Show all abstracts
View Session
- Front Matter: Volume 7041
- Structure and Growth I
- Structure and Growth II
- Plasmonics and Nanostructure I
- Plasmonics and Nanostructure II
- Switchable and Active Films
- Oxide and Semiconductor Films
- Complex Mediums
- Poster Session
Front Matter: Volume 7041
Front Matter: Volume 7041
Show abstract
This PDF file contains the front matter associated with SPIE Proceedings Volume 7041, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.
Structure and Growth I
AFM of self-organised nanoparticle arrays: frequency modulation, amplitude modulation, and force spectroscopy
Adam Sweetman,
Peter Sharp,
Andrew Stannard,
et al.
Show abstract
Frequency modulation (FM) and amplitude modulation (AM) atomic force microscopy have been used to image
self-organised assemblies of octanethiol-passivated Au nanoparticles adsorbed on SiO2/Si(111) samples (where
the oxide is either 200 nm or ~ 2 nm thick). Imaging at negative frequency shifts - i.e. in the attractive force
regime - in FM mode in ultrahigh vacuum we measure nanoparticle heights which are over 50 % larger than
those measured using conventional ("repulsive mode") tapping mode imaging in air. A similar difference in
nanoparticle height is observed for attractive mode imaging in air. For nanoparticles adsorbed on 200 nm thick
oxide layers, force-distance (F(z)) spectra (measured in FM mode) comprise both a van der Waals component
with the conventional power law (1/z2) dependence and a strong electrostatic force which is best fitted using a
logarithmic function of the form ln(1/z).
Stochastic continuum modeling self-assembled epitaxial quantum dot formation
Show abstract
Semiconductor epitaxial self-assembled quantum dots (SAQDs) have potential for electronic and optoelectronic applications
such as high density logic, quantum computing architectures, laser diodes, and other optoelectronic devices. SAQDs
form during heteroepitaxy of lattice-mismatched films where surface diffusion is driven by an interplay of strain energy and
surface energy. Common systems are GexSi1-x/Si and InxGa1-xAs/GaAs. SAQDs are typically grown on a (001) crystal
surface. Self-assembled nanostructures form due to both random and deterministic effects. As a consequence, order and
controllability of SAQD formation is a technological challenge. Theoretical and numerical models of SAQD formation
can contribute both fundamental understanding and become quantitative design tools for improved SAQD fabrication if
they can accurately capture the competition between deterministic and random effects. In this research, a stochastic model
of SAQD formation is presented. This model adapts previous surface diffusion models to include thermal fluctuations in
surface diffusion, randomness in material deposition and the effects of anisotropic elasticity, anisotropic surface energy
and anisotropic diffusion, all of which are needed to model average SAQD morphology and order. This model is applied
to Ge/Si SAQDs which are group IV semiconductor dots and InAs/GaAs SAQDs which are III-V semiconductor dots.
Structure and Growth II
Shadowing growth of biaxially textured nanostructured films
Show abstract
Microstructure of a nanostructured film is not only of fundamental scientific interest but also an important
subject from the practical point of view. In this paper we will discuss the formation of biaxially textured film
under extreme shadowing during growth. Biaxially textured films are not single crystals, but they possess
both the out-of-plane and in-plane preferred orientations. We will also discuss our newly developed reflection
high-energy electron diffraction (RHEED) surface pole figure technique and how we employ this technique to
capture the evolution of growth front texture.
