Adsorptions of Tetrafluorotetracyanoquinodimethane on Entirely and Partially Hydrogenated C(100)-2 x 1 Surfaces

We studied the adsorptions of tetrafluorotetracyanoquinodimethane (F4-TCNQ) on entirely and partially hydrogenated C(100)-2 x 1 Surfaces using density-functional tight-binding and first-principle methods. The results indicate that F4-TCNQ could form hydrogen bonding with surface H atoms of the entirely hydrogenated C(100)-2 x 1 surface, and chemically react with the bare carbon atoms of the partially hydrogenated C(100)-2 x 1 surface. The adsorption of F4-TCNQ induces charge transfer from the diamond surface to F4-TCNQ and the holes left in the diamond surface could increase the conductivity of the diamond surface. It is shown that electron transfer is facilitated by the higher valence band maximum of the diamond surface compared with the energy level of the lowest unoccupied molecular orbital of F4-TCNQ.