Effect of High-Temperature Annealing on Graphene with Nickel Contacts

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.

Laminar Flow-Assisted Metal Etching for the Preparation of High-Quality Transfer-Free Graphene

“…The redshift in G band position is consistent with the influence of thermal annealing on the desorption of p-dopants from the graphene surface . These results demonstrate that vacuum annealing at the appropriate temperature is helpful to remove p-doping adsorbents on graphene, such as water vapor, O 2 , and other oxygen-containing molecules from the ambient environment. , Consequently, the V Dirac value shifts considerably toward 0 V (Figure S12a), and the mobility of these GFET devices increases (Figure S12b) due to reduced contamination on graphene surface . The remaining p-doping indicated by a nonzero V Dirac at ∼8 V can be attributed to SiO 2 defects. ,,, In addition, thermal annealing improves the mobility with an increase of ∼350 and ∼500 cm 2 V –1 s –1 for graphene patterns prepared by the conventional and microfluidic etching methods, respectively (Figure S12b).…”

“…81 These results demonstrate that vacuum annealing at the appropriate temperature is helpful to remove p-doping adsorbents on graphene, such as water vapor, O 2 , and other oxygen-containing molecules from the ambient environment. 83,84 Consequently, the V Dirac value shifts considerably toward 0 V (Figure S12a), and the mobility of these GFET devices increases (Figure S12b) due to reduced contamination on graphene surface. 83 The remaining p-doping indicated by a nonzero V Dirac at ∼8 V can be attributed to SiO 2 defects.…”

Manufacture and characterization of graphene membranes with suspended silicon proof masses for MEMS and NEMS applications

“…The inhomogeneous distribution of stress and doping across the graphene patch might result in correlated variation in the height and position of Raman peaks to some extent. The impact of hightemperature annealing on graphene, such as enhanced hole doping or defects in graphene, has been widely reported on the basis of Raman spectroscopy studies [61][62][63][64] . It was also shown that annealing at temperatures below 500°C in vacuum results in a significant decrease in the "D peak" and "2D peak" due to annealing-induced enhanced doping in graphene, and annealing in a vacuum at temperatures of up to 1000°C results in a significant increase in the "2D peak" with a continuous decrease in the "D peak", indicating the partial removal of the defects and restoration of the damaged lattice 63 .…”

Membranes Coated with Graphene-Based Materials: A Review

“…The cleaning and contact annealing of graphene at increased temperature levels examines the impact of the process on graphene attributes. A detailed comprehension of the changes happening during annealing is extremely significant, and thus has been thoroughly explored by researchers [ 141 ].…”