PROPERTIES OF LEAD SULFIDE FILMS DEPOSITED FROM A COORDINATION COMPOUND [Pb(N2H4CS)2(CH3COO)2]

Abstract

The position and the shape of intrinsic absorption edges was studied by optical spectroscopy. It allowed identifying the value of the band gap for thin lead sulfi de fi lms produced by spray pyrolysis of aqueous solutions of thiourea coordination compounds (TCS). The study of the optical properties of PbS was focsued on determining the values of the band gap for samples which were synthesized in various conditions. The transmission spectra for thin fi lms were determined, which helped to determine the band gap for direct interband transitions by the intrinsic self-absorption edge. Graphical analysis of the intrinsic absorption edge allowed us to identify the type of optical transition and the energy of the intrinsic absorption edge for thin fi lms of lead sulfi de. By X-ray phase analysis the crystal structure of the fi lms was determined. Using the hot probe method at room temperature, we measured the values of electric resistance, differential thermoelectric power, and the resistivity and conductivity of PbS fi lms with different ratios of concentrations of the initial components. The results of X-ray phase analysis showed that fi lms of lead sulfi de with cubic structure are formed as a result of synthesis at all deposition temperatures between 300–450 С. The results of optical studies of PbS thin fi lm structures indicate that lead sulfi de is characterized by direct transitions with a band gap within 0.43 to 0.49 eV. The increase in concentration of thiourea in the initial solution leads to the decrease in the differential thermoelectric power and the increase in conductivity in PbS fi lms.