Federico Ferrarese Lupi | INRIM (original) (raw)

Papers by Federico Ferrarese Lupi

Laser action using non-coupled excitation and detection of microspheres made of Nd 3+ doped bariu... more Laser action using non-coupled excitation and detection of microspheres made of Nd 3+ doped barium-titanium-silicate glass has been demonstrated and measured. The microspheres have also been successfully deposited over Si 3 N 4 strip waveguides with a SiO 2 separation layer, thus enabling the laser emission extraction onto a CMOS compatible photonic circuit. The dynamics of the lasing wavelength and intensity has been studied as a function of the pump power and interpreted in terms of thermal effects generated through non-radiative recombination of the excited ions.

ACS applied materials & interfaces, Jan 8, 2015

Hydroxyl terminated P(S-r-MMA) random copolymers (RCPs) with molecular weight (Mn) spanning from ... more Hydroxyl terminated P(S-r-MMA) random copolymers (RCPs) with molecular weight (Mn) spanning from 1700 up to 69000 g·mol-1 and styrene unit fraction of approximately 61 % were grafted onto a silicon oxide surface and subsequently used to study the orientation of nanodomains with respect to the substrate, in cylinder forming PS-b-PMMA block copolymer (BCP) thin films. When the thickness (H) of the grafted layer is higher than 5-6 nm, perpendicular orientation is always observed due to the efficient decoupling of the BCP film from the polar SiO2 surface. Conversely, if H is lower than 5 nm, the critical thickness of the grafted layer, that allows neutralizing the substrate and promoting the perpendicular orientation of the nanodomains in the BCP film, is found to depend on the Mn of the RCP. In particular, in the case Mn = 1700 g·mol-1, 2.0 nm thick grafted layer is sufficient to promote the perpendicular orientation of the PMMA cylinders in the PS-b-PMMA BCP film. A proximity shieldin...

ACS applied materials & interfaces, Jan 6, 2016

Block copolymer (BCP) self-assembly is expected to complement conventional optical lithography fo... more Block copolymer (BCP) self-assembly is expected to complement conventional optical lithography for the fabrication of next-generation microelectronic devices. In this regard, silicon-containing BCPs with a high Flory-Huggins interaction parameter (χ) are extremely appealing because they form high-resolution nanostructures with characteristic dimensions below 10 nm. However, due to their slow self-assembly kinetics and low thermal stability, these silicon-containing high-χ BCPs are usually processed by solvent vapor annealing or in solvent-rich ambient at a low annealing temperature, significantly increasing the complexity of the facilities and of the procedures. In this work, the self-assembly of cylinder-forming polystyrene-block-poly(dimethylsiloxane-random-vinylmethylsiloxane) (PS-b-P(DMS-r-VMS)) BCP on flat substrates is promoted by means of a simple thermal treatment at high temperatures. Homogeneous PS-b-P(DMS-r-VMS) thin films covering the entire sample surface are obtained w...

Analytical and bioanalytical chemistry, Jan 12, 2016

In the present paper, a reliable and rugged thermogravimetry-gas chromatography-mass spectrometry... more In the present paper, a reliable and rugged thermogravimetry-gas chromatography-mass spectrometry (TGA-GC-MS) method was developed to determine the composition of ultrathin films consisting of binary blends of functional polystyrene (PS) and polymethylmethacrylate (PMMA) grafted to a silicon wafer. A general methodology will be given to address the composition determination problem for binary or even multicomponent polymer brush systems using the PS/PMMA-based samples as a paradigmatic example. In this respect, several distinct tailor-made materials were developed to ensure reliable calibration and validation stages. The analytical method was tested on unknown samples to follow the composition evolution in PS/PMMA brushes during the grafting reaction. A preferential grafting of the PMMA was revealed in full agreement with its preferential interaction with the SiO2 polar surface. Graphical abstract A reliable and rugged thermogravimetry-gas chromatography-mass spectrometry (TGA-GC-MS...

