First-Principle Study of Phosphine Adsorption on Si(001)-2x1-Cl
This paper presents a density functional theory study for phosphine adsorption on a Si(001)-2 × 1 surface covered by a chlorine monolayer, including adsorption on local defects, i.e., mono- and bivacancies in the adsorbate layer (Cl, Cl2), and combined vacancies with removed silicon atoms (SiCl, SiCl2). Activation barriers were found for the adsorbing PH3 to dissociate into PH2 + H and PH + H2 fragments; it was also established that phosphine dissociation on combined vacancies is possible at room temperature. If there is a silicon vacancy on the surface, phosphorus settles in the Si(001) lattice as PH (if the vacancy is SiCl) or as PH2 (if the vacancy is SiCl2). This paper suggests a method to plant a separate phosphorus atom into the silicon surface layer with atomic precision, using phosphine adsorption on defects specially created on a Si(001)-2 × 1–Cl surface with a scanning tunneling microscope tip.