Influence of Solvent on Octadecyltrichlorosilane Nanostructures Fabricated Using Particle Lithography

Abstract

Numerous strategies have been devised to register organosilane monolayers for applications ranging from lubricants to semiconductor surface resists. Of these patterning techniques, particle lithography offers a straightforward and high-throughput method to create periodic arrays of organosilane nanopatterns. Herein, we describe the influence of solvent on the solutionphase formation of periodic arrays of nanopores within octadecyltrichlorosilane (OTS) monolayers using particle lithography. Our systematic study of various compositions of two miscible solvents, anhydrous toluene and bicyclohexyl, demonstrates control over nanopore size and OTS surface coverage. Smaller nanopores are generated from solutions with higher anhydrous toluene composition, and larger nanopores are generated from solutions with higher bicyclohexyl composition. A study of the effect of deposition time on nanopore formation found that at shorter deposition times (<5 min), the nanopore size is limited by diffusion into the water meniscus around the base of the nanoparticle, and at longer deposition times (>15 min), the size of the nanopore is limited by the mesosphere-substrate contact geometry as seen with anhydrous toluene solutions. This ability to regulate nanopore size and surface coverage, while preserving the interpattern periodicity, demonstrates an additional level of hierarchical control over organosilane nanostructure formation and enables a broader range of nanostructures that can be fabricated. ■ INTRODUCTIONThe study of organosilane self-assembled monolayers (SAMs) has garnered tremendous interest since they were first reported by Sagiv in 1980. 1−4 These systems, which are chemically and thermally robust due to covalent bonds formed with the underlying substrate, can also be tailored by varying their terminal functional groups. 5 Adding to their utility, densely packed organosilane SAMs can be prepared on a broad range of substrates, including semiconductor oxides, metal oxides, glass, mica, and quartz. 6−15 To date, numerous strategies have been devised to form and to register organosilane SAMs for applications ranging from lubricants to semiconductor surface resists. 16−28 Particle lithography is one such strategy that offers a straightforward and high-throughput method to fabricate periodic nanopatterns of organosilane SAMs. 10,29−32 In particle lithography, monodispersions of silica (or latex) spheres in water are deposited onto flat surfaces, and close-packed structures with regular interpattern geometries spontaneously assemble as the water evaporates. The resulting two-dimensional arrays serve as templates that guide the formation of organosilane SAMs into ordered nanopatterns. This patterning strategy has been employed to create nanostructures that (i) direct the synthesis of metals, rare earth oxide nanocrystals, and polymer brushes, (ii) capture metal nanoparticles and semiconductor quantum dots, and (iii) respond to changes in the chemical environment. 20,33−42 Given the potential applications, much work has been d...

Using Patterned Self-Assembled Monolayers to Tune Graphene–Substrate Interactions

“…Silica microspheres of three diameters, 1.8, 0.5, and 0.2 μm, were used as templates to vary pore diameter and pitch. As has been seen by others using colloidal lithography for patterning of SAMs, the pitch was determined by the silica sphere diameter and with the pore depth determined by the thickness of the OTS monolayer of ca. 2 nm − with pore diameters ranging from ca.…”

“…Here, as described in the methods section, colloidal lithography was employed to create nanostructured surfaces using silica nanoparticles of 1.8, 0.5, and 0.2 μm in diameter to control the pattern pitch. Following assembly of these spheres into hexagonal patterns on the surface, , OTS SAMs formed in all of the exposed surfaces between the silica particles, which, when the silica particles are removed leaves open pores on the surface of ca. 2 nm in depth with periodic spacing defined by the particle diameter and assembly symmetry.…”

“…dimensions of the colloid used. 23 The pores are then left empty or back-filled with either a different silanedecyltrichlorosilane (C10) or a perfluorophenylazide N-(3-trimethoxysilylpropyl)-4-azido-2,3,5,6-tetrafluorobenzamide (PFPA) to make mixed SAMs onto which graphene is deposited to spatially tailor the chemical interactions between them. As the graphene is seen to conform to the patterned surface, the comparison between empty and C10-or PFPA-filled pores allows us to examine how local structural distortion of the graphene interplays with spatial chemical interactions, including the spatial disruption of the double bond network of the graphene via reaction of the graphene with PFPA, which can be covalently linked to graphene via a ring insertion of the nitrene group.…”

“…To accomplish this, a background SAM of OTS is templated using colloidal lithography onto oxidized silicon wafers to create nanoscale pores of ca. 2 nm in depth in a hexagonal arrangement with the spacing dictated by the dimensions of the colloid used . The pores are then left empty or back-filled with either a different silanedecyltrichlorosilane (C10) or a perfluorophenylazide N -(3-trimethoxysilylpropyl)-4-azido-2,3,5,6-tetrafluorobenzamide (PFPA) to make mixed SAMs onto which graphene is deposited to spatially tailor the chemical interactions between them.…”

Distance-Dependent Measurements of the Conductance of Porphyrin Nanorods Studied with Conductive Probe Atomic Force Microscopy

“…27 We have developed protocols with immersion particle lithography to prepare arrays of nanoholes within organic thin films on surfaces such as gold, mica, and silicon. 27–31 Typically, when a surface that is coated with mesoparticles is immersed in solutions, the particles are displaced. Therefore, an annealing step is critical for immersion particle lithography.…”