AVS 49th International Symposium
    Organic Films and Devices Wednesday Sessions
       Session OF+EL-WeP

Paper OF+EL-WeP6
Formation and Characterization of Ferrocene and Porphyrin Monolayers on Si and Ge Surfaces : Towards a Hybrid Molecular/CMOS Electronic Device

Wednesday, November 6, 2002, 11:00 am, Room Exhibit Hall B2

Session: Organic Films and Devices
Presenter: A.A. Yasseri, University of California Riverside
Authors: A.A. Yasseri, University of California Riverside
Z. Liu, University of California Riverside
R. Dabke, University of California Riverside
V. Malinovskii, North Carolina State University
K.H. Schweikart, North Carolina State University
J.S. Lindsey, North Carolina State University
W.G. Kuhr, University of California Riverside
D.F. Bocian, University of California Riverside
K.M. Roth, University of California Riverside
Correspondent: Click to Email
Construction of a novel hybrid molecular based device may provide the most tractable approach in bridging the gap between modern day semiconductor materials and molecular based devices. Toward this goal, we have examined functionalized monolayers of ferrocene and porphyrin terminated alcohols and thiols covalently linked to mono-crystalline Si and Ge (100) and (111). Electrochemical communication with the surface immobilized molecules was achieved through a covalently anchored Si-O, Si-S or Ge-O and Ge-S tether to photlolithographically patterned surfaces. Silicon microelectrodes were fabricated on heavily doped silicon masked with a thermally grown oxide to define the active electrode area for monolayer assembly. Surfaces were activated via a two-step process. Chemically stable hydride-terminated surfaces, using HF or ammonium fluoride, were reacted with a solution of iodine yielding an iodide functionalized surface. XPS measurements confirm the mechanism for the displacement of surface iodine atoms via a base catalyzed reaction with alcohol terminated iron and zinc-centered ferrocene and porphyrin respectively. Iodide derivitization prior to film deposition chemically facilitates the formation of more densely packed monolayer of porphyrins. Fast scan voltammetry performed on monolayers demonstrate the chemical stability of the films over millions of cycles in an inert atmosphere. Modified AC voltammetry was used to probe the redox kinetics of the semiconductor film junction in order to measure the rate for film oxidation and reduction under an applied potential. Monolayers formed from solution phase assembly reactions were further characterized using scanning probe microscopy.