Theory of scanning tunneling microscopy - methods andapproximations

The direct-transmission and transfer Hamiltonian approaches, as well as various approximations developed for scanning tunneling microscopy are reviewed and compared for a free-electron model. The second approach provides a deeper insight into the imaging process and should enable one to include effects due to tight-binding bands, surface states and adsorbate-induced modifications. Possible new directions of research and remaining challenges are identified. © 1984 Elsevier Science Publishers B.V.