Lluís Marsal | Universitat Rovira i Virgili (original) (raw)

Papers by Lluís Marsal

Proceedings of the 8th Spanish Conference on Electron Devices, CDE'2011, 2011

Alejandra Castro-Carranza, Jairo C. Nolasco, Benjamín Iñíguez, Lluis Marsal, Josep Pallarès. Univ... more Alejandra Castro-Carranza, Jairo C. Nolasco, Benjamín Iñíguez, Lluis Marsal, Josep Pallarès. Universitat Rovira I Virgili, DEEEiA Tarragona , Spain alejandra.castro@urv.cat ... Magali Estrada, Antonio Cerdeira Sección de Electrónica del Estado Sólido SEES CINVESTAV ...

ACS applied materials & interfaces, Jan 12, 2015

Porous alumina photoluminescence-inherent particles are produced and proposed for the development... more Porous alumina photoluminescence-inherent particles are produced and proposed for the development of biomarkers detectors and localized treatment of HepG2 cells. Nanoporous alumina particles (NPAPs) are amorphous, consist of hexagonally ordered nanometric pores in an alumina matrix, have high chemical stability in physiological pH, and exhibit a high inherent photoluminescence in the visible spectrum independently of their size, selectable from nanometers to tens of micrometers. The surface of NPAPs is chemically modified using two different functionalization methods, a multistep method with (3-aminopropyl)triethoxysilane (APTES) and glutaraldehyde (GLTA) and a novel simplified-step method with silane-PEG-NHS. Fourier Transform infrared spectroscopy analysis confirmed the proper surface modification of the particles for both functionalization methods. HepG2 cells were cultured during different times with growing concentrations of particles. The analysis of cytotoxicity and cell viab...

Conference on Electron Devices, 2005 Spanish, 2005

Using the finite-difference time-domain method, the authors analyzed the transmission spectra of ... more Using the finite-difference time-domain method, the authors analyzed the transmission spectra of two dimensional Kerr-nonlinear photonic band gap (PBG) structures. It is found that in these structures the forbidden band gap is red-shifted and broadened with regard to the linear case. It makes it possible to design such photonic devices as the optical limiter, optical diode and all-optical switch.

Optics Communications, 2007

We present an approach of taking the two-photon absorption effect into account and apply it to an... more We present an approach of taking the two-photon absorption effect into account and apply it to analyze an all-optical switch by means of the finite-difference time-domain method. It is shown for a shortened model of the device that the impact of the two-photon absorption on the functionality of the device is drastic. Therefore, under realistic conditions, it should be borne in mind when designing all-optical devices.

Photonics and Nanostructures - Fundamentals and Applications, 2012

The existence of photonic stop bands in the self-assembled arrangement of pores in porous anodic ... more The existence of photonic stop bands in the self-assembled arrangement of pores in porous anodic alumina structures is investigated by means of rigorous 2D finitedifference time-domain calculations. Self-assembled porous anodic alumina shows a random distribution of domains, each of them with a very definite triangular pattern, constituting a quasi-random structure. The observed stop bands are similar to those of photonic quasicrystals or random structures. As the pores of nanoporous anodic alumina can be infiltrated with noble metals, nonlinear or active media, it makes this material very attractive and cost-effective for applications including inhibition of spontaneous emission, random lasing, LEDs and biosensors.

Optical Materials, 2011

We report here the results obtained in surface ablation of RbTiOPO 4 single crystals by femtoseco... more We report here the results obtained in surface ablation of RbTiOPO 4 single crystals by femtosecond laser. We fabricated and characterized one-dimensional (1D) diffraction gratings with different lattice spacings of 15 and 20 lm, and with a sub-modulation of the period introduced in the later. The optical and electronic microscopy characterization and filling factor analysis of these diffraction gratings are reported. We also show that the roughness generated on the grooves by the ablation process can be improved by chemical etching.

