Density functional theory (DFT) study of the gas-phase decomposition of the Cd[(iPr)2PSSe]2 single-source precursor for the CVD of binary and ternary cadmium chalcogenides

Abstract

The chemistry of group II-VI semiconductors has spurred considerable interest in decomposition reaction mechanisms and has been exploited for various technological applications. In this work, computational chemistry was employed to investigate the possible gas-phase decomposition pathways of the mixed Cd[((i)Pr)2PSSe]2 single-source precursor for the chemical vapour deposition of cadmium chalcogenides as thin films. The geometries of the species involved were optimised by employing density functional theory at the MO6/LACVP* level. The results indicate that the steps that lead to CdS formation on the singlet potential energy surface are favoured kinetically over those that lead to CdSe and ternary CdSe(x)S(1-x) formation. On the doublet PES, the steps that lead to CdSe formation are favoured kinetically over those that lead to CdS and CdSe(x)S(1-x) formation. However, thermodynamically, the steps that lead to ternary CdSe(x)S(1-x) formation are more favourable than those that lead to CdSe and CdS formation on both the singlet and the doublet PESs. Density functional theory calculations revealed that the first steps exhibit huge activation barriers, meaning that the thermodynamically favourable process takes a very long time to initiate.

Theoretical studies of the decomposition of Zn[(iPr)2PSSe]2 single-source precursor in the gas phase for the chemical vapor deposition of binary and ternary zinc chalcogenides

“…The reaction pathways for the gas phase decomposition of Zn[( i Pr) 2 PSSe] 2 complex were based on the schemes suggested by Akhtar et al [1] and Opoku et al [2]. These have been indicated in Schemes 1-4 for the Zn[( i Pr) 2 PSSe] 2 single-source precursor.…”

“…The energetics was computed based on the method outlined by Opoku et al [2] and Aniagyei et al [9]. All calculations were carried out with Spartan '10 v1.1.0 Molecular Modeling programs [10] at the DFT M06/LACVP ⁄ level of theory in order to maximize the accuracy on the chemically active electrons of the reactions while minimizing computational time.…”

“…As for any theoretical investigation, we found no closely related reference except that of Akhtar et al [1] and Opoku et al [2] who studied the decomposition mechanism of Pb[(C 6 H 5 ) 2 PSSe] 2 and Cd[( i Pr) 2 PSSe] 2 precursors, respectively using theoretical calculations method. Here, we present a kinetic and thermodynamic study of the decomposition of Zn[( i Pr) 2 PSSe] 2 complex by employing density functional theory (DFT) calculation. Several possible decomposition pathways were proposed, and of those, the most favorable pathway was determined.…”

“…To the best of our knowledge, both energetic information and kinetic data for the decomposition of Zn[( i Pr) 2 PSSe] 2 precursor are quite limited. As for any theoretical investigation, we found no closely related reference except that of Akhtar et al [1] and Opoku et al [2] who studied the decomposition mechanism of Pb[(C 6 H 5 ) 2 PSSe] 2 and Cd[( i Pr) 2 PSSe] 2 precursors, respectively using theoretical calculations method.…”

“…The decomposition of these precursors has been the subject of experimental and theoretical research [1,2]. The study of the reaction mechanism of high-temperature thermal decomposition of single-source precursors is of great interest, because of their efficient route to deposit high-purity materials at low cost and in large volume.…”