K2Te photocathode growth:: A photoemission study
K2Te photocathode growth:: A photoemission study
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DOI：
10.1063/1.371897
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发表时间：
2000-01-01
影响因子：
3.2
通讯作者：
Valeri, S
中科院分区：
文献类型：
--
作者：
Bisero, D;di Bona, A;Valeri, S
X射线光电子能谱（XPS）已被用来研究具有高量子效率（QE）的K-Te薄膜的生长过程，该薄膜在紫外范围内进行光电子发射，该薄膜是通过在超高真空条件下在Mo衬底上顺序沉积Te和K而制备的。薄膜的形成通过不同的步骤进行，其特征是将 QE 增加到与 K2Te 化学计量相对应的饱和值。通过定量、角度分辨 XPS 测量，检测到单层 K 的表面偏析。由不同量的 Te 制备的薄膜表现出相同的 K2Te 化学计量。然而，QE 值却存在显着差异。在 K 沉积过程中检测到从 K 到 Te 的电荷转移，并通过 Te 3d(5/2) 光电发射线的移动进行监测。在 K 蒸发结束时，由于能带弯曲机制，观察到 Te 3d 和 K 2p 光电发射线的移动。还研究了 K2Te 在 254 nm 处的量子效率因氧气暴露而降低的情况，并与 Cs2Te 进行了比较，Cs2Te 目前在紫外激光驱动光注入器中用作光电阴极材料。研究表明，K2Te 比 Cs2Te 更坚固。 QE 退化与 K2Te 表面上 TeO2 的形成有关。 (C) 2000 年美国物理研究所。 [S0021-8979(00)05301-9]。
X-ray photoemission spectroscopy (XPS) has been used to investigate the growth process of K-Te thin layers with high quantum efficiency (QE) for photoemission in the UV range, prepared by sequential deposition of Te and K on a Mo substrate under ultrahigh vacuum conditions. Film formation occurs through different steps, characterized by increasing QE up to a saturation value which correspond to K2Te stoichiometry. By quantitative, angle resolved XPS measurements, surface segregation of one monolayer of K has been detected. Films prepared starting from different amounts of Te exhibit the same K2Te stoichiometry. However, the QE values are significantly different. Charge transfer from K to Te has been detected during K deposition and monitored by the shift of the Te 3d(5/2) photoemission line. At the end of the K evaporation a shift of both Te 3d and K 2p photoemission lines has been observed, due to a band bending mechanism. The degradation by oxygen exposure of the quantum efficiency at 254 nm of K2Te has also been studied and compared with that of Cs2Te, which is currently used as photocathode material in UV-laser driven photoinjectors. It has been shown that K2Te is more rugged than Cs2Te. QE degradation is associated to the formation of TeO2 on the K2Te surface. (C) 2000 American Institute of Physics. [S0021-8979(00)05301-9].