N2-plasma nitridation on Si(111): Its effect on crystalline silicon nitride growth

This study uses a combination of atom-resolved scanning tunneling microscopic and spectroscopic (STM/STS) techniques to investigate the effects of N₂-plasma nitridation on a crystalline β-Si₃N₄ ultrathin film grown on the Si(111) substrate. The proposed two-step growth process, including N₂-plasma nitridation followed by vacuum annealing both at high temperature (~ 900 °C), can substantially improve the atomic and electronic structures of the β-Si₃N₄ having an atomically uniform morphology and stoichiometry. The effects of nitridation and post-annealing temperatures were examined by monitoring the morphological and electronic–structural evolutions of a non-stoichiometric surface. Moreover, the two-step N₂-plasma nitridation process has extremely low activation energy and thus minimizes the thermal energy from the substrate for practical growth of β-Si₃N₄ ultrathin film.