In this preliminary work, we report about porous silicon (PSi) non-symmetric optical microcavitie... more In this preliminary work, we report about porous silicon (PSi) non-symmetric optical microcavities as transducers modified by organic molecular beam deposition (OMBD) of N,N'-1H,1H-perfluorobutyldicyanoperylene-carboxydi-imide (PDIF-CN2), an electrically conductive organic material. PSi is a very effective optical transducer, due to its sponge-like morphology, but not a very good electrical one. Joule evaporation of PDIF-CN2 could improve electrical conductivity of PSi transducer, making the device a dual signal sensor.
Journal of the Royal Society, Interface / the Royal Society, Jan 6, 2015
Porous silicon (PSi) non-symmetric multi-layers are modified by organic molecular beam deposition... more Porous silicon (PSi) non-symmetric multi-layers are modified by organic molecular beam deposition of an organic semiconductor, namely the N,N'-1H,1H-perfluorobutyldicyanoperylene-carboxydi-imide (PDIF-CN2). Joule evaporation of PDIF-CN2 into the PSi sponge-like matrix not only improves but also adds transducing skills, making this solid-state device a dual signal sensor for chemical monitoring. PDIF-CN2 modified PSi optical microcavities show an increase of about five orders of magnitude in electric current with respect to the same bare device. This feature can be used to sense volatile substances. PDIF-CN2 also improves chemical resistance of PSi against alkaline and acid corrosion.
2001 IEEE MTT-S International Microwave Sympsoium Digest (Cat. No.01CH37157), 2001
Abstract Dual mode high temperature superconducting (HTS) filters represent an interesting device... more Abstract Dual mode high temperature superconducting (HTS) filters represent an interesting device class for telecommunication application since they combine a high power handling capability with a miniaturized size. Here we report on the design and realization of dual mode cross slotted filters presenting a more compact size if compared with the traditional dual mode patch filters. Single stage filters operating in C-band with 1% fractional bandwidth have been designed and tested at prototype level by using double sided YBa 2 Cu 3 O 7-x ...
ABSTRACT We probe electron transport across the Au/organic interface based on oriented thin films ... more ABSTRACT We probe electron transport across the Au/organic interface based on oriented thin films of the high-performance n-type perylene diimide semiconductor PDI8-CN2. To this purpose, we prepared organic-on-inorganic Schottky diodes, with Au directly evaporated onto PDI8-CN 2 grown on n-Si. Temperature-dependent current–voltage characteristics and complementary ballistic electron emission microscopy studies reveal that rectification at the Au/PDI8-CN2 interface is controlled by a spatially inhomogeneous injection barrier, that varies on a length scale of tens of nanometers according to a Gaussian distribution with mean value 0.94 eV and standard deviation 100 meV. The former gradually shifts to 1.04 eV on increasing PDI8-CN 2 thickness from 5 nm to 50 nm. Experimental evidences and general arguments further allow to establish the energetics at the Au/PDI8-CN2 interface. Our work indicates injection-limited current flow in PDI8-CN 2 -based devices with evaporated Au electrodes. Furthermore, it suggests chemical reactivity of PDI8-CN2 with both Au and Si, driven by the lateral isocyano groups.
Abstract In high-temperature superconducting (HTS) microwave filters, the requirements for miniat... more Abstract In high-temperature superconducting (HTS) microwave filters, the requirements for miniaturization and high power handling are difficult to match simultaneously. In this paper, we report on the design and realization of HTS filters realized by combining dual-mode cross-slotted and stepped resonators in order to obtain a compact size and a relatively high power handling. Prototype HTS four-pole filters operating in C-band and L-band, with quasi-elliptical responses, on both MgO and LaALO3 substrates, have been designed and ...
The optical properties of thermally evaporated PDI-8CN 2 thin films have been investigated using ... more The optical properties of thermally evaporated PDI-8CN 2 thin films have been investigated using Variable Angle Spectroscopic Ellipsometry (VASE). These layers were deposited on SiO 2 dielectric layers as a means of measuring their properties on a standard interface. Regression analysis was used to determine the optical constants (refractive index and extinction coefficient) across a bandwidth of 300 -900 nm. Anisotropy of the films was investigated, as well as the thickness dependence of the optical constants. This paper presents the results of these investigations.