Small, 2015

Multifunctional SiO2 microtubes for targeted drug delivery are produced with precise control over... more Multifunctional SiO2 microtubes for targeted drug delivery are produced with precise control over shape and size by combining lithography and electrochemical etching. The hollow core is loaded with a lipophilic anticancer drug generating nanopills and an antibody is conjugated to the external surface for cancer cell targeting. Results demonstrate selective killing of neuroblastoma cells that express the cognate receptor.

Small (Weinheim an der Bergstrasse, Germany), 2015

Tumour-targeting silica microtubes are produced by L. F. Marsal, N. H. Voelcker, and co-workers w... more Tumour-targeting silica microtubes are produced by L. F. Marsal, N. H. Voelcker, and co-workers with precise control over shape and size by combining lithography and electrochemical etching. On page 4626, this particular architecture enables the differential functionalization of internal and external surfaces. The hollow microtube core is loaded with a hydrophobic anticancer drug, rendering the tubes nanopills; an antibody is conjugated to the external surface to recognise receptors on a cancer cell. Results demonstrate the selective killing of neuroblastoma cells, representing a step forward in the targeted delivery of hydrophobic drugs.

Small, 2015

Multifunctional SiO2 microtubes for targeted drug delivery are produced with precise control over... more Multifunctional SiO2 microtubes for targeted drug delivery are produced with precise control over shape and size by combining lithography and electrochemical etching. The hollow core is loaded with a lipophilic anticancer drug generating nanopills and an antibody is conjugated to the external surface for cancer cell targeting. Results demonstrate selective killing of neuroblastoma cells that express the cognate receptor.

Journal of Colloid and Interface Science, 2015

Porous silicon (pSi) is a prosperous biomaterial, biocompatible, and biodegradable. Obtaining reg... more Porous silicon (pSi) is a prosperous biomaterial, biocompatible, and biodegradable. Obtaining regularly functionalized pSi surfaces is required in many biotechnology applications. Silane-PEG-NHS (triethoxysilane-polyethylene-glycol-N-hydroxysuccinimide) is useful for single-molecule studies due to its ability to attach to only one biomolecule. We investigate the functionalization of pSi with silane-PEG-NHS and compare it with two common grafting agents: APTMS (3-aminopropylotrimethoxysilane) as electrostatic linker, and APTMS modified with glutaraldehyde as covalent spacer. We show the arrangement of two proteins (collagen and bovine serum albumin) as a function of the functionalization and of the pore size. FTIR is used to demonstrate correct functionalization while fluorescence confocal microscopy reveals that silane-PEG-NHS results in a more uniform protein distribution. Reflection interference spectroscopy (RIfS) is used to estimate the attachment of linker and proteins. The results open a way to obtain homogenous chemical modified silicon supports with a great value in biosensing, drug delivery and cell biology.

Sensors and Actuators B-Chemical, 2005

This paper presents a novel technique for silicon dioxide (SiO 2 ) microneedle fabrication. Micro... more This paper presents a novel technique for silicon dioxide (SiO 2 ) microneedle fabrication. Microneedles are hollow microcapillaries with tip diameters in the range of micrometers. They can be used in the fabrication of microsyringes. These structures can be of high interest in medical and biological applications, such as DNA injection, antibody manipulation and drug delivery, and cell manipulation. Fabrication process is based on electrochemical etching of n-type silicon in hydrofluoric acid (HF) solutions. Basic process flow and etching conditions that ensure a stable pore growth are described. These conditions also determine the geometry of the resulting microneedle structure. Microneedle arrays of different dimensions can be fabricated in a single run on the same wafer. In this work, microneedle arrays with pore diameters ranging from 2 to 5 m, pore lengths from 30 to 140 m and wall thicknesses in the range of 70-110 nm are reported. a research fellow in 1985 where he became Professor in 1996. His research is focussed in semiconductor technology including new solar cell structures and materials, thin film transistors, sensors and MEM'S. He is co-author of about 50 reviewed scientific publications in international journals.

