Influence of hydrogen annealing on the properties of hafnium oxide thin films

Thin films of hafnium oxide were deposited by electron beam evaporation, and were subsequently annealed in hydrogen. X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy, photoluminescence, spectrophotometry, and current–voltage measurements were performed to investigate the structural, chemical, optical, and electrical properties of the films. As-deposited films were amorphous and nearly stoichiometric. Annealing led to crystallization of the films, and reduction of stoichiometry. Photoluminescence measurements revealed the presence of oxygen-related defects. Optically, the films were transparent with a wide band gap, and this was not affected by hydrogen annealing. Moreover, the films were suitable as anti-reflection coatings on silicon. The electrical resistivity of the films was significantly reduced as a result of annealing.

Research highlights
► Hafnium oxide films deposited by e-beam evaporation were annealed in hydrogen.
► XRD revealed that films became ploycrsytalline after annealing at 400° C.
► AFM revealed columnar microstructure.
► XPS showed deviation from stoichiometry with annealing.
► Optical constants and energy gaps were determined.