Abstract: ZnO/SiO₂ materials with different ZnO loadings were prepared by incipient wetness impregnation method in different calcination atmospheres. A home-built laser-induced luminescence spectroscopy setup was applied to studying the luminescent behavior of these materials. The continuous wave He-Cd laser(λ=325 nm) was used as the excitation source. It is found that the samples calcined in air mainly show the orange luminescence band(centered at about 670 nm), but the samples calcined in Ar mainly exhibit the green luminescence band(centered at about 540 nm). Interestingly, the orange luminescence band is changed into the green luminescence band after the ZnO/SiO₂ was treated in air and calcined in Ar again, and the green luminescence band is changed into the orange luminescence band after the ZnO/SiO₂ was treated in Ar and further calcined in air. These results suggest that the visible luminescence bands of ZnO are ascribed to the oxygen vacancies in ZnO. The green luminescence band is ascribed to the state with a high density of oxygen vacancies; and the orange luminescence band is attributed to the state with less oxygen vacancies. The XRD patterns show that ZnO in these materials exists as a wurtzite structure. UV-Vis and Raman spectra indicate that most ZnO is formed in the form of macrocrystal on SiO₂. Our results also demonstrate that the laser-induced luminescence spectroscopy is a powerful technique to characterize the defect sites, particularly the oxygen deficient in semiconductor materials.

Key words: Laser induced luminescence spectroscopy, ZnO, Oxygen vacancy, Green band, Orange band