Fabrication of nanoscale gaps using a combination of self-assembled molecular and electron beam lithographic techniques

Negishi, Ryota; Hasegawa, Tsuyoshi; Terabe, Kazuya; Aono, Masakazu; Ebihara, Takeaki; Tanaka, Hirofumi; Ogawa, Takuji

doi:10.1063/1.2209208

Cited by 60 publications

(55 citation statements)

References 24 publications

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“…This method was then refined for the construction of nanogap electrodes. [107][108][109] After metal deposition by electron-beam lithography and lift-off of the mercaptoalkanoic acid resist by chemical etching, nanogaps were formed with separations determined by the thickness of the mercaptoalkanoic acid layer. As molecular lithography provides a simple, highly reproducible, and economical way of fabricating metallic electrodes separated on the molecular scale, it is especially promising for the construction of arrays of molecular circuits.…”

Section: Molecular Ruler and Nanostructure Template For Nanogap Electmentioning

confidence: 99%

Nanogap Electrodes

2009

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Nanogap electrodes (namely, a pair of electrodes with a nanometer gap) are fundamental building blocks for the fabrication of nanometer‐sized devices and circuits. They are also important tools for the examination of material properties at the nanometer scale, even at the molecular scale. In this review, the techniques for the fabrication of nanogap electrodes, the preparation of assembled devices based on the nanogap electrodes, and the potential application of these nanodevices for analysis of material properties are introduced. The history, the research status, and the prospects of nanogap electrodes are also discussed.

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Section: Molecular Ruler and Nanostructure Template For Nanogap Electmentioning

confidence: 99%

Nanogap Electrodes

2009

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“…9,12 The serial writing process of EBL makes this technique unfavorable for the fabrication of large area and low-cost sensors. Other lithography-based techniques have been used, including molecular rulers 13,14 or atomic layer deposition (ALD), 7 as effective methods to tune the nanogap size even below 2 nm. This, however, involves complicated multistep fabrication processes and produces local defects, which are found to cause fluctuations of the surface-enhanced Raman scattering (SERS) enhancement across the sensing area 7 or between different substrates.…”

mentioning

confidence: 99%

Fabrication of sub-10 nm gap arrays over large areas for plasmonic sensors

Siegfried

Ekinci

Solak³

et al. 2011

Applied Physics Letters

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We report a high-throughput method for the fabrication of metallic nanogap arrays with high-accuracy over large areas. This method, based on shadow evaporation and interference lithography, achieves sub-10 nm gap sizes with a high accuracy of 61.5 nm. Controlled fabrication is demonstrated over mm 2 areas and for periods of 250 nm. Experiments complemented with numerical simulations indicate that the formation of nanogaps is a robust, self-limiting process that can be applied to wafer-scale substrates. Surface-enhanced Raman scattering (SERS) experiments illustrate the potential for plasmonic sensing with an exceptionally low standard-deviation of the SERS signal below 3% and average enhancement factors exceeding 1 Â 10 6 . 1,2 This enhancement phenomenon relies on strongly confined electromagnetic fields generated by localized plasmons on metal nanostructures much smaller than the incident wavelength. 3,4 However, surface enhanced (SE) spectroscopic techniques are not yet routinely used at the industrial level. This is due to poor signal reproducibility, moderate average enhancement factors, and high costs. 5 To increase the signal enhancement, nanogap patterns are currently used: they produce extremely large electromagnetic fields for nano objects separated by a distance below 20 nm. 6 Local enhancement factors up to $10 9 have been reported with a one-dimensional (1D) nanogap pattern, 7 enabling single molecule detection. 8 The fabrication of nanogap arrays has been demonstrated with a variety of techniques. Electron-beam lithography (EBL) is used for direct writing 9 or patterning of shadow masks for angular evaporation. 10,11 With EBL, the pattern can be designed and realized with an exceptional degree of freedom. Due to proximity effects of the electron beam and limitations set by the photoresist liftoff, the resulting metal nanogap dimensions are limited to above roughly 10 nm and a metal layer thickness of below 30 nm. 9,12 The serial writing process of EBL makes this technique unfavorable for the fabrication of large area and low-cost sensors. Other lithography-based techniques have been used, including molecular rulers 13,14 or atomic layer deposition (ALD), 7 as effective methods to tune the nanogap size even below 2 nm. This, however, involves complicated multistep fabrication processes and produces local defects, which are found to cause fluctuations of the surface-enhanced Raman scattering (SERS) enhancement across the sensing area 7 or between different substrates.In this letter, we report the fabrication of homogeneous sub-10 nm gap arrays with high surface densities and over large areas. The fabrication scheme for our nanogap arrays consists of only two stages, lithography and metal layer deposition.In the first step, extreme ultraviolet interference lithography (EUV-IL) is used to provide a 1D line array on the substrate, which is typically float glass or silicon. Details of the EUV lithography, available at the Swiss Light Source, can be found elsewhere. 15 This technique provides high resolu...

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“…For example, electromigration techniques yield arrays of particle-free nanogaps with nearidentical electronic properties. 14 [18][19][20][21][22][23] Some of these approaches may even be applicable to creating arrays of vacant nanogaps in the future. In some instances the partial removal of an insulating layer leads to an unexpected decrease in the junction's resistance.…”

Section: Introductionmentioning

confidence: 99%

Free Standing Nanocrossbar Arrays with Molecular Throughput

Prokopuk¹,

Son²,

Waltz³

2010

Nanosci Nanotechnol Lett

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We report a new approach for fabricating vacant nanocrossbar arrays using a combination of lithography and selective chemical etch. Two parallel arrays of gold wires are lithographically patterned orthogonal to each other with a chromium layer (2-5 nm thick) sandwiched between the wire arrays. A silicon oxide mesh is sputtered over the metal ensemble leaving the crossing points free of the oxide layer. The chromium layer is subsequently removed via selective chemical etch leaving a gold architecture with vertical separations that are on the order of a few nanometers. The silicon oxide mesh anchors the gold wires in place creating a robust nanoarchitecture. The nanogaps can be filled with fluids resulting in a change of the junction's resistance. The variability in the vertical separations between the wires within an array is only a few Angstroms. These results demonstrate that molecular-sized gaps can be created without the use of a molecular template.

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Fabrication of nanoscale gaps using a combination of self-assembled molecular and electron beam lithographic techniques

Cited by 60 publications

References 24 publications

Nanogap Electrodes

Nanogap Electrodes

Fabrication of sub-10 nm gap arrays over large areas for plasmonic sensors

Free Standing Nanocrossbar Arrays with Molecular Throughput

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