Optics Communications, 2009

A theoretical study of a tunable Fabry–Pérot multilayer structure composed of alternating layers ... more A theoretical study of a tunable Fabry–Pérot multilayer structure composed of alternating layers of silicon and liquid crystal is presented and analyzed. The structure possesses two resonant frequencies within the stop band with tunable wavelengths and transmission properties. Tuning is achieved by allowing different orientations of the liquid crystal optical axes within the cavity and within the mirrors, while keeping

Vi Encuentro Franco-Espanol De Quimica Y Fisica Del Estado Solido - Vi Rencontre Franco-Espagnole Sur La Chimie Et La Physique De L Etat Solide, 2010

Europium-doped La 2 O 3 nanocrystalline powders with sizes ranging from 4 nm to 300 nm have been ... more Europium-doped La 2 O 3 nanocrystalline powders with sizes ranging from 4 nm to 300 nm have been obtained by the modified Pechini, hydrothermal with conventional furnace, hydrothermal with microwave furnace, and precipitation with ultrasonic bath methods. X-ray diffraction techniques were used to study the evolution of the prepared gels towards the desired crystalline phase. We determined the size and the morphology of the nanoparticles by electronic microscopy. Finally, we studied and analyzed the luminescence properties of the trivalent europium in the hexagonal La 2 O 3 nanocrystals by photoluminescence and cathodoluminescence.

Physica Status Solidi C: Current Topics in Solid State Physics, Vol 8, No 9, 2011

Abstract Photoluminescent nanopillars are fabricated by replication from nanoporous anodic alumin... more Abstract Photoluminescent nanopillars are fabricated by replication from nanoporous anodic alumina via template wetting using polymer from different chemical families: polyfluorenes, PPV derivatives and thiophenes. The experimental process entails infiltration of a ...

Optical Materials, 2011

We report here the results obtained in surface ablation of RbTiOPO 4 single crystals by femtoseco... more We report here the results obtained in surface ablation of RbTiOPO 4 single crystals by femtosecond laser. We fabricated and characterized one-dimensional (1D) diffraction gratings with different lattice spacings of 15 and 20 lm, and with a sub-modulation of the period introduced in the later. The optical and electronic microscopy characterization and filling factor analysis of these diffraction gratings are reported. We also show that the roughness generated on the grooves by the ablation process can be improved by chemical etching.

Rsc Advances, 2014

ABSTRACT We report a method for the fabrication and selective functionalization of the internal a... more ABSTRACT We report a method for the fabrication and selective functionalization of the internal and external surfaces of high-aspect-ratio hollow silicon dioxide (SiO2) micropillar arrays. The strategy enables independent surface reactions with no cross-contamination. The dual-functionalization is carried out during the fabrication of the micropillars in four steps. First, a sample of macroporous silicon is prepared by electrochemical etching and then it is thermally oxidized to create a thin layer of silicon dioxide on the internal surface of the macropores. Next, the internal surface is functionalized with mercaptopropyl trimethoxysilane (MPTMS). Subsequently, the micropillars are released by etching the back side of silicon wafers using a solution of tetramethylammonium hydroxide (TMAH). Finally, the external surface of the micropillars is chemically modified in a multi-step biofunctionalization with aminopropyl triethoxysilane (APTES), glutaraldehyde (GTA) and bovine serum albumin (BSA). The resulting structures were characterized by scanning electron microscopy and the surface reactions were confirmed by Fourier-transform infrared spectroscopy. The internal and external sides were photolabeled with tetramethyl rhodamine-5-maleimide and fluorescein isothiocyanate (FITC), respectively, and analyzed using fluorescence confocal microscopy. The peculiar three-dimensional (3D) geometry of the micropillars allows these double-active surfaces to be imaged at the same time. Results demonstrated the successful dual-side chemical modification and the feasibility of imaging both internal and external sides. Due to its remarkable architecture and chemical versatility, these micropillar arrays are a promising engineered platform for a range of applications such as biosensing, 3D cell culture and drug delivery.

