Microplasmas for direct, substrate-independent deposition of nanostructured metal oxides

Abstract

A general, substrate-independent method for plasma deposition of nanostructured, crystalline metal oxides is presented. The technique uses a flow-through, micro-hollow cathode plasma discharge (supersonic microplasma jet) with a 'remote' ring anode to deliver a highly-directed flux of growth species to the substrate. A diverse range of nanostructured materials (e.g., CuO, -Fe 2 O 3 , and NiO) can be deposited on any room temperature surface, e.g., conductors, insulators, plastics, fibers, and patterned surfaces, in a conformal fashion. The effects of deposition conditions, substrate type, and patterning on film morphology, nanostructure and surface coverage are highlighted. The synthesis approach presented herein provides a general and tunable method to deposit a variety of functional and hierarchical metal oxide materials on many different surfaces. High surface area, conversion-type CuO electrodes for Li-ion batteries are demonstrated as a proof-of-concept example.The ability to synthesize functional nanoscale materials, as well as to integrate these structures into devices, is fundamental for the development of next-generation micro-and optoelectronic devices, sensors, and energy harvesting and storage technologies [1][2][3][4]. Realization of nanomaterials and multi-scale systems often requires complicated processing steps that may involve a combination of wet chemistry, physical/chemical vapor deposition, vapor-liquid-solid or molecular beam epitaxy, self-and/or directed assembly, lithography, and etching. In addition, both wet and dry conditions, long processing times, high temperatures, vacuum processing, and templates or catalysts can be required. As such, we continually seek to develop general and tunable methods that can easily and rapidly create nanostructured functional materials. For example, atmospheric pressure plasmas [5,6], plasma sprays [7][8][9], and microplasmas [10][11][12][13][14][15][16][17][18][19][20] have shown much promise toward this goal. Extending and adapting such methods in a generic way to different material systems and deposition situations, as well as understanding how plasma operating conditions affect growth processes, is critical for their implementation.

Microplasmas for Advanced Materials and Devices

“…Recently, a versatile microplasma‐based approach ( Figure ) has been demonstrated for direct deposition of crystalline MONS including α‐Fe 2 O 3 , CuO, NiO, and Fe‐doped NiO on different substrates including polymeric materials, conductors, insulators, fibers, and patterned substrates at ambient temperature (Figure a) . The as‐prepared CuO films were used as active electrodes for lithium ion batteries, exhibiting high specific capacity and good electrochemical responses over a large number of voltage sweep cycles (Figure b).…”

“…The insets show top‐down zoom images of the oxide morphology. a–d) Reproduced with permission . Copyright 2016, American Institute of Physics.…”

Plasma-digital nexus: plasma nanotechnology for the digital manufacturing age

“…The use of a remote ring anode made it possible to deliver a highly directed flux of the precursor species to the substrate, depositing them in a conformal fashion regardless of the type of substrate (Mackie, et al, 2016;Mackie and Gordon, 2017). Figure 30 shows similar "agave-like" nanowire morphologies of CuO film on various substrates including conducting, insulating, flexible, patterned and fiber-based substrates, to demonstrate the versatility of this technique (Mackie, et al, 2016). The deposition process was performed at 15 -20 Torr, which is a relatively high pressure in comparison to the nominal vacuum processes while raster scanning the substrate allowed uniform deposition over larger areas.…”

“…This is a viable technique that enables deposition of a variety of functional nanostructured metal oxides on a range of surfaces. (Mackie, et al, 2016;Mackie and Gordon, 2017) Anthony et al demonstrated an all-gas-phase approach for the fabrication of nanocrystal-based lightemitting devices. Silicon nanocrystals synthesis, surface functionalization, and deposition were all performed in a single reactor.…”

White paper on the future of plasma science and technology in plastics and textiles

“…Operated at sub‐ atmospheric pressures, DC discharge jets can be run supersonic so that active species are “spray‐deposited” onto the surface of interest with different morphologies (nanoparticles, dense columnar films, or hierarchical nanostructures, etc.) . In contrast, resorting to nanosecond‐pulsed plasmas paves the way for highly‐controllable plasma polymer deposition and surface functionalization at room temperature …”