Electrical characterization of organic monolayers/silicon hybrid structures

Abstract

Hybrid structures consisting of an n-Si substrate covered with a cationic polyethylenimine layer and an anionic dye layer were fabricated. Their electrical properties were characterized using tunnel current measurements by a tungsten probe. The obtained I-V curves were analyzed using a modified diode equation. We found out that adsorption of the cationic polyelectrolyte decreases the barrier height of n-Si/organic monolayer/W structure, while adsorption of the low molecular weight anionic dye increases it. The results demonstrate that along with thermionic mechanism other ones are present which prevail at low voltage. In particular, electron tunneling dominates for a single monolayer on the silicon substrate, while, apparently, the Pool-Frenkel mechanism is typical for two monolayers.