Articles written in Bulletin of Materials Science
Volume 31 Issue 1 February 2008 pp 67-72 Thin Films
The equilibrium concentrations of various condensed and gaseous phases were calculated from thermodynamic modeling of MOCVD of ZrO2 films using a 𝛽-ketoesterate complex of zirconium as precursor. This leads to the construction of the `CVD phase stability diagram’ for the formation of solid phases. In the reactive ambient of oxygen, the calculations predict carbon-free ZrO2 film over a wide range of process conditions. The thermodynamic yields are in reasonable agreement with experimental observations, though the removal of carbon from the MOCVD grown films is not as complete as the thermodynamic calculations predict.
Volume 31 Issue 5 October 2008 pp 723-728 Thin Films
Thermodynamic calculations, using the criterion of minimization of total Gibbs free energy of the system, have been carried out for the metalorganic chemical vapour deposition (MOCVD) process involving the 𝛽-ketoesterate complex of iron [tris(𝑡-butyl-3-oxo-butanoato)iron(III) or Fe(tbob)3] and molecular oxygen. The calculations predict, under different CVD conditions such as temperature and pressure, the deposition of carbon-free pure Fe3O4, mixtures of different proportions of Fe3O4 and Fe2O3, and pure Fe2O3. The regimes of these thermodynamic CVD parameters required for the deposition of these pure and mixed phases have been depicted in a `CVD phase stability diagram’. In attempts at verification of the thermodynamic calculations, it has been found by XRD and SEM analysis that, under different conditions, MOCVD results in the deposition of films comprising pure and mixed phases of iron oxide, with no carbonaceous impurities. This is consistent with the calculations.
Volume 34 Issue 1 February 2011 pp 11-18
Equilibrium thermodynamic analysis has been applied to the low-pressure MOCVD process using manganese acetylacetonate as the precursor. ``CVD phase stability diagrams” have been constructed separately for the processes carried out in argon and oxygen ambient, depicting the compositions of the resulting films as functions of CVD parameters. For the process conduced in argon ambient, the analysis predicts the simultaneous deposition of MnO and elemental carbon in 1:3 molar proportion, over a range of temperatures. The analysis predicts also that, if CVD is carried out in oxygen ambient, even a very low flow of oxygen leads to the complete absence of carbon in the film deposited oxygen, with greater oxygen flow resulting in the simultaneous deposition of two different manganese oxides under certain conditions. The results of thermodynamic modeling have been verified quantitatively for lowpressure CVD conducted in argon ambient. Indeed, the large excess of carbon in the deposit is found to constitute a MnO/C nanocomposite, the associated cauliflower-like morphology making it a promising candidate for electrode material in supercapacitors. CVD carried out in oxygen flow, under specific conditions, leads to the deposition of more than one manganese oxide, as expected from thermodynamic analysis (and forming an oxide–oxide nanocomposite). These results together demonstrate that thermodynamic analysis of the MOCVD process can be employed to synthesize thin films in a predictive manner, thus avoiding the inefficient trial-and-error method usually associated with MOCVD process development. The prospect of developing thin films of novel compositions and characteristics in a predictive manner, through the appropriate choice of CVD precursors and process conditions, emerges from the present work.
Volume 43, 2020
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