FABRICATION OF METAL OR ALLOY ARTICLES HAVING MICROSTRUCTED AND/OR NANOSTRUCTURED FEATURES

Abstract

New and more cost-efficient methods and compositions are needed for the fabrication of three-dimensional nanostructures and/or microstructures from metals and alloys, including noble metals. In one aspect, a method of fabricating an article comprises selectively depositing a layer of copper oxide on a substrate and electrodepositing a noble metal layer onto the copper oxide layer from a solution comprising a salt of the noble metal and an electrolyte component comprising citrate, sulfite, or mixtures thereof. In being deposited onto the copper oxide layer, the noble metal layer is also selectively deposited relative to the substrate.

Claims

1. A method of fabricating an article comprising: selectively depositing a layer of copper oxide on a substrate; and electrodepositing a noble metal layer onto the copper oxide layer from a solution comprising a salt of the noble metal and an electrolyte component comprising citrate, sulfite, or mixtures thereof.

2. The method of claim 1, wherein the selectively deposited layer of copper oxide is patterned on the substrate.

3. The method of claim 1, wherein the layer of copper oxide is electrodeposited.

4. The method of claim 3, wherein the layer of copper oxide is irradiated in selected areas.

5. The method of claim 4 further comprising dissolving non-irradiated areas of the copper oxide layer.

6. The method of claim 1, wherein noble metal is selected from Groups 8-11 of the Periodic Table.

7. The method of claim 1, wherein the article has structural features on the micron and/or nanometer scale.

8. The method of claim 1, wherein the layer of copper oxide is electrodeposited from solubilized copper salt.

9. The method of claim 8, wherein the solubilized copper salt is separate from the solution comprising the noble metal salt and the electrolyte component.

10. The method of claim 1, wherein the copper oxide layer is not consumed is the electrodeposition of the noble metal layer.

11. The method of claim 1 further comprising coupling the article to a secondary substrate.

12. The method of claim 11 further comprising releasing the article from the substrate via dissolution of the copper oxide layer.

13. The method of claim 2, wherein the layer of copper oxide is patterned according to digital design data of the article.

14. The method of claim 1, wherein the article is employed in heterogeneous catalysis.

15. The method of claim 1, wherein the article is a circuit or circuit component.

16. The method of claim 15, wherein the circuit is an integrated circuit.

17. The method of claim 1, wherein the article is an optical component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 illustrates a layer of Cu.sub.2O selectively deposited on a substrate via microscope-based photoelectrochemical lithography according to some embodiments.

[0009] FIG. 2(a) is a scanning energy dispersive X-ray spectroscopy micrograph showing the location of gold after electrodepositing gold onto a patterned Cu.sub.2O electrode according to some embodiments.

[0010] FIG. 2(b) is a scanning energy dispersive X-ray spectroscopy micrograph showing the location of copper after electrodepositing gold onto a patterned Cu.sub.2O electrode according to some embodiments.

[0011] FIG. 2(c) is a scanning energy dispersive X-ray spectroscopy micrograph showing the location of oxygen after electrodepositing gold onto an electrode patterned with Cu.sub.2O according to some embodiments.

[0012] FIG. 2(d) is a conventional secondary electron (SE)-contrast scanning electron microscopy image of the electrode of FIGS. 2(a)-(c).

DETAILED DESCRIPTION

[0013] Embodiments described herein can be understood more readily by reference to the following detailed description and examples and their previous and following descriptions. Elements, apparatus, and methods described herein, however, are not limited to the specific embodiments presented in the detailed description and examples. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations will be readily apparent to those of skill in the art without departing from the spirit and scope of the invention.

