Theoretical study of the gas-phase decomposition of Pb[[[([C.sub.6][H.sub.5]).sub.2]PSSE].sub.2] single-source precursor for the chemical vapour deposition of binary and ternary lead chalcogenides

A theoretical study of Pb(II) square planar thioselenophosphinate, Pb[[[([C.sub.6][H.sub.5]).sub.2]PSSE].sub.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 Pb[Se.sub.x][S.sub.1-x] formation on both the singlet and the doublet potential energy surface. However, thermodynamically, the steps that lead to ternary Pb[Se.sub.x][S.sub.1-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 Pb[Se.sub.x][S.sub.1-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 Pb[Se.sub.x][S.sub.1-x] is a result of thermodynamic and kinetic factors in controlling the material formed during the deposition process. Key words: density functional theory, thioselenophosphinate, lead, chalcogenides, chemical vapour deposition. On a realise l'etude theorique du thioselenophosphinate plan carre de Pb(II), Pb[[[([C.sub.6][H.sub.5]).sub.2]PSSE].sub.2], precurseur du procede de synthese de chalcogenures de plomb par depot chimique en phase vapeur. Les geometries des especes en presence ont ete optimisees au moyen de la theorie de la fonctionnelle de la densite. Les etats de transition et les intermediaires les reliant entre eux ont ete connectes ont ete confirmes par des analyses de frequence. Les calculs de la theorie de la fonctionnelle de la densite (M06/LACVP*, gaz) revelent que, sur le plan cinetique, les etapes qui conduisent a la formation de PbSe sont plus favorisees que celles conduisant a la formation de PbS et de Pb[Se.sub.x][S.sub.1-x] ternaire sur les surfaces d'energie potentielle du singulet et du doublet. Cependant, sur le plan thermodynamique, celles qui menent a la formation de Pb[Se.sub.x][S.sub.1-x] ternaire sont plus favorisees que celles menant a la formation de PbSe et de PbS formation sur la surface d'energie potentielle du doublet. Sur la surface d'energie potentielle du singulet, une autre voie reactionnelle conduisant a la formation de Pb[Se.sub.x][S.sub.1-x] ternaire est favorisee du point de vue thermodynamique et cinetique par rapport a celle qui conduit a la formation de PbSe et de PbS formation. Les etudes computationnelles indiquent que la decomposition du complexe lors depot chimique en phase vapeur pourrait comporter plus d'une etape et que la formation de Pb[Se.sub.x][S.sub.1-x] ternaire serait donc le resultat de l'influence de facteurs thermodynamiques et cinetiques sur le produit forme au cours du processus de depot. [Traduit par la Redaction] Mots-cles: theorie de la fonctionnelle de la densite, thioselenophosphinate, plomb, chalcogenures, depot chimique en phase vapeur.
Introduction Metal dichalcogenophosphinates represent an important class of organophosphorus compounds that are widely used both in industry and academic research. (1) Structural information such as geometrical and electronic configurations, molecular [...]