Deuterium plasma exposure of rhodium films: Role of morphology and crystal structure

The behavior of rhodium film mirrors with different crystal structure and morphology toward a deuterium plasma is presented. The specular reflectivity of rhodium films was monitored before, during and after exposure. To understand the reflectivity behavior of the rhodium films during exposure, samples were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy and atomic force microscopy. Crystal structure and morphology of rhodium films strongly affect the change of the specular reflectivity during deuterium plasma exposure. In particular, films with few nm crystallite size and granular-like morphology prevent the reflectivity degradation, probably as a consequence of the inhibition of rhodium deuteride sub-superficial layer formation.