1. Microelectronics & Materials Physics Laboratories, Department of Electrical and Information Engineering, EMPART Research Group of Infotech Oulu, University of Oulu, P.O. Box 4500, 90014-FIN Oulu, Finland, and Office of the Chancellor/Departments of Chemistry & Biochemistry and Physics & Astronomy, University of MissouriSt. Louis, St. Louis, Missouri 63121