Effect of grain–grain boundary on ZnO nanorod-based UV photosensor: a complex impedance spectroscopic study

ZnO nanorod-based UV photosensing devices are synthesized using one-pot synthesis method, and their sensing properties are studied with the variation of nanorod growth area. With the variation of electrode position for the maximum growth area, the UV photosensing properties are thoroughly examined. Structural, morphological and optical properties are studied using XRD, FEG-SEM, FEG-TEM and UV–VIS spectroscopy. AC electrical conductivity, dielectric measurements and modulus spectroscopy at room temperature in a frequency range from5 Hz to 5 MHz are performed. During the electrical conduction processes in the sample, the physical parameters of ZnO nanostructures such as dielectric constant, relaxation frequency and electrical conductivity are examined at dark and UV-illuminated condition. The dependence of conductivity, dielectric constants and modulus with frequency and UV on–off conditions are discussed. The correlation between response and recovery time with growth surface area of ZnO nanostructure is established with the help of complex impedance spectroscopy. The imaginary part of electrical modulus versus angular frequency is drawn, and the value of stretch exponent (β) is calculated for maximum and minimum surface area under dark and UV-illuminated condition from where the type of relaxation process is studied.