Suppression and enhancement of deep level emission of ZnO on Si4+ & V5+ substitution

ZnO possess a wide range of tunable properties depending on the type and concentration of dopant. Defects in ZnO due to doped aliovalent ions can generate certain functionalities. Such defects in the lattice do not deteriorate the material properties but actually modifies the material towards infinite number of possibilities. Defects like oxygen vacancies play a significant role in photocatalytic and sensing applications. Depending upon the functionality, defect state of ZnO can be modified by suitable doping. Amount and nature of different dopant has different effect on defect state of ZnO. It depends upon the ionic radii, valence state, chemical stability etc. of the ion doped. Two samples with two different dopants i.e., silicon and vanadium, Zn_1-xSi_xO and Zn_1-xV_xO, for x=0 & 0.020, were synthesized using solgel method (a citric acid-glycerol route) followed by solid state sintering. A comparison of their optical properties, photoluminescence and UV-Vis spectroscopy, with pure ZnO was studied at room temperature. Silicon doping drastically reduces whereas vanadium doping enhances the green emission as compared with pure ZnO. Suppression and enhancement of defect levels (DLE) is rationalized by the effects of extra charge present on Si⁴⁺ & V⁵⁺ (in comparison to Zn²⁺) and formation of new hybrid state (V3d O2p) within bandgap. Reduction of defects in Zn_1-xSi_xO makes it suitable material for opto-electronics application whereas enhancement in defects in Zn_1-xV_xO makes it suitable material for photocatalytic as well as gas sensing application.