Non-contact measurement of the electrical conductivity and coverage density of silver nanowires for transparent electrodes using Terahertz spectroscopy

In this work, a terahertz time-domain spectroscopy (THz-TDS) imaging technique was used for non-contact measurement of the conductivity and coverage density (DC) of silver nanowires (SNWs) as transparent electrodes. The reflection mode of THz-TDS with an incident angle of 30 degrees was used, and the sheet resistance (R-sh) of SNW films was measured using the four-point probe method. The correlations between the THz reflection ratio and Rsh were studied by comparing the results of the four-point probe method and the measured THz reflection ratios. Also, the DC of SNWs was evaluated using THz waveforms with a general refractivity formula. This result matched well with a conventional approximation method using a scanning electron microscope image. Furthermore, defects in the SNWs could be easily detected using the THz-TDS imaging technique. The non-contact THz-TDS measurement method that we developed is expected to be a promising technique for non-contact measurement of the Rsh and DC for transparent conductive electrodes.