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To characterize easily the state of real metal surfaces in ambient environments, we have developed an extremely sensitive technique for surface analysis using photoelectron emission phenomena as a function of temperature. We will call this method temperature-programmed photoelectron emission (TPPE). The emitted electrons are detected by a gas-flow Geiger counter with Q gas. The TPPE measurement is performed by scanning the wavelength of incident UV light at different temperatures in the temperature-increase and subsequent temperature-decrease process between 25 and 350°C. A photoelectron emission (PE) spectrum representing the curve of PE intensity vs wavelength is obtained at each temperature. The number of emitted electrons in a PE spectrum is termed PE total count. The PE total count as a function of the measurement temperature was investigated for 17 kinds of commercial rolled metal sheets. The metals were distinctly classified into two main groups A and B, the former indicating a temperature-dependent PE total count and the latter a virtually temperature-independent PE total count. Group A included Al, Pt, Pb, Cu, Ag, Au and Ni; group B included Ta, Ti, Mo, Pd, W, Fe, Co, Zn, Nb and Sn. With group A, the greater amount of adsorbed oxygen present at the initial surface was found by XPS to change to the oxide oxygen after TPPE measurement. This chemical change is suggested to play a substantial role in the temperature dependence of the PE total count.

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