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Manzo, Michele
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Manzo, Michele
Official Name
Manzo, Michele
Research Output
Now showing 1 - 10 of 13
Publication
Photoreduction of SERS-active metallic nanostructures on chemically-patterned ferroelectric crystals
2012-08-28, Craig Carville, N., Manzo, Michele, Damm, Signe, Castiella, Marion, Collins, Liam, Denning, Denise, Weber, Stefan A. L., Gallo, Katia, Rice, James H., Rodriguez, Brian J.
Photodeposition of metallic nanostructures onto ferroelectric surfaces is typically based on patterning local surface reactivity via electric field poling. Here, we demonstrate metal deposition onto substrates which have been chemically patterned via proton exchange (i.e., without polarization reversal). The chemical patterning provides the ability to tailor the electrostatic fields near the surface of lithium niobate crystals and these engineered fields are used to fabricate metallic nanostructures. The effect of the proton exchange process on the piezoelectric and electrostatic properties of the surface is characterized using voltage modulated atomic force microscopy techniques, which combined with modeling of the electric fields at the surface of the crystal, reveal that the deposition occurs preferentially along the boundary between ferroelectric and proton exchanged regions. The metallic nanostructures have been further functionalized with a target probe molecule, 4-aminothiophenol, from which surface enhanced Raman scattering (SERS) signal is detected, demonstrating the suitability of chemically patterned ferroelectrics as SERS-active templates.
Publication
Photoreduction of metal nanostructures on periodically proton exchanged MgO-doped lithium niobate crystals
2013-10-30, Balobaid, Laila, Craig Carville, N., Manzo, Michele, Collins, Liam, Gallo, Katia, Rodriguez, Brian J.
Local reactivity on periodically proton exchanged lithium niobate (PPE:LN) surfaces is a promising route for the fabrication of regularly spaced nanostructures. Here, using MgO-doped PPE:LN templates, we investigate the influence of the doping on the nanostructure formation as a function of the proton exchange (PE) depth. The deposition is found to occur preferentially along the boundary between MgO-doped LN and the PE region when the PE depth is at least 1.73 μm, however, for
shallower depths, deposition occurs across the entire PE region. The results are found to be consistent with an increased photoconductivity of the MgO-doped LN.
Publication
Influence of annealing on the photodeposition of silver on periodically poled lithium niobate
2016-02-07, Carville, N. Craig, Neumayer, Sabine M., Manzo, Michele, Rodriguez, Brian J., et al.
The preferential deposition of metal nanoparticles onto periodically poled lithium niobate surfaces, whereby photogenerated electrons accumulate in accordance with local electric fields and reduce metal ions from solution, is known to depend on the intensity and wavelength of the illumination and the concentration of the solution used. Here, it is shown that for identical deposition conditions (wavelength, intensity, concentration), post-poling annealing for 10 h at 200°C modifies the surface reactivity through the reorientation of internal defect fields. Whereas silver nanoparticles deposit preferentially on the +z domains on unannealed crystals, the deposition occurs preferentially along 180° domain walls for annealed crystals. In neither case is the deposition selective; limited deposition occurs also on the unannealed –z domain surface and on both annealed domain surfaces. The observed behavior is attributed to a relaxation of the poling-induced defect frustration mediated by Li+ ion mobility during annealing, which affects the accumulation of electrons, thereby changing the surface reactivity. The evolution of the defect field with temperature is corroborated using Raman spectroscopy.
Publication
Interface modulated currents in periodically proton exchanged Mg doped lithium niobate
2016-03-21, Neumayer, Sabine M., Manzo, Michele, Kholkin, Andrei L., Gallo, Katia, Rodriguez, Brian J.
