Investigación del efecto de la temperatura de recocido sobre las propiedades ópticas de películas delgadas de CdSe

Resumen

Introduction: CdSe is an important II–VI semiconducting material due
to its typical optical properties such as small direct band gap (1.7 eV) and
a high refractive index and, thus, a major concern is focused on the investigation of optical properties of CdSe thin films which is important to
promote the performances of the devices of solid -state such as SC (solar cells), thin film transistors, LED (light-emitting diodes), EBPL (electron–beam pumped lasers) and electroluminescent devices. In the present
work, CdSe thin films were deposited by thermal evaporation method and
the results have been analysed and presented. Materials and Methods:
CdSe thin films has been deposited on glass microscopic slides as substrates of (75×25×1 mm) under room temperature using PVD technique.
CdSe blended powders gets evaporated and condensed on the substrate.
The film thickness (t = 100 5 nm) which is measured using Michelson
interferometry method. Transmission spectrum, from 200-1100 nm, are
scanned using two beams UV–VIS Spectrophotometer (6850 UV/Vis.
Spectrophotometer-JENWAY). The deposited films then were annealed
at temperature range of (1500C to 3500C) under vacuum to have a stable phase of the material and prevent surface oxidization. Results and
Discussion: A transmittance spectrum of CdSe thin film is scanned over
wavelength range 200 to 1100 nm using a (6850 UV/Vis. Spectrophotometer-JENWAY) at room temperature. The transmittance percentage
between the as-deposited film and the annealed films change varies from
(17.0%) to (47.0%). It is clearly seen that there is a shift toward higher energy (Blue Shift) in the transmittance spectrum. As annealing temperature
increased the transmittance edge is shifted to the longer wavelength (i.e.,
after annealing the CdSe films shows red shifts in their optical spectra).
The band gap was found within the range 1.966-1.7536 eV for CdSe thin
film. As annealing temperature increases, the Eg continuously decreases.
Conclusions: CdSe thin films have been deposited using Physical Vapor
Deposition (PVD) Technique. It is found that the transmission for asdeposited films is (17%) and increases to (47%) as annealing temperature increases. Beside this the energy gap for as- deposited CdSe film is
(1.966eV) and decreased from (1.909 eV) to (1.7536eV) as the annealing
temperature increases. There is a strong red shift in optical spectrum of
the annealed CdSe films. There is a gradual shift of the annealed films
thin film spectra as compared of bulk CdSe films