Analysis of the persistent photoconductivity in composite nanocrystalline ZnO/Si films produced by co-sputtering at room temperature

The persistent photoconductivity (PPC) behavior in composite nanocrystalline films ZnO(RF)/Si(DC) films grown by co-sputtering was studied. The studied films were produced by fixing the ZnO RF magnetron power at 120 Watts and varying the DC power for the Si target from 0 to 80 Watts. The produced films were structural, optical, and electrical characterized; n-type films were produced for all the composition range. The PPC behavior was studied in samples grown with the composition formed with the ZnO (RF = 120 W)/Si (DC = 20 W) power condition, and by exposing the sample surfaces under continuous or pulsed ultraviolet (UV) radiation (390–400 nm). After applying an extended cleansing period, the PPC characteristic time constants, τ. 63 , were obtained; the turn-off time constant varied from 16.8 to 22.8 s, while the turn-on time constant changed from 24 to 30 s. These periods are linked to the UV light lattice absorption and the corresponding energy relaxation mechanisms. Graphical abstract