Structural, optical and electrical characterization of Ag doped lead chalcogenide (PbSe) thin films

Research and development efforts are currently underway to fabricate a variety of solid state devices. A good deal of information regarding the synthesis, structural, optical and electrical properties of Ag doped lead chalcogenides have been revealed. The bulk polycrystalline (PbSe)100−xAgx ternary chalcogenides are prepared by diffusion technique. The XRD patterns recorded for the (PbSe)100−xAgx thin films prepared by vacuum deposition technique, show that these films are polycrystalline in nature. The optical measurements reveal that the (PbSe)100−xAgx thin films possess direct band gap and the band gap energy decreases with an increase of Ag concentration. The extinction coefficient (k) and refractive index (n) are found to be changing by increasing Ag concentration in PbSe. These results are interpreted in terms of the change in concentration of localized states due to the shift in Fermi level. The dc conductivities of (PbSe)100−xAgx thin films are measured in temperature range 303–403 K. It is observed that the dc conductivity increases at all the temperatures with an increase of Ag content in PbSe system. The experimental data suggests that the conduction is due to thermally assisted tunneling of the charge carriers in the localized states near the band edges. The activation energy and optical band gap are found to decrease with increasing Ag concentration in lead chalcogenide and there are good agreements between these two values.