A new study from NYU Tandon–Brookhaven National Laboratory, which was published in Applied Physics Letters, demonstrates that crystalline hafnium oxide substrates can help stabilize the desired superconducting phase and guide material design. Silicides are promising for quantum technology, but achieving phase purity is still a major hurdle.
Silicides are silicon-metal alloys long used in microelectronics, which are now drawing renewed interest for potential use in quantum hardware. One of the main challenges, however, lies in phase purity: while some silicide phases exhibit superconductivity, others do not, making it difficult to consistently achieve the desired properties .
The research conducted by Brookhaven National Laboratory and NYU Tandon School of Engineering demonstrates how substrate selection affects phase development and interfacial stability in superconducting vanadium silicide films, offering design recommendations for enhancing material quality.
Under the direction of NYU Tandon professor Davood Shahrjerdi, the team concentrated on vanadium silicide, a material that, when cooled to its transition point of 10 Kelvin, or around –263 °C, becomes superconducting, meaning it is able to conduct electricity without resistance. Its relatively high superconducting transition temperature makes it especially appealing for quantum devices operating above traditional millikelvin ranges.
Researchers developed crystalline hafnium oxide substrates and compared them to standard silicon dioxide under the same processing conditions. Hafnium oxide provided increased chemical stability and inhibited undesirable secondary phases, although it deteriorated at higher processing temperatures.
Achieving phase-pure superconducting films requires careful attention to the substrate-film interface. Our findings show that substrate design is an integral aspect of the synthesis process.
Davood Shahrjerdi, Professor, NYU Tandon School of Engineering
Hafnium oxide’s chemical stability turned out to be essential for preserving film quality during processing. Most intriguingly, atomic-resolution imaging revealed potential templating effects, suggesting that the crystalline structure of hafnium oxide could influence both the orientation and phase selection of the silicide grains that form on top. This points to a possible pathway for selectively controlling phase nucleation.
The study offers fundamental insight that applies to various superconducting silicide systems in addition to vanadium silicides. The three recognized principles (structural ordering, thermal stability, and chemical inertness) provide design guidance for substrates used in next-generation quantum devices.
“These findings complement our recent work on physical patterning techniques. Together, they expand the design space for quantum hardware,” noted Shahrjerdi.
The authors of the study include Shahrjerdi, Miguel Manzo-Perez, Moeid Jamalzadeh, and Iliya Shiravand (Ph.D. students at NYU Tandon), as well as Sooyeon Hwang, Kim Kisslinger, and Dmytro Nykypanchuk from the Brookhaven National Laboratory's Center for Functional Nanomaterials.
The study was carried out in part at the NYU Nanofabrication Cleanroom (NYU Nanofab), with characterization assistance from Brookhaven National Laboratory.
Journal Reference:
Manzo-Perez, M. et.al. (2025) Substrate effects on phase formation and interfacial stability in superconducting vanadium silicide thin films. Applied Physics Letters. doi.org/10.1063/5.0291576.