Structural, Optical and Ultra-Violet Photodetection Properties of ZnO Nanorods with Various Aspect Ratios

ZnO nanorods with various lengths were synthesized by a two-stage route (by changing the time of growth between 0-240 min) and were characterized using XRD, SEM, UV–Vis and PL techniques. The SEM and XRD results confirmed a fast growth of (0 0 2) plane in the preferential longitudinal orientation, in contrast to lateral growth and therefore, by increasing the time of hydrothermal growth, nanorods with higher aspect ratios are obtained. Naturally, by increasing the length of nanorods, not only the average transmittance in both near ultraviolet and visible ranges is decreased, but also the PL peaks are red-shifted and extinct. Finally, ultra-violet photodetection of the samples shows that higher active surface area (with respect to the time of growth) is appropriate for photo-induced interactions leading to higher UV-sensitivity.