Question

What happens if mean free path is larger than distance between source and substrate

Answer 1

This is the relation between vapor pressure of  the evaporant and the evaporation rate. If a high  vacuum is established, most molecules/atoms will reach  the substrate • High film deposition rates;

• Less substrate surface damage from impinging atoms as the film is

being formed, unlike sputtering that induces more damage because it

involves high-energy particles;

• Excellent purity of the film because of the high vacuum condition used

by evaporation;

• Less tendency for unintentional substrate heating.without intervening collisions.