Measurement of the Seebeck coefficient

To measure the change ratio of the Seebeck coefficient in response to the concentration of the N-type chemical charrier dopant on the CNT films, we employed a micro-ceramic heater (MS-M1000, SAKAGUCHI E.H. VOC CO.), a K-type thermocouple (T-35K, SAKAGUCHI E.H. VOC Co), and the aforementioned digital multimeter. One end of the channel was locally heated (+5 °C) by the micro-ceramic heater, and the corresponding voltage response was recorded on the digital multimeter, via the K-type thermocouple probed at both ends of the channel. We calculated the Seebeck coefficient of the target CNT film using the Seebeck coefficient of each Alumel terminal, and Chromel terminal of the K-type thermocouple (S_Alumel = −18 µV/K, S_Chromel = 22 µV/K). We then measured the Seebeck coefficient measurement in a dark room under atmospheric pressure and room temperature.