Psst 2014 Home Page, Jan 23, 2014

ACS Applied Materials & Interfaces, 2015

The ordering process of asymmetric PS-b-PMMA block copolymers (BCPs) with molecular weight Mn = 5... more The ordering process of asymmetric PS-b-PMMA block copolymers (BCPs) with molecular weight Mn = 54 kg∙mol-1 is investigated on flat surfaces and on topographically patterned substrates with gratings of ten trenches defined by conventional top down approaches and arranged to form densely packed periodic structures. When the ordering process is accomplished on a flat surface, in a temperature range between 180 and 230 °C, cylindrical nanodomains perpendicularly oriented with respect to the substrate are observed irrespective of annealing temperature. In contrast, when the ordering process occurs on topographically patterned substrates, different phenomena have to be considered. The simultaneous effect of the flow around the gratings and the BCP flux from the zone located between adjacent trenches (mesa) into the inner part of the trenches results in significant thickness variations of the confined BCP film. Therefore, the amount of BCP inside the trenches depends on the width of the mesa region, which acts as a BCP reservoir. Moreover within each trench group, the BCP thickness progressively decreases from the external to the central trenches composing the periodic grating. The thickness variation of the BCP film within the trenches strongly affects the ordering process ultimately leading to different orientation of the microdomains within the trenches. In particular when the annealing temperature is 190 °C a precise confinement of the BCP within the trenches featuring a perpendicular cylinder morphology is observed. At higher temperatures mixed or parallel orientations of the microdomains are obtained depending on the width of the trenches in the periodic grating.

Electrically driven Er 3+ doped Si slot waveguides emitting at 1530 nm are demonstrated. Two diff... more Electrically driven Er 3+ doped Si slot waveguides emitting at 1530 nm are demonstrated. Two different Er 3+ doped active layers were fabricated in the slot region: a pure SiO 2 and a Si-rich oxide. Pulsed polarization driving of the waveguides was used to characterize the time response of the electroluminescence (EL) and of the signal probe transmission in 1 mm long waveguides. Injected carrier absorption losses modulate the EL signal and, since the carrier lifetime is much smaller than that of Er 3+ ions, a sharp EL peak was observed when the polarization was switched off. A time-resolved electrical pump & probe measurement in combination with lock-in amplifier techniques allowed to quantify the injected carrier absorption losses. We found an extinction ratio of 6 dB, passive propagation losses of about 4 dB/mm, and a spectral bandwidth > 25 nm at an effective d.c. power consumption of 120 μW. All these performances suggest the usage of these devices as electro-optical modulators.

Proceedings of SPIE - The International Society for Optical Engineering, 2013

Optoelectronic properties of Er 3+ -doped slot waveguides electrically driven are presented. The ... more Optoelectronic properties of Er 3+ -doped slot waveguides electrically driven are presented. The active waveguides have been coupled to a Si photonic circuit for the on-chip distribution of the electroluminescence (EL) signal at 1.54 μm. The Si photonic circuit was composed by an adiabatic taper, a bus waveguide and a grating coupler for vertical light extraction. The EL intensity at 1.54 μm was detected and successfully guided throughout the Si photonic circuit. Different waveguide lengths were studied, finding no dependence between the waveguide length and the EL signal due to the high propagation losses measured. In addition, carrier injection losses have been observed and quantified by means of time-resolved measurements, obtaining variable optical attenuation of the probe signal as a function of the applied voltage in the waveguide electrodes. An electro-optical modulator could be envisaged if taking advantage of the carrier recombination time, as it is much faster than the Er emission lifetime. Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/07/2013 Terms of Use: http://spiedl.org/terms Proc. of SPIE Vol. 8767 87670I-6 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/07/2013 Terms of Use: http://spiedl.org/terms

Silicon Photonics and Photonic Integrated Circuits III, 2012

The design, optical characterization and sensoristic capability provided by a complementary metal... more The design, optical characterization and sensoristic capability provided by a complementary metal-oxide-semiconductor (CMOS) compatible integrated sensor based on a µ-disk resonator cavity are reported. The working principle of the presented device consists in monitoring the changes in the effective refractive index of the supported optical modes induced by variations of the refractive index of the surrounding material. The detection system has been designed on the base of a high quality factor (Q=1.4x10 4 ) Si-rich Si 3 N 4 (SRSN) µ-disk -emitting in the VIS under optical pumpingbottom coupled to a low loss passive stoichiometric Si 3 N 4 waveguide (WG), with losses values under 1 dB/cm measured in the same spectral region. The PL emission in the VIS range provided by the SRSN enable the use of Si-based detectors, easily integrable using the current CMOS standard technology. Proof of concept measurements performed on the coupled device revealed a good sensitivity of 51.79 nm/RIU (Refractive Index Unit), in accordance with the simulated data, and a minimum detection limit of 1.1 × 10 -3 RIU.

