Contact potential difference measurements on polycrystalline Ni during and after deposition with evaporated Ni in the temperature range 230° ≦ T ≦ 450°C

Abstract

The new pendulum device for measuring contact potential differences has been used in an investigation of the work function Φ r of a polycrystalline Ni electrode relative to an arbitrary fixed value Φ 0 during and after deposition with evaporated Ni in the temperature range 230° ≦ T ≦ 450°C The following important results were obtained. The temperature coefficient of the work function ΔΦ/ ΔT of polycrystalline Ni is a constant in the whole temperature range investigated, if the measuring procedure is performed after cleaning and evaporation onto the Ni target. There is neither a jump in Φ r nor a change of slope in ΔΦ/ ΔT at the Curie point. Quantitatively ΔΦ/ ΔT = -(0.15 ± 0.01) meV °C -1. When the work function Φ r of Ni as a function of temperature is investigated during the time of deposition a markedly altered dependence of Φ r on the temperature T is obtained. All results are discussed qualitatively in terms of the theoretical aspects.