Structural, optical and electrical properties of laser irradiated Pb doped Ga–Se chalcogenide thin films

Using the Transverse Electrical Excitation at Atmospheric Pressure (TEA) nitrogen laser, we had irradiated the amorphous thin films of Ga10Se81Pb9 chalcogenide glass and the results have been discussed in terms of the structural aspects of Ga10Se81Pb9 glass. The observed changes are associated with the interaction of the incident photon and the lone-pairs electrons which affects the band gap. The X-ray structural characterization revealed the amorphous nature of as prepared films and polycrystalline nature of the laser irradiated films. The optical band gap of these thin films is measured by using the absorption spectra as a function of photon energy in the wavelength region 400–1200 nm. It is found that the optical band gap decreases while the absorption coefficient increases with increasing the irradiation time. The decrease in the optical band gap has been explained on the basis of change in nature of films, from amorphous to polycrystalline state, with the increase in exposure time. The dc conductivities and activation energies of these thin films are measured in temperature range 303–403 K. It has been found that the activation energy in Ga10Se81Pb9 chalcogenide thin films decreases whereas the dc conductivity increases at each temperature by increasing the irradiation time.

► Effect of laser-irradiation on structure, optical and electrical properties has been investigated.
► The amorphous/polycrystalline nature has been verified by X-ray diffraction and DSC measurements.
► Laser-irradiation causes a decrease in optical band gap in Ga10Se81Pb9 thin films.
► The decrease in optical band gap can be interpreted on the basis of amorphous–crystalline phase transformation.
► Optical absorption data showed that the rules of the non-direct transitions predominate.