Modelling of chemical processes in the dynamic expansion for pulsed laser deposition

摘要

The material transfer from the target to the substrate involved in pulsed laser deposition is described with respect to chemical reactions in the processing gas atmosphere in order to derive the laser parameters and the processing variables necessary for the deposition of thin films with application-adapted properties. The heating and removal are described by the conversion of the optical energy into internal energy followed by a phase transition form the condensed to the gaseous state. The delivered energy becomes distributed into different channels of decomposition in accordance to the temperature. The dynamics of the volatile species is calculated by the use of non-dissipative continuum mechanical equations of the conservation laws of mass, momentum, and energy. The flow field patterns of the gas phase (density, velocity and pressure) during the material transfer of the polymers PE, PP and PMMA and the ceramic Al_2O_3 are calculated. The modelling calculations are directed towards the spatial and temporal dependence of the total and partial pressures either of the materials to be processed or of the processing gas species. The mathematical models are applied to the polymers PE, PP, and PMMA and to the ceramic Al_2O_3 following the chemical composition in thermodynamic equilibrium. The main emphasis of the calculations is to derive parameters and processing variables for pulsed laser film deposition in the case of other material properties.