Long-time drift induced changes in electrical characteristics of graphene–metal contacts

Abstract

Chemical vapour deposition (CVD) graphene is commonly recognized as promising 2D material for development of electronic devices. However, the long-term drift of electrical parameters still requires deeper understanding before the technological means can be selected for an individual type of the devices. In this work, the changes in the electrical resistance were investigated over long time in the planar samples based on the CVD graphene with Au and Ni contacts. The samples were arranged as arrays of the resistors on a silicon substrate covered with a 250 nm layer of thermally grown silicon dioxide. The annealing in pure argon gas flow at 573 K was used to return the electrical properties of samples to the initial state. The effects of drift and annealing were compared for the three parts of structures, namely the electrical contact, the graphene sheet and the edge of the metal film with a hanging graphene sheet. For these parts, the resistance changes were related to the strain and doping of supported and hanged parts of the graphene sheet. Raman spectroscopy and Kelvin force probe microscopy were used to characterize charge doping, strain and work function in the graphene. The drift was explained in terms of the most prominent changes in the doping, strain and work function detected within the edge zone of the contact. It was proved that the annealing significantly changed the p-type doping and work function in the graphene layer in this edge zone. The properties were almost independent of test conditions in the SiO2 supported graphene. The changes in the contact parameters produced by drift mechanisms were proved being reversible under proper annealing conditions.

Dependence of Electrical Charge Transport on the Voltage Applied across Metal–Graphene–Metal Stack under Fixed Compressing Force

“…As shown in Figure 2a, there is a notable difference in the phase lag between the bare Au surface and the graphene-supported Au film, amounting to approximately 10 degrees. Previous RAMAN spectroscopy studies confirmed that the areas represented by darker regions in the scanned phase image (Figure 2a) indicate the presence of the graphene layer [17]. The cross-section (Figure 2c) along the red solid line in Figure 2b reveals that the distance between the nearest peaks or valleys exceeds the radius of the SPM tip used in our experiments, typically falling within the range of 5-55 nm.…”

“…A thin Au layer was formed on the Si plate using DC magnetron sputtering. Commercial chemical vapor deposition (CVD)-grown graphene monolayer (Graphenea) was then transferred via standardized wet transfer method on the Au film [17]. Pt probe (Pt-rock, model RMN12Pt400B, Bruker, Billerica, MA, USA) was placed on top of the structure and used as an electrode for measurements.…”

Platform for Graphene Sensors Using Printed Circuit Boards and Single Board Computers

“…The most common technique used for creating graphene is chemical vapour deposition (CVD) which can create grain boundaries and regions with varying thickness [7], leading to a difference in resistance and performance between sensors. There is also the issue of doping from environmental sources, mainly water, causing a drift in graphene resistance over time [8].…”