Abstract
We have explored the properties of SiC-based epitaxial graphene grown in a cold wall UHV chamber. The effects of the SiC surface orientation and silicon loss rate were investigated by comparing the characteristics of each formed graphene. Graphene was grown by thermal decomposition on both the silicon (0001) and carbon (000-1) faces of on-axis semi-insulating 6H-SiC with a "face-down" and "face-up" orientations. The thermal gradient, in relation to the silicon flux from the surface, was towards the surface and away from the surface, respectively, in the two configurations. Raman results indicate the disorder characteristics represented by ID/IG down to < 0.02 in Si-face samples and < 0.05 in C-faces over the 1 cm2 wafer surface grown at 1,450°C. AFM examination shows a better morphology in face-down surfaces. This study suggests that the optimum configuration slows the thermal decomposition and allows the graphene to form near the equilibrium. The Si-face-down orientation (in opposition to the temperature gradient) results in a better combination of low disorder ratio, ID/IG, and smooth surface morphology. Mobility of Si-face-down orientation has been measured as high as approximately 1,500 cm2/Vs at room temperature. Additionally, the field effect transistors have been fabricated on both Si-face-down and C-face-down showing an ambipolar behavior with more favorable electron conduction.
Highlights
Graphene is a sheet of graphite consisting of sp2-bonded carbon atoms [1]
In order to investigate the effects of silicon evaporation rate on the film quality, we designed a growth configuration that would allow the minimization of silicon loss and at the same time provide a way to examine the effects of a much higher rate of Si evaporation
It is noted that the morphology has been affected by the silicon and carbon faces in the downward and upward direction
Summary
Graphene is a sheet of graphite consisting of sp2-bonded carbon atoms [1]. The unique material properties of graphene such as extremely high-carrier mobility, semimetallic characteristics, and two-dimensional [2-D] very thin sheet of carbon have attracted a great interest and will lead to the development of nanoelectronics [2,3]. In order to investigate the effects of silicon evaporation rate on the film quality, we designed a growth configuration that would allow the minimization of silicon loss and at the same time provide a way to examine the effects of a much higher rate of Si evaporation. Both the Si-face and C-face of SiC were chemically and mechanically polished [CMP], and the growth was done on both surfaces with the thermal gradient directed towards one surface and away from the other. This arrangement provides a condition for low and high silicon loss at the same time
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