Benchmark characterization of the thermoelectric properties of individual single-crystalline CdS nanowires by a H-type sensor

A precision H-type sensor method has been developed to measure the thermoelectric performance of individual single-crystalline CdS nanowires for the first time. A nanomanipulation probe was used to directly pick up an individual nanowire from the array and place it on the sensor. Our method is generally applicable to any nanowire synthesized in either array or powder form. By simply changing the external electrical circuits, the Seebeck coefficient, thermal conductivity, and electrical conductivity have been measured on the same nanowire sample to ensure high accuracy and reliability. CdS nanowires have a large Seebeck coefficient over 300 μV K^-1 due to their wide band gap, while their thermal conductivity is only one-tenth of that of the bulk material owing to the significant phonon-surface scattering. The figure of merit, ZT, of the CdS nanowire is 0.01 at 320 K, which is larger by two orders of magnitude than the value for a Bi₂S₃ nanowire, showing a trend of rapid increase above 300 K.