Oxidation and moisture barrier layers for wire grid polarizer

1. A wire grid polarizer (WGP) comprising:

ribs located over a surface of a transparent substrate, wherein the ribs are elongated and arranged in a substantially parallel array;

gaps between at least a portion of the ribs; and

a conformal-coating located over the ribs, wherein:

the conformal-coating comprises two layers of different materials, including an oxidation-barrier and a moisture-barrier;

the oxidation-barrier includes aluminum oxide, silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, a rare earth oxide, or combinations thereof;

the moisture-barrier includes hafnium oxide, zirconium oxide, a rare earth oxide, or combinations thereof;

the oxidation-barrier is located between the moisture-barrier and the ribs; and

the oxidation-barrier is distinct from the ribs.

2. The WGP of claim 1 , wherein the oxidation-barrier includes aluminum oxide and the moisture-barrier includes hafnium oxide.

3. A wire grid polarizer (WGP) comprising:

ribs located over a surface of a transparent substrate, wherein the ribs are elongated and arranged in a substantially parallel array, and a material of an exterior surface of the ribs has solubility in water of at least 0.015 grams per liter at 25° C.;

gaps between at least a portion of the ribs; and

a conformal-coating located over the ribs, wherein the conformal-coating includes a barrier layer, the barrier layer including at least one of silicon nitride, silicon oxynitride, silicon carbide, hafnium oxide, and a rare earth oxide.

4. The WGP of claim 3 , wherein a material of an exterior surface of the ribs includes germanium.

5. The WGP of claim 3 , wherein:

the barrier-layer comprises two layers of different materials, including an oxidation-barrier and a moisture-barrier;

the oxidation-barrier includes aluminum oxide, silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, or combinations thereof;

the moisture-barrier includes hafnium oxide, zirconium oxide, or combinations thereof; and

the oxidation-barrier is located between the moisture-barrier and the ribs.

6. The WGP of claim 5 , wherein the oxidation-barrier has a thickness of less than 5 nanometers and the moisture-barrier has a thickness of less than 5 nanometers.

7. The WGP of claim 5 , wherein the oxidation-barrier includes aluminum oxide and the moisture-barrier includes hafnium oxide.

8. The WGP of claim 3 , wherein:

the conformal-coating further comprises a hydrophobic-layer located over the ribs;

the barrier-layer is located between the hydrophobic-layer and the ribs; and

the hydrophobic-layer includes a phosphonate conformal-coating, wherein the phosphonate conformal-coating includes:

where:

each R 1 independently is a hydrophobic group;

Z is a bond to the ribs; and

R 5 is a chemical element or a group.

9. The WGP of claim 8 , wherein

R 5 is —OCH 3 , or Z.

10. The WGP of claim 8 , wherein the hydrophobic-layer further comprises a silane conformal-coating, wherein the silane conformal-coating includes chemical formula (1), chemical formula (2), or combinations thereof:

where:

r is a positive integer;

X is a bond to the ribs; and

each R 3 is independently a chemical element or a group.

11. The WGP of claim 10 , wherein:

each of the ribs includes a rod and a wire;

the wire is reflective;

the rod is absorptive;

X is a bond to the rod; and

Z is a bond to the wire.

12. The WGP of claim 10 , wherein:

X is —O—Si; and

Z is —O-Metal, where Metal is a metal atom.

13. The WGP of claim 8 , wherein the hydrophobic-layer is capable of keeping water on a surface of the ribs in a Cassie-Baxter state.

14. The WGP of claim 3 , wherein:

the conformal-coating further comprises a hydrophobic-layer located over the ribs;

the barrier-layer is located between the hydrophobic-layer and the ribs; and

the hydrophobic-layer includes a silane conformal-coating, wherein the silane conformal-coating includes chemical formula (1), chemical formula (2), or combinations thereof:

where:

r is a positive integer;

X is a bond to the ribs; and

R 3 is independently a chemical element or a group;

each R 1 is independently a hydrophobic group including a perfluorinated group.

15. The WGP of claim 14 , wherein the perfluorinated group includes CF 3 (CF 2 ) n (CH 2 ) m , where 4≤n≤10 and 2≤m≤5.

16. A method of making a wire-grid polarizer, the method comprising:

obtaining an array of ribs located over a surface of a transparent substrate, the ribs being substantially parallel and elongated with gaps between at least a portion of the ribs;

applying an oxidation-barrier, the oxidation-barrier including aluminum oxide, silicon oxide, silicon nitride, silicon oxynitride silicon carbide, or combinations thereof; and

applying a moisture-barrier, the moisture-barrier including hafnium oxide, zirconium oxide, or combinations thereof.

17. The method of claim 16 , further comprising applying a hydrophobic-layer of the conformal-coating by vapor deposition after applying the barrier layer, wherein applying the hydrophobic-layer includes exposing the WGP to a chemical, the chemical including (R 1 ) i PO(R 4 ) j (R 5 ) k , where:

i is 1 or 2, j is 1 or 2, k is 0 or 1, and i+j+k=3;

each R 1 is independently a hydrophobic group;

R 4 is a phosphonate-reactive-group;

each phosphonate-reactive-group is independently selected from: —Cl, —OR 6 , —OCOR 6 , and —OH;

each R 6 is independently an alkyl group, an aryl group, or combinations thereof; and

each R 5 , if any, is any chemical element or a group.

18. The method of claim 17 , wherein the chemical further comprises Si(R 1 ) d (R 2 ) e (R 3 ) g , where:

d is 1, 2, or 3, e is 1, 2, or 3, g is 0, 1, or 2, and d+e+g=4;

R 2 is a silane-reactive-group; and

each silane-reactive-group is independently selected from: —Cl, —OR 6 , —OCOR 6 , —N(R 6 ) 2 , and —OH.

19. The method of claim 16 , further comprising applying a hydrophobic-layer of the conformal-coating by vapor deposition after applying the barrier layer, wherein applying the hydrophobic-layer includes exposing the WGP to a chemical, the chemical including Si(R 1 ) d (R 2 ) e (R 3 ) g , where:

each R 1 is independently a hydrophobic group including CF 3 (CF 2 ) n (CH 2 ) m , where 4≤n≤10 and 2≤m≤5;

d is 1, 2, or 3, e is 1, 2, or 3, g is 0, 1, or 2, and d+e+g=4;

R 2 is a silane-reactive-group;

each silane-reactive-group is independently selected from: —Cl, —OR 6 , —OCOR 6 , —N(R 6 ) 2 , and —OH;

each R 6 is independently an alkyl group, an aryl group, or combinations thereof; and

each R 3 is independently a chemical element or a group.

20. The method of claim 16 , wherein the oxidation-barrier includes aluminum oxide and the moisture-barrier includes hafnium oxide.