Fabrication of Ultra-High Aspect Ratio (>420:1) Al2O3 Nanotube Arraysby Sidewall TransferMetal Assistant Chemical Etching

Abstract

We report a robust, sidewall transfer metal assistant chemical etching scheme for fabricating Al2O3 nanotube arrays with an ultra-high aspect ratio. Electron beam lithography followed by low-temperature Au metal assisted chemical etching (MacEtch) is used to pattern high resolution, high aspect ratio, and vertical silicon nanostructures, used as a template. This template is subsequently transferred by an atomic layer deposition of the Al2O3 layer, followed by an annealing process, anisotropic dry etching of the Al2O3 layer, and a sacrificial silicon template. The process and characterization of the Al2O3 nanotube arrays are discussed in detail. Vertical Al2O3 nanotube arrays with line widths as small as 50 nm, heights of up to 21 μm, and aspect ratios up to 420:1 are fabricated on top of a silicon substrate. More importantly, such a sidewall transfer MacEtch approach is compatible with well-established silicon planar processes, and has the benefits of having a fully controllable linewidth and height, high reproducibility, and flexible design, making it attractive for a broad range of practical applications.

Smart optical cross dipole nanoantenna with multibeam pattern

“…To confirm the fabrication feasibility of the proposed smart cross dipole nano-antenna it should be mentioned that the vertical aspect ratio of this structure is about 20:1, which some methods such as metal assisted chemical etching 40 , nanoimprint lithography and etching 41 and Talbot lithography 42 with aspect ratios of (> 420:1), (> 50: 1) and (> 20:1), respectively, can be used to fabricate it. Also, as the gap between each director is 10 nm, the gaps with 4 to 10 nm spacing can be fabricated using a proper e-beam dose and pattern-developing time 43 .…”

Atomic/molecular layer deposition strategies for enhanced CO2 capture, utilisation and storage materials

“…197–200 The AAO and silicon templates are generally removed by the chemical etching method, while the carbon templates, MOFs, polymers, and biological templates are removed by calcination. Numerous ALD materials have been applied onto these sacrificial templates, including TiO 2 , 201–204 ZnO, 205–207 Al 2 O 3 , 197,198,208 SnO 2 , 38 ZrO 2 , 209 Fe 2 O 3 , 210 Fe 3 O 4 , 211 Ru, 212 Ni/Co, 213 Pt/Ir, 214 TiN/Al 2 O 3 /TiN, 215 Al-doped ZnO (AZO), 216 TiO 2 -Pt, 217 MoS 2 218 and so on. This has resulted in the synthesis of various structured materials, such as nanotube, 185 crescent-shaped half-nanotubes, 219 core–shell, 206 nanopillars, 188 close-packed and non-close-packed inverse-opals, 220,221 tube-in-tube structure, 194 nano-gratings, 187 3D network of metal NWs, 189 3D porous nanostructured metals, 222 metal nanoparticle chains encapsulated in nanotubes, 223,224 nano-porous gyroid, 190 sandwich nanostructures, 191 tube-in-tube structure, 194 nanofibers, 225 etc.…”

Atomic Layer Assembly Based on Sacrificial Templates for 3D Nanofabrication

“…Furthermore, ultra-high aspect ratio Al 2 O 3 nanotube arrays with line widths as small as 50 nm, heights of up to 21 µm, and an aspect ratio of up to 420:1 were successfully fabricated, utilizing reliable sidewall transfer low-temperature Au metal assisted chemical etching (MacEtch) process, as displayed in Figure 3d [36]. This technique combined the advantages of the high aspect ratio nanostructure capabilities of the MacEtch with the sidewall transfer process.…”