ShadowNanosphe

reLithograp

hyPeter J. ShinDepartment of Bioengineering

UC BerkeleyThe BioPOETS

Introduction

• Interested in Batch Fabrication technique for making biosensors (i.e. SERS substrate)

• Wanted features include - low cost manufacturing - regular patterns in large area (6” Si wafer) - very high uniformity

• A. Kosiorek, et al., Shadow Nanosphere Lithography: Simulation and Experiment, Nano Lett., 2004

UC BerkeleyThe BioPOETS

Nanosphere Lithography (NSL)

Metal (Au, Ag) Deposition

Array of

Polystyrene Beads

as Mask

Si Substrate

• Metal deposit with electron beam evaporation (EBE) system

• Control over shape & size of patterns by varying bead radius

UC BerkeleyThe BioPOETS

Nanosphere Lithography (NSL)

Top View Side View

1. Bead Coating(self-assembled monolayers)

2. Deposit Metal

3. Bead Removal(toluene, tape)

UC BerkeleyThe BioPOETS

Nanosphere Lithography (NSL)

Targeted Pattern

scanning electron microscopy (SEM)

image resulting from fabrication process

(image from Van Duyne’s group)

UC BerkeleyThe BioPOETS

Shadow Nanosphere Lithography

* Modified EBE System

– Sample

– Metal source

5. e-beam source

Θ : angle between sample & metal source

α : angle of sample rotation

UC BerkeleyThe BioPOETS

Shadow Nanosphere Lithography

Metal (Au, Ag)

Deposition Θ

αVarying α resulting in nanowire

Sample

Rotation

Varying Θ resulting in complex morphology

UC BerkeleyThe BioPOETS

Shadow Nanosphere Lithography

Θ = 0° & α = 0° leads to conventional NSL

150nm Cr with Θ = 25°

+

15nm Ni with Θ = 0°

Conventional NSL Shadow NSLvs

UC BerkeleyThe BioPOETS

Thank you!

Questions?