N-type organic field-effect transistors (OFETs), based on two perylene diimide semiconductors (PD... more N-type organic field-effect transistors (OFETs), based on two perylene diimide semiconductors (PDI-8 and PDI-8CN2) exhibiting very different air sensitivities, have been fabricated on Si/SiO2 substrates. These OFETs have been electrically characterized in vacuum both in the dark and under white-light illumination by dc transfer and output curves, bias stress experiments and variable temperature measurements. In particular, the combination of variable temperature and light illumination experiments is shown to be a ...
This work presents compact high temperature superconductor microstrip resonators based on Hilbert... more This work presents compact high temperature superconductor microstrip resonators based on Hilbert fractal curves. Their miniaturization performance has been investigated, emphasizing the parameters which allow to obtain a good trade off between compact size and quality factor. Hilbert resonators with different arrangements have been designed and assessed by using full wave simulators. In order to experimentally verify our analysis, a
Abstract In this contribution, a dielectric measurement technique for the evaluation of phase tra... more Abstract In this contribution, a dielectric measurement technique for the evaluation of phase transition temperature and the study of physical aging on polymeric thin films is considered. This kind of measurement provides the possibility of displaying phase transitions with a high degree of precision. Furthermore, it can be considered alternatively to techniques not applicable in the case of thin films, such as Differential Scanning Calorimetry (DSC). In this work, owing to the high sensitivity of the utilized experimental set-up, a glass transition TG ...
Relying on the water-dependent hybrid conductor properties of eumelanin biopolymers, a structural... more Relying on the water-dependent hybrid conductor properties of eumelanin biopolymers, a structurally controlled melanin thin film that can be reversibly switched-on and off by hydration-dehydration cycles and used as a biocompatible platform for stem cell growth and differentiation up to 11 days is reported. A key feature of the new eumelanin-based bioelectronic interface is its remarkable structural regularity and integrity, as the result of an ad hoc fabrication protocol involving ammonia-induced solid state polymerization (AISSP) technology of a 5,6-dihydroxyindole thin film. The AISSP technology is operationally simple and versatile, enabling the preparation of devicequality thin films (AFM and MALDI-MS evidence) on various substrates with efficient chemical control over molecular complexity. Overall the results of this study pave the way for the implementation of tailored eumelanin thin films for bioelectronic devices, e.g., in organic electrochemical transistors (OECTs).
Thanks to their appealing rheological properties, nowadays micellar solutions play a fundamental ... more Thanks to their appealing rheological properties, nowadays micellar solutions play a fundamental role in many industrial sectors, including personal care products, cosmetics and pharmaceuticals. The use of these solutions and their effectiveness in the desired application is, however, strongly dependent on the specific micellar aggregation form and the related degree of entanglement. To this end, it should be mentioned that, still today, the type and size of the micellar aggregates in a solution can be only investigated by using sophisticated laboratory techniques, which are very difficult to be applied directly in real industrial production sites. In this study, we demonstrate that organic electrochemical transistors (OECTs) based on PEDOT:PSS active channels can be used to reveal the presence of worm-like micelles in surfactant-salt aqueous solutions. In the worm-like regime the response of these devices displays distinctive features in comparison with those exhibited when pure surfactant solutions, containing only spherical micelles, are analysed. Our results could pave the way to the development of a new class of portable and user-friendly devices, suitable for the in situ monitoring of morphological transitions, involving micellar aggregates.
We explored the modification of polymeric film conductivity by changing the conducting filler per... more We explored the modification of polymeric film conductivity by changing the conducting filler percentage in the frame of the percolation theory. The polymeric film is a polystyrene (PS) matrix, while the fillers are gold nanoparticles capped with 1-dodecanethiol (Au-DT NPs) and small conjugated molecules 8- hydroxyquinoline (8HQ). Experimental results show, that increasing the Au- DT and 8HQ wt%, film conductivity increases by up to three orders of magnitude due to charge transfer in the 3D network composed by Au- DT NPs and 8HQ.
The dark conductivity of microcrystalline silicon (μc-Si: H) films, deposited in a RF-PECVD syste... more The dark conductivity of microcrystalline silicon (μc-Si: H) films, deposited in a RF-PECVD system varying the RF power in the 15–100 W range, has been investigated as a function of the temperature. Under low electric field condition (103 V/cm), the conductivity of the samples as a function of the exponential of T− 1/4 presents a linear behaviour in the measured temperature range. The density of states near the Fermi level, the range of hopping and the activation energy for hopping have been evaluated using the diffusion ...
