Self-assembled nanocrystalline CdSe thin films

Self-assembled nanocrystalline cadmium selenide (Q-CdSe) thin films of different grain size have been successfully deposited by wet chemical technique. The method allows a controlled formation of the self-assembled structure with different grain size by varying the concentration of surfactant (TOPO) in an electrolyte containing CdCl2, NH4Cl and Na2SeSO3 at pH 8 and temperature 36 °C. Effect of particle size on the structural, optical and morphological properties has been studied and correlated. Atomic force microscopy investigation indicated that the as-deposited films were smooth, compact and exhibited tendency for self-organisation. Size of CdSe nanoparticles can be altered from 18 nm (bulk) to 2.3 nm. The nanocrystalline film shows hexagonal structure. Blue shift has been observed in optical absorption and photoluminescence spectra. The microstructural strain calculated from peak broadening revealed an increase in strain with decreasing particle size.