Surface Potential Measurements of Organic Thin-Film Transistors by Kelvin-Probe Force Microscopy

Abstract

　Kelvin-probe force microscopy (KPFM) is a surface potential mapping technique based on dynamic-mode atomic force microscopy (AFM). It is useful to visualize carrier injection barriers and trapped charges in operating organic thin-film transistors (OTFTs). Since it is desirable to perform KPFM experiments in vacuum conditions, frequency modulation (FM) technique is often used to operate AFM/KPFM. We review two operating modes of KPFM using FM-AFM in vacuum and demonstrate visualization of the carrier injection barriers and trapped charges in OTFTs. We also introduce a method to visualize the transient distribution of the trapped charges being evacuated from the channel of the operating OTFT.