Investigation of orientation and packing of H8Si8O12 arrays on graphite by scanning tunneling microscopy

The layer structures of H8Si8O12 molecules on highly oriented pyrolitic graphite have been investigated by scanning tunneling microscopy. Two kinds of ordered assemblies of H8Si8O12 monolayers are observed, with a unit cell of 6.5 Å × 6.5 Å and 7.2 Å × 9.4 Å, respectively. On the basis of the shapes and sizes of the H8Si8O12 STM images and the heights of the H8Si8O12 monolayers, H8Si8O12 can be adsorbed with one face of its cage structure in contact with the substrate surface or with a tilted orientation.