Controlled Coupling and Occupation of Silicon Atomic Quantum Dots

TL;DR

This paper demonstrates controlled formation, occupation, and tunnel-coupling of silicon atomic quantum dots using scanning tunneling microscopy, enabling room-temperature quantum cellular automata components.

Contribution

It introduces a method to control electron occupation and coupling of silicon dangling bond quantum dots, advancing atomic-scale quantum device fabrication.

Findings

Coulomb repulsion reduces charge in closely spaced DBs.

Electron tunnel-coupling can be controlled and observed.

Room-temperature quantum cellular automata elements demonstrated.

Abstract

It is discovered that the zero-dimensional character of the silicon atom dangling bond (DB) state allows controlled formation and occupation of a new form of quantum dot assemblies. Whereas on highly doped n-type substrates isolated DBs are negatively charged, it is found that Coulomb repulsion causes DBs separated by less than ~2 nm to experience reduced localized charge. The unoccupied states so created allow a previously unobserved electron tunnel-coupling of DBs, evidenced by a pronounced change in the time-averaged view recorded by scanning tunneling microscopy. Direct control over net electron occupation and tunnel-coupling of multi-DB ensembles through separation controlled is demonstrated. Through electrostatic control, it is shown that a pair of tunnel-coupled DBs can be switched from a symmetric bi-stable state to one exhibiting an asymmetric electron occupation. Similarly, the setting of an antipodal state in a square assembly of four DBs is achieved, demonstrating at room temperature the essential building block of a quantum cellular automata device.