Imaging the Acceptor Wave Function Anisotropy in Silicon

TL;DR

This paper presents the first STM images of acceptor wave functions in silicon, revealing their anisotropic shapes and confirming their acceptor nature through experimental and theoretical analysis, which is crucial for quantum device engineering.

Contribution

First direct imaging of acceptor wave functions in silicon using STM, supported by calculations that confirm their anisotropic shape and acceptor character.

Findings

STM images show square ring-like acceptor features

Effective-mass and tight-binding models match experimental images

Acceptors originate from near-surface bismuth implantation

Abstract

We present the first scanning tunneling microscopy (STM) images of hydrogenic acceptor wave functions in silicon. These acceptor states appear as square ring-like features in STM images and originate from near-surface defects introduced by high-energy bismuth implantation into a silicon (001) wafer. Scanning tunneling spectroscopy confirms the formation of a p-type surface. Effective-mass and tight-binding calculations provide an excellent description of the observed square ring-like features, confirming their acceptor character and attributing their symmetry to the light- and heavy-hole band degeneracy in silicon. Detailed understanding of the energetic and spatial properties of acceptor wave functions in silicon is essential for engineering large-scale acceptor-based quantum devices.