Structural and optical study of nanostructure of 4-cyanopyranoquinolinedione (CPQ) thin films

Thin films of 4-cyanopyranoquinolinedione, CPQ, with different thicknesses were deposited by thermal evaporation method. The structural properties of powder and thin films were investigated using X-ray diffraction technique. The crystal structure, lattice parameters and Miller indices of the powder were indexed. The crystalline size, strain and dislocation density were determined for powder and thin films. The optical properties of CPQ thin films were studied using spectrophotometric measurements of both transmittance and reflectance in the wavelength range 200-2500 nm. HOMO-LUMO band gap was determined by cyclic voltammetry. The calculation of optical band gap using absorption coefficient showed that the film has direct allowed transition with 3.02 eV energy gap. The normal dispersion of the refractive index of the films was described by Wemple-DiDomenico single oscillator model. Some dispersion parameters were calculated. Also, the real and imaginary parts of dielectric constant, volume and surface energy loss functions were estimated.