Nature Communications, 2014

Silicon is the material of choice for visible light photodetection and solar cell fabrication. Ho... more Silicon is the material of choice for visible light photodetection and solar cell fabrication. However, due to the intrinsic band gap properties of silicon, most infrared photons are energetically useless. Here, we show the first example of a photodiode developed on a micrometre scale sphere made of polycrystalline silicon whose photocurrent shows the Mie modes of a classical spherical resonator. The long dwell time of resonating photons enhances the photocurrent response, extending it into the infrared region well beyond the absorption edge of bulk silicon. It opens the door for developing solar cells and photodetectors that may harvest infrared light more efficiently than silicon photovoltaic devices that are so far developed.

Nanoscale Research Letters, 2014

A rugate filter based on nanoporous anodic alumina was fabricated using an innovative sinusoidal ... more A rugate filter based on nanoporous anodic alumina was fabricated using an innovative sinusoidal current profile with small current variation. The resulting structure consisted of highly parallel pores with modulations of the pore diameter along the pore axis and with no branching. The effect of the period time and the pore widening post-treatment was studied. From reflectance measurements, it was seen that the position of the reflection band can be tuned by adjusting the period time and the width by pore-widening post-treatments. We tested one of the rugate filters by infiltrating the structure with EtOH and water in order to evaluate its sensing capabilities. This method allows the fabrication of complex in-depth modulated nanoporous anodic alumina structures that open up the possibility of new kinds of alumina-based optical sensing devices.

Conference on Photonic Materials, Devices and Applications, 2005

Macroporous silicon structures have been fabricated by electrochemical etching. Such fabrication ... more Macroporous silicon structures have been fabricated by electrochemical etching. Such fabrication process is known to result in the presence of a thin microporous Si layer at the walls of the macropores and at the surface. Photoluminescence measurements conducted in plan-view and cross-section exhibit a wide emission peak around 650nm which can be attributed to the microporous Si. The combination of a photonic crystal and a light emitter in one structure represents a potential for applications that has not been studied previously. This preliminary study shows the influence of the main fabrication parameters, namely the current density and the etchant solution, on the emission properties of the microporous Si layer.

Proceedings of the 8th Spanish Conference on Electron Devices, CDE'2011, 2011

Alejandra Castro-Carranza, Jairo C. Nolasco, Benjamín Iñíguez, Lluis Marsal, Josep Pallarès. Univ... more Alejandra Castro-Carranza, Jairo C. Nolasco, Benjamín Iñíguez, Lluis Marsal, Josep Pallarès. Universitat Rovira I Virgili, DEEEiA Tarragona , Spain alejandra.castro@urv.cat ... Magali Estrada, Antonio Cerdeira Sección de Electrónica del Estado Sólido SEES CINVESTAV ...

ACS applied materials & interfaces, Jan 12, 2015

Porous alumina photoluminescence-inherent particles are produced and proposed for the development... more Porous alumina photoluminescence-inherent particles are produced and proposed for the development of biomarkers detectors and localized treatment of HepG2 cells. Nanoporous alumina particles (NPAPs) are amorphous, consist of hexagonally ordered nanometric pores in an alumina matrix, have high chemical stability in physiological pH, and exhibit a high inherent photoluminescence in the visible spectrum independently of their size, selectable from nanometers to tens of micrometers. The surface of NPAPs is chemically modified using two different functionalization methods, a multistep method with (3-aminopropyl)triethoxysilane (APTES) and glutaraldehyde (GLTA) and a novel simplified-step method with silane-PEG-NHS. Fourier Transform infrared spectroscopy analysis confirmed the proper surface modification of the particles for both functionalization methods. HepG2 cells were cultured during different times with growing concentrations of particles. The analysis of cytotoxicity and cell viab...

Conference on Electron Devices, 2005 Spanish, 2005

Using the finite-difference time-domain method, the authors analyzed the transmission spectra of ... more Using the finite-difference time-domain method, the authors analyzed the transmission spectra of two dimensional Kerr-nonlinear photonic band gap (PBG) structures. It is found that in these structures the forbidden band gap is red-shifted and broadened with regard to the linear case. It makes it possible to design such photonic devices as the optical limiter, optical diode and all-optical switch.

