From “Parasitic” Association Reactions toward the Stoichiometry Controlled Gas Phase Synthesis of Nanoparticles: A Theoretically Driven Challenge for Experimentalists

Abstract

In the present record a model for the gas-phase reactions during the chemical vapor deposition (CVD) processes of group 13-15 materials is presented, based on the results of extensive quantum-chemical modeling. Thermodynamic criteria have been introduced to evaluate the importance of a range of association reactions. For the organometallic and hydride derivatives, association processes are found to be favorable both thermodynamically and kinetically. Formation of high mass association products takes place under CVD conditions, including laser-assisted CVD. Structural and thermodynamic properties of the most important ring and cluster intermediates have been predicted. The stoichiometry-controlled synthesis of the 13-15 ternary alloys and nanoparticles using cluster compounds as single-source precursors is predicted to be viable. The association pathway described may be generalized to the CVD reactions of many binary materials (12-16, 13-16, 13-15, 14-15, 14-16).

Growth mechanism of catalyst- and template-free group III-nitride nanorods

“…Timoshkin also pointed out earlier the possibility of gas-phase nanoparticle formation in his theoretical study on the stability of rings and clusters in the gas phase during CVD of group III-V materials [22]. On the basis of those conclusions [18][19][20][21][22], we introduced a probable solid-vapor mechanism for InN NR growth by H-MOVPE, featuring random nanoparticle nucleation from stable gas-phase oligomers and subsequent directional growth along the c-axis, in our previous report [16,23]. Experimental observations were fairly consistent with the proposed growth mechanism [16].…”

Growth mechanism of catalyst‐ and template‐free InN nanorods

“…Several other theoretical studies of potential gas phase intermediates in group III element (Al, Ga, and In)-N-H-Cl systems also suggested the formation of thermodynamically stable oligomer species, [Cl 2 (Al, Ga or In)NH 2 ] n , in the gas phase even at elevated temperatures (up to 1000 K) [19][20][21][22]. Based on those conclusions [18][19][20][21][22], a probable solid-vapor mechanism for InN NR growth by H-MOVPE featured with random nanoparticle nucleation from the stable gas phase oligomers and the subsequent directional growth along the caxis was introduced in our previous report [16]. Experimental observations were fairly consistent with the proposed growth mechanism as well [16].…”

“…The InCl 3 forms an ammonia adduct (Cl 3 In:NH 3 ) with NH 3 and the subsequent monomer formation (Cl 2 InNH 2 ) via a HCl elimination leads to the formation of innate In-N bond in monomer [18][19][20][21][22]. The oligomer species ([Cl 2 InNH 2 ] n ), an aggregate of monomers, has been identified to be stable in the gas phase below a certain high temperature (up to 1000 K) [18][19][20][21][22]. The strong intramolecular H-Cl hydrogen bonding and dipoledipole interactions are known to favor the formation of larger oligomer species [21].…”

“…Meanwhile, Timoshkin pointed out the possibility of gas phase nanoparticle formation in his theoretical study on the stability of rings and clusters in the gas phase during the CVD of group III-V materials [18]. Several other theoretical studies of potential gas phase intermediates in group III element (Al, Ga, and In)-N-H-Cl systems also suggested the formation of thermodynamically stable oligomer species, [Cl 2 (Al, Ga or In)NH 2 ] n , in the gas phase even at elevated temperatures (up to 1000 K) [19][20][21][22].…”

Atmospheric pressure chemical vapor deposition mechanism of Al2O3 film from AlCl3 and O2

“…For example, a recent kinetic study on the AlCl 3 /CO 2 /H 2 system identified AlOCl as a major gas phase intermediate which acts as a catalyst to the water-gas shift reaction [7]. Association reactions of the intermediates yield clusters that diffuse to the substrate surface to form the film or serve as nucleus for the formation of particles [23,24]. The Chapman-Enskog equation can be used to estimate the collision diameter or molecular size of the diffusing gaseous species if the diffusivities are known [18][19][20][21][22]25].…”