Superior properties of plasma-assisted room-temperature-grown graphene from STM studies

We report scanning tunneling microscopic and spectroscopic (STM/STS) studies of large-area monolayer graphene grown at room temperature (RT) on Cu foils, Cu (100) and Cu (111) single crystals, and compare the properties of these samples with high-temperature (1000 $^{\circ}$C) CVD-grown graphene. All RT-grown graphene exhibit highly ordered honeycomb structures over $\sim$ 1 cm$^{2}$ areas, smooth surface morphology, much reduced strain (\textless\ 0.1{\%}) and additional Moire patterns for samples grown on single crystals. The structural quality and reduced strain obtained from STM studies are consistent with finds from Raman spectra. In contrast, high-temperature CVD-grown graphene revealed strongly distorted atomic structures and large strain, giving rise to giant pseudo-magnetic fields and charging effects as manifested by the conductance peaks at quantized energies and the strongly enhanced local conductance in highly strained regions. These strain-induced effects are believed to be responsible for the reduced electrical mobility in typical CVD-grown graphene. The superior structural and electronic properties demonstrated by our RT-grown graphene are promising for a wide range of applications. This work was supported by NSF through IQIM at Caltech.