352
L. D. Negro et al.
arrays has direct implications for device engineering, since in addition to the particles
composition/morphology and array geometry, the size of aperiodic arrays can be
tailored to enhance the near field hot spots intensity. In the next section, after a
discussion on the electron beam nanofabrication of DANS, we will introduce few
selected device applications.
9.3 Engineering Applications of Aperiodic Plasmon Arrays
From the discussions in the previous sections, it should be clear that manipulating
the interplay of coherent photonic scattering and near field plasmonic coupling in
aperiodic Fourier space offers novel opportunities to design electromagnetic hot spots
and to control light-matter coupling on the nanoscale for a number of engineering
device applications.
We will discuss in the next sections the nanofabrication of plasmonic DANS and
introduce some engineering device applications that leverage deterministic aperiodicity and metallic arrays of nanoparticles. The interested reader should consult the
reference section for more device applications and in-depth discussions of specific
structures.
9.3.1 Nanofabrication of Aperiodic Plasmon Arrays
In contrast to random media, DANS can be specifically tailored and fabricated using
conventional nanolithographic techniques such as electron beam lithography (EBL)
or Focused Ion Beam (FIB) milling followed by standard metal deposition and etching steps. Our group has recently developed a flexible process flow, as detailed below,
for the nanofabrication of arbitrary arrays of metal nanoparticles for nanoplasmonic
applications. In particular, we developed metallic nanoparticle arrays based on noble
metals, typically Au and Ag, on quartz substrates with a 10 nm layer Indium Tin
Oxide (ITO) to provide conduction. A 180-nm-thick layer of PMMA (PolyMethylMethAcrylate) is then spin coated on top of the cleaned substrate. Subsequently, the
DANS patterns are defined using a Zeiss SUPRA 40VP SEM equipped with a Raith
Beam Blanker and NPGS for nanopatterning.
After developing the resist in a 1:3 solution of MIBK (Methyl IsoButyle Ketone)
and IPA (Isopropanol), a ≥30 nm thick Au/Ag film is deposited on the patterned
surface by electron-beam evaporation. Finally, a liftoff process is performed using
acetone, resulting in the definition of the targeted metal nanoparticle arrays. Within
the same general process flow, nano-perforated metal/dielectric films can also be
obtained using a Reactive Ion Etching (RIE) step immediately after EBL writing.
The concept of our process flow for the fabrication of both metallic nanoparticle
arrays and nano-hole patterns is summarized in Fig. 9.11.
L. D. Negro et al.
arrays has direct implications for device engineering, since in addition to the particles
composition/morphology and array geometry, the size of aperiodic arrays can be
tailored to enhance the near field hot spots intensity. In the next section, after a
discussion on the electron beam nanofabrication of DANS, we will introduce few
selected device applications.
9.3 Engineering Applications of Aperiodic Plasmon Arrays
From the discussions in the previous sections, it should be clear that manipulating
the interplay of coherent photonic scattering and near field plasmonic coupling in
aperiodic Fourier space offers novel opportunities to design electromagnetic hot spots
and to control light-matter coupling on the nanoscale for a number of engineering
device applications.
We will discuss in the next sections the nanofabrication of plasmonic DANS and
introduce some engineering device applications that leverage deterministic aperiodicity and metallic arrays of nanoparticles. The interested reader should consult the
reference section for more device applications and in-depth discussions of specific
structures.
9.3.1 Nanofabrication of Aperiodic Plasmon Arrays
In contrast to random media, DANS can be specifically tailored and fabricated using
conventional nanolithographic techniques such as electron beam lithography (EBL)
or Focused Ion Beam (FIB) milling followed by standard metal deposition and etching steps. Our group has recently developed a flexible process flow, as detailed below,
for the nanofabrication of arbitrary arrays of metal nanoparticles for nanoplasmonic
applications. In particular, we developed metallic nanoparticle arrays based on noble
metals, typically Au and Ag, on quartz substrates with a 10 nm layer Indium Tin
Oxide (ITO) to provide conduction. A 180-nm-thick layer of PMMA (PolyMethylMethAcrylate) is then spin coated on top of the cleaned substrate. Subsequently, the
DANS patterns are defined using a Zeiss SUPRA 40VP SEM equipped with a Raith
Beam Blanker and NPGS for nanopatterning.
After developing the resist in a 1:3 solution of MIBK (Methyl IsoButyle Ketone)
and IPA (Isopropanol), a ≥30 nm thick Au/Ag film is deposited on the patterned
surface by electron-beam evaporation. Finally, a liftoff process is performed using
acetone, resulting in the definition of the targeted metal nanoparticle arrays. Within
the same general process flow, nano-perforated metal/dielectric films can also be
obtained using a Reactive Ion Etching (RIE) step immediately after EBL writing.
The concept of our process flow for the fabrication of both metallic nanoparticle
arrays and nano-hole patterns is summarized in Fig. 9.11.