Optical properties of amorphous/crystalline ZnO nano-powder prepared by solid state reaction

This paper presents a simple and efficient method to prepare amorphous and crystalline ZnO nano-powders via thermal decomposition of the mixture of Zn(CH₃COO)₂·2H₂O and NaHCO₃. X-ray diffraction (XRD) pattern and transmission electron microscope (TEM) images indicated that thermal decomposition of the mixture at 160° C for 3 h, amorphous ZnO powder was obtained. Otherwise, temperature above 160°C, the amorphous ZnO would begin transform into crystalline. Photoluminescence (PL) spectra of amorphous ZnO revealed it had very strong UV emission, but its visible emission was barely observed. The UV intensity of amorphous ZnO was about 3 times of that of crystalline ZnO. This can be explained by quantum size effect.