April 18, 2023 Sean Glass 2003

Two and three-dimensional nanoscale structures for molecularelectronics

Controlled self assembly of charged-stabilized goldnanoparticles into close-packed arrays

Executive Summary

Origins of the project Initial Research The tilting method Coffee Drops & Nanoparticles? Current Status and Future plans

Molecular Electronics

Using Individual Molecules as electronic devices Different paths to achieve molecular devices Planar Devices The Nanocell

The Nanocell

Gold Nanoparticles Molecular Wires Addressable through leads

into the nanocell Programmed to function

as a logic device

Gold Nanoparticle Deposition

Ideal - Hexagonal close packing

Confined to within the Nanocell

Not easily trapped using voltage or magnetic fields

SiO2 Microsphere Deposition

Photonic band gap crystals

Numerous methods previously explored Spinning Tilting Tapered Cell

Ng et al. Nanotechnology 13

My result with 100nm Polyspheres

Tilting Method

Simple & Controllable Setup

Reproducible Highly Adjustable Oven Capable

1st Experiments with Tilting Setup

Temperature / Concentration Constant / Varied Tilt

Polyspheres and Gold Nanoparticles Au: 60nm 100nm

PS: 50nm 100nm 500nm

Results

Best assembly with 0 tilt Assembly at the rim of the drop Polyspheres assembly better than Au

Nanoparticles Distinct layers form with 60nm Au nanoparticles!

Nanoparticle Deposition at the Rim

Occurs at edge of drop. Caused by pinning of edge of drop to surface and

capillary forces that are created as a result during evaporation

From “Capillary flow as the causeof ring stains from driedliquid drops”Robert D. Deegan*, Olgica Bakajin*, Todd F. Dupont†,Greb Huber*, Sidney R. Nagel* & Thomas A. Witten*

Nature, October 22 1995?

Rim Characteristics

Width Order Layers - steps

Hypothesis – Particle Motion

V V-V

Velocity is proportional to height b/ch(t) * v(t) = constant

(Deegan et al. Physical Review E Volume 62 Number 1)

0 tilt

Significant tilt

Layers / steps

Reproducible Consistent layer width

Layer Formation Control Hypothesis

Depends directly on J(r) – the evaporation

profile Depends on temperature

and area of evaporation v(r) depends on J(r) and

the contact angle J(r) depends on T and

surrounding environment

Concentration

Deegen et Al. demonstrated on a macro scalehow different evaporative profiles affect deposition at the contact line

Ongoing work to be done with step formation / control Vary concentration, temperature, and evaporation

profile while fixing tilt Computer Simulation of Model

Further Experiments

Multiple Drops

Ultrasonic bath to increase ordering

IV measurements through Au NP arrays

Special Thanks To

Professor Mark Reed Dr. Ilona Kretzschmar