Preparation and optical properties of NdH3 and EuH2 films

Thin epitaxial films of neodymium and europium have been grown onto CaF2(111). The structural surface analysis reveals a textured character of the Eu samples consisting of three domains, each tilted by 60°. Auger electron spectroscopy has been performed to study the influence of a buffer layer on the protective properties of the palladium cap layer. After loading with hydrogen, the optical properties of the ferromagnetic semiconductors NdH3−δ and EuH2 were determined in the infrared and visible spectral range. A comparison of hydrogenated and deuterated samples clearly associates the phonons in the transmission spectra in the infrared to hydrogen vibrations. Transmission measurements in the visible spectral range yield the optical band gaps. The values of those gaps and the characteristics of the absorption edges are discussed in the context of their participating electronic transitions.