A qualitative approach using room-temperature confocal microscopy was employed to investigate the spatial distribution of shallow and deep oxygen vacancy (VO) concentrations on the polar (00•1) and non-polar (10•0) surfaces of zinc oxide nanowires. Using the spectral intensity variation of the confocal photoluminescence of the green emission at different spatial locations on the surface, the VO concentrations of an individual ZnO nanowire could be obtained. The green emission at different spatial locations on the ZnO nanowire polar (00•1) and non-polar (10•0) surfaces was found to have maximum intensity near the nanowire edges, decreasing to a minimum near the nanowire center. First-principles calculations using simple supercell-slab models were employed to approximate/model the defects on the ZnO nanowire (10•0) and (00•1) surfaces. These calculations give increased insight into the physical mechanism behind the green emission spectral intensity and the characteristics of an individual ZnO nanowire. The highly accurate density functional theory-based full-potential linearized augmented plane-wave plus local orbitals (FP-LAPW + lo) method was used to compute the defect formation energy of the supercell-slabs. Previously, using these supercell-slab models, it was demonstrated through the FP-LAPW + lo method that in the presence of oxygen vacancies at the (00•1) surface, the phase transformation of the supercell-slabs in the graphite-like structure to the wurtzite lattice structure would occur even if the thickness of the graphite-like supercell-slabs were equal to or less than 4 atomic graphite-like layers (Wong, 2013). The spatial profile of the neutral VO defect formation energies from the density functional theory calculations along the ZnO [00•1] and [10•0] directions was found to reasonably explain the spatial profile of the measured confocal luminescence intensity on these surfaces, leading to the conclusion that the green emission spectra of the nanowires probably originated from neutral oxygen vacancies. Another significant result was that the variation in the calculated defect formation energy along the ZnO [00•1] and [10•0] directions showed different behaviors owing to the non-polar and polar nature of these supercell-slabs. These results were important for tuning and understanding the variations in the optical response of ZnO nanowire -based devices in different geometric configurations.Spatial Distribution of Neutral Oxygen Vacancies on ZnO Nanowire Surfaces: an Investigation Combining Confocal Microscopy and First Principles Calculations. Mun Wong, K., Alay-E-Abbas, S.M., Fang, Y., Shaukat, A., Lei, Y.: Journal of Applied Physics, 2013, 114[3], 034901