Computations of STM images of zinc-blende GaN(001) surface

Theoretical study of the formation of STM images of the CaN(0 0 1)-(2 x 2) surface is presented. Calculation of the tunnelling current between the tip and the substrate is based on the non-equilibrium Green-function formalism . Tunnelling current and conductance, calculated for W and Al tips, and dif ferent voltages and distances, are analysed. Our simulations show that for both considered tips, the topography of images, given by unoccupied surface states, correctly reproduces a (2 x 2) reconstruction of the substrate: su rface. Presented results confirm the important role of the tunnelling throu gh d orbitals of the W tip in the process of the STM image formation. (C) 2 001 Elsevier Science Ltd. All rights reserved.