Baddorf Arthur P
Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
Sci Rep. 2023 Aug 18;13(1):13452. doi: 10.1038/s41598-023-40187-5.
Absolute values of work functions can be determined in ultraviolet photoemission spectroscopy (UPS) by measuring the minimum kinetic energy of secondary electrons generated by a known photon energy. However, some samples can produce spectra that are difficult to interpret due to additional intensity below the true secondary electron cutoff. Disordered absorbates on elemental metals add small intensity below the onset for the transition metal surfaces studied, which can be attributed to energy losses after photoelectrons are generated. In contrast, spectra from WO films can produce multiple onsets with comparable intensity which do not fit this model. False onsets (in the context of work function measurements) can be minimized by optimizing experimental detection parameters including limiting analyzer acceptance angles and pass energy. True work functions can be identified by examining the onsets as the sample bias is varied.
在紫外光电子能谱（UPS）中，可以通过测量由已知光子能量产生的二次电子的最小动能来确定功函数的绝对值。然而，由于在真正的二次电子截止以下存在额外的强度，一些样品会产生难以解释的光谱。在研究的过渡金属表面上，元素金属上无序的吸附质会在起始点以下增加小强度，这可归因于光电子产生后的能量损失。相比之下，WO薄膜的光谱会产生多个强度相当的起始点，这不符合该模型。通过优化实验检测参数，包括限制分析器接受角和通过能量，可以将（在功函数测量背景下的）虚假起始点最小化。通过在改变样品偏压时检查起始点，可以识别出真正的功函数。
