Low-Temperature Plasmas for Materials Discovery—InGaN Nanoparticles with Tunable Properties

Nanomaterials continue to offer exciting opportunities to explore materials properties that could enable a vision of sustainable energy production, personalized health care, and new technologies for enhancing the success and well-being of global populations. Further, as devices and applications enabled by nanomaterials mature, there is a need to use scalable and efficient manufacturing strategies for production, which is where plasma reactors enter the picture. Research teams across the world have demonstrated the vast range of nanomaterials that are accessible using plasmas, including some nanoparticles that are difficult or impossible to synthesize using colloidal approaches, and with precision in size, surface properties, and functionality that are prohibited by other vapor-phase methods. One emerging area is in the tunable synthesis of alloyed nanoparticles, which can exhibit complex process-property-function relationships. Here, we present on alloys of indium and gallium nitride nanoparticles made using a flow-through nonthermal plasma reactor.<br/>GaN is a wide-bandgap semiconductor, making it important as a UV source for lighting and communications, and for power transistor applications, as well as potential use as a photocatalyst and in other energy technologies. By contrast, indium nitride (InN) has a bandgap in the infrared, and is an effective optical absorber and can be used in solar photovoltaics and high-speed electronics. Alloyed indium gallium nitride (InGaN) has a tunable bandgap between these extremes, spanning the visible spectrum based on composition. This bandgap tunability has been used in light emission technologies for epitaxially grown layers and fabricated quantum well structures. Previously we have reported on gallium nitride (GaN) nanoparticle synthesis using plasmas, demonstrating size control via adjusting the residence time of the nanoparticles in the plasma. More recently we have synthesized InN nanoparticles in a similar reaction pathway, and we present our results exploring InGaN nanoparticle synthesis including demonstrating bandgap tunability. However, the competing influences of quantum confinement-based bandgap widening, composition-based bandgap adjustment, and internal strain and surface effects introduce a large degree of uncertainty in predicting the bandgap of these materials. This brings about an important opportunity to use the versatility of plasma reactors to uncover the physical, chemical, and mechanical contributions to property and function for InGaN nanoparticles, towards predictable nanomanufacturing. In this presentation, we share our findings on controlling composition, size, and surface of plasma-produced InGaN nanoparticles using a nonthermal plasma reactor, with perspectives on the potential for materials discovery using plasmas.