Stress induced phase transition in Gd2O3 films by ion beam assisted reactive electron beam-physical vapor deposition (EB-PVD)

•High deposition rate leads to mixed cubic/monoclinic phase in Gd2O3 films.•Cubic phase is formed at the interface and stress is relieved by monoclinic phase formation.•1 μm thick fully cubic phase films are grown by lowering deposition rate and increasing temperature.•Ion bombardment induces compressive stress resulting in cubic-to-monoclinic phase transition.

The structural evolution of thick polycrystalline gadolinium oxide (Gd2O3) films deposited by reactive electron beam-physical vapor deposition (EB-PVD) is investigated. High deposition rates (> 5 Å/s) lead to the growth of mixed phase films which are of the cubic phase near the film/substrate interface before forming monoclinic phase as distance from the interface increases. By decreasing the deposition rate to < 1 Å/s for films grown at temperatures of 650 °C, films up to one micron thick have been grown in the pure cubic phase. The growth of the thermodynamically stable cubic phase under these conditions is attributed to both higher surface mobility of the adatoms during growth and to increased tensile stress within the film. Ion beam assisted deposition (IBAD) was then performed to introduce compressive stress into the film resulting in the formation of the monoclinic phase. Wafer curvature, X-ray diffraction, confocal Raman spectroscopy, and scanning electron microscopy are utilized to characterize the film and present evidence for the existence of a stress-induced phase transition in the Gd2O3 films.