Calculating moleculalar flux from deposition rate.

[Ravian]

I have deposition rate of Silicon dioxide as 1000A/minute. I need to calculate molecular flux to the surface. First I tried to use ideal gas theory but since SiO2 is not ideal gas therefore my answer was completely wrong. I am disoriented. Can anybody help. I know the answer is 3.8E15 molecules/cm2 second.
Thanks

PS: It is not homework assignment. I need to calculate it to determine flux ratio.

 

[DragonPetter]

What is the process for deposition?

 

[Ravian]

It is evaporated using e-gun in UHV of around 10-9 Torr.