[0014] Referring now to specific steps of methods described herein, a layer of copper oxide, such as Cu.sub.2O, is selectively deposited on a substrate. Selective deposition of the copper oxide can be achieved by any desired method or technique. In some embodiments, for example, the layer of Cu.sub.2O is selectively deposited via electrodeposition. For example, the electrode can be masked in the desired pattern for selective electrodeposition of Cu.sub.2O. Alternatively, the initial layer of Cu.sub.2O is selectively deposited according to the methods described in PCT Patent Application Serial Number PCT/US2017/049187, which is incorporated herein by reference in its entirety. As described in this PCT application, a layer of Cu.sub.2O is electrodeposited. The Cu.sub.2O layer is irradiated or illuminated in selective areas or sections. Irradiation or illumination can be simultaneous with and/or subsequent to Cu.sub.2O electrodeposition. Irradiation in addition to electrodeposition is termed photoelectrochemical lithography (PECL) herein.

[0015] The non-irradiated or non-illuminated areas are subsequently dissolved or stripped to produce the selectively deposited Cu.sub.2O layer. The selectively deposited Cu.sub.2O layer can comprise copper metal inclusions or nanoparticles, in some embodiments. FIGS. 1(a) and 1(b) illustrate photoelectrochemical lithographic deposition of Cu.sub.2O, according to some embodiments. Photoelectrochemical lithography techniques can provide Cu.sub.2O layers having high spatial resolution, thereby facilitating formation of nanostructures and microstructures on the article. In some embodiments, one or more masking techniques can be employed in Cu.sub.2O deposition. Masking techniques can be employed to direct radiation to selected areas during Cu.sub.2O deposition and/or shield radiation to selected areas. Masking techniques, for example, can be used for positive and negative imaging of Cu.sub.2O deposition.

[0016] Selective deposition of the layer of copper oxide is not limited to electrodeposition via PECL. In some embodiments, the layer of copper oxide can be printed or stenciled on the substrate. Moreover, the copper oxide layer can be fabricated on a separate substrate and transferred to the build substrate for subsequent electrodeposition of the noble metal layer. In some embodiments, for example, the copper oxide layer can be fabricated by one or more lithographic techniques on a non-electrode substrate and transferred to an electrode substrate for electrodeposition of the noble metal layer. In some embodiments, the layer of copper oxide is patterned according to digital design data of the article being fabricated.

[0017] After completion of the copper oxide layer, a noble metal layer is electrodeposited on or over the copper oxide layer from a solution comprising a salt of the noble metal and an electrolyte component comprising sulfite, citrate, or mixtures thereof. Any noble metal ion consistent with the technical objectives and thermodynamics described herein can be employed. In some embodiments, the noble metal ion comprises a noble metal halide or noble metal sulfate. For example, the noble metal salt can comprise AuCl.sub.4, in some embodiments. Other noble metal salts can include those of platinum, palladium, silver, ruthenium and/or iridium.

[0018] As described herein the electrolyte component comprises ions of citrate (C.sub.6H.sub.5O.sub.7.sup.3), sulfite (SO.sub.3.sup.2), or mixtures thereof. Ions of citrate and/or sulfite can be provided as a salt with any suitable counterion consistent with the technical objectives herein. In some embodiments, only citrate or only sulfite is present in the electrodeposition solution. Alternatively, a mixture of citrate and sulfite is present in the noble metal electrodeposition solution. Any desired amount of citrate and/or sulfite can be employed in the electrodeposition solution. In some embodiments, citrate and/or sulfite are present in an amount of 0.1-0.2 mol L.sup.1. Additionally, citrate and sulfite can be present at any ratio consistent with the technical objectives described herein. In some embodiments, the ratio of citrate to sulfite in the electrolyte component ranges from 0.1 to 10. Further, citrate and/or sulfite can be present at any desired ratio relative to the noble metal in the electrodeposition solution. In some embodiments, the ratio of citrate and/or sulfite ratio to the noble metal is selected from Table I.

