AVS 51st International Symposium
    Organic Films and Devices Tuesday Sessions
       Session OF-TuP

Paper OF-TuP9
Characterization of Porphyrin Monolayers Bearing (O, S, and Se) on Si and Au: Towards Hybrid Memory Storage in Electronic Devices

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: A.A. Yasseri, University of California Riverside
Authors: A.A. Yasseri, University of California Riverside
F. Zaera, University of California Riverside
J.S. Lindsey, North Carolina State University
D.F. Bocian, University of California Riverside
Correspondent: Click to Email
We report on the characterization of a novel group of redox-active porphyrin molecules synthesized with terminal chalcogen subunits for attachment on to electro-active surfaces. A series of porphyrins has been prepared and characterized as surface bound redox-active monolayers. The molecules designated as (ZnPBz-,ZnPCH2-) bear two linker types substituted on a meso-position of the porphyrin and are terminated with a diverse series of surface anchor groups in free and protected form (hydroxy, S-acetylthio, and Se-acetylseleno) for attachment to Si (100) and Au (111). Communication with the covalently bound adsorbates is achieved through activation of pre-patterned Si-hydride test-platforms to anchor the Si-O, Si-S, or Si-Se tethers to the surface. Similar monolayers were prepared as SAMs on Au yielding analogous Au-S and Au-Se tethers for comparison. Each porphyrin was investigated on Au and Si surfaces using X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and various electrochemical methods including (fast scan cyclic voltammetry, swept-waveform AC voltammetry, and open circuit amperometry). The objective of the study was to demonstrate the (1) the chemical robustness of monolayer binding through each anchor group to the surface, (2) measure the packing density of the molecular monolayers on each surface, (3) and to probe the influence that terminal surface anchor groups (O, S, Se) and linker type bear on the electron transfer (in presence of applied potential) and charge retention (in absence of applied potential) characteristics of the monolayers on each platform. XPS, FTIR, and voltammetric measurements confirm semi-quantitative displacement of surface di-hydride species with -O, -S, and -Se terminated porphyrins, respectively. The electron transfer kinetics of the Si-O, Si-S, and Si-Se indicate that the kinetics strongly depend on the linker type and surface concentration of the porphyrin monolayers, independent on the substrate used.