Optical properties of thermally evaporated CdS thin films

Abstract

CdS thin films of varying thicknesses were deposited on cleaned glass substrates at room temperature by thermal evaporation technique in a vacuum of about 2 x 10 -5 torr. UV-VIS spectra of the films were studied using the optical transmittance measurements which were taken in the spectral region from 300 nm to 1100 nm. The absorbance and reflectance spectra of the films in the UV-VIS region were also studied. Optical constants such as optical band gap, extinction coefficient, refractive index, optical conductivity and complex dielectric constant were evaluated from these spectra. All the films were found to exhibit high transmittance (~ 60 -93 %), low absorbance and low reflectance in the visible/ near infrared region from ~ 500 nm to 1100 nm. The optical band gap energy was found to be in the range 2.28 -2.53 eV. All the films annealed at 300°C for 4 hours in vacuum (~ 10 -2 torr) showed a decrease in the optical transmittance with its absorption edge shifted towards the longer wavelength, leading to the result that the optical band gap decreases on annealing the films. Also, on annealing crystallinity of the films improves, resulting in decrease in the optical transmittance.

Investigations on the structural, morphological, optical and electrical properties of undoped and nanosized Zn-doped CdS thin films prepared by a simplified spray technique

“…Considering the advantages laid down by Zn-doping of CdS thin films, we focus our work on investigation of physical properties of Zn doped CdS films in order to improve the performance of optoelectronic devices and find their new applications. High quality undoped and doped CdS semiconductor thin films have been prepared by a wide range of methods, such as thermal evaporation [13], spray pyrolysis [14], sputtering [15], pulsed laser deposition (PLD) [16], molecular beam epitaxy (MBE) [17], chemical bath deposition (CBD) [18] and electro Investigations on the structural, morphological, optical and electrical properties of undoped. .…”

Synthesis of Nanocrystalline CdS by SILAR and Their Characterization

“…The experimentally obtained value of is ∼1.0 eV. An activation energy value of 0.9 eV in the low temperature range has been attributed to grain boundarylimited conduction mechanism [26].…”

Synthesis of polymer–PbS nanocomposite by solar irradiation-induced thermolysis process and its photovoltaic applications

“…The observed blue shift could be attributed due to the decrease in crystallite sizes of the films in comparison to the bulk PbS. The sharp increase in absorbance near the fundamental absorption edge for the PbS/PVA film is an indication of good crystalline nature of the films [26]. The optical band gaps of the films were obtained using the following equation [27] for a semiconductor:…”