Diamond: High-power transistors; direct bonding; speedy wafer fabrication.
Researchers from the University of Glasgow, RMIT University, and Princeton University created a new diamond transistor for high-power electronics that remains switched off by default. The performance of the diamond was improved by coating it in hydrogen atoms followed by layers of aluminum oxide.
“The challenge for power electronics is that the design of the switch needs to be capable of staying firmly switched off when it’s not in use to ensure it meets safety standards, but it must also deliver very high power when turned on,” said David Moran, a professor at the University of Glasgow’s School of Engineering, in a statement. “Previous state-of the-art diamond transistors have generally been good at one at the expense of the other – switches which were good at staying off but not so good at providing current on demand, or vice-versa. What we’ve been able to do is engineer a diamond transistor which is good at both, which is a significant development.”
The diamond transistor requires six volts to switch on, which the team says is more than twice the voltage compared to previous diamond transistors, while still delivering high current when activated. When off, its resistance was high enough that there was nearly zero current leakage, measuring below the noise floor of the lab equipment. Key applications include power grids and electric vehicles. [1]
Researchers from the University of Chicago and Argonne National Laboratory developed a method for bonding diamonds directly to materials that integrate easily with either quantum or conventional electronics.
“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,” said Xinghan Guo, a PhD graduate of UChicago, in a statement. “An annealing process enhances the bond and makes it really strong. That’s why our diamond can survive various nanofabrication processes. It differentiates our process from simple placement of diamond on top of another material.”
The team used the technique to directly bond crystalline diamond membranes as thin as 100nm with materials including silicon, fused silica, sapphire, thermal oxide, and lithium niobate without an intermediary substance.
“We’re hoping that our ability to generate these thin films and integrate them in a scalable fashion can lead to something like CMOS-style revolution for diamond-based quantum technologies,” said Alex High, assistant professor at the UChicago Pritzker School of Molecular Engineering, in a statement. [2]
Researchers from the University of Hong Kong, Southern University of Science and Technology, Peking University, Hong Kong Polytechnic University, Harbin Institute of Technology, and University of Stuttgart developed a method to mass produce ultrathin and ultra-flexible high-figure-of-merit diamond membranes that are compatible with existing semiconductor manufacturing technologies.
The team’s single-step edge-exposed exfoliation process can manufacture a freestanding two-inch wafer within 10 seconds. The process produces membranes with sub-micron thickness, sub-nano surface roughness, and 360° bendable flexibility. The researchers used the membrane to make flexible diamond strain sensors that withstood 10,000 cycles at 2% strain. Beyond sensors, they believe the wafers could be fabricated into a variety of electronic, photonic, mechanical, acoustic, and quantum devices. [3]
[1] C. Qu, I. Maini, Q. Guo, A. Stacey, D. A. J. Moran, Extreme Enhancement-Mode Operation Accumulation Channel Hydrogen-Terminated Diamond FETs with Vth < −6 V and High on-Current. Adv. Electron. Mater. 2024, 2400770. https://doi.org/10.1002/aelm.202400770
[2] Guo, X., Xie, M., Addhya, A. et al. Direct-bonded diamond membranes for heterogeneous quantum and electronic technologies. Nat Commun 15, 8788 (2024). https://doi.org/10.1038/s41467-024-53150-3
[3] Jing, J., Sun, F., Wang, Z. et al. Scalable production of ultraflat and ultraflexible diamond membrane. Nature 636, 627–634 (2024). https://doi.org/10.1038/s41586-024-08218-x
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