Twisted ultrathin silicon nanowires: a possible torsion electromechanical nanodevice

TL;DR

This paper investigates ultrathin twisted silicon nanowires as potential nanoscale torsion sensors, analyzing their structural and electronic properties through first principles calculations to enable molecular force measurements.

Contribution

It introduces the concept of using twisted silicon nanowires as torsion nanobalances and provides a detailed first principles analysis of their stability and electronic behavior.

Findings

Pentagonal and hexagonal nanowires are the thinnest stable structures.

All wires exhibit Hooke's law behavior for small twists.

Hydrogenation induces spontaneous twisting and alters electronic properties.

Abstract

Nanowires have been considered for a number of applications in nanometrology. In such a context, we have explored the possibility of using ultrathin twisted nanowires as torsion nanobalances to probe forces and torques at molecular level with high precision, a nanoscale system analogous to the Coulomb's torsion balance electrometer. In order to achieve this goal, we performed a first principles investigation on the structural and electronic properties of twisted silicon nanowires, in their pristine and hydrogenated forms. The results indicated that wires with pentagonal and hexagonal cross sections are the thinnest stable silicon nanostructures. Additionally, all wires followed a Hooke's law behavior for small twisting deformations. Hydrogenation leads to spontaneous twisting, but with angular spring constants considerably smaller than the ones for the respective pristine forms. We observed considerable changes on the nanowire electronic properties upon twisting, which allows to envision the possibility of correlating the torsional angular deformation with the nanowire electronic transport. This could ultimately allow a direct access to measurements on interatomic forces at molecular level.