Green Emission in Fe- and Mn-doped ZnO Nanowires Studied by Magneto-Photoluminescence

The green emission in ZnO, which was reported to result from deep-level transitions and proportional to the concentration of singly ionized oxygen vacancy, is critical for the visible-band optoelectronic application. However, the effective modulation of the green emission intensity is challenging. In this study, the green emission in ZnO nanowires is greatly suppressed by Fe doping and enhanced by Mn-doping during the growth process. Temperature dependent PL spectra demonstrate strong electron-phonon coupling, while magneto-PL show shrinkage of electron wavefunction for ZnO:Fe, these indicate both the electron-dopant energy transfer and decrease of oxygen vacancies in ZnO:Fe suppress the green emission; whereas for ZnO:Mn, its PL spectra show weak temperature and magnetic field dependence, which signify very high concentration of the oxygen vacancies that enhance the green emission.