NSF Award
2333452
While diamonds are prized as gemstones, few realize the immense technological potential that diamond offers for optoelectronic devices. Diamond is a wide-bandgap semiconductor with extraordinarily high thermal conductivity, making it a material of choice for a range of applications including quantum computing, implantable biomedical devices, and high-voltage electronics – applications beyond the traditional cutting bit uses of industrial diamonds. When diamond is made in nanoparticle form, its capabilities increase because of size-induced changes to properties and the ease of incorporating nanoparticles into thin film applications. The challenge is that synthesizing diamond nanoparticles with high quality and in a scalable manner is difficult, and there are many scientific knowledge gaps on how diamond nanoparticles are created. Carbon-carbon bonds can form either graphite or diamond, and control over which bond is generated in reactive processes remains an open problem. This research plan intends to expand on exciting early results indicating that diamond nanoparticles can be formed in low-temperature plasma (LTP) reactors, in an approach that promises new understanding of how diamond can be generated with high quality and high yield. The expected results of this research are the discovery of new reaction pathways to control diamond growth in flow-through LTPs with the capability to select bond formation during the reaction. If successful, this work will enable the creation of diamond nanoparticles for a variety of critical applications, as well as generate new knowledge around bond formation in LTPs for other semiconductor nanomaterials. The proposed research will also be used in conjunction with outreach events to encourage participation of underrepresented groups in engineering.<br/><br/>Low-temperature plasma (LTP) synthesis of nanoparticles has gained growing attention for the ability of these reactors to produce high-quality and tunable-property nanoparticles in a scalable manner. The fundamental challenge in LTP synthesis of nanoparticles is a gap in knowledge about how reactor parameters directly influence nanoparticle growth. This challenge is amplified in the context of the carbon system, which features both sp2 and sp3 hybridization that result in dramatically different carbon-based materials – namely, graphene/graphite and diamond. In this work, based on promising preliminary results, selective bond hybridization in radiofrequency and microwave LTP reactors via control over plasma and reactor parameters will be investigated for synthesis of diamond nanoparticles. Focusing on synthesis of nanoparticles allows for added functional tunability because of size-dependent properties. LTP reactors are unique in that they offer control over a variety of nanocrystal properties, including size, surface functionality, and doping together with controlled deposition using inertial impaction, diffusion, or even direct-write deposition into patterns. This research will produce a map between reactor operating parameters and resulting nanoparticle properties, including discovering the conditions that are required for selected bond hybridization during the reaction. The proposed work will build a fundamental picture of how nanocrystal nucleation and growth occur, filling a critical gap in understanding about the exact energetic and growth condition requirements for diamond synthesis, as compared to graphite synthesis, in LTP reactors.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
