XPS studies of carbon supported films formed by the resistive deposition of manganese

Abstract

The surface and subsurface speciation of carbon-supported vapor-deposited films, prepared by resistively heating manganese chips in the sample chamber of an HP 5950A ESCA spectrometer, have been studied using XPS and argon ion etching. It is shown that the oxide formed in poor vacuum is MnO. Under improved experimental conditions, a mixture of Mn metal and MnO is obtained, but the metal is very reactive to oxygen. For very thick films formed in poor vacuum, the oxide covers a layer of manganese metal. The oxide is no longer evident after 60 h of etching. For the layer of manganese remaining, we have found that the Mn3 s multiplet splitting is smaller than that reported in the literature. The present result is shown to be consistent with magnetic susceptibility measurements on α-Mn. For discontinuous MnO films, argon ion etching causes the Mn2 p binding energy to shift to higher energy. This is inconsistent with reduction to Mn metal, as the binding energy would shift to a lower value for this case.