Density functional theory study of the gas phase decomposition of single-source precursors for the chemical vapour deposition of binary and ternary metal chalcogenides

Thumbnail Image
Journal Title
Journal ISSN
Volume Title
Chemical vapour deposition (CVD) method has been widely exploited to grow high quality thin films of metal chalcogenides. However, in some processes the formation of thin films in the gas phase at higher temperature can be a major obstacle to decreasing the deposition rate, thus the thin films formation reaction can compete with the surface deposition reaction and consume the gas phase reactants, before the vapour reaches the heated substrate surface. A variety of single source precursors have been developed for the deposition of thin films. However, few single source precursors have deposited good quality thin films. Hence it is important to design and develop single source precursors with appropriate physico-chemical properties. In this work, a series of novel metal (Pb, Zn, Cd) complexes of diphenyl- and diisopropyl-thioselenophosphinate were studied. These organometallic complexes were employed as potential single source precursors for the deposition of metal chalcogenides thin films. Metal chalcogenides thin films have potential applications in photovoltaics, solar cells, microelectronics, displays and opto-electronic devices. Density functional theory (DFT) calculations have been shown to be valuable tools for elucidating the various decomposition processes of single source precursors and thus making their development more effective and less costly. The reaction mechanisms involved in the thermal decomposition of the precursors were explored by computing the activation barriers and reaction energies at the density functional theory MO6/LACVP * level of theory. This thesis is made up of the following chapters: 1. Chapter one presents a general introduction on metal chalcogenides, chemical vapour deposition process, single-source precursors and applications of metal chalcogenides. v Literature reports about thin films and their applications, and methods of fabrication of thin films are also presented. 2. Chapter two gives the general introduction on computational chemistry. The molecular mechanics method, semi empirical methods and ab initio methods are also discussed in addition to the hybrid methods and basis sets. 3. Chapters three to six describe the density functional theory at the MO6/LACVP * level of theory for the thermal decompositions of Pb[(C6H5)2PSSe]2, Pb[( i Pr)2PSSe]2, Zn[( i Pr)2PSSe]2 and Cd[( i Pr)2PSSe]2 single-source precursors for the chemical vapour deposition of binary and ternary metal chalcogenides. 4. Chapter seven gives a general conclusion and recommendation for future studies.
A thesis submitted to the Department of Chemistry, College of Science, Kwame Nkrumah University of Science and Technology, Kumasi in partial fulfillment of the requirements for the degree of Master of Philosophy (Inorganic Chemistry)