Effect of Nd doping level on optical and structural properties of ZnO:Nd thin films synthesized by the sol–gel route

ZnO thin films with various Nd doping levels (0%, 1%, 3% and 5%, respectively) have been synthesized by the sol–gel method on glass substrates. X-ray diffraction (XRD) spectra and atom force microscope (AFM) studies reveal that all samples possess hexagonal wurtzite structure without any second phase. 1% Nd doped ZnO thin film has the best crystalline quality. With Nd concentration increases, the grain size reduces gradually. The optical measurements show that with Nd concentration increases, the absorption peak shifts to short wavelength, which indicates that the optical band gap of Nd-doped ZnO thin films increases. All samples have ultraviolet emission centered at 377 nm and strong green emission at 511 nm. The intensity of green emission gradually increases with Nd concentration increases. The emission mechanism is discussed in detail.

► Nd-doping ZnO thin films are synthesized on glass substrates by the sol–gel method. Structural and optical properties dependence of Nd doping concentration is investigated.
► 1% Nd-doping can greatly improve the crystallization quality and ultraviolet emission of ZnO, enlarge band gap and improve the intensity of ultraviolet emission in ZnO thin films.
► With Nd doping concentration increases from 1% to 5%, the intensity of green emission centered at 511 nm is increasing greatly.