Apparatus and methods of electrically conductive optical semiconductor coating

Abstract

A method of coating an optical substrate with a transparent, electrically conductive coating includes depositing a semiconductor coating over a surface of an optical substrate, wherein the semiconductor coating has broadband optical transmittance. A doped semiconductor is applied in a pattern over the semiconductor coating. The doped semiconductor in the pattern is activated for electrical conductivity in the doped semiconductor.

Claims

1. A window comprising: a substrate that is transparent to radiation in at least one wavelength band; and a coating disposed over the substrate, wherein the coating comprises semiconducting regions formed of a first material and electrically conductive regions distributed in a pattern within the coating; and wherein the electrically conductive regions comprise the first material and a dopant.

2. The window as recited in claim 1, wherein the coating has broadband optical transmittance.

3. The window as recited in claim 1, wherein the pattern comprises a grid.

4. The window as recited in claim 1, further comprising a protective layer disposed over the coating.

5. The window as recited in claim 4, further comprising a broadband anti-reflection layer disposed over the protective layer.

6. The window as recited in claim 1, further comprising a broadband anti-reflection layer disposed over the coating.

7. The window as recited in claim 1, wherein the first material comprises at least one of In.sub.2O.sub.3 and ZnO.

8. The window as recited in claim 1, wherein the dopant comprises at least one of Sn, Mo, W, Ti, Al, and Ga.

9. The window as recited in claim 1, wherein the coating has broadband optical transmittance in at least visible and infrared spectral regions.

10. The window as recited in claim 1, wherein the pattern extends over an entire surface of the coating.

11. The window as recited in claim 1, wherein a surface of the coating is smooth.

12. The window as recited in claim 1, wherein the coating and substrate are formed into a window without polishing or planarization.

13. The window as recited in claim 1, wherein the semiconducting and electrically conductive regions of the coating have closely matched indices of refraction to mitigate light scattering.

14. The window as recited in claim 1, wherein the pattern is configured to provide electromagnetic interference (EMI) shielding to the substrate.

15. The window as recited in claim 13, wherein a refractive index difference between the semiconducting and electrically conductive regions of the coating is between 0.82 and 1.22.

16. The window as recited in claim 1, wherein the pattern comprises a plurality of lines.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein:

(2) FIG. 1 is a schematic cross-sectional elevation view of an exemplary embodiment of an optic constructed in accordance with the subject disclosure, showing the semiconductor coating with broadband optical transmittance deposited over the surface of the optical substrate;

(3) FIG. 2 is a schematic cross-sectional elevation view of the optic substrate of FIG. 1, showing dopant atoms applied in a pattern to the semiconductor coating;

(4) FIG. 3 is a schematic cross-sectional elevation view of the optic of FIG. 1, showing the doped semiconductor diffused and activated in the semiconductor coating;

(5) FIG. 4 is a flow diagram of an exemplary embodiment of a process in accordance with the subject disclosure, showing a process for applying doped semiconductor in a pattern using photoresist; and

(6) FIG. 5 is a schematic plan view of the optical substrate in FIG. 1, showing an exemplary grid pattern.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an exemplary embodiment of an optic in accordance with the disclosure is shown in FIG. 1 and is designated generally by reference character 100. Other embodiments of optics in accordance with the disclosure, or aspects thereof, are provided in FIGS. 2-5, as will be described. The systems and methods described herein can be used to provide electrically conductive coatings on optics such as windows, wherein the coatings have broadband optical transmittance.

(8) A method of coating an optical substrate 102 with a transparent, electrically conductive coating includes depositing a semiconductor coating 104 over a surface of an optical substrate, wherein the semiconductor coating has broadband optical transmittance. The semiconductor coating 104 can include at least one of Indium Oxide (In.sub.2O.sub.3) or Zinc Oxide (ZnO). The semiconductor coating 104 can have broadband optical transmittance in at least visible and infrared spectra such as long wave infrared, for example. Depositing the semiconductor coating 104 can include depositing the semiconductor coating with the semiconductor coating undoped. Depositing the semiconductor coating 104 can include depositing the semiconductor coating over a surface of the optical substrate 102 in its entirety, e.g., the top surface of optical substrate 102 as oriented in FIG. 1.

