Laboratory for Nanofabrication of Nanodevices

Padova, Italy

Laboratory for Nanofabrication of Nanodevices

Padova, Italy
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Brigo L.,University of Padua | Grenci G.,CNR Institute of Materials | Ba L.,University of Padua | Carpentiero A.,CNR Institute of Materials | And 7 more authors.
Microelectronic Engineering | Year: 2011

Natively porous hybrid organic-inorganic sol-gel systems have been engineered to be used as functional positive photoresists, aimed to the realization of microsensors in a single-step process. Interesting results have been obtained combing three main sol-gel system features: the direct patternability through X-ray lithography, being processable without the addition of a photocatalyst; the functionalizability, properly designing the organic component of the hybrid network or incorporating active species; the open micro or mesoporosity, tailored by the synthesis process and precursor choice. The photoprocessable porous films have been synthesized starting from a Bridged Polysilsesquioxane (BPS) precursor, 1,4-bis(triethoxysilyl)benzene. The correlation between chemical properties of the sol-gel material and its patternability is described in detail. X-ray exposure leads to a progressive alkyl and aromatic compound elimination and promotes inorganic condensation in the system, allowing the selective dissolution of irradiated cross-linked films in suitable etchants. Patterns of final resolution lower than 100 nm have been realized on BPS-based films synthesized in acid conditions, a procedure that allows to take advantage of a straightforward embedding protocol for active species in the sol-gel matrix. The BPS-based system has been doped with a covalently linked quinolinium dye, obtaining thin sensing films patternable by X-ray lithography. A feasibility test for the fabrication of optical microdevices, where fluorescence properties are obtained directly on the patterned coatings, has been provided. © 2011 Elsevier B.V. All rights reserved.

Giorgis V.,CNR Institute of Materials | Zilio P.,University of Padua | Ruffato G.,University of Padua | Massari M.,Laboratory for Nanofabrication of Nanodevices | And 4 more authors.
Optics Express | Year: 2014

We investigate in detail the optical response of dense split ring resonator (SRR) arrays as a function of their thickness, for normally impinging light in the VIS-NIR spectral range. We find that, for sufficiently tall SRRs, several vertical Fabry-Perot resonances can be excited, which may interact with the well-known horizontal SRR resonant paths. Furthermore, we analyze the possibility to exploit these nanostructures to detect bio-chemical quantities. In particular, we find that the coexistence of vertical and horizontal resonances yields an increased sensitivity. Well ordered, large arrays of thick SRRs are obtained by exploiting a fabrication process based on X-Ray Lithography. A very good agreement is found between numerical and measured transmittances. A preliminary detection test evidences the potential of this geometry as a sensing platform. ©2014 Optical Society of America

Gazzola E.,University of Padua | Gazzola E.,Laboratory for Nanofabrication of Nanodevices | Brigo L.,University of Padua | Zacco G.,Laboratory for Nanofabrication of Nanodevices | And 7 more authors.
Plasmonics | Year: 2014

Plasmonic nanostructures exhibit a variety of surface plasmon polariton (SPP) modes, with different characteristic properties. While a single metal dielectric interface supports a single-interface SPP mode, a thin metal film can support extended long range SPPs and strongly confined short range SPPs. When the coupling between the incident light and the SPP is provided through a diffraction grating, it is possible to azimuthally rotate the grating with respect to the scattering plane, introducing the possibility to propagate the SPP along an arbitrary direction. We present a theoretical and experimental analysis of the coupling conditions for long range and short range SPPs under this configuration. We also investigate the propagation length of the modes depending on the propagation direction with respect to the grating grooves, showing in particular that the long range SPP propagation length can be sensibly enhanced with respect to the null-azimuth case. © 2013 Springer Science+Business Media New York.

