Ballistic emission spectroscopy and imaging of a buried metal-organic interface

Abstract

Metal organic interfaces have been under intensive scientific investigation over the past few years with the objective of improving devices based on organic materials. In this study, we report the first results on spectroscopy and imaging of a buried metal-organic interface using ballistic electron emission microscopy (BEEM). Unlike photoexcitation-based experiments, which typically average over large interfacial areas, BEEM enables direct observation of local interface band structure with nanometer resolution. The interface of silver (Ag) - polyparaphenylene (PPP, a blue emitter with high photoluminescence efficiency) is investigated. Multiple injection barriers and spatial non-uniformity of carrier injection are observed. Possible causes for these features will be discussed. The BEEM current images are found to correlate marginally with the surface topography of the silver film.