Biomedical Engineering Reference
In-Depth Information
The nanoparticle arrays were fabricated using electron beam
lithography (EBL) on quartz substrates. The fabrication process
flow begins with 180 nm of PMMA 950 (Poly-Methyl MethAcrylate)
spin coated on top of the substrate, followed by a soft bake at
180
◦
C for 20 min. The nanopatterns were written using a Zeiss
SUPRA 40VP SEM equipped with Raith beam blanker and NPGS for
nanopatterning.Afterdevelopingtheresistina3:1solutionofMIBK
(methylisobutyle ketone) and isopropanol, a thin metal stack was
deposited on the patterned surface by electron-beam evaporation.
Thestackconsistedofa2nmCradhesionlayerfollowedbya28nm
Aulayer.Alift-offprocesswasthenperformedusingheatedacetone.
The SEMs of fabricated arrays are shown in Figs. 11.11 and
11.12. In particular, GA,
τ
,
μ
,and
π
spirals were fabricated
and the corresponding far-field diffraction patterns experimentally
measured (Fig. 11.11c,d andFig. 11.12c,d).
Figure 11.11
SEM micrographs of (a) GA spiral and (b)
τ
spiral gold
nanoparticle arrays on a fused silica substrate. Measured far-field diffrac-
tion patterns for (c)
ϕ
spiral and (d)
τ
spiral, taken from respective arrays
shown in Fig. 11.a and b.
