Hole–Mask Colloidal Lithography

Abstract

Self-organization of colloidal particles on surfaces to form 2D or 3D nanofabrication templates has been explored actively in the past decade as an effective bottom-up method to produce a plethora of nanoarchitectures with diverse functionalities. Specifically, several elegant approaches to pattern surfaces with large-scale 2D arrays of nanosized structures through lateral self-assembly of colloidal spheres have been developed. These methods are commonly termed colloidal lithography (CL). A frequently used version of CL, nanosphere lithography (NSL) employs organized 2D colloidal crystals with a hexagonal close-packed motif as an evaporation mask, often in combination with reactive ion etching. Evaporation through the holes between close-packed nanospheres defines the resulting pattern, and in many applications material deposition conditions such as evaporation angle or specific deposition technique (e.g., sputtering, thermal deposition) are used to vary the achieved patterns. With this method facile production of vast planar arrays of diverse nanostructures has been accomplished. [1][2][3][4][5][6][7][8] In an alternative approach, referred to here as sparse colloidal lithography (SCL), charged colloidal beads are utilized in a similar manner as in NSL. [9,10] This method, developed in our group, enables facile production of large areas (several cm 2 ) of nanoscopic features like holes in thin films, disc-, ringand crescent-shaped structures with overall sizes currently down to 20 nm and which occupy 10 to 50 % of the total surface area. [11][12][13][14][15][16] The size distribution of SCL-fabricated nanostructures is largely determined by the size dispersions of the masking colloids and is typically less than 5 % for colloids with average diameters > 100 nm and up to 10 % for smaller colloids. In contrast to NSL, a sparse monolayer of colloidal particles defines the evaporation/etch mask in SCL. The convenience of this technique, employing charged polystyrene (PS) nanoparticles as etch and/or evaporation mask, has recently been demonstrated in a variety of applications such as investigation of fibroblast response to nanotopography, [17] model catalysts of Pt/alumina and Pt/ceria [18] and in the study of optical properties of macroscopic arrays of supported metallic nanostructures like discs, crescents, or rings or nanoholes in optically thin films. [11,13,14,16] In spite of the general advantage of facile bottom-up nanofabrication and a large variety of possible nanostructural motifs, SCL has so far been subject to limitations in producing nanostructures composed of materials with unfavourable etching selectivity, that is, where the substrate or polystyrene etch rates compete with the etch rate of the actual materials of the nanostructure. Examples of such systems are Pt on Au or Au-silica hybrid structures on glass. Another disadvantage of the method is the necessity of the reactive oxygen treatment for the PS mask removal so that nanostructures composed of the materials prone to oxidation (like Ag or Ru) rap...

Large‐Area Low‐Cost Plasmonic Nanostructures in the NIR for Fano Resonant Sensing

“…We fabricate asymmetric double split-ring-resonators (ADSRRs) by hole-mask colloidal nanolithography [27][28][29][30] and vary the degree of asymmetry to study the evolution of the Fano resonance. Thermal annealing [ 31 ] is utilized to improve the modulation depth of the Fano resonance or to turn off the coupling.…”

Interaction effects on the magneto-optical response of magnetoplasmonic dimers

“…The diameter of the disks ranges from 130 to 150 nm. They were obtained by hole mask colloidal lithography, metal evaporation, and lift off [24]. The internal structure of the disks is presented in the rightmost panel of Fig.…”

Time-Resolved Indirect Nanoplasmonic Sensing Spectroscopy of Dye Molecule Interactions with Dense and Mesoporous TiO2 Films

“…Figure 1a is a schematic illustration of the dense TiO 2 INPS sensor chip structure used in the first part of the present work. It consists of Au nanodisks fabricated by hole-mask colloidal lithography (HCL), 9 covered with a thin (12−70 nm) sputtered TiO 2 film. A scanning electron microscopy (SEM) image of such a sample is shown in Figure 1c.…”

“…Gold (Au) plasmonic nanodisks with a diameter of 110 nm and a height of 20 nm were fabricated on circular soda lime glass slides by HCL. 9 The compact flat TiO 2 films were deposited on top of the Au nanodisks by reactive sputtering from a Ti target (FHR MS150 sputter system). For the mesoporous TiO 2 film, a soda lime glass substrate with Au nanodisks was first coated with a 12 nm TiO 2 film by sputtering.…”