Calculations of pathways of precise P incorporation into chlorinated Si(100) surface

The precise incorporation of a phosphorus atom into a silicon surface is essential for the fabrication of nanoelectronic devices in which the active area is formed from single impurities. The most accurate approach employs scanning tunneling microscopy lithography, which may be done with atomic precision. However, the accuracy decreases when phosphorus is incorporated into the surface because P substitutes one of two neighboring Si atoms with equal probability. Here, the P-Si exchange mechanism was studied theoretically on a chlorinated Si(100) surface with an asymmetric configuration of Cl vacancies surrounding the P atom. Density functional theory was used to estimate the activation barriers and exchange rates between a P atom and neighboring Si atoms on a Si(100)-2 × 1-Cl surface with three Cl vacancies. The calculation of various P-Si exchange pathways revealed that phosphorus has a higher probability of substituting one Si atom than the others due to the asymmetric configuration of Cl vacancies. Based on the theoretical study of the P-Si exchange mechanism and experimental results from previous studies, a scheme for controlled P incorporation into the silicon surface without uncertainty is proposed.