New method to bond diamonds to other materials could enable advanced quantum devices

Researchers at the University of Chicago and Argonne National Laboratory have made a significant stride in materials science.

They have developed a new technique that allows them to directly bond diamonds to a variety of materials. This includes common substrates like silicon and sapphire.

This breakthrough addresses a major challenge in integrating diamond into both quantum and conventional electronics. This opens up exciting possibilities for improved device performance and new applications in quantum technologies.

Diamond is highly valued in electronics and quantum technology due to its durability, thermal conductivity, and chemical stability.

“Diamond stands alone in terms of its material properties, both for electronics—with its wide band gap, very best thermal conductivity, and exceptional dielectric strength—and for quantum technologies—it hosts nitrogen vacancy centers that are the gold standard for quantum sensing at room temperature,” explained Asst. Prof. Alex High from UChicago Pritzker School of Molecular Engineering (PME).

Overcoming the challenges

For quantum technologies, diamond hosts nitrogen vacancy centers. These are defects in the diamond lattice that can be used for quantum sensing at room temperature. However, there are some challenges with diamonds when it comes to using them for quantum devices.

“It’s homoepitaxial, meaning it only grows on other diamonds , and integrating diamond into quantum or conventional computers, quantum sensors, cellphones, or other devices would mean sacrificing the diamond’s full potential or using large, expensive chunks of the precious material,” said the researchers in a press release.

The research team’s method directly bonds diamonds to various materials without any intermediary layers. This technique involves a two-step process.

First, they treat the surfaces of both the diamond and the substrate material to make them attractive to each other. This treatment creates “dangling bonds” on the diamond surface, essentially making it “sticky.”

Second, they carefully bring the two surfaces together, ensuring they are perfectly flat. An annealing process then strengthens the bond, making it robust enough to withstand the rigors of nanofabrication processes.

Enabling ultra-thin diamond membranes

This breakthrough allows for the integration of ultra-thin diamond membranes, as thin as 100 nanometers, with other materials.

“Instead of the several-hundred microns thick bulk diamonds typically used to study quantum qubits, the team bonded crystalline membranes as thin as 100 nanometers while still maintaining a spin coherence suitable for advanced quantum applications,” added the press release.

This is a significant improvement over previous methods that required larger, microscopic chunks of diamond.

“We make a surface treatment to the diamond and carrier substrates that makes them very attractive to each other. And by ensuring we have a pristine surface roughness, the two very flat surfaces will be bonded together,” stated Xinghan Guo, the first author of the study.

“An annealing process enhances the bond and makes it really strong. That’s why our diamond can survive various nanofabrication processes.”

Far-reaching implications

The implications of this research are far-reaching. It has the potential to revolutionize quantum computing, quantum sensing, and even conventional electronics like cell phones and computers.

For example, in quantum sensing, this technology could enable the development of highly sensitive biosensors that can detect minute changes in biological systems.

“This new technique has the potential to greatly influence the ways we do quantum and even phone or computer manufacturing,” concluded Avery Linder, paper co-author.