QUANTUM POINT-CONTACT ON GRAPHITE SURFACE

The conductance through a quantum point contact created by a sharp and hard metal tip on the graphite surface has features which to our know ledge have not been encountered so far in metal contacts or in nano-wi res. In this paper we first investigate these features which emerge fr om the strongly directional bonding and electronic structure of graphi te: and provide a theoretical understanding for the electronic conduct ion through quantum point contacts. Our study involves molecular-dynam ics simulations to reveal the variation of interlayer distances and at omic structure at the proximity of the contact that evolves by the tip pressing toward the surface. The effects of the elastic deformation o n the electronic structure, state density at the Fermi level, and crys tal potential are analyzed by performing self-consistent-field pseudop otential calculations within the local-density approximation. It is fo und that the metallicity of graphite increases under the uniaxial comp ressive strain perpendicular to the basal plane. The quantum point con tact is modeled by a constriction with a realistic potential. The cond uctance is calculated by representing the current transporting states in Laue representation, and the variation of conductance with the evol ution of contact is explained by taking the characteristic features of graphite into account. It is shown that the sequential puncturing of the layers characterizes the conductance. [S0163-1829(98)02936-1].