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

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 H2S at 1 x 10(-8) Torr at 800 degrees C. 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 x 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 similar to 750 degrees C 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. (C) 2014 Elsevier B.V. All rights reserved.