Mari E.,University of Padua | Anzolin G.,ICFO - Institute of Photonic Sciences | Tamburini F.,University of Padua | Prasciolu M.,CNR Institute of Neuroscience | And 6 more authors.
Optics Express | Year: 2010

In this paper we present the fabrication process and tests of two different types of l = 2 spiral phase plates (SPPs), designed for an Optical Vortex Coronagraph (OVC) in the visible wavelength regime. Each phase mask is realized dividing the spirals area in sectors respectively of 8 and 512 of levels using lithographic nanofabrication approach. The SPPs produces different optical vortices (OVs) with topological charge l that depends on the number of steps and on the wavelength. We found that the residual light in the central dark region of the OV tends to zero as the number of steps increases. © 2010 Optical Society of America.

Brigo L.,University of Padua | Pistore A.,University of Padua | Grenci G.,CNR Institute of Neuroscience | Carpentiero A.,CNR Institute of Neuroscience | And 4 more authors.
Microelectronic Engineering | Year: 2010

The direct nanopatterning of a novel hybrid organic-inorganic sol-gel film based on bridged polysilsesquioxanes (BPS) using X-ray synchrotron radiation is reported. The main advantages of a direct fabrication technique with respect to conventional photolithography are represented by the possibility to bypass some typical post-exposure lithographic steps and to avoid the use of a sacrificial layer. The distinctive features rendering hybrid BPS-based material innovative for photolithographic applications are: the patternability as resist, the positive tone behaviour exhibited under X-ray irradiation, the porous structure demonstrated at low temperature, and the possibility to widely tailor material electro-optical and structural properties to experimental needs. A systematic investigation of the interactions between sol-gel BPS films based on the bis(triethoxysilyl)benzene precursor and soft X-rays is conducted. Under X-ray exposure, BPS-based films suffer structural changes attributed to the organic bridge breaking, and become soluble in suitable acidic aqueous solutions, producing final lithographies of sub-micron resolution, high contrast and good edge definition. © 2009 Elsevier B.V. All rights reserved.

Lee K.H.,Nanyang Technological University | Romanato F.,University of Padua | Romanato F.,Laboratory for Nanofabrication of Nanodevices | Kang H.K.,Nanyang Technological University | Wong C.C.,Nanyang Technological University
Sensors and Actuators, B: Chemical | Year: 2010

We present a method to explore the full sensitivity of grating coupled surface plasmon resonance (GCSPR) sensors on an azimuthally rotatable grating by optimizing the polarization angle of the incident light. This is the condition where double surface plasmons polaritons (SPPs) can be excited by a single wavelength [1]. This configuration provides a sensitivity up to 950°/RIU compared to a system without azimuthal control [2]. We show here that the sensitivity of this configuration is only achievable when the polarization angle of the incident light is optimized. This is due to the excitation of a fully coupled SPP (as can be observed as a deeper dip in the reflectivity spectra) which is only possible using the optimized polarization angle in an azimuthally rotated grating. This result in a well-defined, sharper spectrum and the positions of the minima are more obvious. The figure of merit (FOM) increases by 50-100% compared to spectra collected using p-polarized light. We demonstrate this sensitivity using a dodecanethiol (C12) self-assembled monolayer (SAM) on a Au grating surface, representing a thickness difference of 1.5 nm compared to the uncoated grating. Using the new configuration with optimized polarization angle, a shift in resonance angle as large as 3.6° can be observed. In principle, we expect the refractive index resolution of this method to be on the order of 5 × 10-7 RIU. © 2010 Elsevier B.V. All rights reserved.

