Suspending Effect on Low-Frequency Charge Noise in Graphene Quantum Dot

TL;DR

This study investigates charge noise in graphene quantum dots, revealing that suspension above the substrate does not significantly reduce noise, which is mainly caused by edge states rather than substrate disorders, impacting device coherence.

Contribution

The paper demonstrates that suspending graphene quantum dots does not significantly decrease 1/f charge noise, highlighting edge states as the primary noise source.

Findings

Charge noise in graphene QDs is larger than in macroscopic FETs and increases with temperature.

Suspending the QD does not significantly reduce noise levels.

Edge states dominate the 1/f noise, affecting device coherence.

Abstract

Charge noise is critical in the performance of gate-controlled quantum dots (QDs). Here we show the 1/f noise for a microscopic graphene QD is substantially larger than that for a macroscopic graphene field-effect transistor (FET), increasing linearly with temperature. To understand its origin, we suspended the graphene QD above the substrate. In contrast to large area graphene FETs, we find that a suspended graphene QD has an almost-identical noise level as an unsuspended one. Tracking noise levels around the Coulomb blockade peak as a function of gate voltage yields potential fluctuations of order 1 "{\mu}eV", almost one order larger than in GaAs/GaAlAs QDs. Edge states rather than substrate-induced disorders, appear to dominate the 1/f noise, thus affecting the coherency of graphene nano-devices.