Role of Seed Layer Crystalline Quality in Photoresponse Performance of Hydrothermally Grown ZnO Nanorods

We investigated the effects of the crystalline state for seed layers (SLs) on the growth morphology and material characteristics for hydrothermally grown ZnO nanorods (NRs). For this, preheating (PH) at different temperatures (100–300 °C) and O(2) plasma treatment (PT) for 9 min were performed during the growth of SLs on p-Si by the aqueous solution-based method to provide the characteristic change on the NR growth platform. An improvement in material properties was achieved from the ZnO NRs grown on the SL crystals of enhanced crystalline quality in terms of the increased preferred orientation (002), the higher UV emission with suppressed deep-level emissions, the recovery of O/Zn stoichiometry, and the reduction of various intrinsic defects. Ultraviolet photodiodes of a p-Si/n-ZnO-NR structure fabricated under the SL conditions of O(2) PT and PH at 100 °C showed a significantly enhanced on-off current ratio of ~90 at +5 V and faster photoresponse characteristics presenting a reduction in the fall time from 16 to 9 s.