Researchers at The University of Texas at Dallas have developed a technique that could remove one of the challenges to scaling the production of silicon quantum devices. The researchers outlined their method, which provides greater control and precision during the fabrication process, in a study published online May 28 and in the July print edition of the Journal of Vacuum Science & Technology B. Silicon is the preferred material for the base of quantum devices because of its compatibility with conventional semiconductor technology.

The problem with conventional HDL is that it can be easy for the operator to pluck the wrong atom of hydrogen resulting in creation of qubits at unwanted locations. Using the STM for HDL requires a higher voltage than for imaging, which too often causes the tip to crash into the surface sample, forcing the operator to start over.

The researchers were working on their solution to the STM tip-crash problem when they discovered a more precise method for manipulating the surface atoms.

“Conventional lithography cannot achieve the requisite atomic precision,” Moheimani said. “The issue is that we are using a microscope to do lithography; we’re using a device to do something it’s not designed for.”

The researchers found that they could achieve higher precision by performing HDL in imaging mode, rather than the conventional lithography mode, with some adjustments to the voltage and a change to the STM’s feedback control system.

“We realized that we could actually use this method to remove hydrogen atoms in a controlled fashion,” Moheimani said. “This came as a surprise. It’s one of those things that happens during experiments, and you try to explain it and take advantage of it.”

https://www.utdallas.edu/news/science-technology/hydrogen-splitting-2020/