Hydrogen induced lattice expansion and site occupation analyzed by ion beam methods

Abstract We study the absorption of H in ultrathin crystalline Fe/V stacks using elastic recoil detection (ERD) and resonant nuclear reaction analysis (NRA) combined with Rutherford backscattering spectrometry (RBS). Probing with the resonant 1H (15N,αγ) 12C nuclear reaction allows us to profile the hydrogen concentration with high depth resolution, while ERD permits us to quantify the integral hydrogen inventory while minimizing possible ion-beam induced hydrogen desorption. We perform angular scans in order to directly identify the interstitial site occupancy. A detailed analysis of channeling patterns permits us the deduction of crystal strain in as-deposited films as well as H-loaded targets. We observe tetragonal strain formation resulting in c/a = 1.06 and find qualitative indications for tetrahedral site occupation.