Interaction of phosphine with Si(100) from core-level photoemission and real-time scanning tunneling microscopy

Abstract

In this paper, we investigate the interaction of phosphine $\left({\mathrm{PH}}_3\right)$ on the $\mathrm{Si}\mathrm{}\left(100\right)-2\mathrm{}\times 1$ surface at temperatures between 635 and 900 K. The hydrogen desorption, growth mode, surface morphology, and chemical composition and ordering of the surface layer are examined by synchrotron radiation core-level photoemission and real-time high-temperature scanning tunneling microscopy. The $\mathrm{P}\hspace{0.5em}2p$ core-level spectra indicate that decomposition of ${\mathrm{PH}}_n$ is complete above $\sim 550$ K and the maximum P coverage is strongly influenced by the growth temperature, which governs the coverage of H-terminated sites. The scanning tunneling microscopy (STM) images taken at real time during ${\mathrm{PH}}_3$ exposure indicate that a surface phosphorus atom readily and randomly displaces one Si atom from the substrate. The ejected Si diffuses, nucleates, and incorporates itself into islands or step edges, leading to similar growth behavior as that found in Si chemical vapor deposition. Line defects both perpendicular and parallel to the dimer rows are observed on the nearly P-saturated surface. Perpendicular line defects act as a strain relief mechanism. Parallel line defects result from growth kinetics. STM images also indicate that incorporating a small amount of phosphorus eliminates the line defects in the $\mathrm{Si}\mathrm{}\left(100\right)-2\mathrm{}\times n$ surface.