Silicon Photonics VIII, 2013

In this work, the optoelectronic properties of silicon light emitting field-effect transistors (L... more In this work, the optoelectronic properties of silicon light emitting field-effect transistors (LEFETs) have been investigated. The devices have been fabricated with silicon nanocrystals in the gate oxide and a semitransparent polycrystalline silicon gate. We compare the properties of LEFET with a more conventional MOS-LED (two-terminal light-emitting capacitor) with the same active material. The ~45 nm thick gate siliconrich oxide is deposited in a size-controlled multilayer geometry by low pressure chemical vapor deposition using standard microelectronic processes in a CMOS line. The multilayer stack is formed by layers of silicon oxide and silicon rich silicon oxide. The nanocrystal size and the tunneling barrier width are controlled by the thickness of silicon-rich silicon oxide and stochiometric silicon oxide layers, respectively. The silicon nanocrystals have been characterized by means of spectrally and time resolved photoluminescence, high resolution TEM, and x-ray photoelectron spectroscopy. Resistivity of the devices, capacitance, and electroluminescence under direct and pulsed injection current scheme have been studied and here reported. The optical power density and the external quantum efficiency of the LEFETs will be compared with the MOS-LED results. This study will help to develop practical optoelectronic and photonic devices via accurate modeling and engineering of charge transport and exciton recombination in silicon nanocrystal arrays.

physica status solidi (a), 2013

ABSTRACT The block copolymer self-assembly provides a reliable tool for the planar organization o... more ABSTRACT The block copolymer self-assembly provides a reliable tool for the planar organization of materials at the nanoscale. In this paper, we review our recent achievements in the case of the polystyrene-b-poly(methyl-methacrylate) (PS-b-PMMA) polymeric mixture. By the proper choice of deposition and treatment parameters, one can adjust the thickness of the deposited material and transfer the block copolymer cylindrical organization to the material inclusions into the matrix. Silicon nanocrystals (Si-ncs) have been used as the active material to process, due to its interesting electrical and optical properties for electronic and photonic applications. This material has been fabricated in the form of well-defined arrays over a macroscopic surface, either by electron beam deposition or by ion beam synthesis. A further, crucial step toward the fabrication of the active area of the device is the formation of Si nanoparticle arrays onto sub-micrometric trenches defined by graphoepitaxy. The periodicity and the topography of the trenches highly affect the possibility of a conformal deposition of the ordered block polymeric mask, and consequently, of the reproduction of the patterned array of nanocrystals.

Journal of Clinical Virology, 2015

Elevated HPV infection rates have been described in HIV-positive males, placing these subjects at... more Elevated HPV infection rates have been described in HIV-positive males, placing these subjects at high risk of anal neoplasia. Bivalent, quadrivalent, and nonavalent vaccines to prevent HPV infection have been developed, and recently proposed for gender-neutral immunization programs. In order to estimate the benefit that could be obtained by vaccination of HIV-positive men who have sex with men (MSM), we aimed at describing the frequency of multiple and vaccine-targeted HPV infections in MSM enrolled in an anal cancer screening program. The anal cancer screening program was conducted between July 2009 and October 2012. Mucosal anal samples were tested for HPV DNA using MY09/MY11 PCR primers and, if positive, genotyped using the CLART2HPV Clinical Array (35HPV types). A total of 220 MSM were screened and 88.6% were positive for HPV DNA: in 86.5% at least one high-risk (HR) type was found and in 13% only low-risk (LR) HPV were found. Multiple infections accounted for 84.5% of HPV DNA-positive cases and overall 160 different HPV genotype combinations were recognized (only three combinations were detected in more than one patient each). Based on strain coverage, at least one vaccine-targeted HPV type was found in 38.9%, 64%, and 78.4% of cases when considering bivalent, quadrivalent and nonavalent vaccines, respectively. At least one HR vaccine-targeted strain was found in 39% of MSM for bivalent and quadrivalent vaccines, and in 64% of cases for nonavalent prevention. Anal HPV infections in unvaccinated mostly HIV-infected MSM are highly prevalent. The majority of this population has multiple infections with an extremely heterogeneous number of genotype combinations. The nonavalent vaccine could theoretically have prevented a minimum of one HR HPV type in two thirds of subjects.

