Figure 8.

Scanning electron micrographs of InP nanowires grown from gold catalysts with different thickness-to-height ratios, showing the role of the catalyst’s aspect ratios in determining the properties of the grown NW array. The metal pattern realized on the substrate prior to growth consisted of five gold disks with a fixed thickness of 17 nm and varying diameters. Starting from the left, the catalyst diameters were: 50, 100, 200, 400, and 800 nm, corresponding to gold catalysts thickness-to-height ratios of about 1/3, 1/6, 1/12, 1/24, and 1/47. As shown in the image, for thickness-to-height ratios of 1/3 and 1/6, each individual catalyst originates a single nanowire. For lower aspect ratios, the catalysts are unstable and tend to split into many small catalyzing particles, giving rise to the growth of multiple inhomogeneous nanowires. (Reprinted with permission of Ref. [125]).