Near infra-red light detection enhancement of plasmonic photodetectors

Nowadays numerous are the applications interested in exploiting near infrared light detection like LiDAR (at 850 - 950 nm wavelengths), NIR spectroscopy, quantum computation, and the detection of light from NIR emitting scintillators. Silicon based single photon avalanche diodes (SPAD) could be a valid device achieving high detection efficiency and high timing resolution. Moreover, they can provide single photon sensitivity in large areas if arranged in extended arrays named Silicon Photomultipliers (SiPM). Nevertheless, the Photon Detection Efficiency (PDE) of standard SiPMs in the NIR range is strongly limited by the relatively low Si absorption coefficient, leading to an absorption depth much larger than the typical active thickness of Si SPAD, i.e. 18 μm at 850 nm compared to some few μm’s. Hence, the performance of Si based detectors in NIR range is still inadequate for almost all the cited applications. A potential solution to overcome the limited Si absorption coefficient is to couple these photodetectors with a structure supporting highly confined light such as plasmonic oscillations, thus increasing the absorption. In recent years, the development in nanophotonic demonstrated that the interphase between metallic nanostructured and dielectric surface can support Surface Plasmon Polaritons (SPP) i.e. electrons collective oscillation highly confined along the thickness of the device. Some of these interesting nanostructured are: i) 1- and 2-dimensional gratings; ii) bullseye structures; iii) nano-pillars and nano-holes arrays. Among those, 1D and 2D metallic nanograting are the most promising structures considering their feasibility and possible integration with Si based photodetector and SiPM technologies. In this contribution, we investigated the integration of a bidimensional metallic plasmonic nanograting structure on state of art photodetectors (PDs). For ease of production and characterization, the test devices consisted of conventional Silicon photodiodes instead of a proper SPAD. The PDs have been produced at the facility of Fondazione Bruno Kessler (Trento, Italy) using a custom CMOS-like microfabrication process similar the one used for FBK-SiPM technology. The previous described metallic nanograting is directly fabricated on a PDs by i) Electron Beam Lithography (EBL), ii) silver deposition, and iii) lift-off. Afterwards, the quantum efficiency (QE) of the produced samples have been measured in (450-1100) nm range. The first results are promising with an enhancement of about 45% at 950 nm with respect to the reference PD without any plasmonic nanostructured on top

Imaging of Antiferroelectric Dark Modes in an Inverted Plasmonic Lattice [Dataset]

6 pages. -- S1. Transversal electric field distribution for the SLR at 1.57 eV. -- S2. Simulated electric field and charge distributions for a threesome of slits. -- S3. Simulated electric field and charge distributions for the simplest local dark mode of the inverted honeycomb lattice. -- S4. Profiles of the EELS signal and the simulated electric field along the slits for the antiferroelectric dark modes. -- S5. Array of the magnetic dipoles over the structure used to simulate antiferroelectric dark modes.Plasmonic lattice nanostructures are of technological interest because of their capacity to manipulate light below the diffraction limit. Here, we present a detailed study of dark and bright modes in the visible and near-infrared energy regime of an inverted plasmonic honeycomb lattice by a combination of Au+ focused ion beam lithography with nanometric resolution, optical and electron spectroscopy, and finite-difference time-domain simulations. The lattice consists of slits carved in a gold thin film, exhibiting hotspots and a set of bright and dark modes. We proposed that some of the dark modes detected by electron energy-loss spectroscopy are caused by antiferroelectric arrangements of the slit polarizations with two times the size of the hexagonal unit cell. The plasmonic resonances take place within the 0.5–2 eV energy range, indicating that they could be suitable for a synergistic coupling with excitons in two-dimensional transition metal dichalcogenides materials or for designing nanoscale sensing platforms based on near-field enhancement over a metallic surface.Peer reviewe

Tuning piezoresistive transduction in nanomechanical resonators by geometrical asymmetries

Under the terms of the Creative Commons Attribution (CC BY) license to their work.The effect of geometrical asymmetries on the piezoresistive transduction in suspended double clamped beam nanomechanical resonators is investigated. Tapered silicon nano-beams, fabricated using a fast and flexible prototyping method, are employed to determine how the asymmetry affects the transduced piezoresistive signal for different mechanical resonant modes. This effect is attributed to the modulation of the strain in pre-strained double clamped beams, and it is confirmed by means of finite element simulations.The research leading to these results received funding from the European Union's Seventh Framework Programme FP7/2007-2013, under Grant Agreement No. 318804 (SNM). Support is also acknowledged from project Force for future (CSD2010-00024).Peer Reviewe

