Wet-transfer of CVD-grown graphene onto sulfur-protected W(110)

摘要

Graphene, grown by chemical vapor deposition, is transferred onto W(110) surface with a protective sulfur layer. Sulfur was adsorbed on the W(110) surface in ultrahigh vacuum (UHV) by reaction with H_2S at 1 × 10~(-8) Torr at 800 ℃ Low-energy electron diffraction and scanning tunneling microscopy (STM) measurements show that an ordered sulfur adsorbate layer is formed on W(110) with a 1 × 5 superstructure. The monolayer of sulfur subsequently protects the W(110) surface from oxidation during wet-transfer of CVD-grown graphene. After the graphene transfer, the sample is re-introduced to UHV and characterized by STM, Auger electron spectroscopy, x-ray and ultraviolet photoemission spectroscopy. The adsorbed sulfur layer prevents carbide formation, by reaction of graphene with tungsten, to annealing temperatures of at least ～750 ℃ in vacuum. Finally, photoemission measurements of the graphene/S/W(110) interface indicates p-type doping of graphene due to charge transfer at the interface as a consequence of the high work function of the W(110)-S substrate.