dr. Yuanyuan Hu: Scanning Kelvin Probe Microscopy Studies on Device Physics of Organic Field-effect Transistors
|Wanneer:||do 21-05-2015 13:00 - 14:00|
Scanning Kelvin Probe Microscopy (SKPM) is a powerful tool for studying the micro-structure and electronic structure in organic films and devices. By recording the topography and electrical potential information of sample surface simultaneously, SKPM technique can help to relate the transport properties to film structure, and provide invaluable information regarding charge injection, distribution, trapping and electronic structure in OFETs.
In this presentation, I will introduce some results we have achieved on understanding the device physics of OFETs by SKPM. First, we used SKPM to study the effect of molecule asymmetry on device performance in high-mobility, solution processable N-type OFETs. By comparing two molecules with the same conjugated core, but with either symmetric or asymmetric side chain substituents, and investigating their transport properties as well as film growth modes with SKPM, we elucidate the relationship between the molecule asymmetry and final FET performance. Then I will show the work we have done to clarify the effect of dielectric dipole disorder on density of states in OFETs. Specifically, we used SKPM to extract the density of states (DOS) in rubrene single-crystal FETs with two different polymer dielectrics. The influence of the gate dielectric dipoles on the density of states of organic semiconductors, i.e. the broadening effect can be directly seen from the measurement. We also investigated the degree of the broadening effect quantitatively and discussed its correlation with the FET performance.