Theoretical study of the gas-phase decomposition of Pb[(C6H5)2PSSe]2 single-source precursor for the chemical vapour deposition of binary and ternary lead chalcogenides

Abstract

A theoretical study of Pb(II) square planar thioselenophosphinate, Pb[(C6H5)2PSSe]2 precursor for the chemical vapour deposition process of preparing lead chalcogenides, has been carried out. The geometries of the species were optimized by employing the density functional theory. The transition states as well as the linked intermediates linking them were confirmed with frequency analyses. The density functional theory calculation (M06/LACVP*, gas) reveals that kinetically, the steps that lead to PbSe formation are more favourable than those that lead to PbS and ternary PbSexS1−x formation on both the singlet and the doublet potential energy surface. However, thermodynamically, the steps that lead to ternary PbSexS1−x formation are more favourable than those that lead to PbSe and PbS formation on the doublet potential energy surface. On the singlet potential energy surface, an alternative route leading to the formation of ternary PbSexS1−x is more favoured on both thermodynamic and kinetic grounds than those that lead to PbSe and PbS formation. The computational studies indicate that the decomposition of the complex in chemical vapour deposition may involve more than one step, and thus the formation of ternary PbSexS1−x is a result of thermodynamic and kinetic factors in controlling the material formed during the deposition process.