Selectively enhanced oxygen vacancies in undoped polycrystalline ZnO as a consequence of Multi-Step Sintering

With a motivation to investigate the simultaneous effect of sintering temperature and sintering time in tandem on defect distributions in polycrystalline undoped ZnO a new technique called Multi-step sintering (MSS) has been deliberately designed. Systematic investigations on structural parameters suggest the rigorous defect propagation along a-axis of the unit cell. We report the unwavering nature of Zinc interstitials (Zni) and the complexes of Zni with oxygen vacancies (Vo) with sintering temperature. The enhanced and broad green emission in Photoluminescence spectroscopy reveals the existence of surplus Vo in the sample. The band gap narrowing at 800 °C and enhanced Raman modes in Raman scattering experiment confirms the existence of excess oxygen vacancies and make MSS successful technique to tailor the intrinsic defects without any extrinsic doping.