Optical Materials, 2011

In this work we will give an overview of the optical properties of Si nanoclusters coupled to Er ... more In this work we will give an overview of the optical properties of Si nanoclusters coupled to Er 3+ ions in SiO 2 matrices produced by reactive magnetron co-sputtering. We have divided the work into two separate studies realised on the same samples, which are the result of a thorough optimisation work. The first one have been realised in order to get a clear picture of the interaction mechanism. On the second we will show a quantitative evaluation of the potential performances from a material point of view (determination of the whole optically active Er 3+ content, excitable by direct or indirect means) and actual performance in a waveguide device (determination of internal gain values).

Laser Physics, 2013

Laser action using non-coupled excitation and detection of microspheres made of Nd 3+ doped bariu... more Laser action using non-coupled excitation and detection of microspheres made of Nd 3+ doped barium-titanium-silicate glass has been demonstrated and measured. The microspheres have also been successfully deposited over Si 3 N 4 strip waveguides with a SiO 2 separation layer, thus enabling the laser emission extraction onto a CMOS compatible photonic circuit. The dynamics of the lasing wavelength and intensity has been studied as a function of the pump power and interpreted in terms of thermal effects generated through non-radiative recombination of the excited ions.

Journal of Lightwave Technology, 2000

In this paper, we report on the first attempt to design, fabricate, and test an on-chip optical a... more In this paper, we report on the first attempt to design, fabricate, and test an on-chip optical amplifier which works at 1540 nm and can be electrically driven. It is based on an asymmetric silicon slot waveguide which embeds the active material. This is based on erbium-doped silicon rich silicon oxide. We describe the horizontal asymmetric slot waveguide design which allows us to get a high field confinement in a nanometer thick active layer. In addition, we detail the complex process needed to fabricate the structure. The waveguides have been characterized both electrically as well as optically. Electroluminescence can be excited by hot carrier injection, due to impact excitation of the Er ions. Propagation losses have been measured and high values have been found due to processing defects. Pump and probe measurements show a voltage dependent strong attenuation of the probe signal due to free carrier accumulation and absorption in the slot waveguide region. At the maximum electrical pumping level, electroluminescence signal is in the range of tens of W/cm and the overall loss of the device is only dB. Despite not demonstrating optical amplification, this study shines some light on the path to achieve an all-silicon electrically driven optical amplifier.

Journal of Lightwave Technology, 2000

We demonstrate the high potential of an optical integrated sensor which monitors the changes of t... more We demonstrate the high potential of an optical integrated sensor which monitors the changes of the effective refractive index of the resonant optical modes induced by variations of the refractive index of the surrounding material. The detection system is a CMOS compatible structure based on a visible light emitting Si-rich Si N -disk coupled to a passive Si N waveguide placed underneath. We present a complete optical characterization of the active material in the isolated ( -disk) and combined (plus coupled waveguide) photonic systems. The material has been optimized to obtain bright cavities with high quality factors. As a final result, we demonstrate that the sensor can achieve a sensitivity of 36 nm/RIU for small refractive index changes and a minimum detection limit of RIU. This structure can be used as a building block for detection systems with increased complexity, in which demultiplexing and detection could be readily integrated on the same chip.

Journal of Applied Physics, 2012

Dopant effects on the photoluminescence of interstitial-related centers in ion implanted silicon ... more Dopant effects on the photoluminescence of interstitial-related centers in ion implanted silicon J. Appl. Phys. 111, 094910 (2012) Above-room-temperature photoluminescence from a strain-compensated Ge/Si0.15Ge0.85 multiple-quantumwell structure Appl. Phys. Lett. 100, 141905 (2012) Capability of photoluminescence for characterization of multi-crystalline silicon J. Appl. Phys. 111, 073504 Investigation of defect states in heavily dislocated thin silicon films

Applied Physics Letters, 2011

Nanotechnology, 2014

This work reports experimental findings about the evolution of lateral ordering of lamellar micro... more This work reports experimental findings about the evolution of lateral ordering of lamellar microdomains in symmetric PS-b-PMMA thin films on featureless substrates. Phase separation and microdomain evolution are explored in a rather wide range of temperatures (190-340°C) using a rapid thermal processing (RTP) system. The maximum processing temperature that enables the ordering of block copolymers without introducing any significant degradation of macromolecules is identified. The reported results clearly indicate that the range of accessible temperatures in the processing of these self-assembling materials is mainly limited by the thermal instability of the grafted random copolymer layer, which starts to degrade at T > 300°C, inducing detachment of the block copolymer thin film. For T ⩽ 290°C, clear dependence of correlation length (ξ) values on temperature is observed. The highest level of lateral order achievable in the current system in a quasi-equilibrium condition was obtained at the upper processing temperature limit after an annealing time as short as 60 s.