Here we report an investigation of the growth of picene by supersonic molecular beam deposition o... more Here we report an investigation of the growth of picene by supersonic molecular beam deposition on thermal silicon oxide and on a self-assembled monolayer of hexamethyldisiloxane (HMDS). In both cases film morphology shows a structure with very sharp island edges and well-separated islands which size and height depend on the deposition conditions. Picene films growth on bare silicon covered with hydrophobic HDMS shows islands characterized by large regular crystallites of several micrometers; on the ...
ABSTRACT In the present work, we investigated the bias stress (BS) effect taking place in inkjet-... more ABSTRACT In the present work, we investigated the bias stress (BS) effect taking place in inkjet-printed n-type N,N'-bis(n-octyl)-1,6-dicyanoperylene-3,4:9,10-bis(dicarboximide) (PDI8-CN2) transistors fabricated on SiO2 gate dielectric. PDI8-CN2 films were deposited from solvent systems able to improve the layer structural uniformity. These devices were found to exhibit largely negative threshold voltages (V-th) and operate both as accumulation- and depletion-mode transistors. Hence, the BS phenomenon was analyzed by recording the I-DS(t) time curves when the devices were driven under both negative and positive gate-source voltages (V-GS). The BS measurements performed in this work confirm the conventional decay of the I-DS(t) when positive V-GS values (charge accumulation regime) are applied. On the other hand, I-DS(t) increases very rapidly when the devices are polarized with negative V-GS (charge depletion regime). The data achieved for the inkjet-printed devices were also compared with those measured under the same stressing conditions for a device fabricated by evaporating PDI8-CN2 on the same SiO2 substrate type. All the experimental observations reported in this work support the validity of a recently-proposed model, prompting for the occurrence of electrochemical reactions involving PDI8-CN2 molecules and ambient agents (i.e. O-2 and H2O) as origin of the BS phenomenon in these n-type field-effect transistors.
Abstract The use of high-temperature superconducting films for the fabrication of antennas allows... more Abstract The use of high-temperature superconducting films for the fabrication of antennas allows us to realize radiating structures that are small in size and have a very high efficiency. In this paper, we investigate the properties of a novel compact antenna obtained by crossing a square patch with diagonal and transverse slots. Single patch antennas, with both linear and circular polarization operating in the X-band, with a size reduction of about 40% as compared to conventional square patches, have been designed and tested at prototype ...
In this preliminary work, we report about porous silicon (PSi) non-symmetric optical microcavitie... more In this preliminary work, we report about porous silicon (PSi) non-symmetric optical microcavities as transducers modified by organic molecular beam deposition (OMBD) of N,N'-1H,1H-perfluorobutyldicyanoperylene-carboxydi-imide (PDIF-CN2), an electrically conductive organic material. PSi is a very effective optical transducer, due to its sponge-like morphology, but not a very good electrical one. Joule evaporation of PDIF-CN2 could improve electrical conductivity of PSi transducer, making the device a dual signal sensor.
Journal of the Royal Society, Interface / the Royal Society, Jan 6, 2015
Porous silicon (PSi) non-symmetric multi-layers are modified by organic molecular beam deposition... more Porous silicon (PSi) non-symmetric multi-layers are modified by organic molecular beam deposition of an organic semiconductor, namely the N,N'-1H,1H-perfluorobutyldicyanoperylene-carboxydi-imide (PDIF-CN2). Joule evaporation of PDIF-CN2 into the PSi sponge-like matrix not only improves but also adds transducing skills, making this solid-state device a dual signal sensor for chemical monitoring. PDIF-CN2 modified PSi optical microcavities show an increase of about five orders of magnitude in electric current with respect to the same bare device. This feature can be used to sense volatile substances. PDIF-CN2 also improves chemical resistance of PSi against alkaline and acid corrosion.
2001 IEEE MTT-S International Microwave Sympsoium Digest (Cat. No.01CH37157), 2001
Abstract Dual mode high temperature superconducting (HTS) filters represent an interesting device... more Abstract Dual mode high temperature superconducting (HTS) filters represent an interesting device class for telecommunication application since they combine a high power handling capability with a miniaturized size. Here we report on the design and realization of dual mode cross slotted filters presenting a more compact size if compared with the traditional dual mode patch filters. Single stage filters operating in C-band with 1% fractional bandwidth have been designed and tested at prototype level by using double sided YBa 2 Cu 3 O 7-x ...
