Robust, High-Density Zinc Oxide Nanoarrays by Nanoimprint Lithography-Assisted Area-Selective Atomic Layer Deposition

Polymer templates realized through a combination of block copolymer lithography (BCL) and nanoimprint lithography (NIL) are used to direct atomic layer deposition (ALD) to obtain high-quality ZnO nanopatterns. These patterns present a uniform array of ZnO nanostructures with sub-100 nm feature and spatial resolutions, exhibiting narrow distributions in size and separation, and enhanced mechanical stability. The process benefits from the high lateral resolutions determined by the copolymer pattern, controlled growth rates, material quality and enhanced mechanical stability from ALD and repeatability and throughput from NIL. The protocol is generic and readily extendible to a range of other materials that can be grown through ALD. By virtue of their high feature density and material quality, the electrical characteristics of the arrays incorporated within MOS capacitors display high hole-storage density of 7.39 × 10¹⁸ cm^–3, excellent retention of ∼97% (for 1000 s of discharging), despite low tunneling oxide thickness of 3 nm. These attributes favor potential application of these ZnO arrays as charge-storage centers in nonvolatile flash memory devices.