Laser action using non-coupled excitation and detection of microspheres made of Nd 3+ doped bariu... more Laser action using non-coupled excitation and detection of microspheres made of Nd 3+ doped barium-titanium-silicate glass has been demonstrated and measured. The microspheres have also been successfully deposited over Si 3 N 4 strip waveguides with a SiO 2 separation layer, thus enabling the laser emission extraction onto a CMOS compatible photonic circuit. The dynamics of the lasing wavelength and intensity has been studied as a function of the pump power and interpreted in terms of thermal effects generated through non-radiative recombination of the excited ions.

ACS applied materials & interfaces, Jan 8, 2015

Hydroxyl terminated P(S-r-MMA) random copolymers (RCPs) with molecular weight (Mn) spanning from ... more Hydroxyl terminated P(S-r-MMA) random copolymers (RCPs) with molecular weight (Mn) spanning from 1700 up to 69000 g·mol-1 and styrene unit fraction of approximately 61 % were grafted onto a silicon oxide surface and subsequently used to study the orientation of nanodomains with respect to the substrate, in cylinder forming PS-b-PMMA block copolymer (BCP) thin films. When the thickness (H) of the grafted layer is higher than 5-6 nm, perpendicular orientation is always observed due to the efficient decoupling of the BCP film from the polar SiO2 surface. Conversely, if H is lower than 5 nm, the critical thickness of the grafted layer, that allows neutralizing the substrate and promoting the perpendicular orientation of the nanodomains in the BCP film, is found to depend on the Mn of the RCP. In particular, in the case Mn = 1700 g·mol-1, 2.0 nm thick grafted layer is sufficient to promote the perpendicular orientation of the PMMA cylinders in the PS-b-PMMA BCP film. A proximity shieldin...

ACS applied materials & interfaces, Jan 6, 2016

Block copolymer (BCP) self-assembly is expected to complement conventional optical lithography fo... more Block copolymer (BCP) self-assembly is expected to complement conventional optical lithography for the fabrication of next-generation microelectronic devices. In this regard, silicon-containing BCPs with a high Flory-Huggins interaction parameter (χ) are extremely appealing because they form high-resolution nanostructures with characteristic dimensions below 10 nm. However, due to their slow self-assembly kinetics and low thermal stability, these silicon-containing high-χ BCPs are usually processed by solvent vapor annealing or in solvent-rich ambient at a low annealing temperature, significantly increasing the complexity of the facilities and of the procedures. In this work, the self-assembly of cylinder-forming polystyrene-block-poly(dimethylsiloxane-random-vinylmethylsiloxane) (PS-b-P(DMS-r-VMS)) BCP on flat substrates is promoted by means of a simple thermal treatment at high temperatures. Homogeneous PS-b-P(DMS-r-VMS) thin films covering the entire sample surface are obtained w...

Analytical and bioanalytical chemistry, Jan 12, 2016

In the present paper, a reliable and rugged thermogravimetry-gas chromatography-mass spectrometry... more In the present paper, a reliable and rugged thermogravimetry-gas chromatography-mass spectrometry (TGA-GC-MS) method was developed to determine the composition of ultrathin films consisting of binary blends of functional polystyrene (PS) and polymethylmethacrylate (PMMA) grafted to a silicon wafer. A general methodology will be given to address the composition determination problem for binary or even multicomponent polymer brush systems using the PS/PMMA-based samples as a paradigmatic example. In this respect, several distinct tailor-made materials were developed to ensure reliable calibration and validation stages. The analytical method was tested on unknown samples to follow the composition evolution in PS/PMMA brushes during the grafting reaction. A preferential grafting of the PMMA was revealed in full agreement with its preferential interaction with the SiO2 polar surface. Graphical abstract A reliable and rugged thermogravimetry-gas chromatography-mass spectrometry (TGA-GC-MS...

