Spectroscopy and Imaging of Metal-Organic Interfaces using BEEM

Keywords:
BEEM, Schottky barrier, organics, interface, imaging, spectroscopy

Abstract:
Charge injection from metal electrodes to organics is a subject of intense scientific investigation for organic electronics. Ballistic Electron Emission Microscopy enables spectroscopy and imaging of buried interfaces with nanometer resolution. Spatial non-uniformity of carrier injection is observed in Ag-PPP (poly-paraphenylene) interface and Ag-MEHPPV interfaces. Possible reasons are discussed. BEEM current images are found to correlate only marginally with the surface topography of the silver film. The transmission function of the Ag-PPP interface is also determined by evaluating from the derivative of the measured BEEM spectrum, and comparing with theory and Metal Inorganic Semiconductor (MIS) interfaces. This agrees well with the theoretical calculations on metal-phenyl ring interfaces. We demonstrate that patches of low Schottky barrier can nucleate current filaments and are likely responsible for the switching behavior observed in metal-organics.

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Nanotech 2005 Conference Program Abstract