Observation of Buried Phosphorus Dopants near Clean Si(100)-(2x1) with Scanning Tunneling Microscopy

TL;DR

This study uses scanning tunneling microscopy to detect individual phosphorus dopants near clean Si(100)-(2x1) surfaces, revealing their charge signatures and dependence on sample voltage, and providing insights into surface and bulk electronic interactions.

Contribution

It demonstrates the ability to identify single phosphorus dopants on clean silicon surfaces and analyzes their electronic signatures and surface interactions.

Findings

Dopants show charge-induced band bending signatures in STM images.

Signature strength depends on sample voltage and dopant depth.

Surface state bands extend into the bulk conduction band, affecting dopant signatures.

Abstract

We have used scanning tunneling microscopy to identify individual phosphorus dopant atoms near the clean silicon (100)-(2x1) reconstructed surface. The charge-induced band bending signature associated with the dopants shows up as an enhancement in both filled and empty states and is consistent with the appearance of n-type dopants on compound semiconductor surfaces and passivated Si(100)-(2x1). We observe dopants at different depths and see a strong dependence of the signature on the magnitude of the sample voltage. Our results suggest that, on this clean surface, the antibonding surface state band acts as an extension of the bulk conduction band into the gap. The positively charged dimer vacancies that have been observed previously appear as depressions in the filled states, as opposed to enhancements, because they disrupt these surface bands.