Numerical modelling of the droplet vaporization for design and operation of liquid-pulsed CVD
This article presents an approach for modeling the vaporization of droplets of solvent and precursor mixture under vacuum in the pulsed-pressure CVD process. The pulsed direct liquid injection apparatus with ultrasonic atomizer has been demonstrated as a controllable and reliable alternative to the bubbler and carrier gas system. Design variables include the reactor base and peak pressures, solution injection volume, precursor concentration, and reactor surface temperature in the flash evaporation zone. The numerical modeling solves mass, heat and momentum continuity equations on liquid droplets and is intended to evaluate the relative roles of the physical chemistry properties and reactor parameters in the fast vaporization of droplets. The sensitivity analysis proposed here shows that the vaporization time of the pulsed liquid CVD system is mainly dependent on the heating available in the flash evaporation zone, then on the thermodynamic properties of the liquid solution. The practical example of TTIP (Titanium Isopropoxide) delivery is presented to select the solvent and design the thermal conditions for optimal evaporation efficiency and sharpest reactor pressure rise.