An infrared (IR) laser with a wavelength of 1064 nm was used as an optothermal source. The drain current in the ZnO NW can be increased or decreased by the IR illumination depending on the polarization orientation of the PZT substrate. For example, as shown in the figure, when the n-type ZnO NW is placed on top of the PZT substrate with up polarization, the bound positive charges on the PZT surface attract the electron carriers in the ZnO NW. When the PZT was illuminated by the IR laser, the increase in temperature reduced the polarization of the material and thus decreased the density of the positive bound charges near the nanowire. As a result, the electron carrier concentration in the ZnO NW decreases resulting in a decreased drain current. On the other hand, IR illumination on a PZT with down polarization decreases the polarization and negative bound charge density near the nanowire. Consequently, the electron carrier concentration in the ZnO NW increases and thereby increases the drain current.

Suits remote or wireless applications

It is known that when the laser is in the UV range, photocurrent can be generated in ZnO. Consequently, combining the photocurrent behaviour in the UV range and the optothermal gating effect in the IR range, broadens the opportunities for nanoscale optoelectronic devices. The optothermal feature of the device is especially suitable for remote or wireless applications.

Additional information can be found in the journal Nanotechnology.