Psst 2014 Home Page, Jan 23, 2014

ACS Applied Materials & Interfaces, 2015

The ordering process of asymmetric PS-b-PMMA block copolymers (BCPs) with molecular weight Mn = 5... more The ordering process of asymmetric PS-b-PMMA block copolymers (BCPs) with molecular weight Mn = 54 kg∙mol-1 is investigated on flat surfaces and on topographically patterned substrates with gratings of ten trenches defined by conventional top down approaches and arranged to form densely packed periodic structures. When the ordering process is accomplished on a flat surface, in a temperature range between 180 and 230 °C, cylindrical nanodomains perpendicularly oriented with respect to the substrate are observed irrespective of annealing temperature. In contrast, when the ordering process occurs on topographically patterned substrates, different phenomena have to be considered. The simultaneous effect of the flow around the gratings and the BCP flux from the zone located between adjacent trenches (mesa) into the inner part of the trenches results in significant thickness variations of the confined BCP film. Therefore, the amount of BCP inside the trenches depends on the width of the mesa region, which acts as a BCP reservoir. Moreover within each trench group, the BCP thickness progressively decreases from the external to the central trenches composing the periodic grating. The thickness variation of the BCP film within the trenches strongly affects the ordering process ultimately leading to different orientation of the microdomains within the trenches. In particular when the annealing temperature is 190 °C a precise confinement of the BCP within the trenches featuring a perpendicular cylinder morphology is observed. At higher temperatures mixed or parallel orientations of the microdomains are obtained depending on the width of the trenches in the periodic grating.

Electrically driven Er 3+ doped Si slot waveguides emitting at 1530 nm are demonstrated. Two diff... more Electrically driven Er 3+ doped Si slot waveguides emitting at 1530 nm are demonstrated. Two different Er 3+ doped active layers were fabricated in the slot region: a pure SiO 2 and a Si-rich oxide. Pulsed polarization driving of the waveguides was used to characterize the time response of the electroluminescence (EL) and of the signal probe transmission in 1 mm long waveguides. Injected carrier absorption losses modulate the EL signal and, since the carrier lifetime is much smaller than that of Er 3+ ions, a sharp EL peak was observed when the polarization was switched off. A time-resolved electrical pump & probe measurement in combination with lock-in amplifier techniques allowed to quantify the injected carrier absorption losses. We found an extinction ratio of 6 dB, passive propagation losses of about 4 dB/mm, and a spectral bandwidth > 25 nm at an effective d.c. power consumption of 120 μW. All these performances suggest the usage of these devices as electro-optical modulators.

Proceedings of SPIE - The International Society for Optical Engineering, 2013

Optoelectronic properties of Er 3+ -doped slot waveguides electrically driven are presented. The ... more Optoelectronic properties of Er 3+ -doped slot waveguides electrically driven are presented. The active waveguides have been coupled to a Si photonic circuit for the on-chip distribution of the electroluminescence (EL) signal at 1.54 μm. The Si photonic circuit was composed by an adiabatic taper, a bus waveguide and a grating coupler for vertical light extraction. The EL intensity at 1.54 μm was detected and successfully guided throughout the Si photonic circuit. Different waveguide lengths were studied, finding no dependence between the waveguide length and the EL signal due to the high propagation losses measured. In addition, carrier injection losses have been observed and quantified by means of time-resolved measurements, obtaining variable optical attenuation of the probe signal as a function of the applied voltage in the waveguide electrodes. An electro-optical modulator could be envisaged if taking advantage of the carrier recombination time, as it is much faster than the Er emission lifetime. Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/07/2013 Terms of Use: http://spiedl.org/terms Proc. of SPIE Vol. 8767 87670I-6 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/07/2013 Terms of Use: http://spiedl.org/terms

Silicon Photonics and Photonic Integrated Circuits III, 2012

The design, optical characterization and sensoristic capability provided by a complementary metal... more The design, optical characterization and sensoristic capability provided by a complementary metal-oxide-semiconductor (CMOS) compatible integrated sensor based on a µ-disk resonator cavity are reported. The working principle of the presented device consists in monitoring the changes in the effective refractive index of the supported optical modes induced by variations of the refractive index of the surrounding material. The detection system has been designed on the base of a high quality factor (Q=1.4x10 4 ) Si-rich Si 3 N 4 (SRSN) µ-disk -emitting in the VIS under optical pumpingbottom coupled to a low loss passive stoichiometric Si 3 N 4 waveguide (WG), with losses values under 1 dB/cm measured in the same spectral region. The PL emission in the VIS range provided by the SRSN enable the use of Si-based detectors, easily integrable using the current CMOS standard technology. Proof of concept measurements performed on the coupled device revealed a good sensitivity of 51.79 nm/RIU (Refractive Index Unit), in accordance with the simulated data, and a minimum detection limit of 1.1 × 10 -3 RIU.

