Roy Kanak, Gopinath Chinnakonda S
Center of Excellence on Surface Science, CSIR-National Chemical Laboratory , Dr. Homi Bhabha Road, Pune, Maharashtra 411 008, India.
Anal Chem. 2014 Apr 15;86(8):3683-7. doi: 10.1021/ac4041026. Epub 2014 Mar 10.
Valence band (VB) changes and hence electronic structure evolution was directly observed with low kinetic energy (KE) electrons at near ambient pressure (NAP) conditions with He I photon source in a custom built laboratory ambient pressure photoelectron spectrometer (Lab-APPES). Polycrystalline Cu surfaces were gradually oxidized in O2 to Cu2O, to a mixture of Cu2O + CuO, and finally to CuO between 300 and 625 K and at NAP. Typical VB features for Cu, Cu2O, and CuO were observed, and the results corroborate well with core level and Auger spectral changes. High mean free path associated with low KE electrons, very low or no inelastic scattering, and effective pumping and the design of electrostatic lens regime help to minimize the electron attenuation at NAP conditions. The present results extend the capabilities of the APPES tool to explore the in situ evolution of electronic structure of materials at NAP and high temperatures.
在一个定制的实验室环境压力光电子能谱仪（Lab-APPES）中，利用氦I光子源，在近环境压力（NAP）条件下，用低动能（KE）电子直接观察到价带（VB）变化以及由此产生的电子结构演变。多晶铜表面在300至625K之间且处于NAP条件下，在O2中逐渐氧化为Cu2O，再到Cu2O + CuO的混合物，最终氧化为CuO。观察到了Cu、Cu2O和CuO的典型价带特征，结果与芯能级和俄歇光谱变化很好地吻合。与低动能电子相关的高平均自由程、极低或无非弹性散射、有效的抽气以及静电透镜系统的设计有助于在NAP条件下最小化电子衰减。目前的结果扩展了环境压力光电子能谱仪工具在NAP和高温下探索材料电子结构原位演变的能力。
