Schematic structure of diamond:H surface undergoing different ALD processes and their resulting interface electronic properties with diamond:H/MoO3 versus diamond:H/HyMoO3−x transistors. (A) Application of a typical MoO3 ALD process on diamond:H, resulting in surface termination degradation. (B and C) Modified ALD process of MoO3 and HyMoO3−x for preserving diamond:H termination. Right side from top to bottom: Schematic cross-sectional diagram with interface atomistic representations of diamond:H/MoO3 (top) and diamond:H/HyMoO3−x (bottom) FETs and their respective electronic band energy structures with different oxidation state ratios. CB, conduction band; VB, valence band. Credit: Science Advances (2018). DOI: 10.1126/sciadv.aau0480
Replacing the classic transistor metals with diamond could help bring in the next wave of engines for cars and spacecrafts.
A team of researchers from the Australian National University has developed a new type of diamond-based ultra-thin transistor that could be more durable and outperform the parts used in high-radiation environments like rocket or car engines.
“Diamond is the perfect material to use in transistors that need to withstand cosmic ray bombardment in space or extreme heat within a car engine, in terms of performance and durability,” Zongyou Yin, PhD, from the ANU Research School of Chemistry, said in a statement.
According to Yin, applications like car engines and spacecrafts currently use Silicon Carbide (SiC) and Gallium Nitride (GaN) for transistors. These compounds are often limited by their performance in extremely high-power and hot environments.
“Diamond, by contrast to Silicon Carbide and Gallium Nitride, is a far superior material to use in transistors for these kinds of purposes,” Yin said. “Using diamond for these high-energy applications in spacecraft and car engines will be an exciting advancement in the science of these technologies.”
The researchers modified the surfaces of special forms of tiny, flat diamonds, which enabled them to grow ultra-thin materials on top to make the transistors. The new materials consists of a deposit of hydrogen atoms with layers of hydrogenated molybdenum oxide.
According to the study, diamond-based 2D electronics are entering a new era by using transition-metal oxides (TMO) as surface acceptors rather than previously used molecular-like unstable acceptors.
“The growing demands for electronic devices with higher performance in power, frequency, energy efficiency, and a lower form factor are driving the need to find alternative functionalization of novel semiconductors with more desirable intrinsic properties,” the authors write. “In some of the newly discovered semiconductors, more efficient and simplified doping methods such as charge-transfer doping are becoming prevalent.
“We develop a novel approach for synthesizing a smooth, uniform, and ultrastable TMO surface acceptor thin layer with tunable electronic properties, allowing a superior 2D electrostatic match at the diamond.”
The diamond transistor is currently in the proof-of-concept stage.
“We anticipate that we could have diamond transistor technology ready for large-scale fabrication within three to five years, which would set the base for further commercial market development,” he said.
The study was published in Science Advances.
