This difference is likely the result of TDMAT being more efficiently entrained in the carrier gas flow due the smaller diffusion coefficient of TDMAT relative to water, resulting from the larger collision diameter and mass of TDMAT.
TDMAT and water were chosen because they are prototypical ALD precursors which, due to the large difference in mass and collision diameters, have significantly different mass diffusivity values.
Relative to rigid spheres with collision diameter s for low-energy collisions, Lennard-Jones molecules have a slightly smaller cross-section for high-energy collisions that are almost head-on, due to strong repulsive forces.
for square-well potentials characterized by collision diameter [[sigma].sub.km], well-depth [[epsilon].sub.km], and well-width [[sigma].sub.km]([R.sub.SW-1]):
[[sigma].sub.k] collision diameter for the Lennard-Jones 6-12 intermolecular potential
where [Gamma] is the gamma function, [[sigma].sub.i] and [[epsilon].sub.i] represent purecomponent collision diameters and potential well depths, respectively, and an empirical averaging procedure is employed to estimate these parameters for collisions between dissimilar molecules.