Nanolithography on thin layers of PMMA using atomic force microscopy

A new technique for producing nanometre scale patterns on thin layers (<30 nm thick) of PMMA on silicon is described. The method consists of inducing the local modification of the PMMA by applying a positive voltage between the silicon and an atomic force microscope (AFM) tip. At voltages larger than 28 V, it is observed that a hole is directly produced on the PMMA. The silicon surface is simultaneously oxidized even in the case where a hole has not been created. Monitoring of the electrical current through the AFM tip during the application of the voltage allows elucidating the mechanism of the PMMA removal. The process is used to define nanometre scale electrodes by combining the AFM lithography with electron beam lithography, metal deposition and lift-off processes. © 2005 IOP Publishing Ltd.Peer reviewe

Arrays of suspended silicon nanowires defined by ion beam implantation: mechanical coupling and combination with CMOS technology

We present the fabrication, operation, and CMOS integration of arrays of suspended silicon nanowires (SiNWs). The functional structures are obtained by a top-down fabrication approach consisting in a resistless process based on focused ion beam irradiation, causing local gallium implantation and silicon amorphization, plus selective silicon etching by tetramethylammonium hydroxide, and a thermal annealing process in a boron rich atmosphere. The last step enables the electrical functionality of the irradiated material. Doubly clamped silicon beams are fabricated by this method. The electrical readout of their mechanical response can be addressed by a frequency down-mixing detection technique thanks to an enhanced piezoresistive transduction mechanism. Three specific aspects are discussed: i) the engineering of mechanically coupled SiNWs, by making use of the nanometer scale overhang that it is inherently-generated with this fabrication process, ii) the statistical distribution of patterned lateral dimensions when fabricating large arrays of identical devices, and iii) the compatibility of the patterning methodology with CMOS circuits. Our results suggest that the application of this method to the integration of large arrays of suspended SiNWs with CMOS circuitry is interesting in view of applications such as advanced radio frequency band pass filters and ultra-high-sensitivity mass sensors.SNM (FP7-ICT-2011-8)) and Nanointegra (TEC2015-69864-R)Peer reviewe

Fabrication of functional electromechanical nanowire resonators by focused ion beam implantation

A fast and flexible fabrication method that allows the creation of silicon structures of various geometries is presented. It is based on the combination of focused ion beam local gallium implantation, selective silicon etching, and diffusive boron doping. The structures obtained by this resistless method are electrically conductive. Freely suspended mechanical resonators of different dimensions and geometries have been fabricated and measured. The resulting devices present a good electrical conductivity which allows the characterization of their high-frequency mechanical response by electrical read-out.This work is supported by the European Seventh Framework Programme (FP7) within the project SNM: single nanometer manufacturing for beyond CMOS devices and by national funding from FORCE-for-FUTURE (CSD2010-00024) and SGR-NANONEMS (2014 SGR 1025). J. Ll. is enrolled in the UAB’s PhD program in material science.Peer Reviewe

Carbon nanotubes as platforms for electrochemical and electronic detection of biorecognition processes

Trabajo presentado a la Conferencia "BNC-b Research Meeting" celebrada en Barcelona el 14 de julio de 2011.This work was financially supported by the Ministry of Education and Science of Spain (Project CTQ2009-13873) M. Pacios acknowledges a FPI predoctoral grant.Peer reviewe

DNA hybridization detection by electrochemical impedance spectroscopy using interdigitated gold nanoelectrodes

7 páginas, 5 figuras, 1 tabla.A DNA biosensor is presented that is based on gold interdigitated nanoelectrodes of 100 nm width and 250 nm pitch. A single-strand oligonucleotide acts as the capture probe. Because of its nanometer dimensions, the device shows improved sensitivity when compared to similar systems. This encouraged us to perform a direct and unlabelled detection. After incubation with the DNA target, the impedance spectrum was recorded between 1 kHz and 10 MHz to obtain the net capacitance change. The use of a biotinylated DNA signalling probe permitted the integration of an amplification stage in a sandwich format that employs streptavidin-modified gold nanoparticles. The strategy was preliminarily tested by detecting the breast cancer related BRCA1 gene, where the noncomplementary, wild and mutated forms were easily differentiated at a concentration level of 3 μM (corresponding to a 30 pmol quantity).Financial support for this work has been provided by the Ministry of Education and Science (MEC, Madrid, Spain) through project NANOBIOMED (Consolider-Ingenio 2010, Project CSD2006-00012) and by the Department of Innovation, Universities and Enterprise (DIUE) from the Generalitat de Catalunya.Peer reviewe