Nanotwinned silver alloy film with controlled architecture
View Patent ↗A technique for forming a material including nanotwinned silver crystals in solid solution with a solute that exhibits enhanced strength and desirable electrical conductivity, as compared to coarse-grained material. Synthesis of nanotwinned silver alloy material is achieved by cooling of a substrate and co-deposition of silver and the solute. Controlling the processing conditions of synthesis allows for tailoring of the nanostructure and mechanical properties of the nanotwinned silver alloy material. A material including nanotwinned silver crystals in solid solution with a solute also is described.
1. A method comprising:
cooling a substrate; and
co-depositing silver (Ag) and a solute on the cooled substrate using sputtering at a rate of deposition greater than about 1.5 nm/s to form a material comprising a plurality of Ag crystals in solid solution with the solute,
wherein a twinned boundary between at least two Ag crystals has a spacing of between about 3 and about 70 nanometers (nm), and
wherein the solute is at least about 0.3 atomic percent (at. %) of the material, and less than about 10 at. % of the material.
2. The method of claim 1 , wherein cooling the substrate comprises exposing the substrate to liquid nitrogen for at least about 30 minutes.
3. The method of claim 1 , wherein the Ag and the solute are magnetron sputtered on to the substrate for about 2 hours.
4. The method of claim 3 , wherein Ag and the solute are magnetron sputtered with a plurality of cathodes of a magnetron sputtering apparatus in a confocal geometry.
5. The method of claim 1 , wherein a first rate of deposition of Ag and a second rate of deposition of the solute each decreases when measured in a radial direction from the center of the substrate.
6. The method of claim 1 , wherein a rate of formation of the material on the substrate varies depending on the radial distance from the center of the substrate.
7. The method of claim 1 , wherein the material comprises at least a face-centered cubic (fcc) Ag phase and a non-fcc Ag phase.
8. The method of claim 7 , wherein the volume fraction of the non-fcc Ag phase in the material varies depending on the radial distance from the center of the substrate.
9. The method of claim 7 , wherein the non-fcc Ag phase comprises a 4-hexagonal Ag phase.
10. The method of claim 1 , further comprising rotating the substrate while co-depositing Ag and the solute on the substrate.
11. The method of claim 1 , wherein the substrate is selected from the group consisting of silicon, amorphous carbon, steel, tantalum, copper, ceramic, glass, and polymers.
12. The method of claim 1 , wherein the solute comprises at least one of copper, iron, palladium, gold, or aluminum.