Physical properties of electron beam evaporated CdTe and CdTe:Cu thin films

Abstract

In this paper, we report on physical properties of pure and Cu doped cadmium telluride (CdTe) films deposited onto corning 7059 microscopic glass substrates by electron beam evaporation technique. X-ray diffraction study showed that all the deposited films belong to amorphous nature. The average transmittance of the films is varied between 77% and 90%. The optical energy band gap of pure CdTe film is 1.57 eV and it decreased to 1.47 eV upon 4 wt. % of Cu addition, which may be due to the extension of localized states in the band structure. The refractive index of the films was calculated using Swanepoel method. It was observed that the dispersion data obeyed the single oscillator of the Wemple-Didomenico model, from which the dispersion energy (Ed) parameters, dielectric constants, plasma frequency, and oscillator energy (Eo) of CdTe and CdTe:Cu films were calculated and discussed in detail with the light of possible mechanisms underlying the phenomena. The variation in intensity of photoluminescence band edge emission peak observed at 820 nm with Cu dopant is due to the change in surface state density. The observed trigonal lattice of Te peaks in the micro-Raman spectra confirms the p-type conductive nature of films, which was further corroborated by the Hall effect measurement. The lowest resistivity of 6.61 × 104 Ω cm was obtained for the CdTe:Cu (3 wt. %) film.

Microstrucral, Optical and Electrical Characteristics of Cu-doped CdTe Nanocrystalline Films for Desinging of Absorber Layer in Solar Cell Applications

“…%. This is in accordance with the reported huge reductions in the electrical resistivity of CdTe single crystals [55][56][57][58] and thin films [13,60] upon incorporated tiny amount of Cu.…”

“…Several deposition techniques have been used to fabricate CdTe thin films, such as rf sputtering. [7], chemical bath deposition, [8], pulsed laser deposition [9], close-range sublimation [10], electro deposition [11], thermal evaporation [12] and Electron beam evaporation [13]. Nevertheless, the difficult duty is to obtain a stoichiometic CdTe films to better design the absorber layer in the solar cell structure, since defects and/or impurities generated during the deposition process will affect the optoelectronic properties of prepared thin films, thereby changing the efficiency of the solar cells [14,[15][16][17].…”

The viability of alternative and nontoxic chlorine containing compounds for thermal treatment of ultrathin CdTe (≤1.0 μm) films

“…All the films showed relatively strong peaks at 124, 140,165, and 320 cm −1 which correspond to the scattering of hexagonal Te, Te/CdTe TO (Transverse optical mode), CdTe LO (Longitudinal optical mode), and second (2LO) overtone, respectively. 38,39 The presence of the LO modes is an indication of the high crystalline quality of these CdTe films. Besides, the presence of Te modes as observed indicates that the CdTe films are Te rich.…”

Optical properties of AlN layers obtained by magnetron sputtering

“…It can be seen that irradiation leads to a significant reduction of the layers absorption in the short and medium wave range of the spectrum (below 800 nm). The refractive index of the deposited films have been determined from their normal incidence transmission spectra by Swanepoel method [30]. In this method, the refractive index of the layer is given as:…”