Center Produces New Nanowires that Can Increase Capacity for Power Storage Ten-fold

Achievement date: 
2016
Outcome/accomplishment: 

Diamond-shaped silicon nanowires with sharp corners have been produced by the Nanomanufacturing Systems for Mobile Computing and Mobile Energy Technologies (NASCENT) center, an NSF-funded Nanosystems Engineering Research Center (NERC) headquartered at The University of Texas at Austin. The nanowires can provide more than 90 percent more storage capacity than exists currently and may increase capacitance ten-fold.

Impact/benefits: 

Such nanowires are used in applications from ultra-high sensitivity sensors to high-density energy storage devices such as capacitors and batteries. These nanowires are produced using nanoshape imprinting followed by imprint-assisted Metal Assisted Chemical Etching (iMACE), which can be scaled up to fabricate wafer-scale devices with high throughput and high yield.

Explanation/Background: 

The imprint lithography is used to define a gold mesh with diamond holes, which acts as a catalyst for iMACE, an anisotropic wet etch technique that uses hydrogen peroxide, hydrogen fluoride, and distilled water. The process includes fabricating large arrays of diamond-shaped nanowires, which can be used as a parallel connection of many surrounded gate metal-oxide-semiconductor capacitors. This method relies on atomic layer deposition to deposit the dielectric hafnium oxide, an electric insulator, and a tin top gate metal.

The capacitance of the diamond nanowires is 18.44 µF/cm2/µm compared to 9.67 µF/cm2/µm for circular nanowire capacitors, a 90.62 percent increase in capacitance per projected area per unit pillar height. This increased capacitance validates the ability to preserve nanoshape cross-section during patterning and deep etching over large areas. Lithographic scaling to 10nm half-pitch, compared to the 100 nm half-pitch of the Center’s nanowires, has the potential to further increase capacitance by a factor of ten.