Abstract
Graphene has shown great potential for ultra-high frequency electronics. However, using graphene in electronic devices creates a requirement for electrodes with low contact resistance. Thermal annealing is sometimes used to improve the performance of contact electrodes. However, high-temperature annealing may introduce additional doping or defects to graphene. Moreover, an extensive increase in temperature may damage electrodes by destroying the metal–graphene contact. In this work, we studied the effect of high-temperature annealing on graphene and nickel–graphene contacts. Annealing was done in the temperature range of 200–800 °C and the effect of the annealing temperature was observed by two and four-point probe resistance measurements and by Raman spectroscopy. We observed that the annealing of a graphene sample above 300 °C increased the level of doping, but did not always improve electrical contacts. Above 600 °C, the nickel–graphene contact started to degrade, while graphene survived even higher process temperatures.
Highlights
In the past 15 years, graphene has attracted an enormous amount of interest from the scientific community
The graphene sample was spin-coated with a poly(methyl methacrylate) (PMMA) film of 100 nm thickness
We observed that annealing of a graphene sample at temperatures above 200−300 ◦C may cause an unintentional p-type doping
Summary
In the past 15 years, graphene has attracted an enormous amount of interest from the scientific community. A lot of work has been dedicated to finding good electrical contacts for graphene and other 2D materials [1,2,3,4]. For this purpose, many metals (e.g., Ag, Al, Au, Co, Cr, Cu, Fe, Ni, Pd, Pt, and Ti) have been tested [2,3,4,5,6,7]. The thermal annealing of samples has been shown to enhance the electric contact between nickel and graphene [9,10,11,12]
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