Silicon Photonics VIII, 2013

In this work, the optoelectronic properties of silicon light emitting field-effect transistors (L... more In this work, the optoelectronic properties of silicon light emitting field-effect transistors (LEFETs) have been investigated. The devices have been fabricated with silicon nanocrystals in the gate oxide and a semitransparent polycrystalline silicon gate. We compare the properties of LEFET with a more conventional MOS-LED (two-terminal light-emitting capacitor) with the same active material. The ~45 nm thick gate siliconrich oxide is deposited in a size-controlled multilayer geometry by low pressure chemical vapor deposition using standard microelectronic processes in a CMOS line. The multilayer stack is formed by layers of silicon oxide and silicon rich silicon oxide. The nanocrystal size and the tunneling barrier width are controlled by the thickness of silicon-rich silicon oxide and stochiometric silicon oxide layers, respectively. The silicon nanocrystals have been characterized by means of spectrally and time resolved photoluminescence, high resolution TEM, and x-ray photoelectron spectroscopy. Resistivity of the devices, capacitance, and electroluminescence under direct and pulsed injection current scheme have been studied and here reported. The optical power density and the external quantum efficiency of the LEFETs will be compared with the MOS-LED results. This study will help to develop practical optoelectronic and photonic devices via accurate modeling and engineering of charge transport and exciton recombination in silicon nanocrystal arrays.

physica status solidi (a), 2013

ABSTRACT The block copolymer self-assembly provides a reliable tool for the planar organization o... more ABSTRACT The block copolymer self-assembly provides a reliable tool for the planar organization of materials at the nanoscale. In this paper, we review our recent achievements in the case of the polystyrene-b-poly(methyl-methacrylate) (PS-b-PMMA) polymeric mixture. By the proper choice of deposition and treatment parameters, one can adjust the thickness of the deposited material and transfer the block copolymer cylindrical organization to the material inclusions into the matrix. Silicon nanocrystals (Si-ncs) have been used as the active material to process, due to its interesting electrical and optical properties for electronic and photonic applications. This material has been fabricated in the form of well-defined arrays over a macroscopic surface, either by electron beam deposition or by ion beam synthesis. A further, crucial step toward the fabrication of the active area of the device is the formation of Si nanoparticle arrays onto sub-micrometric trenches defined by graphoepitaxy. The periodicity and the topography of the trenches highly affect the possibility of a conformal deposition of the ordered block polymeric mask, and consequently, of the reproduction of the patterned array of nanocrystals.

Journal of Clinical Virology, 2015

Elevated HPV infection rates have been described in HIV-positive males, placing these subjects at... more Elevated HPV infection rates have been described in HIV-positive males, placing these subjects at high risk of anal neoplasia. Bivalent, quadrivalent, and nonavalent vaccines to prevent HPV infection have been developed, and recently proposed for gender-neutral immunization programs. In order to estimate the benefit that could be obtained by vaccination of HIV-positive men who have sex with men (MSM), we aimed at describing the frequency of multiple and vaccine-targeted HPV infections in MSM enrolled in an anal cancer screening program. The anal cancer screening program was conducted between July 2009 and October 2012. Mucosal anal samples were tested for HPV DNA using MY09/MY11 PCR primers and, if positive, genotyped using the CLART2HPV Clinical Array (35HPV types). A total of 220 MSM were screened and 88.6% were positive for HPV DNA: in 86.5% at least one high-risk (HR) type was found and in 13% only low-risk (LR) HPV were found. Multiple infections accounted for 84.5% of HPV DNA-positive cases and overall 160 different HPV genotype combinations were recognized (only three combinations were detected in more than one patient each). Based on strain coverage, at least one vaccine-targeted HPV type was found in 38.9%, 64%, and 78.4% of cases when considering bivalent, quadrivalent and nonavalent vaccines, respectively. At least one HR vaccine-targeted strain was found in 39% of MSM for bivalent and quadrivalent vaccines, and in 64% of cases for nonavalent prevention. Anal HPV infections in unvaccinated mostly HIV-infected MSM are highly prevalent. The majority of this population has multiple infections with an extremely heterogeneous number of genotype combinations. The nonavalent vaccine could theoretically have prevented a minimum of one HR HPV type in two thirds of subjects.

Optical Materials, 2011

In this work we will give an overview of the optical properties of Si nanoclusters coupled to Er ... more In this work we will give an overview of the optical properties of Si nanoclusters coupled to Er 3+ ions in SiO 2 matrices produced by reactive magnetron co-sputtering. We have divided the work into two separate studies realised on the same samples, which are the result of a thorough optimisation work. The first one have been realised in order to get a clear picture of the interaction mechanism. On the second we will show a quantitative evaluation of the potential performances from a material point of view (determination of the whole optically active Er 3+ content, excitable by direct or indirect means) and actual performance in a waveguide device (determination of internal gain values).

