Initial growth of insulating overlayers of NaCl on Ge(100) observed by scanning tunneling microscopy with atomic resolution

Abstract

The epitaxial growth start of an insulating NaCl film on a Ge(100) surface was directly imaged by scanning tunneling microscopy. Atomic resolution was achieved for islands of the first NaCl double layer with upright-standing NaCl dipoles. The tunneling current is preferentially determined by occupied Ge states extending into the NaCl layer. The results corroborate and extend the earlier proposed ``carpetlike'' growth mode of the NaCl layer over monoatomic Ge steps, even for small NaCl islands submonolayer coverage. \textcopyright{} 1996 The American Physical Society.