Reinforced membrane based on crosslink reaction between water soluble sulfonated carbon nanotubes and sulfonated polystyrene
Show abstract
Reinforced films based on sulfonated polystyrene cross-linked with water-soluble sulfonated carbon nanotubes were fabricated using a free-standing film-making method. Transmission and scanning
electron microscopy, X-ray photoelectron spectroscopy, and thermo-gravimetric analysis were used to verify the cross-linking reaction. The mechanical properties of these films demonstrated that the tensile
strength increases with an increase in the sulfonated nanotube concentration. At 5 wt% nanotube loading, the tensile strength increased 84% compared with polymer containing no nanotube loading. The relationships between structure and mechanical properties are discussed and a possible direction for making ultra thin and ultra lightweight film is proposed
Multilayer alumina and titania optical coatings prepared by atomic layer deposition
Show abstract
The microstructure and optical properties of alumina and titania multilayer coatings prepared using atomic layer deposition (ALD) has been investigated. The titania layers were prepared using TiCl4+H2O as the precursors while two different precursors, Al(CH3)3+H2O and AlCl3+H2O, were used to deposit the alumina layers. The results show that ALD can be used to produce amorphous, stoichiometric alumina and titania thin films with uniform thicknesses at low temperatures (120 °C). An antireflective coating design based on 4 alternating layers of titania and alumina was prepared and the resulting reflectance compared to theoretical calculations. The results demonstrate that ALD is a suitable technique for the deposition of optical thin films at temperatures compatible with thermally sensitive substrates.
Plasmonics and Nanostructure I
Sensitivity enhancement of guided wave surface plasmon resonance sensors using top nano dielectric layer
Show abstract
Surface plasmon resonance (SPR) and guided wave SPR (GWSPR) are widely used in sensing. Efforts to improve the
sensitivity and stability of these sensors are done by using different multilayer nanostructures such as with the long
range SPR and the use of combinations of materials such as gold and silver. Silver based SPR sensors have high
sensitivity but a poor stability because of the interactions with water and air. We have shown both theoretically and
experimentally that by using the silver based SPR sensor with a 10-15 nm top layer of dielectric film with a high value
of the real part ε' of the dielectric function, it is possible to improve the sensitivity of the sensor by few times. The
imaginary part ε'' of the top nano layer's permittivity needs to be small enough in order to reduce the losses and get
sharper dips. The stability of the sensor is also improved because the nano layer is protecting the silver from
interacting with the environment. The calculated evanescent field is enhanced near the top layer - analyte interface,
thus the enhancement is due to this and due to an increase of the interaction length as a waveguiding effect.
Tailoring coupling of light to local plasmons by using Ag nanorods/dielectric layer/mirror sandwich structures
Show abstract
The optical properties of the sandwich structures of Ag nanorod array (NRA)/dielectric layer/Ag mirror have
been investigated theoretically and experimentally. Calculations based on a simple model by treating the NRAs
as uniform effective media indicate that the antireflection condition is realized by changing the thickness of
the dielectric layer and that the Ag nanorods absorb most of the incident light. The designed structures have
been successfully fabricated by taking advantages of the dynamic oblique-angle deposition technique. Under the
experimental antireflection condition, Raman scattering measured on the Ag NRA in the near infrared region
exhibits significant enhancement. This indicates that the local electric field close to the Ag nanorods can be
controlled by the interference of light in the nanostrutured sandwiches.
Porosity effect on surface plasmon resonance from metallic sculptured thin films
Show abstract
When a sculptured thin film (STF), made of a metal and ≤ 50 nm thick, is used in lieu of a dense layer
of metal in the Kretschmann configuration, experimental data for a STF comprising parallel tilted nanowires
shows that a surface plasmon resonance (SPR) can still be excited. As the porosity of the chosen STF increases,
experimental data and numerical simulations indicate the SPR dip with respect to the angle of incidence of the
exciting plane wave widens and eventually disappears, leaving behind a a vestigial peak near the onset to the
total-internal-reflection regime.
Applications of nanostructured porous silicon in the field of optical sensing
Show abstract
Photonic crystals of finite thickness based on porous silicon were designed aiming at their subsequent use in the field of
optical chemical- and bio-sensing. These structures consist in nanometric porous silicon rods arranged as to form a
triangular lattice embedded into a silicon slab, resulting in dielectric structures that have two-dimensional periodicity and
the use of index guiding to confine light in the third dimension. These structures enable the fabrication of photonic
crystals in thin dielectric slab systems. The photonic band structure for the odd and even modes was calculated as a
function of the thickness of the slab, finding a significant dependence on this parameter. The existence of a photonic
band gap for even modes was verified and its size was maximized. In addition, the component of electric and magnetic
field distribution perpendicular to the two-dimensional plane for the lowest-order even guided mode was analyzed.
