Sputtering is the vacuum deposition workhorse in which ion bombardment knocks atoms off a solid target onto a substrate, and the 2026 literature shows it moving from a commodity coating step into epitaxy-grade territory for superconductors, GaN power devices and photovoltaic contact stacks.
Summary
The parameters that decide outcomes are few but unforgiving. Reactive gas partial pressure sets the phase: in Cu-O films, increasing oxygen partial pressure drives Cu2O to Cu2O/Cu4O3 to CuO, and boron doping widens the window in which the useful mixed-valence phases survive. Buffer layers set the crystallography: delta-NbN grows epitaxially on TiN-buffered sapphire at room temperature with picometre-scale surface roughness, described as the lowest reported, and vanadium films on an Nb buffer show more uniform lattice orientation and smaller grains than V grown directly on silicon. Target quality and availability set the material palette: dense Ca(OH)2 targets, otherwise hard to make because heating dehydrates the material, have been produced at up to 98 per cent theoretical density by cold sintering at 100 to 300 degrees C and 400 MPa, and scaled to 2-inch diameter for CaO film deposition. Geometry matters too, because deposition is line-of-sight: on microwire scaffolds inclined at 0, 30 and 45 degrees, CoFe/IrMn film thickness falls systematically with inclination, and the exchange bias field tracks it.
Evidence base
- 4 May 2026: a sputtering-based in-situ silicide template only 0.5 nm thick, demonstrated across 25 metallic species, produced GaN epitaxial films on Si(111) with low vertical resistance and ohmic behaviour, and served as a platform for MOCVD overgrowth.
- 18 June 2026: room-temperature sputtering produced single-crystalline delta-NbN on TiN-buffered c-sapphire with picometre-scale surface roughness, reported as the lowest to date.
- 5 May 2026: Ti/Cu multilayers sputtered with periods from 4 to 52.5 nm lost periodic contrast at 4 nm due to Cu-Ti intermixing, and only became regular at larger periods.
- 2 June 2026: cold sintering at 100 to 300 degrees C and 400 MPa produced Ca(OH)2 sputtering targets at up to 98 per cent theoretical density, scaled to 2-inch diameter, without thermal dehydration.
- 30 June 2026: comparing Au/Co/Au stacks, MBE growth gave sharper interfaces and a narrower Au(111) rocking-curve width than magnetron sputtering.
- 1 July 2026: a CuInSe2 bottom cell at 1.0 eV reached 16 per cent efficiency with VOC above 550 mV, and no systematic influence of oxygen flow during sputtering of the GaOx-adjacent oxide layer was found.
Open questions
- Can sputtered multilayers be made periodic below a 4 nm period, or is interfacial intermixing a hard floor that pushes short-period applications to MBE?
- Do sputtered V or NbN resonators reach internal quality factors competitive with established Nb and Ta processes, and is the loss surface-dominated in a way that deposition changes can fix?
- Does the cold-sintering route to sputtering targets scale beyond 2-inch diameter and generalise beyond calcium hydroxide to other thermally unstable target chemistries?
- Does the interface-sharpness deficit of sputtering versus MBE actually degrade device performance in interface-sensitive applications such as CISS spin valves, or is it only visible in structural characterisation?
Assessment drafted 2026-08-31 from up to 18 KB sources using the technology-scorecard framework; scores are a draft read pending review.