Full text loading...
(a) Graphene and n-type semiconductor in separated systems. (b) Graphene and n-type semiconductor connected into one system in which the effect of interfacial states is also taken into account. Definition of symbols: φm and φg are the work functions of metal and neutral graphene, respectively. χ is the electron affinity of the semiconductor and Eg is band gap. qφn is the energy difference between the bottom energy of the conduction band Ec and the Fermi level EF . φBn0 is the barrier height. φ0 is the neutral level of the interfacial states above valance band Ev . Δg is the work function shift of graphene relative to the Dirac points. Δtr is the potential drop on the interfacial gap di between graphene.
Tapping mode AFM images of an isolated SLG sheet on an n-GaN (a) and a p-GaN (e) substrate. The green lines across the boundary between graphene and GaN indicate the profile for the heights shown in (b) and (f) at approximately 0.9 nm for both the n-GaN and p-GaN samples. Inset: Diagram of integrated C-AFM and Raman measurements with an Au-coated AFM tip. (c) and (g) Raman spectra (632.8 nm laser wavelength) obtained from the corresponding red spots in (a) and (e). a.u., arbitrary units. (d) and (h) Local I-V curves, acquired from bare n- and p-GaN (black lines) substrates and graphene sheets (red lines), respectively. Insets: schematic band structures of Au/n-GaN and graphene/n-GaN in (d) and Au/p-GaN and graphene/p-GaN in (h), which demonstrates the barrier heights and the Fermi level shift. The values are listed in Table I.
The calculated and experimental barrier heights (symbols are marked in the insets of Figures 2(d) and 2(h)).
Article metrics loading...