Plasmonics and Nanostructure II
Review of surface-wave propagation at the planar interface of a columnar or chiral sculptured thin film and an isotropic substrate
Show abstract
Electromagnetic surface waves are known to propagate along metal-dielectric interfaces (surface plasmon-polaritons) as well as along dielectric-dielectric interfaces (Dyakonov waves) if the two dielectrics have different
spatial symmetries. Columnar and sculptured thin films, which are optically biaxial nanomaterials, may be
grown on either metallic or dielectric substrates. Both surface plasmon-polaritons and Dyakonov waves can
exist at the interface of a thin film and an appropriate substrate. The direction of propagation relative to the
thin-film morphology is, in general, limited, and depends on the material and the vapor deposition angle used
during fabrication. At the interface of a chiral sculptured thin film and an isotropic dielectric substrate, surface-wave propagation occurs over a much wider angular range and may allow for the first experimental observation
of a Dyakonov wave. The characteristic properties of the surface wave, such as phase speed and decay rate,
are dependant on the direction of propagation and the vapor deposition angle. As engineered nanomaterials,
thin films offer a controllable medium for surface-wave propagation which may be tailored to exhibit specific
characteristics. The porosity of the thin films may also offer certain technological advantages.
Excitation of surface plasmon polaritons at the interface of a metal and a sculptured nematic thin film
Show abstract
A sculptured nematic thin film (SNTF) is an assembly of parallel nanowires that bend in a fixed plane orthogonal
to the substrate on which the film is deposited. The absorbances, reflectances, and transmittances of linearly
polarized, obliquely incident light were calculated for a planar SNTF-metal interface in the Kretschmann configuration. Empirical data on aluminum for the metal and titanium-oxide SNTFs were used for the calculations.
The solution of the boundary-value problem for the Kretschmann configuration revealed that more than one
surface-plasmon-polariton (SPP) waves can be excited at the planar interface of a thin metal film and an SNTF.
Comparative study of enhanced fluorescence from nano sculptured thin films
Show abstract
When an electromagnetic wave interacts with a nano structured metallic surface or a nanoparticle, the electromagnetic
fields near the surface are greatly enhanced by factors up to 1000. This phenomenon is due to two processes: (i) the
'lightning rod' effect, conventionally described as the crowding of the electric field lines at a sharp metallic tip and (ii)
the excitation of localized surface plasmons at the metal surface. Both are responsible for the enhancement of
fluorescence, second-harmonic generation and Raman scattering. For metal nanoparticles often both processes are
involved in creating the localized enhanced near field. Since sculptured thin films (STFs) can have a rod like structure
and an overall large porosity, it is expected that these structures will exhibit enhanced fluorescence and Raman signals.
Results of comparative study of surface enhanced fluorescence are presented from STFs containing metal nano
structures. The highest enhancement is found for Ag based STFs giving an enhancement factor of x14.
Metal nanowhiskers synthesized by high-temperature glancing angle deposition
Show abstract
We have demonstrated high-temperature glancing angle deposition (HT-GLAD) of Al on a heated substrate with
trench patterns. The nanowhiskers grow not only on the illuminated sidewall but also on the shadowed sidewalls,
while few nanowhiskers grow on the shadowed region at the bottom of the trenches. In addition, the size and
number of nanowhiskers growing on the sidewall depend strongly on the angle between the incident direction of
the vapor flux and the trench directions, although actual angle of inicidence of the vapor flux on the sidewall
is kept constant. In order to understand the peculiar growth of Al nanowhiskers, novel transport processes of
Al atoms other than surface diffusion need to be elucidated. The reflective scattering on the sidewalls of the
trenches is likely to play an important role in the growth of nanowhiskers. On the other hand, we demonstrate
the HT-GLAD of metals other than Al. It has been found that nanowhiskers of Cu, Ag, Au, Mn, Fe, Co, Ni
and Zn as well as Al grow on the substrates of SiO2. The robustness in the selection of materials suggests that
HT-GLAD is a general method for growing metal nanowhiskers. However, since growth mode of nanowhisker is complicated, further detailed investigation is required for fully understanding of the growth mechanisms of the nanowhiskers by HT-GLAD.
