The Interplay of Seeding Substrates with Different Thickness and Properties of ZnO Nanorods Electrodeposited for Different TCO Applications
摘要
According to the lattice match rule, the final properties and the quality of electrodeposited nanostructured ZnO are improved when they are deposited on a lattice-matched substrate. In this work, ZnO nanorods have been improved by growing onto ITO substrates seeded with a series of seed layers of ZnO using a simple two-step electrodeposition method. The effect of ZnO seed layer thickness on the structural. morphological. optical. and electrical properties of ZnO nanorods was studied by using x-ray diffraction, atomic force microscope, scanning electron microscopy, ultraviolet–visible absorption spectroscopy, electrochemical impedance spectroscopy, and photocurrent Mott–Schottky plots, and photocurrent. The measurements of x-ray diffraction showed that all the samples were a highly pure ZnO NRs and crystallized in a hexagonal würtzite-type structure with a phase preferentially orientated along the c-axis. The crystallite size increased from 47.4450 nm to 56.6993 nm, while micro-strain decreased from 7.3059 × 10−4 to 6.1136 × 10−4 with the increase in ZnO seed layer thickness. Atomic force microscopy and scanning electron microscopy measurements indicated the surface topography, roughness, verticality, density, and diameter of the nanorods with the change of the thickness of the seed layer. The optical bandgap energy was found to correlate inversely with the Urbach energy and surface roughness as a function of ZnO seed layer thickness. Photocurrent measurements confirm the n-type conductivity for all the samples except from the Mott–Schottky plots. Changes in the photocurrent response and the charge transfer resistance are discussed as a function of ZnO seed layer thickness.