ABSTRACT We probe electron transport across the Au/organic interface based on oriented thin films ... more ABSTRACT We probe electron transport across the Au/organic interface based on oriented thin films of the high-performance n-type perylene diimide semiconductor PDI8-CN2. To this purpose, we prepared organic-on-inorganic Schottky diodes, with Au directly evaporated onto PDI8-CN 2 grown on n-Si. Temperature-dependent current–voltage characteristics and complementary ballistic electron emission microscopy studies reveal that rectification at the Au/PDI8-CN2 interface is controlled by a spatially inhomogeneous injection barrier, that varies on a length scale of tens of nanometers according to a Gaussian distribution with mean value 0.94 eV and standard deviation 100 meV. The former gradually shifts to 1.04 eV on increasing PDI8-CN 2 thickness from 5 nm to 50 nm. Experimental evidences and general arguments further allow to establish the energetics at the Au/PDI8-CN2 interface. Our work indicates injection-limited current flow in PDI8-CN 2 -based devices with evaporated Au electrodes. Furthermore, it suggests chemical reactivity of PDI8-CN2 with both Au and Si, driven by the lateral isocyano groups.
Abstract In high-temperature superconducting (HTS) microwave filters, the requirements for miniat... more Abstract In high-temperature superconducting (HTS) microwave filters, the requirements for miniaturization and high power handling are difficult to match simultaneously. In this paper, we report on the design and realization of HTS filters realized by combining dual-mode cross-slotted and stepped resonators in order to obtain a compact size and a relatively high power handling. Prototype HTS four-pole filters operating in C-band and L-band, with quasi-elliptical responses, on both MgO and LaALO3 substrates, have been designed and ...
The optical properties of thermally evaporated PDI-8CN 2 thin films have been investigated using ... more The optical properties of thermally evaporated PDI-8CN 2 thin films have been investigated using Variable Angle Spectroscopic Ellipsometry (VASE). These layers were deposited on SiO 2 dielectric layers as a means of measuring their properties on a standard interface. Regression analysis was used to determine the optical constants (refractive index and extinction coefficient) across a bandwidth of 300 -900 nm. Anisotropy of the films was investigated, as well as the thickness dependence of the optical constants. This paper presents the results of these investigations.
N-type organic field-effect transistors (OFETs), based on two perylene diimide semiconductors (PD... more N-type organic field-effect transistors (OFETs), based on two perylene diimide semiconductors (PDI-8 and PDI-8CN2) exhibiting very different air sensitivities, have been fabricated on Si/SiO2 substrates. These OFETs have been electrically characterized in vacuum both in the dark and under white-light illumination by dc transfer and output curves, bias stress experiments and variable temperature measurements. In particular, the combination of variable temperature and light illumination experiments is shown to be a ...
This work presents compact high temperature superconductor microstrip resonators based on Hilbert... more This work presents compact high temperature superconductor microstrip resonators based on Hilbert fractal curves. Their miniaturization performance has been investigated, emphasizing the parameters which allow to obtain a good trade off between compact size and quality factor. Hilbert resonators with different arrangements have been designed and assessed by using full wave simulators. In order to experimentally verify our analysis, a
Abstract In this contribution, a dielectric measurement technique for the evaluation of phase tra... more Abstract In this contribution, a dielectric measurement technique for the evaluation of phase transition temperature and the study of physical aging on polymeric thin films is considered. This kind of measurement provides the possibility of displaying phase transitions with a high degree of precision. Furthermore, it can be considered alternatively to techniques not applicable in the case of thin films, such as Differential Scanning Calorimetry (DSC). In this work, owing to the high sensitivity of the utilized experimental set-up, a glass transition TG ...
Relying on the water-dependent hybrid conductor properties of eumelanin biopolymers, a structural... more Relying on the water-dependent hybrid conductor properties of eumelanin biopolymers, a structurally controlled melanin thin film that can be reversibly switched-on and off by hydration-dehydration cycles and used as a biocompatible platform for stem cell growth and differentiation up to 11 days is reported. A key feature of the new eumelanin-based bioelectronic interface is its remarkable structural regularity and integrity, as the result of an ad hoc fabrication protocol involving ammonia-induced solid state polymerization (AISSP) technology of a 5,6-dihydroxyindole thin film. The AISSP technology is operationally simple and versatile, enabling the preparation of devicequality thin films (AFM and MALDI-MS evidence) on various substrates with efficient chemical control over molecular complexity. Overall the results of this study pave the way for the implementation of tailored eumelanin thin films for bioelectronic devices, e.g., in organic electrochemical transistors (OECTs).
