Optical Properties of CuAl2S Alloyed Thin Films Prepared Using Enhanced Successive Ionic Layer Adsorption and Reaction Method

The synthesis of CuAl2S alloyed thin films, have been deposited using enhanced successive ionic layer adsorption and reaction (SILAR). The substrates were prepared by soaking them in aqua regia for 48hours, washed with detergent, rinsed in de-ionized water and were allowed to dry in air. The complexing agent used was 3M of aqueous solution of ammonia (NH4OH), 1.0M solution of hydrated copper sulphate (CuSO4:5H2O) was used as cation source and 2.3M solution thiourea (SC(NH2)2)as anionic source and 0.5M of aluminum sulphate(Al2(SO4)3 as the alloying source material. The deposition of CuAl2S alloyed thin films were carried out at room temperature of 230C. The films were annealed at varying times of 1hour-2hours and varying temperatures of 1000C-2500C. The structural properties of the films were determined using XRD for crystal structures and SEM for morphological studies. The XRD patterns of CuAl2S of samples C and D grown under the same conditions but different annealing temperatures of 1500C and 2000C and annealing times of 1hr and 2hrs respectively, have one diffraction peak each at 2θ =24.940 and 2θ=24.930 with the grain sizes of the alloys of 3.5674nm and 3.5688nm respectively. The atomic concentrations were determined using EDX. The add-atoms of Cu, Al and S found on sample C are 3.33mol/dm3, 2.14mol/dm3 and 3.27mol/dm3 respectively. EDX for sample D, the concentrations of the add-atoms of Cu, Al and S are 1.97 mol/dm3, 2.09mol/dm3 and 3.42mol/dm3 respectively. The transmittance was measured by UV-double beam spectrophotometer in the wavelength range of 200nm to 1200nm.Other optical properties such as absorbance, reflectance, absorption coefficient, optical constants, optical conductivity, dielectric constants, and optical band gaps were determined, using relevant equations. The band gaps were determined from the graph of (αhv)2 against the photon energy, hv, by extrapolation of the straight portion of the curves where (αhv)=0. The band gaps of samples A, B, C, D and E are 3.74±0.05eV, 3.69±0.05eV, 3.66±0.05eV, 3.62±0.05eV and 3.60±0.05eV respectively with p-type property. Due to the high transmittance exhibited in the visible and near infrared regions of electromagnetic spectrum by the films, it can be found useful as effective material for transparent conducting electrodes for photo-electronic applications, solar control coatings, tint on eyeglasses, poultry house warmer, sensors for gaseous substances and solar cell fabrications.