Fabrication And Characterization Of ZnO Nano-crystalline Films Prepared By Electrodeposition

A two-electrode system was employed to fabricate c-axis oriented ZnO films on a FTO wafer and p-Si(100) substrate in a mixed Zn(NO3)2/KNO3 aqueous electrolyte. We obtained ZnO nano-crystaline films with different morphology and characteristics by adjusting the parameters in the electrodeposition process. It was discovered the morphology and structure were strongly affected by adjusting deposition voltage and applying ultrasonic wave.The film growth mode was different at different voltage, which is island growth at lower voltage and layer growth at higher voltage. With the increase of voltage, the growth mode would undergo a gradual transition from island mode to island-layer combined mode, and then to layer mode last if voltage was higher than 2.8V. In this paper, X-ray diffraction, scanning electron microscopy, UV-VIS and UV-FLU spectroscopy were employed to analyze the phase structure, surface morphology, optical absorption and stimulated luminescence properties, respectively.It was found that the (002) peak intensity of XRD patterns increased apparently with the increase of deposition voltage. The grain shapes were typically hexagonal in different samples with the grain size between 100~400 nm. The optical band gap of nano-crystalline films is between 3.32~3.34eV, due to different grain sizes. The grain sizes of film were growing up and the transmittance with the increasing of deposition voltage and time. If applied ultrasonic wave to the deposition process, the grain size of films decreased, because the inhibitory effect of ultrasonic vibration to the crystal overgrowth. Film growth would selectively nucleate at the initial stage if the substrates were selectively corroded. As a result, we can fabricate flower-like nano-crystalline film. The stimulated luminescence peak of flower-like nano-crystalline film would blue shift. The ZnO/Si heterojunction showed apparent PN junction properties under bias voltage. Under light illumination, the n-ZnO/p-Si diode presented a remarkable photocurrent effect.