ABSTRACT
Ternary thin films of Iron Copper Sulphide (FeCuS), Iron Zinc Sulphide (FeZnS), Lead Silver Sulphide (PbAgS), Copper Silver Sulphide (CuAgS) and Copper Zinc Sulphide (CuZnS) were
grown using cheap and simple solution growth technique with EDTA, TEA and NH3 as
complexing agents. The deposited films were characterized using PYE-UNICO-UV-2102 PC
spectrophotometer, and optical microscopy. The results suggest that some of the films have
crystal structures. From the spectral analysis of absorbance/transmittance, the optical and solid
state properties were deduced. The other optical properties so obtained include the reflectance,
absorption coefficient, refractive index, extinction coefficient, optical conductivity and thickness, while the solid state properties are dielectric constant and band gap energy.
For all the five categories of thin films grown (i.e. FeCuS, FeZnS, PbAgS, CuAgS and
CuZnS), absorbance was high in UV and low in VIS-NIR-regions, while the
transmittance were low in UV-region and high in VIS-NIR-regions. The reflectances
were high in UV-region and low in the VIS-NIR-regions.
For FeCuS, FeZnS, PbAgS, CuAgS and CuZnS, the absorption coefficient ranged from
0.1x106 m-1 to 1.65x106 m-1, 0.2x106 m-1 to 2.3x106 m-1, 0.5x106 m-1 to 0.9x106 m-1, 0.5x106 m-1 to 1.28x106 m-1 and 0.24x106 m-1 to 1.6x106 m-1, respectively. The real part of
the refractive index ranged from 1.2 to 2.3, 0.72 to 2.3, 0.1 to 2.3, 1.94 to 2.28 and 1.6 to
2.3, respectively. The corresponding values of optical conductivity ranged from
0.03x1014 s-1 to 0.6x1014 s-1, 0.07x1014 s-1, 0.06x1014 s-1 to 0.6x1014 s-1, 0.24x1014 s-1 to 0.6x1014 s-1 and 0.12x1014 s-1 to 0.6x1014 s-1, respectively. The extinction coefficient,
ranged from 0.005 to 0.038, 0.004 to 0.056, 0.010 to 0.140, 0.025 to 0.064 and 0.008 to
0.082, respectively. The direct band gap ranged from 2.4eV to2.8eV for FeCuS, 2.9eV
for FeZnS, 1.5eV to 2.1eV for PbAgS, 2.3eV for CuAgS and 2.2eV to 2.4eV for CuZnS.
The values of the indirect band gap were in the range 0.6eV to 1.0eV for FeCuS, 1.9eV
for FeZnS, 0.3eV to 0.8eV for PbAgS, 1.1eV for CuAgS and 0.4eV to 0.9eV for CuZnS.
The real part of the dielectric constant ranged from 1.4 to 5.2, 0.7 to 5.2, 0.4 to 5.2, 3.8 to
5.2 and 2.2 to 5.2, respectively, while the corresponding imaginary part of the dielectric
constant ranged from 0.008 to 0.136, 0.008 to 0.164, 0.010 to 0.390, 0.100 to 0.290 and
0.030 to 0.360, respectively.
The range of band gaps, 1.5eV to 2.9eV makes the films suitable for solar cells
fabrication; this is in agreement with the finding for the film FeCdS.
