Nanostructures will dominate next-generation energy technologies. Progress in nanofabrication increasingly allows design flexibility control of structural geometry and material combinations to achieve high performance multifunctional 3-D nanostructures for energy harvesting and storage. Such designs derive advantage from high surface areas, ultrathin films, structures with high aspect ratios, heterogeneous materials combinations, and control over 3-D profiles of material compositions and nanostructure shapes. Self-assembly, self-alignment, and self-limiting reactions enable both nanofabrication of desired energy nanostructures and their scaling to unprecedented levels of integration.

 

Atomic layer deposition (ALD) plays a pivotal role in this paradigm because of its intrinsic attributes: thickness control at the atomic scale; exceptional conformality to apply this control in the most demanding of nanogeometries; and a growing portfolio of ALD materials choices from new precursors and processes. As a result, ALD is becoming common, even pervasive, in nanostructure-based energy research, spanning applications from heterogeneous nanowires to passivating electrochemical layers and high-efficiency catalytic nanostructures.

 

Two primary challenges will determine whether ALD’s potential is realized in next-generation energy technology.

 

First, integration of ALD with other processes into suitable process sequences determines how well nanostructure designs can be fabricated and tailored for the energy application. For example, in high aspect ratio trenches, pores, or aperiodic porous materials, ALD films can be highly conformal or tapered “top-down” to thinner layers deeper in the structure, while electrodeposited films can be grown “bottom-up” from a working electrode at the bottom, together offering more design flexibility in vertical profiles than does either process alone.

 

Second, scaleup of ALD equipment, processes, and control is required for cost-effective ALD manufacturing. Significant efforts are already underway to develop these technologies, notably including roll-to-roll and other high throughput approaches, as well as atmospheric pressure ALD to circumvent the cost and complexity of vacuum-based equipment.

 

* Supported by the US Department of Energy, Office of Basic Energy Sciences as part of an Energy Frontier Research Center, and by the Laboratory for Physical Sciences.