Conductivity in Mg doped lithium niobate (Mg:LN) plays a key role in the reduction of photorefraction and therefore doping is widely exploited in optical devices. However, charge transport through Mg:LN and across interfaces such as electrodes also yields potential electronic applications in devices with switchable conductivity states. Furthermore, the introduction of proton exchanged (PE) phases in Mg:LN enhances ionic conductivity thus providing tailorability of conduction mechanisms and functionality dependent on sample composition. To facilitate the construction and design of such multifunctional electronic devices based on periodically PE Mg:LN or similar ferroelectric semiconductors, fundamental understanding of charge transport in these materials, as well as the impact of internal and external interfaces is essential. In order to gain insight into polarization and interface dependent conductivity due to band bending, UV illumination, and chemical reactivity, multi composite wedge shaped samples consisting of polar orientated Mg:LN and PE phases, were investigated using conductive atomic force microscopy. In Mg:LN, three conductivity states (on/off/transient) were observed under UV illumination, controllable by the polarity of the sample and the externally applied electric field. Measurements of currents originating from electrochemical reactions at metal electrode - PE phase interfaces demonstrate a memresistive and rectifying capability of the PE phase. Furthermore, internal interfaces such as domain walls and Mg:LN - PE phase boundaries were found to play a major role in the accumulation of charge carriers due to the polarization gradients, which can lead to increased currents. The insight gained from these findings yield the potential for multifunctional applications such as switchable UV sensitive micro- and nanoelectronic devices and bistable memristors.
Publication
Plasmon Enhanced Raman From Ag Nanopatterns Made Using Periodically Poled Lithium Niobate and Periodically Proton Exchanged Template Methods
2012-09, Damm, Signe, Craig Carville, N., Rodriguez, Brian J., Manzo, Michele, Gallo, Katia, Rice, James H.
We study Ag nanopattern arrays formed using ferroelectric lithography based on two separate approaches, i.e., periodically poled lithium niobate (PPLN) and periodically proton exchanged (PPE) template methods. We demonstrate that such nanoarrays are plasmon active. Raman spectroscopy was applied to study molecular probe 4-aminothiophenol (4-ABT) absorbed onto a silver nanostructured array. The observed Raman spectra show peaks arising from b2 modes, which occur for plasmon enhanced Raman from 4-ABT in place of a1 modes, which occur in normal Raman scattering. We demonstrate that the PPLN and PPE substrates possess different plasmonic properties with PPE creating a stronger SERS signal relative to PPLN substrates.
Publication
Thickness, humidity, and polarization dependent ferroelectric switching and conductivity in Mg doped lithium niobate
2015-12-28, Neumayer, Sabine M., Strelcov, Evgheni, Manzo, Michele, Rodriguez, Brian J., et al.
Mg doped lithium niobate (Mg:LN) exhibits several advantages over undoped LN such as resistance to photorefraction, lower coercive fields, and p-type conductivity that is particularly pronounced at domain walls and opens up a range of applications, e.g., in domain wall electronics. Engineering of precise domain patterns necessitates well founded knowledge of switching kinetics, which can differ significantly from that of undoped LN. In this work, the role of humidity and sample composition in polarization reversal has been investigated under application of the same voltage waveform. Control over domain sizes has been achieved by varying the sample thickness and initial polarization as well as atmospheric conditions. In addition, local introduction of proton exchanged phases allows for inhibition of domain nucleation or destabilization, which can be utilized to modify domain patterns. Polarization dependent current flow, attributed to charged domain walls and band bending, demonstrates the rectifying ability of Mg:LN in combination with suitable metal electrodes that allow for further tailoring of conductivity.
Publication
Growth mechanism of photoreduced silver nanostructures on periodically proton exchanged lithium niobate: Time and concentration dependence
2013-05-08, Craig Carville, N., Manzo, Michele, Denning, Denise, Gallo, Katia, Rodriguez, Brian J.
Photodeposition of metallic nanostructures
onto ferroelectric surfaces, which have been chemically patterned using a
proton exchange process, has recently been demonstrated. By varying the
molar concentration of the AgNO3
solution and the illumination time, one can determine the initial
nucleation sites, control the rate of nucleation and the height of
silver nanostructures formed, and study the mechanisms by which these
processes occurs. The nanoparticles are found to deposit preferentially
in the boundary between ferroelectric and proton exchanged regions, in
an area proton exchanged via lateral diffusion under the masking layer
used for chemical patterning, consistent with our previous results.
