Integrating vertically aligned carbon nanotubes on micromechanical structures

Teh, W. H.; Smith, C. G.; Teo, K. B. K.; Lacerda, R. G.; Amaratunga, G. A. J.; Milne, W. I.; Castignolles, M.; Loiseau, Annick

doi:10.1116/1.1591743

Cited by 10 publications

(4 citation statements)

References 9 publications

(7 reference statements)

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“…When heating positive-tone 950 K PMMA above the glass transition temperature of 110 °C, the resist viscosity drops and PMMA starts flowing slowly [30], which can be used for 3D pattern-ing [31]. Thermal reflow of negative-tone PMMA has been reported before [32], making it very attractive for 3D EBL in that regime, especially for microlens fabrication. However, we were not able to observe any change in the resist shape when heating up the inverted resist.…”

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confidence: 99%

Using low-contrast negative-tone PMMA at cryogenic temperatures for 3D electron beam lithography

et al. 2016

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We report on a 3D electron beam lithography (EBL) technique using polymethyl methacrylate (PMMA) in the negative-tone regime as a resist. First, we briefly demonstrate 3D EBL at room temperature. Then we concentrate on cryogenic temperatures where PMMA exhibits a low contrast, which allows for straightforward patterning of 3D nano- and microstructures. However, conventional EBL patterning at cryogenic temperatures is found to cause severe damage to the microstructures. Through an extensive study of lithography parameters, exposure techniques, and processing steps we deduce a hypothesis for the cryogenic PMMA's structural evolution under electron beam irradiation that explains the damage. In accordance with this hypothesis, a two step lithography technique involving a wide-area pre-exposure dose slightly smaller than the onset dose is applied. It enables us to demonstrate a >95% process yield for the low-temperature fabrication of 3D microstructures.

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confidence: 99%

Using low-contrast negative-tone PMMA at cryogenic temperatures for 3D electron beam lithography

et al. 2016

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“…However, many new applications would be enabled if CNTs, and microstructures in general, could be fabricated in arbitrarily slanted directions. Electric fields [12] and plasmas [13] have been used to control the growth direction of CNTs. However, these methods require an advanced CVD apparatus incorporating an electric field and always result in the same growth angle over the entire substrate.…”

Section: Introductionmentioning

confidence: 99%

Controlled growth orientation of carbon nanotube pillars by catalyst patterning in microtrenches

Volder

Tawfick

Hart

2009

TRANSDUCERS 2009 - 2009 International Solid-State Sensors, Actuators and Microsystems Conference

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We present a novel method for controlling the growth orientation of individual carbon nanotube (CNT) microstructures on a silicon wafer substrate. Our method controls the CNT forest orientation by patterning the catalyst layer used in the CNTs growth on slanted KOH edges. The overlap of catalyst area on the horizontal bottom and sloped sidewall surfaces of the KOH-etched substrate enables precise variation of the growth direction. These inclined structures can profit from the outstanding mechanical, electrical, thermal, and optical properties of CNTs and can therefore improve the performance of several MEMS devices. Inclined CNT microstructures could for instance be used as cantilever springs in probe card arrays, as tips in dip-pen lithography, and as sensing element in advanced transducers.

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“…These films may be used in transistors [7], chemical sensors [8], flow sensors [9] and electrical contacts [10]. Vertically-aligned CNT arrays have been grown by PECVD on suspended thinfilms [11], and by thermal CVD on sidewalls of SiO 2 structures by gas-phase delivery of the catalyst using ferrocene as a catalyst precursor [12,13]. Low-temperature CNF growth on a 3D carbon fibre matrix where carbon fibres were acting as a scaffold for CNF growth was recently achieved [14].…”

Section: Introductionmentioning

confidence: 99%

Uniform and selective CVD growth of carbon nanotubes and nanofibres on arbitrarily microstructured silicon surfaces

Hart¹,

Boskovic²,

Chuang³

et al. 2006

Nanotechnology

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Carbon nanotubes (CNTs) and nanofibres (CNFs) are grown on bulk-micromachined silicon surfaces by thermal and plasma-enhanced chemical vapour deposition (PECVD), with catalyst deposition by electron beam evaporation or from a colloidal solution of cobalt nanoparticles. Growth on the peaked topography of plasma-etched silicon 'micrograss' supports, as well as on sidewalls of vertical structures fabricated by deep-reactive ion etching demonstrates the performance of thermal CVD and PECVD in limiting cases of surface topography. In thermal CVD, uniform films of tangled single-walled CNTs (SWNTs) coat the structures despite oblique-angle effects on the thickness of the catalyst layers deposited by e-beam evaporation. In PECVD, forests of aligned CNFs protrude from areas which are favourably wet by the colloidal catalyst, demonstrating selective growth based on surface texture. These surface preparation principles can be used to grow a wide variety of nanostructures on microstructured surfaces having arbitrary topography, giving substrates with hierarchical microscale and nanoscale surface textures. Such substrates could be used to study cell and neuronal growth, influence liquid-solid wetting behaviour, and as functional elements in microelectronic and micromechanical devices.

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Integrating vertically aligned carbon nanotubes on micromechanical structures

Cited by 10 publications

References 9 publications

Using low-contrast negative-tone PMMA at cryogenic temperatures for 3D electron beam lithography

Using low-contrast negative-tone PMMA at cryogenic temperatures for 3D electron beam lithography

Controlled growth orientation of carbon nanotube pillars by catalyst patterning in microtrenches

Uniform and selective CVD growth of carbon nanotubes and nanofibres on arbitrarily microstructured silicon surfaces

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