Size-dependent effects on electrical contacts to nanotubes and nanowires

TL;DR

This paper investigates how size influences electrical contact properties in nanotubes and nanowires, revealing that side contacts reduce Schottky barriers and that doping strategies become less effective at smaller diameters, with implications for device design.

Contribution

It demonstrates that size-dependent effects significantly alter contact behavior in Q1D structures, providing new insights into contact engineering for nanotube and nanowire devices.

Findings

Schottky barriers are reduced in Q1D structures compared to bulk.

Heavily doping becomes ineffective for smaller nanowire diameters.

Q1D structures are less sensitive to Fermi level pinning effects.

Abstract

Metal-semiconductor contacts play a key role in electronics. Here we show that for quasi-one dimensional (Q1D) structures such as nanotubes and nanowires, side contact with the metal only leads to weak band realignment, in contrast with bulk metal-semiconductor contacts. Schottky barriers are much reduced compared with the bulk limit, and should facilitate the formation of good contacts. However, the conventional strategy of heavily doping the semiconductor to obtain Ohmic contacts breaks down as the nanowire diameter is reduced. The issue of Fermi level pinning is also discussed, and it is demonstrated that the unique density of states of Q1D structures makes them less sensitive to this effect. Our results agree with recent experimental work, and should apply to a broad range of Q1D materials.