Switchable and Active Films
Frequency and percolation dependence of the observed phase transition in nanostructured and doped VO2 thin films
Show abstract
The response to applied electric fields of vanadium dioxide thin films above and below the phase transition is shown
experimentally to depend on the size of grains if below ~200nm across, and on aluminum doping above a critical
concentration. Tc drops as doping level increases, but does not depend on grain size. The observed phase transition
undergoes a remarkable qualitative shift as the applied field goes from optical to low frequencies. The expected insulator
to metal transition is found at optical frequencies, but at low frequencies an insulator-to-insulator transition occurs.
Optical switching at both T < Tc and T > Tc is nearly independent of doping level and grain size. In contrast dc properties
in both phases are quite sensitive to both factors. The band gaps predicted by optical and dc data differ, and densities of
states change with doping level. Lattice or electron dynamics alone cannot yield such behaviour, but it can arise if there
is a transient phase change. The way doping and grain size can support such a phase is discussed. Only individual
nanograins need to switch phases coherently to explain data, not the whole sample. Resistance as a function of
composition across the transition was derived using effective medium compositional analysis of optical data at
temperatures in the hysteresis zone. Expected percolation behaviour does not arise in such an analysis, with the observed
thresholds different when heating and cooling, and they occur at temperatures which differ from the usual Tc values.
All-optical switching based on optical control of energy transfer between thin-film layers
Show abstract
The migration of electronic excitation energy between individual particles is a well-studied phenomenon. The ability to
exert optical control over this transfer of energy is the subject of much recent research, and it forms the basis for a
potential all-optical switching device. In detail, near-field energy transfer from an excited donor nanoparticle (following
previous light absorption) to an acceptor particle can, under suitable conditions, be activated or deactivated by the input
of a non-resonant laser beam, i.e. optical switching action occurs. It is envisaged that an all-optical device utilizing the
described mechanism will involve nanoparticles contained within thin-film deposits on a pair of parallel substrates.
Nanolithography is the technique offering the best prospects for the deposition and tailoring of nanoparticles within each
optically active layer. This paper gives a theoretical analysis of the non-linear response mechanism, termed optically
controlled resonance energy transfer (OCRET). The concept of transfer fidelity, signifying the accuracy of mapping
input to designated output, is introduced and its key determinants are identified. Analysis shows that, at reasonable
levels of laser intensity, cross-talk to unsought destinations can be effectively extinguished. The advantage of
constructing these donor and acceptor thin-film layers around an ultra-thin spacer material (which is suitably transparent)
is discussed, and potential applications beyond simple switching are outlined, including logic gates and optical buffers.
Oxide and Semiconductor Films
Ultraviolet optical functions of ZnO and Ga2O3 thin films
Show abstract
Oxide semiconductors are essentially stable and environmental-friendly materials as well as possessing unique
multifunctional properties in conjunction with ultraviolet (UV) to deep UV (DUV) optical functions. Among them
ZnO and Ga2O3, having the bandgaps of about 3.3 and 4.9eV, respectively, are the promising candidates for exploring
their UV applications. This paper reports recent advances of ZnO and Ga2O3 semiconductors focusing on their UV to
DUV optical functions and device applications. Since ZnO has reached to the actual application stage and future
development of the growth with chemical vapor deposition (CVD) is now strongly requested for mass production, here
we introduce a novel CVD growth technique, that is, ultrasonic spray assisted CVD, allowing safe and low-cost growth
of high quality ZnO-based films. Homoepitaxy on ZnO substrates resulted in step-flow growth, which has hardly been
achieved by metalorganic CVD. Ga2O3 is expected for its DUV functions being supported by the availability of Ga2O3
bulk substrates. We show the potential applications of Ga2O3 substrates for highly sensitive DUV photodetectors as
well as homoepitaxial step-flow growth of Ga2O3 thin films by molecular beam epitaxy.
Reconfigurable photonic crystal filters for multi-band optical filtering on a monolithic substrate
Show abstract
Many applications require the ability to image a scene in several different narrow spectral bands simultaneously.
