昇温光電子放出法によるさまざまな実用金属表面の観察

光電子放出量の温度依存性のXPS解析との対比

抄録

To easily characterize the state of real metal surfaces in ambient environments, we have developed an extremely sensitive technique for the surface analysis using photoelectron emission phenomena depending on temperature. We call this method temperature programmed photoelectron emission (TPPE). The emitted electrons were detected by a gas-flow Geiger counter with Q gas. A PE spectrum representing the curve of the PE intensity vs. wavelength was obtained at different temperatures in the temperature-increase and subsequent temperature-decrease process between 25 and 350°C. The number of emitted electrons in a PE spectrum (PE total count) as a function of the measurement temperature was investigated for 17 kinds of rolled metal sheets that were cleaned in acetone. The metals were distinctly classified into five groups A-I (Al, Pt, Pb), A-II (Ag, Cu, Au, Ni), B-III (Ta), B-IV (Pd, W, Ti, Mo), and B-V (Nb, Fe, Zn, Co, Sn). The A groups indicated a temperature dependent PE total count, while the B groups indicated a virtually temperature independent PE total count. With the A groups a greater amount of the adsorbed oxygen that was present on the initial surface was found by XPS to change to oxide oxygen after TPPE measurement, with the exception of Al. This chemical change is suggested to play a substantial role in the temperature dependence of the PE total count. With the B groups oxide oxygen existed predominantly on the initial surface, resulting in little change in the chemical state of the oxygen. It is suggested that the ability of the metals in gas chemisorption is closely related to the TPPE behavior.