In this work, we show that high QE Cs3Sb films grown on lattice-matched strontium titanate (STO) substrates have a factor of 4 smoother, chemically uniform surfaces compared to those traditionally grown on disordered Si surfaces. We perform simulations to calculate roughness induced MTE based on measured topographical and surface-potential variations on the Cs3Sb films grown on STO and show that these variations are small enough to have no consequential impact on the MTE and, hence, the brightness.