Influence of thermal annealing on the structural and optical properties of CdSe nanoparticles

CdSe nanocrystals of similar to 3-4 nm size have been synthesized by hot-injection method. The influence of thermal annealing in air- or N-2-atomosphere oil the morphology and optoelectronic properties of synthesized CdSe nanoparticles has been elucidated. The CdSe nanoparticles showed phase transformation upon annealing in air at 350 degrees C from nanocrystalline sphalerite cubic (Zinc Blende, beta-CdSe) structure to hexagonal (Wurtzite, alpha-CdSe) Structure with a binding energy (Cd 3d(5/2) peak) shift of 0.70 eV. Remarkable differences in the morphology and optoelectronic properties between air- and N-2- annealed CdSe nanoparticles were clearly observed. The intensity of PL emission increased substantially after annealing in air or N-2-atmosphere at 250 and 350 degrees C, respectively, indicating the improvement of crystallinity and surface passivation characteristics of the CdSe nanocrystals. (C) 2009 Elsevier B.V. All rights reserved.