Guided Assembly of Gold Colloidal Nanoparticles on Silicon Substrates Prepatterned by Charged Particle Beams

Abstract

Colloidal gold nanoparticles represent technological building blocks which are easy to fabricate while keeping full control of their shape and dimensions. Here, we report on a simple two-step maskless process to assemble gold nanoparticles from a water colloidal solution at specific sites of a silicon surface. First, the silicon substrate covered by native oxide is exposed to a charged particle beam (ions or electrons) and then immersed in a HF-modified solution of colloidal nanoparticles. The irradiation of the native oxide layer by a low-fluence charged particle beam causes changes in the type of surface-terminating groups, while the large fluences induce even more profound modification of surface composition. Hence, by a proper selection of the initial substrate termination, solution pH, and beam fluence, either positive or negative deposition of the colloidal nanoparticles can be achieved.

Fabrication of Single‐Nanocrystal Arrays

“…This is commonly referred to as AFM nanoxerography and can be performed in parallel using electrode stamps, inspired by microcontact printing soft lithography . While the resolution of these stamps is limited by the standard of the lithographic technique used to make them, advances in focused particle beam technologies suggest this is a promising route to high resolution arrays of single nanocrystals …”

“…However, when the voltage pulses were decreased to +30 V and spaced 50 nm apart, they observed deposition of a single gold nanowire, only 1.7 nm in diameter, elongated along the line of charged dots proving that even the smallest of nanocrystals can be electrostatically printed with extremely high resolution. While this works well for AFM‐based nanoxerography, as well as surface charging with electron beams or ion beams, the scalable equivalent, electrical NIL, is still limited by the large size of the stamps used to transfer charge 83b,d,e,91. We are not aware of any example in the literature where a scalable nanoxerography approach has been used to assembly single, sub 50 nm nanocrystals from suspension.…”

Additive nanomanufacturing – A review

“…These charged surfaces are easily created by the application of a DC voltage between electrodes, 134 although alternative methods of charge patterning down to hundreds of nanometres can also be used to direct the 2D assembly of components. 135,136,137 Electrophoresis has been criticised for being limited to the manipulation of charged objects. However, the ability to functionalise nanoparticles with surface monolayers 138 enables a wide variety of nanoparticles to be manipulated.…”

Survey of Plasmonic Nanoparticles: From Synthesis to Application

“…Representative images of selected gold nanoparticle assemblies prepared via different top‐up approaches. a) Lines of gold nanoparticles assembled via wrinkle drying, b) gold particle hexamer assembled via a templated approach, c) gold particle pyramid assembled via a nanomanipulator, d) gold nanorods assembled via capillary forces, e) gold nanoparticles assembled via differences in the surface hydrophilicity, and f) oriented assembly of gold nanorods . Scale bars: a = 1 μm; b = 50 nm; c = 100 nm; d–f = 500 nm.…”

“…Charged particle beams are another method to pattern surfaces in a way that electrostatic interactions guide the deposition of particles. However, Kolibal et al revised the view that the particle beam leads to subsurface charging. Instead, the authors propose a mechanism, which is based on the alteration of the surface chemistry.…”