TABLE-US-00001 TABLE I Ratio of citrate and/or sulfite ratio to noble metal Chemical Species Ratio to Noble Metal C.sub.6H.sub.5O.sub.7.sup.3 5-20 SO.sub.3.sup.2 5-20
The electrodeposition solution containing the noble metal salt and electrolyte component can exhibit a basic pH. In some embodiments, the electrodeposition solution has a pH of 9-13. The basic pH facilitates retention of the copper oxide layer.

[0019] Electrodeposition of the noble metal layer can be administered for any desired duration. Electrodeposition of the noble metal layer does not consume the layer of copper oxide, such as Cu.sub.2O, thereby precluding the need for redeposition of the copper oxide layer during article fabrication. This is in contrast to prior techniques wherein deposition of the noble metal layer consumes the Cu.sub.2O layer via a galvanic replacement reaction. Considerations governing duration of the electrodeposition can include specific identity of the noble metal, noble metal deposition rate, desired thickness or dimensions of the noble metal layer, and desired spatial resolution of structural features of the article. Articles fabricated according to methods described herein can exhibit structural features on the micron and/or nanometer scale. In some embodiments, articles fabricated according to methods described herein can have structural features of 1-50 m, such as 10-20 m.

[0020] In some embodiments, the article is coupled to a secondary substrate. A secondary substrate can have any desired composition and/or functionality. A secondary substrate can be an electrically insulating material or polymeric material, in some embodiments. Once coupled to the secondary substrate, the article can be released from the build substrate via dissolution of the copper oxide layer.

[0021] Articles produced according to methods described herein can comprise circuits and/or circuit components, including integrated circuits and circuit interconnects. Articles can also include various optical components, textured surfaces, and low-friction tribological surfaces. Articles can also include microstructured and/or nanostructured catalytic surfaces and structures, including catalytic surfaces and structures for heterogeneous catalysis. In some embodiments, catalytic structures produced according methods described herein exhibit flow through architectures and/or high surfaces areas. In some embodiments, catalytic structures can have surfaces areas of 50 m.sup.2/g to 1,000 m.sup.2/g. For example, articles produced according to methods described herein can be electrodes or electrode surfaces for conducting catalysis, including heterogeneous catalysis.

[0022] These and other embodiments are further illustrated in the following non-limiting example.

Example 1Article Fabrication

[0023] The article provided in FIG. 1 was fabricated by the electrodeposition of Cu.sub.2O from an electrodeposition bath of lactate stabilized CuSO.sub.4. (See Lowe et al., J. Mater. Chem. A, 5, 21765-21772). The contrast was generated by the influence of patterned illumination with light of energy in excess of the band gap of Cu.sub.2O (E>2.0 eV). Here a 470 nm (blue) LED was used as the illumination source (E=2.6 eV). The patterned surface was formed by projecting light through a conventional, chrome-on-glass photolithography mask constituting the desired, transferrable pattern. The projected illumination was then miniaturized by a microscope objective, then displayed on the surface of the electrode where Cu.sub.2O was being electrodeposited.

[0024] The Cu.sub.2O layer fabrication for article shown in FIG. 2 followed similar protocol as FIG. 1, though through a different photolithography mask. After the Cu.sub.2O layer was formed, the electrode was used as the substrate for Au electrodeposition using the AuCl.sub.4/citrate/sulfite solution. The electrochemical details (electrode held at potentials sufficiently negative to reduce the AuCl.sub.4 to Au metal). The scanning electron micrographs (in FIG. 2) show that the Au preferentially deposited on the areas of the Cu.sub.2O where the illumination stimulated the local growth. It is noted that compositions and methods described herein are not limited to the present example. Any suitable photolithographic method can be used to selectively deposit Cu.sub.2O. Moreover, electrodeposition conditions of the noble metal may be set to the specific identity of the noble metal and pH of the electrodeposition solution.

[0025] Various embodiments of the invention have been described in fulfillment of the various objectives of the invention. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations thereof will be readily apparent to those skilled in the art without departing from the spirit and scope of the invention.