Self-assembled CaF2 nanostructures on silicon

A method for chemical imaging of CaF2, CaF1, and Si by scanning tunneling s pectroscopy is presented. This method is utilized for identifying the growt h regimes of CaF2 and CaF1 on stepped Si(111)7X7. For CaF2 on Si(111), we f ind random islands, stripes, and ordered islands, depending on the supersat uration. For CaF2 on a CaF1 monolayer on Si(111), we find regular stripes t hat are continuous and separated from each other. CaF2 structures are attac hed to the bottom edge of a step when growing directly on Si, but they pref er the top of a step edge when growing on a CaF1 buffer layer. These highly regular, linear arrays of CaF2 stripes and dots can serve as masks for ass embling more sophisticated nanostructures. (C) 1999 American Vacuum Society . [S0734-2101(99)12204-8].