Using a short illumination time (3 min), we are able to determine that
the initial nucleation of the silver nanostructure, having a width of
0.17±0.02µm and a height of
1.61±0.98nm, occurs near the edge of the reactive ion etched area
within this lateral diffusion region. Over longer illumination times (15
min), we find that the silver deposition has spread to a width of
1.29±0.06µm, extending across the entire lateral diffusion region. We report that at a high molar concentration of AgNO3 (10¯² M), the amount of silver deposition for 5 min UV illumination is greater (2.88±0.58nm) compared to that at low (10¯4M)
concentrations (0.78±0.35nm), however, this is not the case for
longer time periods. With increasing illumination time (15 min),
experiments at 10¯4 M had greater overall deposition, 6.90±1.52nm, compared to 4.50±0.76nm at 10 ¯² M. For longer exposure times (30min) at 10 ¯² M the nanostructure height is 4.72±0.59nm, suggesting a saturation
in the nanostructure height. The results are discussed in terms of the
electric double layer that forms at the crystal surface. There is an
order of magnitude difference between the Debye lengths for 10¯² and 10¯4 M solutions, i.e., 3.04 vs. 30.40nm, which suggests the Debye length plays a role in the availability of Ag+ ions at the surface.
Publication
Surface enhanced luminescence and Raman scattering from ferroelectrically defined Ag nanopatterned arrays
2013-08, Damm, Signe, Craig Carville, N., Manzo, Michele, Rodriguez, Brian J., Rice, James H., et al.
Ag nanopatterned arrays prepared using
periodically proton exchanged templates have been demonstrated to
support surface enhanced luminescence. Fluorescence lifetime imaging
reveals that luminescence intensity is greatest on Ag and that the
lifetime of the molecular probe is reduced, in line with a surface
enhanced luminescence mechanism. Studies establish that the substrate
simultaneously supports surface enhanced luminescence and Raman
scattering. Spatial dependence along the nanopatterned arrays shows
<7% variation in Raman scattering signal intensity, offering high
reproducibility for practical applications. Fluorophores emitting near
the plasmon absorption maxima are enhanced 4-fold.
Publication
Nanoscale characterization of β-phase HxLi1−xNbO3 layers by piezoresponse force microscopy
2014, Manzo, Michele, Denning, Denise, Rodriguez, Brian J., Gallo, Katia
We investigate a non-destructive approach for the characterization of proton exchanged layers in LiNbO3 with sub-micrometric resolution by means of piezoresponse force microscopy (PFM). Through systematic analyses, we identify a clear correlation between optical measurements on the extraordinary refractive index and PFM measurements on the piezoelectric d 33 coefficient. Furthermore, we quantify the reduction of the latter induced by proton exchange as 83 ± 2% and 68 ± 3% of the LiNbO3 value, for undoped and 5 mol. % MgO-doped substrates, respectively.
Publication
Direct shape control of photoreduced nanostructures on proton exchanged ferroelectric templates
2013-01-31, Balobaid, Laila, Craig Carville, N., Manzo, Michele, Gallo, Katia, Rodriguez, Brian J.
Photoreduction on a periodically proton exchanged ferroelectric crystal leads to the formation of periodic metallic nanostructures on the surface. By varying the depth of the proton exchange (PE) from 0.59 to 3.10 µm in congruent lithium niobate crystals, the width of the lateral diffusion region formed by protons diffusing under the mask layer, can be controlled. The resulting deposition occurs in the PE region with the shallowest PE depth, and preferentially in the lateral diffusion region for greater PE depths. PE depth-control provides a route for the fabrication of complex metallic nanostructures with controlled dimensions on chemically patterned ferroelectric templates.