We have a molecule that we are thinking of annealing/depositing onto a substrate in ultra-high vacuum (UHV). From our past experience, we know that the molecule sublimates around 90C at 10mtorr. Would this start sublimating right away at room-temperature if exposed to 10E-11 torr (i.e. UHV)? In general, is there some formula for approximating at around what temperature the molecule will start to sublimate in UHV?
Sublimation depends on partial pressure of sublimating material, not on total atmospheric pressure.
dear Derek Oh ;
Sublimation is caused by the absorption of heat which provides enough energy for some molecules to overcome the attractive forces of their neighbours and escape into the vapour phase. Since the process requires additional energy, it is an endothermic change. The enthalpy of sublimation (also called heat of sublimation) can be calculated by adding the enthalpy of fusion and the enthalpy of vaporization.
or you can find the phase diagram of your material like the following diagram to know at what temperature you can sublimate it
Sublimation depends on partial pressure of sublimating material, not on total atmospheric pressure.
Dear Mahmood H. M. , firstly, this is not a "scientific discussion", but answering a question. Secondly, please show where did you mentioned "partial pressure", then we can discuss who should apologize.
- Badges
- Science topic
- Similar topics
- Engineering
- Materials Engineering
- Annealing