Optical and structural properties of catalyst-free synthesized leaves like CdS films

Leaves like CdS films were grown on catalyst-free Si(100) and quartz substrates by vapor transport of CdS powder at 850 degrees C. Randomly aligned nanoleaves with different shapes were observed. X-ray diffraction analysis revealed that the leaves like CdS is a single phase nature with hexagonal crystal structure. The optical functions of CdS films have been determined by ellipsometry investigations from 400 - 1100 nm. A two layer model employing the Cauchy dispersion model for the main layer and Bruggeman effective medium approximation (BEMA) for the surface layer was found to be sufficient and reasonable. The obtained optical constants were compared with those obtained by other preparation methods. The transmittance has high values while the reflectance has low values in the wavelength range 450 - 2500 nm. A direct optical band gap value of 2.41 eV and Urbach energy of 2671 meV were obtained.