Photoluminescence of ZnSe nanocrystals obtained by spin-coating method

Abstract

Synthesis of the nanoparticles has made great strides in the field of nanotechnologies particularly in optoelectronics. Reading information by lasers on solid supports, as example, is performed by wide gap semiconductor thin films. From fundamental research, several theories were proposed to explain the physical properties of this new class of materials. ZnSe nanoparticles incorporated in polystyrene films were deposited by spin-coating method on glass substrates. X-rays diffraction measurement confirms the incorporation of ZnSe with a cubic structure and nanometer size, in the polystyrene matrix. Optical characterization by UV - visible spectroscopy shows a shift of the edge of absorption toward great energies compared to the bulk crystal and the presence of broad peak witch is due to the creation of excitons in ZnSe nanocrystals. This displacement of the edge is due to quantum confinement induced by the low size of ZnSe crystallites. The width of the peaks enables us to estimate the distribution of crystallite size. Photoluminescence spectrum of films is formed by four (04) bands. The band in 432 nm (2.867 eV) is attributed to the transition band to band. The second in 471 nm (2.633 eV) is due to the transition between defect levels in the gap. The last, at 624 nm (2.366 eV), is assigned to the transition between levels in the gap created by the vacant Zn sites while the shoulder located at 408 nm (3.040 eV) is probably due to the polystyrene.