Atomic layer deposition of fluoride thin films
A secondary electron emissive coating. The coating is formed by atomic layer deposition of CaF 2 on a substrate by ALD half cycle exposure of an alkaline metal amidinate and ALD half cycle exposure of a fluorinated compound, where the deposition occurs at a reaction temperature greater than a highest sublimation temperature of the first metal precursor and the second metal precursor and less than 50° C. above the highest sublimation temperature.
1. A method of forming a secondary electron emissive coating comprising:
providing a substrate within an atomic layer deposition reactor; and
depositing a coating of CaF 2 by an atomic layer deposition process including at least one cycle of:
pulsing a first metal precursor comprising an alkaline metal amidinate into the reactor for a first metal precursor pulse time;
purging the reactor of the first metal precursor;
pulsing a second precursor comprising a fluorinated compound into the reactor for a second precursor pulse time; and
purging the reactor of the co-reactant precursor;
wherein the depositing occurs at a reaction temperature greater than a highest sublimation temperature of the first metal precursor and the second metal precursor and less than 50° C. above the highest sublimation temperature.
2. The method of claim 1 , wherein the substrate is an aluminum compound.
3. The method of claim 1 , wherein the substrate is AlF 3 .
4. The method of claim 1 , wherein the first metal precursor is [Ca(amd) 2 ] 2 .
5. The method of claim 4 , wherein the second precursor is selected from the group consisting of HF, HF-pyridine, WF 6 , TaF 5 , MoF 6 , and NbF 5 .
6. The method of claim 5 , wherein the second precursor is HF or HF-pyridine.
7. The method of claim 6 , wherein the reaction temperature is less than 200° C.
8. The method of claim 1 , wherein depositing the coating comprises at least 10 atomic layer deposition cycles.
9. The method of claim 4 , wherein depositing the coating comprises at least 40 atomic layer deposition cycles.
10. The method of claim 1 , wherein the reaction temperature is 25° C.-50° C. above the highest sublimation temperature.