Micro-Raman scattering spectroscopy study of Li-doped and undoped ZnO needle crystals

ZnO nanostructures have attracted great attention for possible applications in optoelectronic and spintronic devices. The electrical resistivity because of carriers can be improved by the introduction of Li ions, as Li is a possible dopant for achieving p-type ZnO. We have carried out a comprehensive micro-Raman scattering study of the phonons in 1% Li- and undoped ZnO needle crystals grown and annealed at 1073 K for 1 and 2 h under oxygen environment. Phonon mode of doped and undoped ZnO does not show any measurable shift for the doping concentration of 1%. As line width is related to point defect density, we find for both Li- and undoped ZnO crystals the crystallinity is improving towards the tip of the needle crystals.