Low-Frequency Noise in Graphene Tunnel Junctions

Abstract

Graphene tunnel junctions are a promising experimental platform for single molecule electronics and biosensing. Ultimately their noise properties will play a critical role in developing these applications. Here we report a study of electrical noise in graphene tunnel junctions fabricated through feedback-controlled electroburning. We observe random telegraph signals characterized by a Lorentzian noise spectrum at cryogenic temperatures (77 K) and a 1/ f noise spectrum at room temperature. To gain insight into the origin of these noise features, we introduce a theoretical model that couples a quantum mechanical tunnel barrier to one or more classical fluctuators. The fluctuators are identified as charge traps in the underlying dielectric, which through random fluctuations in their occupation introduce time-dependent modulations in the electrostatic environment that shift the potential barrier of the junction. Analysis of the experimental results and the tight-binding model indicate that the random trap occupation is governed by Poisson statistics. In the 35 devices measured at room temperature, we observe a 20-60% time-dependent variance of the current, which can be attributed to a relative potential barrier shift of between 6% and 10%. In 10 devices measured at 77 K, we observe a 10% time-dependent variance of the current, which can be attributed to a relative potential barrier shift of between 3% and 4%. Our measurements reveal a high sensitivity of the graphene tunnel junctions to their local electrostatic environment, with observable features of intertrap Coulomb interactions in the distribution of current switching amplitudes.

Single-molecule quantum-transport phenomena in break junctions

“…Such a robust analysis is useful, for example, when reporting on molecular switches. Switching may have several underlying mechanisms, some of which are not related to the internal structure of the molecule but could instead be attributable to mechanical instability of the junctions or changes in the electronic coupling between the molecule and the electrodes 131 , changes in the electrostatic environment (including the substrate) 132 or the presence of ions that are needed to stabilize the molecule 133 .…”

Universal 1/f type current noise of Ag filaments in redox-based memristive nanojunctions

“…Moreover, nanometer scale conductors are known to be especially sensitive to internal or environmental fluctuations. [20][21][22] For this reason, the thorough characterization and understanding of electronic noise in atomic scale metallic filaments represent a fundamental prerequisite toward their practical applications in neuromorphic computing.…”

Single molecule electronic devices with carbon-based materials: status and opportunity

“…This issue serve as another challenge in this field as some studies on the noise characteristics of graphene structures have been reported at cryogenic temperatures and under high vacuum. 68,69…”