Interface characterization of molecular-monolayer/SiO2 based molecular junctions

We present a correlation of the results of dc-current–voltage (IV) and ac-capacitance–voltage (CV) measurements with vibrational spectroscopy of Au/monolayer/SiO2/Si structures to establish an improved understanding of the interactions at the buried metal/monolayer and dielectric/silicon interfaces. A novel backside-incidence Fourier-transform infrared-spectroscopy technique was used to characterize the interaction of the top-metallization with the organic monolayers. Both the spectroscopic and electrical results indicate that Au has a minimal interaction with alkane monolayers deposited on SiO2 via silane chemistry. An intriguing negative-differential-resistance and hysteresis is observed in the IV measurements of Au/alkane/SiO2/Si devices. It is unlikely that this behavior is intrinsic to the simple alkane monolayers in these structures. We attribute the observed IV features to charge trapping and detrapping at both the alkane/SiO2 and the Si/SiO2 interfaces.