CAREER: Nanostructure Growth from the Vapor Phase

Rensselaer Polytechnic Institute, Troy NY

Investigators

Abstract

NON-TECHNICAL DESCRIPTION: The focus of this integrated research and education effort is to develop an understanding of how atoms from the vapor phase condense on surfaces and assemble into nanostructures. In particular, the project studies the effect of the impingement angle of the condensing atoms with respect to where the atoms will ultimately be incorporated into the growing nanostructures, and also uses energetic ions to control the movement of the condensed atoms on the nanostructure surfaces. This research provides the basic scientific understanding required to build refractory nanopipes and nanorods, which have a wide range of potential applications including high-throughput gas purification for the hydrogen economy, coatings for high-temperature bearings in fuel-efficient jet-engines and gas-turbines, and corrosion resistant nanoscale catalyst support structures for fuel cells. The research effort is complemented by an integrated education and outreach effort which includes university-level course and research development as well as the design and construction of a "Materials Machine" in a local Science Museum, so that 5-to-12-year old children learn about atomic aspects of materials and nanostructure synthesis by experimenting with ping-pong ball size "atoms". TECHNICAL DETAILS: This research builds on two distinct techniques for micro/nanostructure-control during layer deposition: (a) glancing angle deposition is based on local atomic shadowing effects to create uniquely shaped nanostructures and (b) low-energy ion-assisted growth tailors microstructures through controlled surface diffusion. The key novelty of the proposed project is to combine these two approaches and apply them to the growth of nitride layers in order to build nanostructures with unique new electro-mechanical, catalytic, and tribological functionalities. The specific goals are to (i) quantify anisotropic surface diffusion rates and atomic shadowing effects by studying surface island nucleation and growth kinetics on CrN and TiN (001) and (111) surfaces as a function of N2 partial pressure, ion-irradiation flux, lateral mound spacing, and deposition angle, and (ii) grow arrays of nanopipes and nanorods with variable concentration, spacing, and width, and develop a quantitative model for their formation mechanism.