Electronic and optical properties of Mn impurities in ultra-thin ZnO nanowires: Insights from density-functional theory

In this work we have employed density-functional theory with hybrid functionals to investigate the atomic and electronic structure of bare and hydrogenated Mn-doped ZnO nanowires with small diameter. We determine changes in magnetic and electronic structure of Mn-doped ZnO nanowires due to surface effects, such as hydrogen adsorption on the surface, presence of oxygen vacancies and dangling bonds. In the absence of passivation on the nanowire surface, the manganese atoms segregate to the surface, whereas under hydrogen adsorption the incorporation of Mn is energetically more favourable at inner sites. The presence of additional oxygen vacancies does not produce signficant changes in magnetic moments, although it produce significant changes in charge localization.