ZnO nanorod arrays on n-type Si(111) substrates for pH measurements

ZnO nanorod arrays were grown directly on n-Si (111) substrates using an aqueous solution method aiming at integration with Si-based device technology. The growth of the ZnO nanorod arrays was found to be influenced by the thickness of the native oxide layer on Si substrates. A dense array of about 200 nm diameter nanorods was obtained from the thick equimolar aqueous solution containing 100 mM of zinc nitrate hexahydrate and hexamethylenetetramine, while the solution with lower concentrations resulted in scattered corn-shaped ones. Electrochemical potential in electrolyte of the ZnO nanorod arrays on Si (111) substrates was studied and found to have a slope of -50 mV/pH, suggesting a potential application to future sensing nanosystems.