Researchers demonstrates substrate design principles for scalable superconducting quantum materials

(Press-News.org) Silicides — alloys of silicon and metals long used in microelectronics — are now being explored again for quantum hardware. But their use faces a critical challenge: achieving phase purity, since some silicide phases are superconducting while others are not.

The study, published in Applied Physics Letters by NYU Tandon School of Engineering and Brookhaven National Laboratory, shows how substrate choice influences phase formation and interfacial stability in superconducting vanadium silicide films, providing design guidelines for improving material quality.

The team, led by NYU Tandon professor Davood Shahrjerdi, focused on vanadium silicide, a material that becomes superconducting (able to conduct electricity without resistance) when cooled below its transition temperature of 10 Kelvin, or about -263°C. Its relatively high superconducting transition temperature makes it attractive for quantum devices that operate above conventional millikelvin temperatures.

Researchers engineered crystalline hafnium oxide substrates and compared them with standard silicon dioxide under identical processing conditions. Hafnium oxide offered greater chemical stability and suppressed unwanted secondary phases, though it degraded under the highest processing temperatures.

"Achieving phase-pure superconducting films requires careful attention to the substrate-film interface," said Shahrjerdi. "Our findings show that substrate design is an integral aspect of the synthesis process.”

The chemical stability of hafnium oxide proved crucial for maintaining film quality during processing. Most intriguingly, atomic-resolution imaging suggested that the crystalline structure of hafnium oxide may influence the orientation and phase selection of overlying silicide grains, pointing to possible templating effects that could enable selective phase nucleation.

The research provides fundamental insights that extend beyond vanadium silicides to other superconducting silicide systems. The principles identified — chemical inertness, thermal stability, and structural ordering — offer design guidelines for next-generation quantum device substrates.

"These findings complement our recent work on physical patterning techniques," noted Shahrjerdi. "Together, they expand the design space for quantum hardware."

In addition to Shahrjerdi, the paper’s authors are Miguel Manzo-Perez, Moeid Jamalzadeh, and Iliya Shiravand (Ph.D. students at NYU Tandon); and Sooyeon Hwang, Kim Kisslinger, and Dmytro Nykypanchuk from the Center for Functional Nanomaterials at Brookhaven National Laboratory. The work was conducted in part at the NYU Nanofabrication Cleanroom (NYU Nanofab) with characterization support from Brookhaven National Laboratory.

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