Abstract
Hydroxyethyl cellulose (HEC) doped with 3 wt% erbium nitrate film was prepared by casting from solution. The effect of plasma treatment on optical properties of composite film was investigated. The optical absorbance was measured in the wavelength region of 200-800 nm. . Electronic transition was proved to be direct allowed for pristine and plasma treated film. Tauc's plots were used to determine the optical band gap (E-opt) of the samples under study. The energy gap was 5.30 eV for untreated composite film and the treated samples at 10, 20 and 30 min have lower values of optical band gap, 5.22, 5.20 and 4.90 eV respectively. It was also found that the Urbach energy values (E-e) were decreased under different plasma treatment times. It begins with 1.46 eV for untreated sample till it reaches 0.72 eV for 30-minute treated sample. Wemple-DiDomenico model parameters such as, oscillator energy, dispersion energy and zero-frequency refractive index values were calculated and their variations with plasma were studied. The color parameters for composite film are noticeably affected under plasma treatment. (C) 2021 THE AUTHORS. Published by Elsevier BV on behalf of Faculty of Engineering, Alexandria University.