Speaker
Description
We present a simple technique based on a bottom-up approach to assembling single-walled carbon nanotubes (SWCNTs) in between two metal electrodes, making the SWCNT photodetectors with the capability of being operated at room temperature. This technique is known as dielectrophoresis (DEP) that exploits an electric field across the microelectrode gap with an application of a high-frequency AC field. As the geometry of the electrodes is different, the resulting imbalance of electric field intensity leads to a net force that pulls the nanotubes suspended in a liquid to attract the metal. In this work, an oscilloscope was used to monitor the change of a voltage drop across a constant resistor (1k$\Omega$), connecting in series with the electrodes, to justify the close-circuit condition during the DEP assembly. By varying the SWCNT concentrations in Toluene from 0.01 $\mu$g/ml to 0.42 $\mu$g/ml, we were able to deposit the nanotubes in the electrode gaps at different densities, ranging from individuals to densely-packed networks. After the device fabrication, we performed photocurrent measurement by optical excitation using a near-infrared laser (NIR) ($\lambda$ = 975 nm) and then evaluated the device’s photoresponsivity at different laser powers of up to 450 mW. Further work on a temporal measurement will be needed to verify the time response of the devices. Based on our experimental results, the DEP technique can permit various nanomaterials to be deposited into micrometre or nanoscale-gapped electrodes for further development of nanoelectronics on transparent and flexible non-conductive substrates.
