MTL Annual Report

The vapor-liquid-solid mechanism for growth of single-crystal whiskers and wires was originally discovered in the 1960s, but it has gained new interest in the last decade as a way to fabricate high-performance nanoscale electronic devices below the limits of photolithography.  Although a great deal of attention has been focused on the electronic properties of Si and III-V nanowires, many of the physical mechanisms involved in growing these single-crystal wires remain unclear.

We have investigated the importance of catalyst size and shape in controlling growth morphology by using evaporated island catalysts, catalysts derived from dewetted thin films, and commercially available nanoparticles.  By optimizing catalyst processing conditions and combining them with specific topographies or templates, such as inverted pyramid arrays or silicon dioxide gratings, we can achieve precise control over catalyst placement and subsequent nanowire placement. This study also examines the role of growth conditions by controlling temperature, partial pressures of reactants, and pre-growth annealing.  These parameters have been determined to be critical not only to stable and repeatable growth of Si and III-V nanowires, but also to controlling the relative orientation and defect generation at the substrate-wire interface ^[1]. Recent results have included the discovery of a two-step kinetic growth model for silicon nanowire growth ^[2]and the demonstration of InP/GaP axial nanowire heterostructures on Si substrates.

1. S.T. Boles, C.V. Thompson and E.A. Fitzgerald, “Influence of indium and phosphine on Au-catalyzed InP nanowire growth on Si substrates,” J. Cryst. Growth, vol. 311, pp. 1446-1450, 15 Feb., 2009. [↩]
2. S.T. Boles, E.A. Fitzgerald, C.V. Thompson, C.K.F. Ho, and K.L. Pey, “Catalyst proximity effects on the growth rate of Si nanowires,” J. Appl. Phys., vol. 106, p. 044311, 15 Aug. 2009. [↩]