Absorption filters commonly used to generate RGB color filters do not have the flexibility and narrow band filtering
ability. Conventional multi-layer dielectric filters require control of film thickness to change the resonant wavelength.
This makes it difficult to fabricate a mosaic of multiple narrow spectral band transmission filters monolithically. This
paper extends the previous work in adjusting spectral transmission of a multi-layer dielectric filter by drilling a periodic
array of subwavelength holes through the stack. Multi-band photonic crystal filters were modeled and optimized for a
specific case of filtering six optical bands on a single substrate. Numerical simulations showed that there exists a
particular air hole periodicity which maximizes the minimum hole diameter. Specifically for a stack of SiO2 and Si3N4 with the set of filtered wavelengths (nm): 560, 576, 600, 630, 650, and 660, the optimal hole periodicity was 282 nm. This resulted in a minimum hole diameter of 90 nm and a maximum diameter of 226 nm. Realistic fabrication tolerances
were considered such as dielectric layer thickness and refractive index fluctuations, as well as vertical air hole taper. It
was found that individual layer fluctuations have a minor impact on filter performance, whereas hole taper produces a
large peak shift. The results in this paper provide a reproducible methodology for similar multi-band monolithic filters in
either the optical or infrared regimes.
Complex Mediums
Effective properties of membrane photonic crystals
Show abstract
Wave propagation in thin nanostructured films in the low frequency regime is studied. By means of a two-scale
analysis, it is shown that the medium can be homogenized, i.e. described by effective electromagnetic parameters.
The effective permeability and permittivity are obtained by solving a set of partial differential equations. A
numerical aproach based on the Fourier Modal Method is proposed in order to solve these equations.
Circular polarization emission from an external cavity diode laser
Show abstract
We construct an external cavity diode laser (ECDL) comprising structurally left-handed chiral sculptured-thin-film
(STF) mirrors for pure circular-polarized (CP) emission, and observed single mode, left-handed CP lasing performance.
The extinction ratio of CP output was found to increase rapidly near the threshold of the injection-current for the laser
diodes.
Review of the role of dielectric anisotropy in Dyakonov surface-wave propagation
Show abstract
Surface waves (SWs) are localized waves that travel along the planar interface between two different mediums
when certain dispersion relations are satisfied. If both mediums have purely dielectric constitutive properties,
the characteristics of SW propagation are determined by the anisotropy of both mediums. Surface waves are then
called Dyakonov SWs (DSWs), after Dyakonov who theoretically established the possibility of SW propagation
at the planar interface of an isotropic dielectric and a positive uniaxial dielectric. Since then, DSW propagation
guided by interfaces between a variety of dielectrics has been studied. With an isotropic dielectric on one
side, the dielectric on the other side of the interface can be not only positive uniaxial but also biaxial. DSW
propagation can also occur along an interface between two uniaxial or biaxial dielectrics that are twisted about
a common axis with respect to each other but are otherwise identical.
Recently, DSW propagation has been studied taking (i) uniaxial dielectrics such as calomel and dioptase
crystals; (ii) biaxial dielectrics such as hemimorphite, crocoite, tellurite, witherite, and cerussite; and (iii)
electro-optic materials such as potassium niobate. With materials that are significantly anisotropic, the angular
regime of directions for DSW propagation turns out to be narrow. In the case of naturally occurring crystals,
one has to accept the narrow angular existence domain (AED). However, exploiting the Pockels effect not only
facilitates dynamic electrical control of DSW propagation, but also widens the AED for DSW propagation.
Photoconductivity on nanocrystalline ZnO/TiO2 thin films obtained by sol-gel
Show abstract
In this paper we report results on the synthesis, characterization and photoconductivity behaviour of amorphous
and nanocrystalline ZnO/TiO2 thin films. They were produced by the sol-gel process at room temperature by using the
spin-coating method and deposited on glass substrates. The ZnO/TiO2 films were synthesized by using tetrabutyl
orthotitanate and zinc nitrate hexahydrate as the inorganic precursors. The samples were sintered at 520°C for 1 hour.