Optics Communications, 2007

We present an approach of taking the two-photon absorption effect into account and apply it to an... more We present an approach of taking the two-photon absorption effect into account and apply it to analyze an all-optical switch by means of the finite-difference time-domain method. It is shown for a shortened model of the device that the impact of the two-photon absorption on the functionality of the device is drastic. Therefore, under realistic conditions, it should be borne in mind when designing all-optical devices.

Photonics and Nanostructures - Fundamentals and Applications, 2012

The existence of photonic stop bands in the self-assembled arrangement of pores in porous anodic ... more The existence of photonic stop bands in the self-assembled arrangement of pores in porous anodic alumina structures is investigated by means of rigorous 2D finitedifference time-domain calculations. Self-assembled porous anodic alumina shows a random distribution of domains, each of them with a very definite triangular pattern, constituting a quasi-random structure. The observed stop bands are similar to those of photonic quasicrystals or random structures. As the pores of nanoporous anodic alumina can be infiltrated with noble metals, nonlinear or active media, it makes this material very attractive and cost-effective for applications including inhibition of spontaneous emission, random lasing, LEDs and biosensors.

Optical Materials, 2011

We report here the results obtained in surface ablation of RbTiOPO 4 single crystals by femtoseco... more We report here the results obtained in surface ablation of RbTiOPO 4 single crystals by femtosecond laser. We fabricated and characterized one-dimensional (1D) diffraction gratings with different lattice spacings of 15 and 20 lm, and with a sub-modulation of the period introduced in the later. The optical and electronic microscopy characterization and filling factor analysis of these diffraction gratings are reported. We also show that the roughness generated on the grooves by the ablation process can be improved by chemical etching.

Small, 2015

Multifunctional SiO2 microtubes for targeted drug delivery are produced with precise control over... more Multifunctional SiO2 microtubes for targeted drug delivery are produced with precise control over shape and size by combining lithography and electrochemical etching. The hollow core is loaded with a lipophilic anticancer drug generating nanopills and an antibody is conjugated to the external surface for cancer cell targeting. Results demonstrate selective killing of neuroblastoma cells that express the cognate receptor.

Small (Weinheim an der Bergstrasse, Germany), 2015

Tumour-targeting silica microtubes are produced by L. F. Marsal, N. H. Voelcker, and co-workers w... more Tumour-targeting silica microtubes are produced by L. F. Marsal, N. H. Voelcker, and co-workers with precise control over shape and size by combining lithography and electrochemical etching. On page 4626, this particular architecture enables the differential functionalization of internal and external surfaces. The hollow microtube core is loaded with a hydrophobic anticancer drug, rendering the tubes nanopills; an antibody is conjugated to the external surface to recognise receptors on a cancer cell. Results demonstrate the selective killing of neuroblastoma cells, representing a step forward in the targeted delivery of hydrophobic drugs.

Small, 2015

Multifunctional SiO2 microtubes for targeted drug delivery are produced with precise control over... more Multifunctional SiO2 microtubes for targeted drug delivery are produced with precise control over shape and size by combining lithography and electrochemical etching. The hollow core is loaded with a lipophilic anticancer drug generating nanopills and an antibody is conjugated to the external surface for cancer cell targeting. Results demonstrate selective killing of neuroblastoma cells that express the cognate receptor.

