Effect of Surface Adsorption of Ba, O, and BaO on the Work Function of Different Hafnium Phases

The effect of crystal structure on the electron-emission properties of thin hafnium films whose surfaces were modified with Ba and O atoms or BaO molecules was investigated using density functional theory (DFT/PBE) as implemented in the SIESTA software package. Cubic, hexagonal, and triclinic Hf structures were considered. It was established that a five-layer slab model is sufficient to reproduce the work function of bulk hafnium. For unmodified Hf, the work function ranges from 3.20 to 4.16 eV and depends strongly on the crystal structure.