报告题目： Contactless Measurement of Charge CarrierMobility with Microwave Probe

报 告 人：Yusuke Tsutsui

报告时间：9 am,14th, Oct, 2019

报告地点：材料学院301会议室

主办单位：材料科学与技术学院

报告人简介：

Yusuke Tsutsui: PI, Department of Molecular Engineering, Graduate School of Engineering, Kyoto University.

报告摘要：

Numerous organic materials have been newly designed and synthesized recently because they are believed to be potential candidates for flexible and low-cost electronics. Charge carrier switching speed, very important for the high-speed computing, in the organic materials is now on the same order of or even beyond amorphous silicon for elegantly prepared device with great care.  A variety of semiconducting materials with high charge carrier mobility have been studied by using analytical techniques such as Field-Effect Transistor (FET), Space-Charge Limited Current (SCLC) and Time-Of-Flight (TOF). There are also alternate current based techniques e.g. impedance spectroscopy that provides a lot of information, for example, on the carrier trapping and injection mechanisms.  These measurement systems, however, detect the long range transport of charge carrier including the undesirable effects like scattering by grain boundary.  In order to extract intrinsic charge carrier mobility, special techniques are usually needed to overcome these undesirable effects and it hampers rapid evaluation of the newly designed materials.

Microwave technique Time-Resolved Microwave Conductivity (TRMC) without electrodes nor long range carrier transport allows us to evaluate the intrinsic charge carrier mobility of materials and believed to provide the solutions to the above situation.  In the presentation, basics of the measurement technique, some variations in TRMC technique, and their application on organic materials will be introduced.  Flash-Photolysis TRMC (FP-TRMC) is laser-based technique where charge carrier mobility can be evaluated in completely non-contacting way i.e., without fabrication of the device.  Such a non-contacting nature is of great importance for the rapid evaluation of the newly designed materials due to the huge diversity of chemical structure in the organic materials compared to that of inorganic materials.

From the point of the view of most electronic devices, charge carriers are transported at the interfaces consisting of metals, semiconductors, insulators, and so on.  Nevertheless, there have been limited technologies to selectively monitor the charge carrier motions at interfaces.  For the rapid evaluation of intrinsic charge carrier transporting properties at interfaces, we have recently developed new microwave based measurement system: Field-Induced Time Resolved Microwave Conductivity (FI-TRMC).  Although this method requires the device fabrication process, it provides a lot of information under much closer situation to the actual operation of the device.