Researchers at Cornell University have developed a new sputtering process using krypton gas that deposits high-quality superconducting tantalum films on silicon wafers at a relatively low temperature of 200 degrees Celsius. This breakthrough could simplify the integration of tantalum into commercial quantum computing chips, according to a study published in Nature Materials.
Tantalum is a promising superconductor for quantum processors due to its long coherence times, but its high melting point (over 3,000°C) has made it difficult to deposit without damaging sensitive substrates. The Cornell team, led by Professor Gregory Fuchs, found that using krypton ions instead of the more common argon allows tantalum to form a crystalline, superconducting phase at much lower temperatures.
In tests, the krypton-sputtered tantalum films exhibited critical temperatures around 4.4 Kelvin, comparable to films made with conventional high-temperature methods. The process also reduced surface oxidation, a common source of qubit decoherence, improving the material's performance in prototype quantum devices.
This advance addresses a key manufacturing bottleneck, potentially enabling the production of larger, more reliable superconducting quantum chips. The researchers emphasize that further work is needed to scale the process and integrate it with existing semiconductor fabrication lines.
