Self-organization of nanospheres in trenches on silicon surfaces

Abstract

The selective deposition and self‐assembly of nanospheres from a colloidal suspension in trenches on silicon surfaces is investigated using conventional light, confocal laser scanning and scanning electron microscopy. Trenches with widths of one to several nanosphere diameters are formed on silicon surfaces by photolithography and reactive ion etching. The spreading knife convective self‐assembly technique is employed to distribute the nanosphere suspension on the pre‐patterned surface. It is shown that this technique is particularly useful in combination with a functionalized surface where a self‐assembled molecular monolayer changes the contact angle such that sphere deposition takes place almost exclusively in the trenches. By this, lines selectively filled with a chain of beads with a length of 0.5 mm have been achieved.

Nanosphere lithography for device fabrication

“…16,17 Recently, we achieved the selective self-organization of spheres within a trench formed by optical lithography on a silicon wafer, using a doctor-blade-based NSL technique. 18,19 Sphere deposition can be largely suppressed by a self-assembled layer of octadecyltrichlorosilane molecules on the substrate top surface: see Figure 2(a). Using this arrangement, we can create pairs of opposing metallic tips with nanometric tip radii within the trench.…”

A template-assisted self-organization process for the formation of a linear arrangement of pairs of metallic tips

“…As all these parameters can be easily controlled, an optimum velocity of the contact line can be determined such that the layer porosity ε corresponds to that of a continuous close-packed monolayer, 0.395, on a flat surface. In our experiment in [11] we determined a velocity which allows to deposit spheres exclusively in a single trench at the wafer surface. If one uses parallel trenches instead of a single one, the relative surface fraction S where spheres should be arranged can be tuned.…”

“…Moving the sample under the blade with a constant velocity leads to a three phase contact line between the suspension, the substrate and the surrounding gas phase, which is drawn across the sample. The sphere assembly usually occurs at this contact line [12], but due to the hydrophobicity of the OTS covered surface, sphere deposition on the flat Si top surface is suppressed and exclusively occurs inside the trenches [11].…”

“…One of the key issues in order to exploit nanometric structures on a solid surface in real-world applications is the construction of connections between nanoobjects and their macroscopic environment. Recently we have demonstrated that it is possible to use a template-assisted self-assembly technique to arrange nanospheres selectively in a long close-packed line within a trench etched into the surface of silicon [11]. In the present paper it is investigated if this technique can also be used in sets of narrow spaced, parallel trenches.…”

Directed Self-Assembly of Polystyrene Nanospheres by Direct Laser-Writing Lithography

“…Despite the other NSs deposition methods that have been proposed so far, such as doctor blading [22] or Langmuir-Blodgett coating [23], in this work, we used the spin coating technique. Such choice was motivated by the aim to develop proper protocols to promote the applicability of DSA processing in industrial nanomanufacturing already relying on this method.…”