Close‐Packed Gold‐Nanocrystal Assemblies Deposited with Complete Selectivity into Lithographic Trenches

Abstract

Close‐packed gold‐nanocrystal assemblies are selectively deposited into trenches (300 nm × 300 nm) fabricated by electron‐beam lithography. The base of the trenches consists of highly doped silicon with 30 nm silica walls. The assemblies are formed using electric‐field mediated deposition of8 nm gold spheres from organic solvents.

Centimetre scale assembly of vertically aligned and close packed semiconductor nanorods from solution

“…Herman has successfully used this approach to assemble 0D semiconductor nanocrystals into densely packed coatings 22 whereas more recently we have used electrophoresis to selectively assemble gold nanocrystals into lithographic channels with close packed order. 23 In this communication we direct the assembly of 1D nanorods into vertically aligned and close packed assemblies that completely cover centimetre sized substrates. The deposition occurs layer by layer, in a time controlled process, and is independent of rod aspect ratio.…”

“…Interparticle repulsion between like charged particles while depositing is expected to be instrumental in the resultant closepacking of the nanorods as it allows particles to find their preferred location in the growing assembly where the potential well of repulsive and attractive forces to neighbouring rods is at a minimum. 23 Further monolayer HRSEM images from different samples (Fig. 2a and Fig.…”

Electrophoretic Deposition of Poly(3-decylthiophene) onto Gold-Mounted Cadmium Selenide Nanorods

“…Accordingly, four additional simulations under the effects of a static electric field of 0.0195 V/Å were also carried out. Typical external electric field intensities in experiment are estimated to be of the order of 1 V/μm, [8][9][10][11][12][13][14] so the external fields here are necessarily some two orders of magnitude larger than experiment, in order to induce EPD within an amenable timescale for large-system (half-million-atom) MD (say, within 50 ns), but are relatively small in intensity in comparison to intrinsic electric fields in condensed aqueous phases, for instance (1.5-2.5 V/Å), 30 and to previous non-equilibrium MD of electrophoresis by the authors. 31,32 As will be shown below (cf.…”

“…2A. Although these rods are much smaller than those used experimentally, [8][9][10][11][12][13][14] which would typically be in the 6-8 nm diameter and roughly 30 nm length range, the inter-rod spacing and cross-sectional rod areas were chosen to conform in approximate proportional ratio to typical experimental dimensions and rod coverage per unit area. [9][10][11][12][13][14] It was desired to study EPD of polymers onto the rod arrays using direct MD, rather than in between the rods: experimentally, EPD between rods does rely on several parameters that are difficult to achieve, and, especially, control, such as removal of surfactant while retaining the architecture.…”

“…5 Similar devices using metal oxide electrodes and high-workfunction anodes (e.g., Ag and Au) have been developed recently to reduce oxidation problems in lower-workfunction cathodes and degradation of the indium tin oxide (ITO)-poly(ethylenedioxythiophene) (PEDOT) interface in conventional solar cells. 6,7 Although these structures are challenging to fabricate, Ryan et al have made considerable progress in recent years via electrophoretic deposition (EPD) of nanocrystal and nanorod electrodes of differing charge from organic (toluene) solutions, to achieve a good degree of vertical nanorod alignment, 8,9 and also in the formation of nanorod assemblies in electric fields. [10][11][12][13][14] These advances have the distinct advantage of being solution-processable, rather than requiring vacuum techniques.…”