Method for growing crystalline optical films on Si substrates which may optionally have an extremely small optical loss in the infra-red spectrum with hydrogenation of the crystalline optical films

Patent metadata

Field	Value
Publication number	US-11788183-B2
Application number	US-202117206927-A
Country	US
Kind code	B2
Filing date	Mar 19, 2021
Priority date	May 20, 2020
Publication date	Oct 17, 2023
Grant date	Oct 17, 2023

Abstract

A process enables growing thick stoichiometric crystalline and preferably IR-transparent optical PCMO material on Si and other substrates. Sputter deposition is carried out in oxygen-free inert gas (e.g., Ar) environment, which helps to prevent decomposition of the PCMO material over the substrate. In the disclosed process, there is no need to add a seed layer prior to PCMO deposition. Moreover, no post-deposition annealing is needed in a high-temperature and high-pressure oxygen furnace, but an anneal provides certain additional benefits in terms of improved transparency at IR wavelengths. Over a long deposition time for a thick PCMO film on the high temperature (≥450° C.) substrates, the PCMO deposition is made repeated cycles of deposition of the PCMO material at the high temperature, each deposition cycle being followed by cooling the PCMO-deposited substrate to a substantially lower temperature (<50° C.). If an anneal is applied in a hydrogen environment that will cause hydrogenation of the PCMO film which yields PCMO films with an extremely small optical loss (i.e., optical extinction coefficient k<0.001) over the entire IR range.

First claim

What is claimed is:

1. A method of growing a stoichiometric crystalline IR-transparent Phase-Change Correlated Transition Metal Oxide (PCMO) optical film of a desired thickness on a substrate, the method comprising:
a. heating the substrate to a temperature at least equal to the temperature of crystallization of a PCMO material to be deposited thereon in an oxygen-free gas environment,
b. depositing the PCMO material onto the substrate while at said temperature at least equal to the temperature of crystallization of the PCMO material;
c. cooling the substrate with the PCMO material deposited thereon to a temperature substantially less than the temperature of crystallization of the PCMO material in an oxygen-free gas environment;
d. heating the substrate previously cooled at step c to a temperature at least equal to the temperature of crystallization of the PCMO material to be deposited thereon in an oxygen-free gas environment,
e. depositing the PCMO material onto previously deposited PCMO material while at said temperature at least equal to the temperature of crystallization of the PCMO material; and
f. repeating steps c, d and e until said desired thickness of the PCMO optical film on the substrate is obtained.

2. The method of claim 1 wherein in steps b, and e, depositing occurs by sputtering in an oxygen-free gas environment that includes hydrogen to thereby dope the deposited PCMO material with hydrogen.

3. The method of claim 2 wherein in steps b, and e, the oxygen-free gas environment includes nitrogen.

4. The method of claim 1 wherein no seed layer for the PCMO material is deposited on the substrate between steps a and b.

5. A process for growing Phase-Change Correlated Transition Metal Oxide (PCMO) material on a substrate, the PCMO material being deposited on the substrate in a plurality of deposition steps in an oxygen-free gas environment at an elevated temperature during each deposition step, the plurality of deposition steps being separated from each other by a cooling step wherein the elevated temperature of the oxygen-free gas environment is reduced to a temperature substantially less than said elevated temperature.

6. The process of claim 5 wherein the elevated temperature is at least equal to the temperature of crystallization of the PCMO material to be deposited and wherein the temperature substantially less than said elevated temperature is no more than 100° C.

7. The process of claim 6 wherein the temperature substantially less than said elevated temperature is no more than 50° C.

8. The process of claim 5 wherein the substrate does not require a seed layer to be provided thereon prior to PCMO deposition.

9. The process of claim 5 wherein a post-deposition annealing process is performed on the substrate with the PCMO material deposited thereon in an environment containing at least hydrogen.

10. The process of claim 5 wherein the deposited PCMO material is stoichiometric.

11. The process of claim 5 wherein a difference between said elevated temperature and said temperature substantially less than said elevated temperature is more than 300° C.

12. The process of claim 11 wherein said temperature substantially less than said elevated temperature is no more than 50° C.

13. The process of claim 5 where the deposited PCMO material is selected from the group consisting of NdNiO 3 , SmNiO 3 , PrNiO 3 , EuNiO 3 , and GdNiO 3 and combinations thereof and wherein the deposited PCMO material is deposited by sputtering.

14. The process of claim 5 wherein the deposited PCMO material is stoichiometric NdNiO 3 .

15. The process of claim 14 wherein the atomic ratio of Ni to Nd atoms in the deposited stoichiometric NdNiO 3 is about 1.1 to 1.0.

16. The method of claim 5 wherein in the plurality of deposition steps occur in an oxygen-free gas environment that includes hydrogen to thereby dope the deposited PCMO material with hydrogen.

17. The method of claim 16 wherein the oxygen-free gas environment includes nitrogen.

Assignees

• Hrl Lab Llc

Inventors

• Son Kyung-Ah
• Moon Jeong-Sun
• Seo Hwa Chang
• Kremer Richard M
• Quarfoth Ryan G
• Crowell Jack A
• Taboada Mariano J
• Doria Joshua M
• Welch Terry B

Classifications

• C23C14/08 Primary

  Oxides (C23C14/10 takes precedence) · CPC title

• C23C14/35

  by application of a magnetic field, e.g. magnetron sputtering {(C23C14/3457 takes precedence)} · CPC title

• C23C14/5846

  Reactive treatment · CPC title

• C23C14/541

  Heating or cooling of the substrates · CPC title