Oxygen Vacancy: An Electron-Phonon Interaction Decoupler to Modulate the Near-Band-Edge Emission of ZnO Nanorods

Through in situ control of the growth condition in the vapor phase transport and condensation, we intentionally prepared ZnO nanorods with different concentrations of oxygen vacancy (V-O), as confirmed by the X-ray photoelectron spectra. A spectral shift in the ultraviolet (UV) emission between these nanorods, as large as similar to 80 meV, has been observed in the room temperature photoluminescence (PL) spectra, showing strong correlation to the V-O concentration. With the help of the variable-temperature PL, this spectral shift is clearly attributed to the different spectral contributions of the free exciton emission and its phonon replicas. Furthermore, a remarkable variation in the electron-phonon interaction strength among these samples is unambiguously revealed by the Raman spectra, which is in good consistence with the Huang-Rhys parameters obtained from the PL. This study implies that V-O in ZnO nanostructures not only modulates the visible emission as intensively previously investigated but also significantly suppresses the electron-phonon interaction strength and therefore tailor the UV (near-band-edge) emission property. This finding is useful to design and fabricate ZnO-based high-performance short-wavelength photonic and optoelectronic devices on the nanoscale.