Ballistic Electron Emission Microscopy on CoSi${}_2$/Si(111) interfaces: band structure induced atomic-scale resolution and role of localized surface states

TL;DR

This paper uses a theoretical model to explain atomic-scale resolution in BEEM experiments on CoSi${}_2$/Si(111) interfaces, highlighting the influence of band structure and surface states on electron focusing and current behavior.

Contribution

It introduces a Keldysh Green's function approach to elucidate how band structure and surface states produce atomic resolution and current anticorrugation in BEEM.

Findings

Hot electrons form a focused beam due to band structure effects.

Localized surface states cause anticorrugation of BEEM current.

Bulk and surface band structures are crucial for understanding BEEM data.

Abstract

Applying a Keldysh Green`s function method it is shown that hot electrons injected from a STM-tip into a CoSi${}_2$/Si(111) system form a highly focused beam due to the silicide band structure. This explains the atomic resolution obtained in recent Ballistic Electron Emission Microscopy (BEEM) experiments. Localized surface states in the $(2 \times 1)$-reconstruction are found to be responsible for the also reported anticorrugation of the BEEM current. These results clearly demonstrate the importance of bulk and surface band structure effects for a detailed understanding of BEEM data.