Relaxation effects in NiMnSb-Half-Heusler thin films

The Half-Heusler alloy NiMnSb is an important material which will possibly enable the fabrication of spintronic devices due to it's unusual half-metallic properties. It can be grown in high crystalline quality on InGaAs/InP substrates, however, as for all heteroepitaxial systems mechanical stress is an important factor which influences crystalline quality, film growth, and magnetic properties. We present several series of X-ray measurements on MBE-grown NiMnSb thin films on InP(111) and InP(001) substrates. Reciprocal space mapping and X-ray reflectivity were measured using the six-circle-diffractometer at BW2, HASYLAB, Hamburg. Structural properties like the critical thickness for pseudomorphic growth, relaxation, and interface roughnesses are discussed. Caused by different substrate orientations the systems show differences in relaxation. Furthermore the influence of exposure to air was investigated by capping some of the samples.