Local charge transfer doping in suspended graphene nanojunctions

TL;DR

This study investigates how different metal electrodes affect charge transfer doping in nanoscale graphene transistors, revealing electrode-dependent shifts in charge neutrality point and the influence of channel length.

Contribution

It demonstrates that platinum electrodes induce positive charge transfer doping in graphene, with effects diminishing as channel length increases, providing insights into electrode-graphene interactions.

Findings

Platinum electrodes cause a significant positive shift in charge neutrality point.

Gold electrodes show negligible charge neutrality point shift.

Charge transfer effects decrease with increasing channel length.

Abstract

We report electronic transport measurements in nanoscale graphene transistors with gold and platinum electrodes whose channel lengths are shorter than 100 nm, and compare them with transistors with channel lengths from 1 \textmu{}m to 50 \textmu{}m. We find a large positive gate voltage shift in charge neutrality point (NP) for transistors made with platinum electrodes but negligible shift for devices made with gold electrodes. This is consistent with the transfer of electrons from graphene into the platinum electrodes. As the channel length increases, the disparity between the measured NP using gold and platinum electrodes disappears.