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.
@article{arxiv.1406.3919,
title = {Suspending Effect on Low-Frequency Charge Noise in Graphene Quantum Dot},
author = {Xiang-Xiang Song and Hai-Ou Li and Jie You and Tian-Yi Han and Gang Cao and Tao Tu and Ming Xiao and Guang-Can Guo and Hong-Wen Jiang and Guo-Ping Guo},
journal= {arXiv preprint arXiv:1406.3919},
year = {2015}
}