High-resolution electron energy loss spectroscopy of chloroaluminum phthalocyanine ultrathin films

High-resolution electron energy loss spectra (HREELS) were measured for ultrathin films of chloroaluminum phthalocyanine (ClAlPc) deposited on a cleaved HOPG surface in order to investigate the molecular orientation and its thickness dependence. It was found that for the monolayer film ClAlPe molecules lie flat on the HOPG surface without heat treatment. With increase in the film thickness, the molecules become oriented at a tilt. The result show a marked difference from the orientation of ClAlPc molecules on MoS2, where the molecules lie tilt on MoS2 in the as-grown monolayer. (C) 1998 Elsevier Science B.V.