Growth and characterization of ZnSe nanocrystals synthesized using solvothermal process

ZnSe nanocrystals with zinc blende structure are synthesized by solvothermal process at 1-h, 3-h and 5-h reaction times in a mixed solvent of hydrazine hydrate [H₆N₂O], ammonia [NH₃] and de-ionized water. Zinc acetate [(CH₃COO)₂ Zn; 2H₂O] and sodium selenite [Na₂SeO₃] are, respectively, used as precursors for zinc and selenium ions. X-ray diffraction (XRD) and scanning electron microscope (SEM) study show that the crystallinity and the chemical purity of the compound improve with increase in reaction duration. SEM images show formation of bulk rod-shaped ZnO particles in samples prepared at 1-h and 3-h reaction times, which is absent in the 5-h sample. TGA measurements also show that the ZnSe nanocrystals synthesized in this process have high purity and the nanocrystals prepared for longer duration have improved purity as well as higher thermal stability. In Raman measurements, nanocrystalline nature such as surface phonon (SP) mode and phonon line width broadening are observed. The observed variation of the relative intensities of the phonon modes follows the differences in the size of nanocrystals, in which the relative strength of the transverse optical (TO) phonon mode is found to increase with nanocrystals size and the SP phonon relative strength on the other hand decreases.