Journal of Colloid and Interface Science, 2015

Porous silicon (pSi) is a prosperous biomaterial, biocompatible, and biodegradable. Obtaining reg... more Porous silicon (pSi) is a prosperous biomaterial, biocompatible, and biodegradable. Obtaining regularly functionalized pSi surfaces is required in many biotechnology applications. Silane-PEG-NHS (triethoxysilane-polyethylene-glycol-N-hydroxysuccinimide) is useful for single-molecule studies due to its ability to attach to only one biomolecule. We investigate the functionalization of pSi with silane-PEG-NHS and compare it with two common grafting agents: APTMS (3-aminopropylotrimethoxysilane) as electrostatic linker, and APTMS modified with glutaraldehyde as covalent spacer. We show the arrangement of two proteins (collagen and bovine serum albumin) as a function of the functionalization and of the pore size. FTIR is used to demonstrate correct functionalization while fluorescence confocal microscopy reveals that silane-PEG-NHS results in a more uniform protein distribution. Reflection interference spectroscopy (RIfS) is used to estimate the attachment of linker and proteins. The results open a way to obtain homogenous chemical modified silicon supports with a great value in biosensing, drug delivery and cell biology.

Sensors and Actuators B-Chemical, 2005

This paper presents a novel technique for silicon dioxide (SiO 2 ) microneedle fabrication. Micro... more This paper presents a novel technique for silicon dioxide (SiO 2 ) microneedle fabrication. Microneedles are hollow microcapillaries with tip diameters in the range of micrometers. They can be used in the fabrication of microsyringes. These structures can be of high interest in medical and biological applications, such as DNA injection, antibody manipulation and drug delivery, and cell manipulation. Fabrication process is based on electrochemical etching of n-type silicon in hydrofluoric acid (HF) solutions. Basic process flow and etching conditions that ensure a stable pore growth are described. These conditions also determine the geometry of the resulting microneedle structure. Microneedle arrays of different dimensions can be fabricated in a single run on the same wafer. In this work, microneedle arrays with pore diameters ranging from 2 to 5 m, pore lengths from 30 to 140 m and wall thicknesses in the range of 70-110 nm are reported. a research fellow in 1985 where he became Professor in 1996. His research is focussed in semiconductor technology including new solar cell structures and materials, thin film transistors, sensors and MEM'S. He is co-author of about 50 reviewed scientific publications in international journals.

Optics Communications, 2009

A theoretical study of a tunable Fabry–Pérot multilayer structure composed of alternating layers ... more A theoretical study of a tunable Fabry–Pérot multilayer structure composed of alternating layers of silicon and liquid crystal is presented and analyzed. The structure possesses two resonant frequencies within the stop band with tunable wavelengths and transmission properties. Tuning is achieved by allowing different orientations of the liquid crystal optical axes within the cavity and within the mirrors, while keeping

Vi Encuentro Franco-Espanol De Quimica Y Fisica Del Estado Solido - Vi Rencontre Franco-Espagnole Sur La Chimie Et La Physique De L Etat Solide, 2010

Europium-doped La 2 O 3 nanocrystalline powders with sizes ranging from 4 nm to 300 nm have been ... more Europium-doped La 2 O 3 nanocrystalline powders with sizes ranging from 4 nm to 300 nm have been obtained by the modified Pechini, hydrothermal with conventional furnace, hydrothermal with microwave furnace, and precipitation with ultrasonic bath methods. X-ray diffraction techniques were used to study the evolution of the prepared gels towards the desired crystalline phase. We determined the size and the morphology of the nanoparticles by electronic microscopy. Finally, we studied and analyzed the luminescence properties of the trivalent europium in the hexagonal La 2 O 3 nanocrystals by photoluminescence and cathodoluminescence.

Physica Status Solidi C: Current Topics in Solid State Physics, Vol 8, No 9, 2011

Abstract Photoluminescent nanopillars are fabricated by replication from nanoporous anodic alumin... more Abstract Photoluminescent nanopillars are fabricated by replication from nanoporous anodic alumina via template wetting using polymer from different chemical families: polyfluorenes, PPV derivatives and thiophenes. The experimental process entails infiltration of a ...

Optical Materials, 2011

We report here the results obtained in surface ablation of RbTiOPO 4 single crystals by femtoseco... more We report here the results obtained in surface ablation of RbTiOPO 4 single crystals by femtosecond laser. We fabricated and characterized one-dimensional (1D) diffraction gratings with different lattice spacings of 15 and 20 lm, and with a sub-modulation of the period introduced in the later. The optical and electronic microscopy characterization and filling factor analysis of these diffraction gratings are reported. We also show that the roughness generated on the grooves by the ablation process can be improved by chemical etching.

