Photoconductivity characteristics of ZnO nanoparticles assembled in nanogap electrodes for portable photodetector applications

In the present report, ZnO nanoparticles of size ∼9 nm have been assembled by optimized dielectrophoresis process on the pre-fabricated nanogap (60 nm) electrodes. The fabricated ZnO nanoparticles based nano-device was studied for its I-V characteristic and typical non-linear semiconducting behavior was observed. When illuminated with ultraviolet (UV) radiation of wavelength 365 nm, a tremendous change in conductivity of almost one order of magnitude was observed indicating a high sensitivity of the fabricated nano-device. Temporal photoresponse characteristics were studied at a fixed level of UV illumination intensity (1.0 mW/cm²) and the response time under 10 ms was recorded. The photoresponse curve exhibited a perfect rise and recovery without any slow component. Absence of slow component in the photoresponse characteristic suggested that shallow trapping centers were inactive and the photoconductivity could be due to the true quantum yield of photogenerated charge carriers through interband and deep trapping centers transitions.