STUDY OF STRUCTURE AND POLYMERIZATION OF EPITAXIALLY GROWN SIPC(OH)2 THIN-FILMS BY HIGH-RESOLUTION ELECTRON-MICROSCOPY

Thin films of SiPc(OH)2 (Pc = phthalocyanine) were formed epitaxially on the (001) surface of mica by vacuum deposition and were then polymerized by heat treatment. The molecular packing of the SiPc(OH)2 was determined by electron diffraction and high-resolution electron microscopy as triclinic P1BAR having dimensions a = 0.727, b = 1.307, c = 0.688 nm, alpha = 102.5, beta = 104.2, and gamma = 97.4-degrees. This monomer crystal grows with its c-axis parallel to the a-axis of the substrate mica and its bc-plane parallel to the (001) surface of mica. By heat treatment at 320-degrees-C, the SiPc (OH)2 polymerized with the c -axis of the polymer parallel to the c-axis of the monomer. At 420-degrees-C, the c-axis of the polymer became parallel to the a*-axis of the monomer (i.e., perpendicular to the film surface). From high-resolution electron microscopy of partially polymerized specimens, the polymerization was shown to start at the edges of small monomer crystals. This may be considered to be due to the volume expansion during the polymerization. (C) 1993 John Wiley & Sons, Inc.