Scanning tunneling microscopy study of platinum deposited on graphite by metalorganic chemical vapor deposition

Article abstract of DOI:10.1016/0039-6028(93)90458-V

The growth of thin Pt(111) films on highly oriented pyrolytic graphite (HOPG) by metalorganic chemical vapor deposition has been followed by scanning tunneling microscopy. Depositions were carried out on substrates held at 205°C and contacted with intersecting streams of H₂ and of He saturated with (η⁵-C₅H₄CH₃)Pt(CH₃)₃. The deposition was monitored by the appearance of methane in the product stream. Deposition initiated almost immediately, in contrast with earlier studies showing a significant induction period for deposition on glass. The deposits obtained after several minutes at 205°C consisted of Pt clusters with diameters ranging from 8 to 80 angstrom along with some very much larger Pt islands. The deposits were morphologically very rough with rather well defined facet orientation. The step heights of the terraces ranged from 20 to 54 angstrom. Oval shaped disks free of apparent dislocations were also observed. One of the larger crystallites investigated was 2074 × 1482 angstrom² and 200 angstrom in height. The deposits were non-uniform throughout the deposition. The initial crystal growth under CVD was by island nucleation, followed by a growth mode that produced a random rough surface after the islands coalesced. At early stages the films are preferentially oriented with (111) crystallites parallel to the HOPG basal plane; further growth, however, leads to a poly-crystalline deposit.