Zero bias UV detection and precursor effect on properties of ZnO nanorods grown by hydrothermal method on SiO2/p-Si substrate

Abstract

Here we present the effect of the precursor chemistry on the properties of ZnO nanorods prepared by using the hydrothermal method. The nanorods were grown over RF-sputtered 50 nm ZnO seed layers on integrated circuits compatible highly lattice mismatched SiO2/p-Si substrates. Two zinc sources namely zinc acetate and zinc nitrate were dissolved in solvent (a solution of deionized water and hexamethylenetetramine) in parallel to grow the highly conducting, vertically-aligned ZnO nanorods. Surface morphology and crystal structure of NRs were investigated using scanning electron microscope and X-ray diffraction. Nanorods synthesized in zinc acetate precursor's solution were highly crystalline and sparsely packed with well defined hexagonal top surface compared to nanorods grown in zinc nitrate precursors. Elemental composition of nanorods was studied using X-ray photoelectron spectroscopy. The oxygen and zinc observed in all the nanorods, zinc acetate synthesized nanorods show high atomic percentage of these two elements. To test the electrical and photo detection properties of the ZnO nanorods a metal semiconductor metal (MSM) structure was fabricated by depositing Ti/Au ohmic contacts over the nanorods. The MSM structure fabricated over the nanorods synthesized by using zinc nitrate precursor shows zero bias UV detection not reported up to present. The conducting properties of the nanorods were obtained from the current-voltage characteristics measurements of the MSM photosensor, and it is observed that the zinc acetate synthesized NRs were highly conducting. The UV detection capability of the MSM photosensor were tested by exposing UV light from light emitting diodes of same power and different wavelength. The ZnO NRs grown in zinc nitrate precursor shows high photosensitivity.