Rsc Advances, 2014

ABSTRACT We report a method for the fabrication and selective functionalization of the internal a... more ABSTRACT We report a method for the fabrication and selective functionalization of the internal and external surfaces of high-aspect-ratio hollow silicon dioxide (SiO2) micropillar arrays. The strategy enables independent surface reactions with no cross-contamination. The dual-functionalization is carried out during the fabrication of the micropillars in four steps. First, a sample of macroporous silicon is prepared by electrochemical etching and then it is thermally oxidized to create a thin layer of silicon dioxide on the internal surface of the macropores. Next, the internal surface is functionalized with mercaptopropyl trimethoxysilane (MPTMS). Subsequently, the micropillars are released by etching the back side of silicon wafers using a solution of tetramethylammonium hydroxide (TMAH). Finally, the external surface of the micropillars is chemically modified in a multi-step biofunctionalization with aminopropyl triethoxysilane (APTES), glutaraldehyde (GTA) and bovine serum albumin (BSA). The resulting structures were characterized by scanning electron microscopy and the surface reactions were confirmed by Fourier-transform infrared spectroscopy. The internal and external sides were photolabeled with tetramethyl rhodamine-5-maleimide and fluorescein isothiocyanate (FITC), respectively, and analyzed using fluorescence confocal microscopy. The peculiar three-dimensional (3D) geometry of the micropillars allows these double-active surfaces to be imaged at the same time. Results demonstrated the successful dual-side chemical modification and the feasibility of imaging both internal and external sides. Due to its remarkable architecture and chemical versatility, these micropillar arrays are a promising engineered platform for a range of applications such as biosensing, 3D cell culture and drug delivery.

Nature Communications, 2014

Silicon is the material of choice for visible light photodetection and solar cell fabrication. Ho... more Silicon is the material of choice for visible light photodetection and solar cell fabrication. However, due to the intrinsic band gap properties of silicon, most infrared photons are energetically useless. Here, we show the first example of a photodiode developed on a micrometre scale sphere made of polycrystalline silicon whose photocurrent shows the Mie modes of a classical spherical resonator. The long dwell time of resonating photons enhances the photocurrent response, extending it into the infrared region well beyond the absorption edge of bulk silicon. It opens the door for developing solar cells and photodetectors that may harvest infrared light more efficiently than silicon photovoltaic devices that are so far developed.

Nanoscale Research Letters, 2014

A rugate filter based on nanoporous anodic alumina was fabricated using an innovative sinusoidal ... more A rugate filter based on nanoporous anodic alumina was fabricated using an innovative sinusoidal current profile with small current variation. The resulting structure consisted of highly parallel pores with modulations of the pore diameter along the pore axis and with no branching. The effect of the period time and the pore widening post-treatment was studied. From reflectance measurements, it was seen that the position of the reflection band can be tuned by adjusting the period time and the width by pore-widening post-treatments. We tested one of the rugate filters by infiltrating the structure with EtOH and water in order to evaluate its sensing capabilities. This method allows the fabrication of complex in-depth modulated nanoporous anodic alumina structures that open up the possibility of new kinds of alumina-based optical sensing devices.

Conference on Photonic Materials, Devices and Applications, 2005

Macroporous silicon structures have been fabricated by electrochemical etching. Such fabrication ... more Macroporous silicon structures have been fabricated by electrochemical etching. Such fabrication process is known to result in the presence of a thin microporous Si layer at the walls of the macropores and at the surface. Photoluminescence measurements conducted in plan-view and cross-section exhibit a wide emission peak around 650nm which can be attributed to the microporous Si. The combination of a photonic crystal and a light emitter in one structure represents a potential for applications that has not been studied previously. This preliminary study shows the influence of the main fabrication parameters, namely the current density and the etchant solution, on the emission properties of the microporous Si layer.