Tamburini F.,University of Padua | Mari E.,University of Padua | Sponselli A.,University of Padua | Thide B.,Swedish Institute of Space Physics | And 4 more authors.
New Journal of Physics | Year: 2012

We have shown experimentally, in a real-world setting, that it is possible to use two beams of incoherent radio waves, transmitted on the same frequency but encoded in two different orbital angular momentum states, to simultaneously transmit two independent radio channels. This novel radio technique allows the implementation of, in principle, an infinite number of channels in a given, fixed bandwidth, even without using polarization, multiport or dense coding techniques. This paves the way for innovative techniques in radio science and entirely new paradigms in radio communication protocols that might offer a solution to the problem of radio-band congestion. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Tamburini F.,University of Padua | Thide B.,Swedish Institute of Space Physics | Thide B.,University of Padua | Mari E.,University of Padua | And 4 more authors.
New Journal of Physics | Year: 2012

Our recent paper (Tamburini et al 2012 New J. Phys. 14 033001), which presented results from outdoor experiments that demonstrate that it is physically feasible to simultaneously transmit different states of the newly recognized electromagnetic (EM) quantity orbital angular momentum (OAM) at radio frequencies into the far zone and to identify these states there, has led to a comment (Tamagnone et al 2012 New J. Phys. 14 118001). These authors discuss whether our investigations can be regarded as a particular implementation of the multiple-input-multiple-output (MIMO) technique. Clearly, our experimental confirmation of a theoretical prediction, first made almost a century ago (Abraham 1914 Phys. Z. XV 914-8), that the total EM angular momentum (a pseudovector of dimension length × mass × velocity) can propagate over huge distances, is essentially different from - and conceptually incompatible with - the fact that there exist engineering techniques that can enhance the spectral capacity of EM linear momentum (an ordinary vector of dimension mass × velocity). Our OAM experiments (Tamburini et al 2012 New J. Phys. 14 033001; Tamburini et al 2011 Appl. Phys. Lett. 99 204102-3) confirm the availability of a new physical layer for real-world radio communications based on EM rotational degrees of freedom. The next step is to develop new protocols and techniques for high spectral density on this new physical layer. This includes MIMO-like and other, more efficient, techniques. © IOP Publishing and Deutsche Physikalische Gesellschaft.

Lee K.H.,Nanyang Technological University | Lim X.Y.,Nanyang Technological University | Wai K.W.,Nanyang Technological University | Romanato F.,Nanyang Technological University | And 3 more authors.
Journal of Nanoscience and Nanotechnology | Year: 2011

In order to form tapered nanocapillaries, we investigated a method to vary the nanopore diameter along the porous anodic alumina (PAA) channels using multi-step anodization. By anodizing the aluminum in either single acid (H 3PO 4) or multi-acid (H 2SO 4, oxalic acid and H 3PO 4) with increasing or decreasing voltage, the diameter of the nanopore along the PAA channel can be varied systematically corresponding to the applied voltages. The pore size along the channel can be enlarged or shrunken in the range of 20 nm to 200 nm. Structural engineering of the template along the film growth direction can be achieved by deliberately designing a suitable voltage and electrolyte together with anodization time. Copyright © 2011 American Scientific Publishers All rights reserved.

Ruffato G.,University of Padua | Romanato F.,Laboratory for Nanofabrication of Nanodevices | Romanato F.,CNR Institute of Neuroscience
COMPEL - The International Journal for Computation and Mathematics in Electrical and Electronic Engineering | Year: 2013

Purpose - The purpose of this paper is to simulate and analyze the excitation and propagation of surface plasmon polaritons (SPPs) on sinusoidal metallic gratings in conical mounting. Design/methodology/approach - Chandezon's method has been implemented in MATLAB environment in order to compute the optical response of metallic gratings illuminated under azimuthal rotation. The code allows describing the full optical features both in far- and near-field terms, and the performed analyses highlight the fundamental role of incident polarization on SPP excitation in the conical configuration. Findings - Results of far-field polarization conversion and plasmonic near-field computation clearly show that azimuthally rotated metallic gratings can support propagating surface plasmon with generic polarization. Originality/value - The recent papers experimentally demonstrated the benefits in sensitivity and the polarization phenomenology that are originated by an azimuthal rotation of the grating. In this work, numerical simulations confirm these experimental results and complete the analysis with a study of the excited SPP near-field on the metal surface. Copyright © 2013 Emerald Group Publishing Limited. All rights reserved.

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