Thanks to their appealing rheological properties, nowadays micellar solutions play a fundamental ... more Thanks to their appealing rheological properties, nowadays micellar solutions play a fundamental role in many industrial sectors, including personal care products, cosmetics and pharmaceuticals. The use of these solutions and their effectiveness in the desired application is, however, strongly dependent on the specific micellar aggregation form and the related degree of entanglement. To this end, it should be mentioned that, still today, the type and size of the micellar aggregates in a solution can be only investigated by using sophisticated laboratory techniques, which are very difficult to be applied directly in real industrial production sites. In this study, we demonstrate that organic electrochemical transistors (OECTs) based on PEDOT:PSS active channels can be used to reveal the presence of worm-like micelles in surfactant-salt aqueous solutions. In the worm-like regime the response of these devices displays distinctive features in comparison with those exhibited when pure surfactant solutions, containing only spherical micelles, are analysed. Our results could pave the way to the development of a new class of portable and user-friendly devices, suitable for the in situ monitoring of morphological transitions, involving micellar aggregates.
We explored the modification of polymeric film conductivity by changing the conducting filler per... more We explored the modification of polymeric film conductivity by changing the conducting filler percentage in the frame of the percolation theory. The polymeric film is a polystyrene (PS) matrix, while the fillers are gold nanoparticles capped with 1-dodecanethiol (Au-DT NPs) and small conjugated molecules 8- hydroxyquinoline (8HQ). Experimental results show, that increasing the Au- DT and 8HQ wt%, film conductivity increases by up to three orders of magnitude due to charge transfer in the 3D network composed by Au- DT NPs and 8HQ.
The dark conductivity of microcrystalline silicon (μc-Si: H) films, deposited in a RF-PECVD syste... more The dark conductivity of microcrystalline silicon (μc-Si: H) films, deposited in a RF-PECVD system varying the RF power in the 15–100 W range, has been investigated as a function of the temperature. Under low electric field condition (103 V/cm), the conductivity of the samples as a function of the exponential of T− 1/4 presents a linear behaviour in the measured temperature range. The density of states near the Fermi level, the range of hopping and the activation energy for hopping have been evaluated using the diffusion ...
Here we report an investigation of the growth of picene by supersonic molecular beam deposition o... more Here we report an investigation of the growth of picene by supersonic molecular beam deposition on thermal silicon oxide and on a self-assembled monolayer of hexamethyldisiloxane (HMDS). In both cases film morphology shows a structure with very sharp island edges and well-separated islands which size and height depend on the deposition conditions. Picene films growth on bare silicon covered with hydrophobic HDMS shows islands characterized by large regular crystallites of several micrometers; on the ...
ABSTRACT In the present work, we investigated the bias stress (BS) effect taking place in inkjet-... more ABSTRACT In the present work, we investigated the bias stress (BS) effect taking place in inkjet-printed n-type N,N'-bis(n-octyl)-1,6-dicyanoperylene-3,4:9,10-bis(dicarboximide) (PDI8-CN2) transistors fabricated on SiO2 gate dielectric. PDI8-CN2 films were deposited from solvent systems able to improve the layer structural uniformity. These devices were found to exhibit largely negative threshold voltages (V-th) and operate both as accumulation- and depletion-mode transistors. Hence, the BS phenomenon was analyzed by recording the I-DS(t) time curves when the devices were driven under both negative and positive gate-source voltages (V-GS). The BS measurements performed in this work confirm the conventional decay of the I-DS(t) when positive V-GS values (charge accumulation regime) are applied. On the other hand, I-DS(t) increases very rapidly when the devices are polarized with negative V-GS (charge depletion regime). The data achieved for the inkjet-printed devices were also compared with those measured under the same stressing conditions for a device fabricated by evaporating PDI8-CN2 on the same SiO2 substrate type. All the experimental observations reported in this work support the validity of a recently-proposed model, prompting for the occurrence of electrochemical reactions involving PDI8-CN2 molecules and ambient agents (i.e. O-2 and H2O) as origin of the BS phenomenon in these n-type field-effect transistors.
Abstract The use of high-temperature superconducting films for the fabrication of antennas allows... more Abstract The use of high-temperature superconducting films for the fabrication of antennas allows us to realize radiating structures that are small in size and have a very high efficiency. In this paper, we investigate the properties of a novel compact antenna obtained by crossing a square patch with diagonal and transverse slots. Single patch antennas, with both linear and circular polarization operating in the X-band, with a size reduction of about 40% as compared to conventional square patches, have been designed and tested at prototype ...
Uploads
Papers by Mario Barra