The obtained films were characterized by X-ray diffraction (XRD), optical absorption (OA), infrared spectroscopy (IR)
and scanning electronic microscopy (SEM) studies. Photoconductivity studies were performed on amorphous and
nanocrystalline (anatase phase) films to determine the charge transport parameters. The experimental data were fitted
with straight lines at darkness and under illumination at 310 nm, 439 nm and 633 nm. This indicates an ohmic behavior.
The Φμτ and Φl0 parameters were fitted by least-squares with straight lines (nanocrystalline films) and polynomial fits (amorphous films).
Poster Session
Blue photoluminescence of PECVD SiC-based films
Show abstract
Amorphous and nanocrystalline SiC films enriched by oxygen were deposited by a PECVD technique using
methyltrichlorosilane as a gas-precursor at substrate temperature in the range of 200-350 °C. X-ray diffraction (XRD) of
the film deposited at 350°C exhibited the presence of SiC nano-crystallites. In this film the bright blue
photoluminescence (PL) with spectrum that has a double-peak structure at 415 and 437 nm was obsearved at room
temperature. The film was annealed at 650 and 850 °C in vacuum. Annealing at 650 °C strongly enhanced blue-white
photoemission with maximum intensity around 470 cm-1. Moderate annealing was found to lead to strengthening the C-H,
C-C and Si-C bonds as well as to increasing of a size of SiC grains embedded in the amorphous Si:C:O:H matrix. A
further increase of annealing temperature up to 850 °C caused a drop of PL.
Basing on an analysis of experimental data and first principles simulations of several hydrogenated SiC and Si
nanoclusters, we suggest that the blue PL in as-deposited nc-SiC:H film and related Si-based nanostructures can be
assigned to the radiative recombination in a radiative center (RC) located at the nanocrystallite surface, whereas the
excitation of electron-hole pares occurs in nanocrystallite cores. It follows from our calculations that O-O structural
groups can be considered as a radiative recombination centers. The recombination at band tails of the amorphous Si:C:O:H tissue (or at the oxygen-related defect states in a-SiOx, in the case of Si nanostructures) gives rise to a shoulder around 470 nm.
Nano-structured surface plasmon resonance sensor for sensitivity enhancement
Jae-Ho Kim,
Hyo-Sop Kim,
Jin-Ho Kim,
et al.
Show abstract
A new nano-structured SPR sensor was devised to improve its sensitivity. Nano-scaled silica particles were used as the
template to fabricate nano-structure. The surface of the silica particles was modified with thiol group and a single layer
of the modified silica particles was attached on the gold or silver thin film using Langmuir-Blodgett (LB) method.
Thereafter, gold or silver was coated on the template by an e-beam evaporator. Finally, the nano-structured surface with
basin-like shape was obtained after removing the silica particles by sonication. Applying the new developed SPR sensor
to a model food of alcoholic beverage, the sensitivities for the gold and silver nano-structured sensors, respectively, had
95% and 126% higher than the conventional one.
Different sensing layers for SPR sensing of organic vapours
Show abstract
In this work we present a theoretical and experimental work due to develop a performing configuration for gas-sensing
through the employ of Surface Plasmon Resonance effect.
Different sensing layers have been studied and tested on our optical bench assembly. Metallic (Au) and bimetallic
(Ag/Au) layers have been properly designed through simulations and then have been realized through electron-beam
evaporation. TiO2 and TiO2 - Au doped layers have been deposited on the top of some of the metallic samples. These
layers were prepared by the sol gel route. This kind of material is expected to be suitable as a gas sensor for its
nanosized structure and its stability.
The optical bench configuration for the experimental exploitation of SPR is presented. It is based on a collimated beam, a
rotational stage with a triangular prism and a single photodiode.
Finally the sensing properties of the different sensing layers prepared was tested to some organic vapours. Preliminary
results are presented.
