Biomedical Engineering Reference
In-Depth Information
(a)
(b)
ф - Rotation
α - Rotation
Incident vapor
α
Substrate
Normal
Growing
nanostructures
Shadowed
region
QCM
vapor
flux
PVD
Source
Substrate
(c)
Vapor direction
2 µm
FIGURE 5.3
Schematic.of.oblique.angle.deposition.(OAD).or.glancing.angle.deposition.(GLAD)..(a).Typical.GLAD.apparatus.
that.consists.of.a.rotation.stage.with.substrate.angle.adjustment..(©.2007.Springer..Used.with.permission.).(b).
Conceptual. illustration. of. column. growth.. (c). Example. of. shadowing. effect. with. lithographically. patterned.
substrate.(unpublished).
growth.atoms.condense.and.form.nuclei,.resulting.in.geometrical.shadowing.of.regions.
of.the.substrate.that.prevents.ilm.growth.in.those.regions..The.resulting.ilm.consists.of.
columns. that. grow. off. the. nuclei. and. are. inclined. in. the. direction. of. the. vapor. source..
Therefore,.the.porosity.of.the.ilm.can.be.controlled.by.simply.changing.the.incident.angle..
Since. the. growth. process. uses. thermal. or. e-beam. evaporation,. various. materials. can. be.
used.for.GLAD,.including.materials.metals,.metal.oxides,.silicon,.silicon.oxides,.and.even.
their.combination.
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.The.glancing.angle.deposition.(GLAD).is.a.combination.of.OAD.and.
carefully.controlled.substrate.motion.(Figure.5.3a).to.fabricate.a.wide.variety.of.nanostruc-
ture. morphologies,. ranging. from. simple. nanostructures. like. close-packed. nanospheres.
and.tilt.nanowires.to.more.complex.ones.such.as.chevron.and.helical.posts
77c
.and.nano-
tubes. (Figure. 5.4a).
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. GLAD. can. also. be. combined. with. various. lithography. techniques,.
including. EBL,
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. NSL,
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. and. conventional. photolithography,
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. to. grow. highly. ordered.
nanostructure.arrays.on.a.large.scale,.as.shown.in.Figure.5.4b..GLAD.techniques.can.also.
be.used.to.fabricate.heteronanostructures,.including.gold-coated.silicon.“matchsticks”.for.
biosensing. applications
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. and. gold-titanium. dioxide-gold. sandwich. structures. for. LSPR.
substrates.
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