Hall-effect Measurement of Organic Semiconductor Layers Using Micro-scale Electrode Chips

A new micro-electrode structure for Hall-effect measurements of organic semiconductor layers was proposed. The equations for the Hall-effect measurements based on the van der Pauw method indicate that narrower electrode gaps can decrease the resistance between contact points and enable Hall-effect measurement even for higher resistance materials such as organic semiconductors. According to this “scaling rule”, we fabricated a new electrode chip which consists of four small finger electrodes with a gap of micrometer-scale between diagonally opposite electrodes. In order to demonstrate the validity of this concept, Hall-effect measurements for FeCl₃-doped poly(3,4-ethylenedioxythiophene) (PEDOT) was performed using this new electrode structure, revealing that a 10-µm-gap electrode chip is effective for evaluating carrier concentration of down to around 10¹⁹ cm^-3. These Hall electrode chips are quite useful for quantitative analysis of carrier concentration and ca rier mobility in organic semiconductor materials.