RESUMEN
A mild two-step method of black phosphorus (BP) flake thinning was demonstrated in this article. Slight ultraviolet-ozone (UVO) radiation followed by an argon plasma treatment was employed to oxidize mechanically exfoliated BP flakes and remove the surface remains of previous ozone treatment. The annealing process introduced aims to reduce impurities and defects. Low damage and efficient electronic devices were fabricated in terms of controlling the thickness of BP flakes through this method. These results lead to an important step toward the fabrication of high-performance devices based on two-dimensioned materials.
RESUMEN
Controllable growth of metal nanostructures on epitaxial graphene (EG) is particularly interesting and important for the applications in electric devices. Bi nanostructures on EG/SiC are fabricated through thermal decomposition of SiC and subsequent low-flux evaporation of Bi. The orientation, atomic structure, and thickness-dependent electronic states of Bi are investigated by scanning tunneling microscopy/spectroscopy. It is found that metallic Bi nanoflakes and nanorods prefer to grow on the SiC buffer layer region with higher diffusion barrier, but Bi nanoribbons are formed on regularly ordered EG. Although the thicker Bi nanoribbons of 11 monolayers on EG are still metallic, the thinner ones become semiconducting owing to the interfacial effect. This indicates that the electronic states and physical properties of Bi are substrate-dependent. The results are helpful for the design of Bi- and graphene-based electronic and spintronic devices.
RESUMEN
Graphene as the thinnest material has an extremely large specific surface area, and thus the physical properties of graphene based devices should be sensitively dependent on the contacted metals. Moreover, the interfacial interaction between graphene and metals is complicated and it is difficult to probe. In this paper, epitaxial graphene is prepared by thermal decomposition of 6H-SiC(0001), and then Ag is deposited on it. It is found that the morphology and distribution of Ag particles on graphene domains are independent of the graphene thickness. The Ag particles induce the surface enhanced Raman scattering (SERS) effect and the doping effect in epitaxial graphene. The enhancement factor of SERS as well as the splitting of the G band and the shift of the 2D band decreases with increasing graphene thickness, which can be ascribed to the weakened interaction between Ag and EG. This is confirmed by the charge transfer between the Ag atom and epitaxial graphene on 6H-SiC predicted by first-principles calculations. The results are helpful to the design and development of graphene-based composites and devices.