Diamond bonding technology could improve both quantum and conventional electronics

Schematic diagram of plasma-activated bonding of diamond films. Credit: Nature Communications (2024). DOI: 10.1038/s41467-024-53150-3
Synthetic diamond is durable, inert, stiff, thermally conductive, and has good chemical properties, making it an excellent material for both quantum and conventional electronics. But there’s one problem. Diamonds only like diamonds.
It is homoepitaxial, meaning it grows only on top of other diamonds, and incorporating diamonds into quantum or conventional computers, quantum sensors, mobile phones, or other devices will maximize diamonds’ potential. This means sacrificing or using large and expensive chunks of precious materials.
“Diamond stands alone in terms of its material properties, both in the field of electronics with its wide bandgap, very good thermal conductivity and exceptional dielectric strength, and in the field of quantum technology. It hosts a nitrogen vacancy center, which is the gold standard for sensing, at room temperature,” said Associate Professor at the University of Chicago Pritzker School of Molecular Engineering (PME). Professor Alex High. “But as a platform, it’s actually pretty terrible.”
A paper recently published in Nature Communications from the University of Chicago PME’s Institute for Advanced Study and Argonne National Laboratory explores how diamonds can be bonded directly to materials that can be easily integrated with quantum or conventional electronics. We have solved a major hurdle faced by researchers working with
“We have a surface treatment that makes the diamond and the carrier substrate very attractive to each other, and by ensuring a nice surface roughness, the two very flat surfaces bond together.” said lead author Xinghan Guo. from Chicago PME in the spring.
“The annealing process strengthens the bond and makes it very strong, which is why our diamonds can withstand a variety of nanofabrication processes. This allows our process to simply attach diamonds on top of another material. It is different from placing it in
Using this technique, the researchers directly bonded diamond to materials such as silicon, fused silica, sapphire, thermal oxides, and lithium niobate, without the use of intermediate materials that act as “glues.”
Instead of bulk diamond, typically hundreds of microns thick, used to study quantum qubits, the researchers bonded crystalline films as thin as 100 nanometers while maintaining spin coherence suitable for advanced quantum applications. did.
complete defect
Unlike jewelers, quantum researchers prefer slightly imperfect diamonds. By precisely manipulating defects in the crystal lattice, researchers create durable qubits that are ideal for quantum computing, quantum sensing, and other applications.
“Diamond is a wide bandgap material and is inert. In fact, it behaves very well and has excellent thermal and electronic properties,” said co-author of the paper, University of Chicago PME and Argonne said F. Joseph Heermans, who also holds a post at the university. “Its raw physical properties tick many boxes that make it useful for a variety of fields. Until now, it has been very difficult to integrate it with different materials.”


A new paper from the Institute for Advanced Study at the University of Chicago PME and Argonne National Laboratory shows a new way to bond diamond directly into materials that can be easily integrated with quantum or conventional electronics. Here, a transmission electron microscopy image shows a nanoscale 10 nm thick diamond film (right side) bonded to sapphire (left side). Credit: Guo et al.
However, until now it has been difficult to incorporate thin diamond films directly into devices, requiring larger but finer blocks of material. Co-author Avery Linder, a fourth-year student at the Chicago School of Engineering, likened building sensitive quantum devices from these diamonds to trying to make a grilled cheese sandwich from an entire block of cheddar.
University of Chicago PME Assistant Professor Peter Maurer, co-author of this paper, is a researcher in quantum biotechnology, which uses innovative quantum techniques to more precisely measure the workings of fundamental biological processes at the micro- and nanoscale. We are working on sensing.
“We have overcome many challenges associated with connecting diamond-based quantum sensors with intact biological targets, but we have also successfully overcome many of the challenges associated with connecting diamond-based quantum sensors with intact biological targets, but we have also demonstrated the ability to connect diamond-based quantum sensors to commercially available microscopes and diagnostic devices without losing readout efficiency. Their integration into measurement equipment remains an open challenge,” Maurer said.
“This new work led by Alex’s lab on bonding diamond films avoids many of these problems and brings us an important step closer to applications.”
sticky diamond
In diamond, each carbon atom shares electrons with four other carbon atoms. These electron-sharing bonds, called covalent bonds, create the hard and durable internal structure of the gemstone.
But when there are no other carbon atoms nearby to share electrons with, so-called “dangling bonds” form on isolated atoms looking for a partner. By creating diamond surfaces filled with these dangling bonds, the team was able to bond nanometer-scale diamond wafers directly to other surfaces.
“You can think of it like a sticky surface, because it wants to stick to something else,” Linder says. “Basically what we’ve done is create sticky surfaces and put them together.”
The researchers have patented the process and are commercializing it through the University of Chicago’s Polsky Center for Entrepreneurship and Innovation.
“This new technology could have a major impact on quantum and even how phones and computers are manufactured,” Linder said.
High inherited the new diamond technology from the long-standing complementary metal-oxide-semiconductor (CMOS) technology, from the large discrete transistors in laboratories in the 1940s to the powerful, tiny integrated circuits found in today’s computers and phones. compared to the progress of
“We hope that the ability to produce these thin films and integrate them in a scalable way will lead to something like a CMOS-style revolution in diamond-based quantum technologies,” he said.
Further information: Xinghan Guo et al. Directly bonded diamond films for heterogeneous quantum and electronic technologies, Nature Communications (2024). DOI: 10.1038/s41467-024-53150-3
Provided by University of Chicago
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