Characterization of PbWO4 thin films formed by the pulsed laser welding technique

Abstract

Herein thin films of PbWO4 were formed from bilayers of Pb/WO3 by the pulse laser welding technique (PLW) within couple of seconds in an argon atmosphere. Thin films of Pb (100 nm)/WO3 (500 nm) were deposited by the thermal evaporation technique under a vacuum pressure of 10−5 mbar. The films were then exposed to a pulse laser beam of fixed amplitude and variable pulse width (0.1–10 ms). The produced films were characterized by means of X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and optical spectrophotometry techniques. An almost pure phase (∼90%) of tetragonal PbWO4 was achieved after the pulse width exceeds 5.0 ms. PbWO4 thin films produced by the PLW technique exhibited a direct and indirect energy band gaps of 2.27 eV and 3.52 eV, respectively. Energy band tails of widths of 1.35 eV were found dominant in these films. In addition fitting of the dielectric resonance spectra for Pb/WO3 and PbWO4 thin films indicated that the formation of PbWO4 was accompanied with a decrease in the high frequency dielectric constant, a decrease in the free hole concentration and an increase in the electronic friction in the films. The fast method of obtaining PbWO4 thin films and the formation of the direct band gap being 2.27 eV together with the nonlinear dielectric and optical properties make the PbWO4 films obtained by the PLW technique suitable for optoelectronic technology.