Optical properties of silver nanorod arrays prepared by oblique angle deposition
Show abstract
In this work, we use oblique incident deposition technique to fabricate silver nanorod arrays (NRA). It is found that the
orientation of nanorod growth does not obey the traditional tangent rule (empirical relation between the deposition angle
and column growth angle). The maximum Ag nanorods tilt angle with respect to the substrate normal can reach to 76
deg. The Ag nanorods almost lie on the substrate and the array behaves as a polarizer. The transmittance versus the
polarization direction of normal incident ray is presented in this paper. For a Ag nanorod array with thickness 220 nm
and nanorod tilt angle 76 deg, the extinction ratio at wavelength 632.8 nm becomes 0.12 that is better than previous
work. The extinction ratio of the polarizer would be further reduced to be less than 0.05 by arranging an isotropic Ag
film between the Ag nanorod array and the substrate. On the other hand, it is interesting to show that Ag nanorod array is
isotropic for normal incident ray with any polarization direction at a certain critical wavelength λc. In the wavelength
range λ>λc, the maximum absorption occurs when the polarization is TM mode (electric field direction parallel to the
deposition plane). In the wavelength range λ<λc, the maximum absorption occurs when the polarization is TE mode
(electric field direction perpendicular to the deposition plane). The critical wavelengths for Ag nanorod arrays fabricated
by different deposition angles are measured and analyzed in this paper.
Large area assembled periodic nanoarrays by block copolymer templating and glancing angle deposition
Show abstract
The use of self-assembled block copolymer structures to direct the formation of large area nanoscale features could
provide a silicon-based fabrication-compatible means to supplement conventional lithographic techniques. Here, self-assembled
monolayers of polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer were utilized as
structural elements for the production of pseudo-hexagonal close packed metallic nanoarrays. Metal ion loading of the
P2VP block with simple aqueous solutions of anionic metal complexes is accomplished via protonation of this basic
block, rendering it cationic; electrostatic attraction leads to a high local concentration of metal complexes within the
protonated P2VP domain. The ordering of the copolymer micelles can be enhanced by solvent vapor annealing. The
resulting templated large area metallic nanoclusters can serve as periodic seeds to grow nanofibrous thin films, which
inherit the periodicity of the underlying seeds, by glancing angle deposition (GLAD). GLAD offers a high level of
control over the composition and porosity of thin films microstructures, and has been used to make uniform and highly
porous thin film architectures for applications such as photonic crystals.
Analysis of silver columnar thin films by atomic force microscopy
Show abstract
Analyses of the top-surface morphology of columnar thin films (CTFs) of silver, grown by a
combination of the usual oblique-angle-deposition technique with very fast substrate rotation,
confirm that silver CTFs consist of more isolated and quasiperiodically distributed nanowires
for higher vapor incidence angle during deposition. The top surfaces then are well-suited for
the exploitation of surface-enhanced Raman scattering and localized surface-plasmon
resonance.
Effect of alloy addition and growth conditions on the formation of Mg-based bioabsorbable thin films
Show abstract
Magnesium is an essential mineral in the human body and has recently been studied as a bioabsorbable material for use
in cardiac stents. New areas of application can be found in bone plates, bone screws, and orthopedic implants.
Magnesium alone has a corrosion rate much too high for use in such applications and has been alloyed with various
elements to improve corrosion resistance. The use of vapor deposition to create Mg alloys for the above applications has
not been attempted although certain properties of non-equilibrium alloys, namely corrosion resistance, can be improved.
Using vapor deposition the characterization of the growth of magnesium alloy thin films has been done utilizing various
alloying elements, substrate temperatures, post-deposition treatments, and substrate positions. The results point towards
a growth mode controlled by crystallization of the Mg. Mg Sculptured thin films (STFs) are used to demonstrate these
effects and potential solutions while also providing a route to control nanoscale surface morphology to enhance cell
growth, cell attachment, and absorption properties. The results of the study are presented in terms of x-ray diffraction
data, microscopy analysis of growth evolution, and corrosion testing. This magnesium alloy research utilizes a dual
source deposition method that has also provided insight about some of the growth modes of other alloy STFs.
Engineering of surface morphology using dip coatings and etching has been used in biomedical materials to enhance
certain application specific surface properties. STF technology potentially provides a path to merge the advantages of
non-equilibrium alloy formation and engineering nanoscale surface morphology.