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-2021363629-A1
Application number	US-202117206927-A
Country	US
Kind code	A1
Filing date	Mar 19, 2021
Priority date	May 20, 2020
Publication date	Nov 25, 2021
Grant date	—

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

1 . A method of growing a stoichiometric crystalline IR-transparent 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 sputtered thereon to a temperature substantially less than the temperature of crystallization of the PCMO material in an oxygen-free gas environment; d. heating the previously cooled substrate 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 the previously sputtered 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 d, 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 d, the oxygen-free gas environment also includes nitrogen.

4 . The method of claim 1 wherein after step f, the substrate with the PCMO material deposited thereon is annealed in an oxygen-free gas environment that includes hydrogen to thereby dope the deposited PCMO material with hydrogen.

5 . The method of claim 4 wherein, the oxygen-free gas environment also includes nitrogen.

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

7 . A process for growing PCMO material on Si and other substrates, the PCMO material being deposited on the substrate in a plurality of deposition steps, preferably by sputtering, 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.

8 . The process of claim 7 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.

9 . The process of claim 8 wherein the temperature substantially less than said elevated temperature is no more than 50° C.

10 . The process of claim 7 wherein the substrate does not require a seed layer to be provided thereon prior to PCMO deposition.

11 . The process of claim 7 wherein a post-deposition annealing process is performed on the substrate with the PCMO material deposited thereon in an environment containing at least hydrogen.

12 . The process of claim 7 wherein the deposited PCMO material is stoichiometric.

13 . The process of claim 7 wherein a difference between said elevated temperature and said temperature substantially less than said elevated temperature is more than 300° C.

14 . The process of claim 13 wherein said temperature substantially less than said elevated temperature is no more than 50° C.

15 . The process of claim 7 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.

16 . The process of claim 7 wherein the deposited PCMO material is stoichiometric NdNiO 3 .

17 . The process of claim 16 wherein the atomic ratio of Ni to Nd atoms in the deposited stoichiometric NdNiO 3 is about 1.1 to 1.0.

18 . A process for growing IR-transparent PCMO optical films on substrates, with an optical extinction coefficient k <0.001 over an infrared range of wavelengths, the process including:
i. pre-cleaning a substrate in a substantially oxygen-free gas environment; ii. depositing a PCMO material on the pre-cleaned substrate in the substantially oxygen-free gas environment at an elevated temperature to thereby form a PCMO deposited substrate; iii. cooling the PCMO deposited substrate to a lower temperature in the substantially oxygen-free gas environment, the lower temperature being at least 300° C. lower than said elevated temperature; and iv. annealing the PCMO deposited substrate in a hydrogen environment for hydrogenation of the PCMO material at an annealing temperature less than said elevated temperature but greater than said lower temperature.

19 . The process of claim 18 wherein the PCMO material is annealed in the hydrogen environment at a temperature of approximately 200° C.

20 . The process of claim 18 wherein the hydrogen environment is provided by a forming gas (preferably comprising approximately 10% H 2 +90% N 2 , at approximately a 5 sccm flow rate and at approximately 1 atm pressure).

21 . The process of claim 18 wherein the substrate material is Si.

22 . The process of claim 19 wherein the Si substrate material has a 100 crystallographic orientation.

23 . The process of claim 18 wherein the depositing the PCMO material on the substrate occurs an inert gas environment.

24 . The process of claim 18 wherein the pre-cleaning occurs in by plasma sputtering in a RF Magnetron Sputter deposition chamber.

25 . The process of claim 18 wherein PCMO material is deposited in a RF Magnetron Sputter deposition chamber at a substrate temperature substantially equal to or greater than the PCMO crystallization temperature (e.g., ≥450° C. for SmNiO 3 and NdNiO 3 ).

26 . The process of claim 18 wherein the annealing time required for the hydrogenation of the PCMO material is dependent on the particular PCMO material selected and the thickness of the PCMO material deposited on the substrate, for example, a four times repeated annealing of a two-hour annealing process for a NdNiO 3 film on the substrate.

27 . The process of claim 18 wherein the annealing occurs without the presence of a catalytic transition material such as Pt.

28 . The process of claim 18 where the PCMO material is selected from the group consisting of NdNiO 3 , SmNiO 3 , PrNiO 3 , EuNiO 3 , and GdNiO 3 and combinations thereof.

29 . The process of claim 28 wherein the PCMO material is NdNiO 3 .

30 . A process of making a PCMO crystalline film deposited on a substrate essentially transparent at infrared wavelengths, the process comprising loading the PCMO crystalline film deposited on said substrate in an annealing machine, providing a substantially oxygen-free environment which includes at least some hydrogen in said annealing machine and subjecting the PCMO crystalline film deposited on said substrate in said annealing machine to one or more annealing cycles to thereby hydrogen dope the PCMO crystalline film deposited on the substrate.

31 . The process of claim 30 where the PCMO material is selected from the group consisting of NdNiO 3 , SmNiO 3 , PrNiO 3 , EuNiO 3 , and GdNiO 3 and combinations thereof.

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

• C23C14/5846

  Reactive treatment · CPC title

• C23C14/35

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

• C23C14/08 Primary

  Oxides (C23C14/10 takes precedence) · CPC title

• C23C14/541

  Heating or cooling of the substrates · CPC title