AVS 53rd International Symposium
    Surface Science Monday Sessions
       Session SS2-MoM

Paper SS2-MoM11
Image and Image-Derived States Formed by Molecular Thin Film Structures

Monday, November 13, 2006, 11:20 am, Room 2004

Session: Gas-Surface Reaction Dynamics
Presenter: E.T. Jensen, University of Northern B.C., Canada
Authors: E.T. Jensen, University of Northern B.C., Canada
L. Sanche, Universite de Sherbrooke, Canada
Correspondent: Click to Email
Electron transport through and interaction with molecular thin films is an area of much current interest. In this work, electron image states formed at molecular interfaces have been used to enhance the trapping of low energy electrons by adsorbed 'detector' molecules.@footnote 1@ A magnetically collimated low energy electron beam (electron energies between 0 and 10eV) is incident upon prepared molecular thin films, and the formation of stable anions at the surface are monitored using a charge trapping technique.@footnote 2@ We have studied thin films prepared on a cold (T=15K) polycrystalline platinum substrate. Molecular films are grown on top of a 10ML thick Kr spacer layer, to isolate the film from the metal substrate. On this Kr/Pt substrate we have grown various thin molecular films (1-10ML thick) that support image states. We have studied image states formed at the surface of methanol, 1-butanol, n-octane and difluoromethane thin films. Low energy electron transmission spectra show that all these films display a conduction band gap near the vacuum level, which is crucial in supporting long-lived image states. To detect the image states formed by these molecular thin films, we introduce submonolayer quantities of 'detector' molecules that can be dissociated by low energy electrons to create stable anions (CH@sub 3@I, CH@sub 3@Br, CH@sub 3@Cl) or which support stable molecular anions (CO@sub 2@). We have studied image state enhanced electron trapping at the molecular film-vacuum interface. We have also created and studied molecular film 'quantum well' type structures in which the detector molecules are placed in a Kr spacer between two molecular thin films- in the region between two films an image-state derived quantum well state can be identified. @FootnoteText@ @footnote 1@ K. Nagesha and L. Sanche, Phys. Rev. Lett. 81, (1998) 5892.@footnote 2@ K. Nagesha, J. Gamache, A.D. Bass and L. Sanche, Rev. Sci. Inst. 68, (1997) 3883.