Collaborative Research: GOALI: Nanocrystal Formation and Morphology in Nonthermal Plasmas

Award Abstract

CTS-0500332

Principal Investigator: Uwe R. Kortshagen

Institution: University of Minnesota - Twin Cities

Proposal Title: Collaborative Research: GOALI: Nanocrystal Formation and Morphology in Nonthermal Plasmas

Crystalline nanoparticles are intensely studied as building blocks for a wide variety of novel nanoscale systems and devices. Among nanoparticle materials silicon plays an important role due to its excellent electronic properties, its wide use in microelectronics manufacturing, its low toxicity, and the absence of environmental hazards. Low-pressure plasmas-partly ionized gases created at only a fraction of the atmospheric pressure-offer several unique properties that are highly beneficial for the synthesis of crystalline silicon nanoparticles. Plasmas allow for high processing rates based on the efficiency of direct gas-to-particle conversion. Compared to other gas phase processes, plasmas offer the advantage that particles are unipolarly negatively charged, which strongly suppresses or completely avoids detrimental agglomeration of nanoparticles.

This Collaborative Research/GOALI project focuses on the study of a plasma process that was shown to yield high-quality silicon nanoparticles with highly unique virtually perfect cubic shapes. Particles are highly uniform in size and exhibit virtually no detectable crystal defects. Nanocrystals of this kind appear to be ideal building blocks for nanoscale devices such as novel vertical Schottky barrier transistors or light emitting devices. While the research will focus on a particular plasma process, the studies will help to answer much broader unresolved questions. Among those are how crystalline particles can be formed in a plasma environment that is close to room temperature, and why silicon particles would assume the highly unusual cubic shape, which is ideal for device applications but is not the equilibrium shape for pure silicon particles.

The technical studies aim at finding the currently unknown relations between plasma proper-ties and the properties of the synthesized particles. The project pursues four goals: (1) the ex-perimental characterization of the plasma properties in the synthesis process; (2) the experimen-tal study of particle properties including their size distribution, particle crystallinity, and mor-phology; (3) the numerical study of the plasma properties and plasma dynamics caused by the presence of particles; and (4) the atomic simulation study of the relation between the process plasma conditions and the particle crystallinity and morphology. Tasks (1)-(3) will be pursued by the group at the University of Minnesota, task (4) by the group at the University of Maryland. The GOALI industrial partner is InnovaLight, Inc., based in St. Paul, MN, a company that pur-sues the development of solid state light sources based on silicon nanocrystals.

The leverage provided by an NSF-IGERT project for 'Nanoparticle Science and Engineer-ing' will enhance the broader impact of this project. The involvement of at least three graduate students and minority undergraduate students will foster the integration of research and training and the involvement of underrepresented groups. The close collaboration with InnovaLight will ensure rapid knowledge transfer to industry. This will enable and accelerate the development of potential commercial applications such as more energy-efficient light sources as well as elec-tronic devices and biomedical diagnostics. This project is co-funded by NSF and the U.S. De-partment of Energy under the NSF/DOE Partnership for Basic Plasma Science and Engineering.