Persistent enhancement of the carrier density in electron irradiated InAs nanowires

TL;DR

This study demonstrates that electron irradiation in ultra high vacuum persistently increases the surface free carrier density in InAs nanowires, significantly enhancing their conductivity primarily through surface defect formation.

Contribution

It reveals that surface defects caused by electron irradiation are the main factor increasing conductivity, contrasting with bulk defect effects.

Findings

Conductivity increases persistently after electron irradiation.

Surface free carrier concentration is the key factor.

Surface defects dominate over bulk defects in affecting properties.

Abstract

We report a significant and persistent enhancement of the conductivity in free-standing non intentionnaly doped InAs nanowires upon irradiation in ultra high vacuum. Combining four-point probe transport measurements performed on nanowires with different surface chemistries, field-effect based measurements and numerical simulations of the electron density, the change of the conductivity is found to be caused by the increase of the surface free carrier concentration. Although an electron beam of a few keV, typically used for the inspection and the processing of materials, propagates through the entire nanowire cross-section, we demonstrate that the nanowire electrical properties are predominantly affected by radiation-induced defects occuring at the nanowire surface and not in the bulk.