High-purity, erbiumhydride thin films have been deposited onto alpha-Al2O3 and oxidized Si by reactive sputtering methods. Rutherford backscattering spectrometry and elastic recoil detection show that films deposited at temperatures of 35, 150 and 275 degrees C have a composition of 3H:1Er. Erbium trihydride films consist of a face-centered cubic erbium sub-lattice with a lattice parameter in the range of 5.11-5.20 angstrom. The formation of cubic ErH3 is intriguing, because previous studies demonstrate a single trihydride phase with a hexagonal metal sub-lattice. The formation of a stable, cubic trihydride phase is attributed to a large, in-plane stress resulting from ion beam sputter deposition. (C) 2012 Elsevier B. V. All rights reserved.