Investigation on organic thin film transistors (TFT) by Kelvin probe force microscopy (KPFM)

Abstract

Using Kelvin Probe Force Microscopy (KPFM), we performed surface-potential measurements on operating organic thin-film transistors (TFTs). Several parameters inaccessible through current-voltage measurements were determined, namely the source and drain resistances separately, the threshold voltage and the electric field along the channel. We show that the source resistance is always higher than the drain resistance, and non-linear intrinsic behavior is demonstrated in some cases. The threshold voltage extracted by KPFM is different from that extracted from current-voltage measurements. By analyzing the tip response using calibration samples, the electric field at the source/channel interface can be estimated within a small error margin.