Laser Physics, 2013

Laser action using non-coupled excitation and detection of microspheres made of Nd 3+ doped bariu... more Laser action using non-coupled excitation and detection of microspheres made of Nd 3+ doped barium-titanium-silicate glass has been demonstrated and measured. The microspheres have also been successfully deposited over Si 3 N 4 strip waveguides with a SiO 2 separation layer, thus enabling the laser emission extraction onto a CMOS compatible photonic circuit. The dynamics of the lasing wavelength and intensity has been studied as a function of the pump power and interpreted in terms of thermal effects generated through non-radiative recombination of the excited ions.

Journal of Lightwave Technology, 2000

In this paper, we report on the first attempt to design, fabricate, and test an on-chip optical a... more In this paper, we report on the first attempt to design, fabricate, and test an on-chip optical amplifier which works at 1540 nm and can be electrically driven. It is based on an asymmetric silicon slot waveguide which embeds the active material. This is based on erbium-doped silicon rich silicon oxide. We describe the horizontal asymmetric slot waveguide design which allows us to get a high field confinement in a nanometer thick active layer. In addition, we detail the complex process needed to fabricate the structure. The waveguides have been characterized both electrically as well as optically. Electroluminescence can be excited by hot carrier injection, due to impact excitation of the Er ions. Propagation losses have been measured and high values have been found due to processing defects. Pump and probe measurements show a voltage dependent strong attenuation of the probe signal due to free carrier accumulation and absorption in the slot waveguide region. At the maximum electrical pumping level, electroluminescence signal is in the range of tens of W/cm and the overall loss of the device is only dB. Despite not demonstrating optical amplification, this study shines some light on the path to achieve an all-silicon electrically driven optical amplifier.

Journal of Lightwave Technology, 2000

We demonstrate the high potential of an optical integrated sensor which monitors the changes of t... more We demonstrate the high potential of an optical integrated sensor which monitors the changes of the effective refractive index of the resonant optical modes induced by variations of the refractive index of the surrounding material. The detection system is a CMOS compatible structure based on a visible light emitting Si-rich Si N -disk coupled to a passive Si N waveguide placed underneath. We present a complete optical characterization of the active material in the isolated ( -disk) and combined (plus coupled waveguide) photonic systems. The material has been optimized to obtain bright cavities with high quality factors. As a final result, we demonstrate that the sensor can achieve a sensitivity of 36 nm/RIU for small refractive index changes and a minimum detection limit of RIU. This structure can be used as a building block for detection systems with increased complexity, in which demultiplexing and detection could be readily integrated on the same chip.

Journal of Applied Physics, 2012

Dopant effects on the photoluminescence of interstitial-related centers in ion implanted silicon ... more Dopant effects on the photoluminescence of interstitial-related centers in ion implanted silicon J. Appl. Phys. 111, 094910 (2012) Above-room-temperature photoluminescence from a strain-compensated Ge/Si0.15Ge0.85 multiple-quantumwell structure Appl. Phys. Lett. 100, 141905 (2012) Capability of photoluminescence for characterization of multi-crystalline silicon J. Appl. Phys. 111, 073504 Investigation of defect states in heavily dislocated thin silicon films

Applied Physics Letters, 2011

Nanotechnology, 2014

This work reports experimental findings about the evolution of lateral ordering of lamellar micro... more This work reports experimental findings about the evolution of lateral ordering of lamellar microdomains in symmetric PS-b-PMMA thin films on featureless substrates. Phase separation and microdomain evolution are explored in a rather wide range of temperatures (190-340°C) using a rapid thermal processing (RTP) system. The maximum processing temperature that enables the ordering of block copolymers without introducing any significant degradation of macromolecules is identified. The reported results clearly indicate that the range of accessible temperatures in the processing of these self-assembling materials is mainly limited by the thermal instability of the grafted random copolymer layer, which starts to degrade at T > 300°C, inducing detachment of the block copolymer thin film. For T ⩽ 290°C, clear dependence of correlation length (ξ) values on temperature is observed. The highest level of lateral order achievable in the current system in a quasi-equilibrium condition was obtained at the upper processing temperature limit after an annealing time as short as 60 s.