(9) With reference now to FIG. 2, the semiconductor coating 104 is doped to form a pattern 108 (shown in FIG. 5) of doped semiconductor 106 in the semiconductor coating 104. Doping the semiconductor coating 104 to form a pattern 108 can include at least one of applying the dopant by ion implantation, applying the dopant by thin film coating, or by any other suitable process. The doped semiconductor can include at least one of Sn, Mo, W, Ti, Al, Ga, or any other suitable material for electrical conductivity. For example, if the semiconductor coating 104 includes undoped In.sub.2O.sub.3, the doped semiconductor 106 can include In.sub.2O.sub.3 doped with Sn, Mo, W, or Ti. In another example, if the semiconductor coating 104 includes undoped ZnO, the doped semiconductor 106 can include ZnO doped with Al or Ga.

(10) Referring now to FIG. 3, the doped semiconductor 106 in the pattern 108 is activated for electrical conductivity in the doped semiconductor 106, e.g., to increase the electrical conductivity of doped semiconductor 106 after it is applied to semiconductor coating 104. Activating the doped semiconductor 106 can include at least one of heat-treating or laser annealing the doped semiconductor 106. Doping the semiconductor coating 104 and activating the doped semiconductor 106 can include diffusing the doped semiconductor through the semiconductor coating 106 to the optical substrate 102, as shown in FIG. 3.

(11) With reference now to FIG. 4, doping the semiconductor coating to form a pattern 108 can include applying a photoresist over the semiconductor coating 102, as indicated by box 110. As indicated by box 112 in FIG. 4, the photoresist can be selectively exposed and developed in the pattern 108 that is shown in FIG. 5. The dopant can be applied to the semiconductor coating 104 through openings in the photoresist, as indicated by box 114 in FIG. 4, e.g., by ion implanting or depositing doped coating over the photoresist. The photoresist can then be removed to leave the doped semiconductor in the pattern 108 on the semiconductor coating 104, as indicated by box 116 in FIG. 4.

(12) Referring now to FIG. 5, the pattern 108 of doped semiconductor 106 can be configured to provide electromagnetic interference (EMI) shielding to the optical substrate, e.g., in any suitable grid pattern. For example, for EMI shielding a broadband optic with a grid having optical transmittance in visible and long wave infrared, a square grid with 5-micron wide lines with 140 micron spacing between the grid lines can be used. Doping the semiconductor coating 104 to form the pattern 108 can include doping a surface of the semiconductor coating 104 so that surface of the semiconductor coating 104 is covered in its entirety with the pattern 108 as shown in FIG. 5. The grid pattern 108 shown in FIG. 5 is schematic and is not necessarily to scale.

(13) With reference again to FIG. 3, a protective coating 118 can be applied over the semiconductor coating 104 and doped semiconductor 106 before activating the doped semiconductor 106. The method can include depositing a broadband anti-reflection coating 120 over the protective coating 118. It is also contemplated that a broadband anti-reflection coating 120 can be applied directly over the semiconductor coating 104 and doped semiconductor 106, e.g., omitting protective coating 118. Although illustrated as a single layer, the broadband anti-reflection coating can consist of multiple layers.

(14) The activated doped semiconductor 106, semiconductor coating 104, and optical substrate 102 can be formed into an optic 100, e.g., a window, that has an electrically conductive coating for EMI shielding, heating, or the like, without etching. The activated doped semiconductor 106, semiconductor coating 104, and optical substrate 102 can be formed into finished optic 100, such as a window, without polishing or post-process planarization because the surface of optic 100 is already smooth after the pattern 108 is formed. The activated doped semiconductor 106 and semiconductor coating 104 have closely matched indices of refraction to mitigate visible and near infrared light scattering through the grid pattern. If the ratio of the indices of refraction of the doped semiconductor and semiconductor coating is between 0.82 and 1.22, the interface reflection will be less than 1% at normal incidence. For example, the indices of refraction of doped and undoped In.sub.2O.sub.3 at 632.8 nm are about 2.00 and 1.77, respectively. The index ratio of 1.13 produces a reflection of only 0.37%.

(15) The methods and systems of the present disclosure, as described above and shown in the drawings, provide for electrically conductive coatings with superior properties including broadband optical transmittance. While the apparatus and methods of the subject disclosure have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the scope of the subject disclosure.