metal particles, and previously-used nanotube-nucleating catalytic particles are relatively large, e.g., on the order of 10-50 nm.
As may be appreciated from the foregoing, it would be advantageous to provide a method of controlling the diameter of nanowires and reducing the diameter to a select size. It would be particularly advantageous to provide a method for the synthesis. of small diameter nanowires, e.g., those having a diameter of about 10 nm or smaller. It also would be advantageous to provide nanowires that are aligned in parallel and untangled to allow for, among other things, nano-interconnection in an orderly manner without sideway shorting between adjacent contact pads or devices. This invention discloses nanowire structures and methods for fabricating small diameter nanowires that provide these advantages. Further advantageous may appear more fully upon considering the detailed description given below.
The invention embraces a nanowire structure that may be used to fabricate small diameter and aligned nanowires, e.g., having a diameter of less than 50 nm and more preferably, less than 10 nm. The structure includes an alloy substrate that is at least two-phased; it is comprised of at least a first phase and a second phase, wherein the first phase is catalytic and the second phase is less catalytic than the first phase (weakly or non-catalytic). A plurality of small diameter nanowires are grown from the first phase of the alloy substrate. Each one of the plurality of nanowires can be substantially vertically aligned relative to the substrate and preferably, the average deviation from full vertical alignment is less than 25 degrees, and more preferably less than 15 degrees. The alloy substrate is fabricated with an alloy system of catalytic and non (or less) catalytic elements that are phase separated, e.g., they may be spinodally decomposed or subjected to nucleation-and-growth transformation to achieve the phase-separated substrate comprising the first and second phases.
The invention further compris