Voltage dependent displacement current as a tool to measure the vacuum level shift caused by self-assembled monolayers on aluminum oxide

We present charge extraction by a linearly increasing voltage measurements on diodes based on an n-channel naphthalenetetracarboxylic acid diimide semiconductor and an aluminum oxide blocking layer. Results show a large displacement current (roughly 15 times that expected from the geometrical capacitance), which we associate with trap filling in the oxide. The trap density is calculated to be on the order of 10(19) cm(-3), in agreement with preceding work. We present a way of using the displacement current as a tool for probing the vacuum level shift caused by modifying the oxide surface with self-assembled monolayers in operating devices. (C) 2013 AIP Publishing LLC.