X-ray photoelectron spectroscopy characterization and morphology of MgO thin films grown on single-crystalline diamond (100)

The morphology and composition of MgO films grown on single-crystalline diamond (100) have been studied. MgO thin films were deposited in the substrate temperature range from room temperature (RT) to 723 K by means of electron beam evaporation using a MgO powder source. Atomic force microscopy images indicated that the film grown at RT without O₂ supply was relatively uniform and flat whereas that deposited in oxygen ambient yielded higher growth rates and rough surface morphologies. X-ray photoelectron spectroscopy analyses demonstrate that the MgO film deposited at RT without O₂ has the composition closest to that of the stoichiometric MgO and that a thin contaminant layer composed mainly of magnesium peroxide (before etching) or hydroxide (after etching) was unintentionally formed on the film surface, respectively.These results will be discussed in relation to the interaction among the evaporated species and intentionally supplied oxygen molecules at the growth front as well as the interfacial energy between diamond and MgO.