Time-scale analysis for the synthesis of thin-film deposition reaction kinetics models

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1438375PI: Raymond AdomaitisInstitution: University of Maryland College ParkSome electronic materials, such as photovoltaic materials for solar cells, are manufactured in specialized chemical reactors in which gas-phase reactant molecules deposit on a surface to form a thin film of the product material. The routes that molecules take from the gas phase to the thin film involve a complex set of chemical reactions that must be well understood in order to produce materials with the desired properties. To describe mathematically the overall process of film growth, a system of equations can be derived to track the various chemical species inside the reactor and on the surface of the growing film. This project involves developing new methods for analyzing the system of equations, and comparing the results of the analysis with experimental data for deposition processes such as atomic layer deposition (ALD) and chemical vapor deposition (CVD). The results of the project will provide scientists and engineers with a new tool for predicting the performance of ALD and CVD reactors. The project will provide a training ground for graduate students in an important area of reaction engineering and will provide research opportunities for interested undergraduate students as well. Software that is developed during the project will be made available to the research and industrial communities.This project will investigate the mathematical structure of differential-algebraic (DAE) systems of equations describing surface reaction species during ALD and CVED thin film deposition processes. A reaction network factorization procedure will be developed that partitions surface reaction and deposition species dynamic balances into sets of relatively slow (deposition), fast (equilibrium), and instantaneous (conserved) modes. The project will determine conditions under which the factorization works, the importance of fixed points of the equations, and reaction fluxes of chemical species. Example deposition processes of varying complexity will be analyzed, including some with spatially distributed deposition. Results that correlate rates of film growth with reactor conditions will be compared with experimental data.