Microneedles are newly developed biomedical devices, whose advantages are mainly in the non-invasiveness, discretion and versatility of use both as diagnostics and as therapeutics tool. In fact, they can be used both for drugs delivery in the interstitial fluids and for the analysis of the interstitial fluid. In this work we present the preliminary results for two devices based on micro needles in PolyEthylene (Glycol). The first for the drugs delivery includes a membrane whose optical reflected wavelength is related to the concentration of drug. Here, we present our preliminary result in diffusion of drugs between the membrane and the microneedles. The second device is gold coated and it works as electrode for the electrochemical detection of species in the interstitial fluid. A preliminary result in detection of glucose will be shown.
Porous silicon (PSi) non-symmetric multilayers are modified by organic molecular beam deposition of an organic semiconductor, namely the N,N’-1H,1H-perfluorobutyldicyanoperylene-carboxydi-imide (PDIF-CN<sub>2</sub>). Joule evaporation of PDIF-CN<sub>2</sub> into the PSi sponge-like matrix not only improves but also adds transducing skills, making this solid-state device a dual (optical and electrical) signal sensor for biochemical monitoring. PDIF-CN<sub>2</sub> modified PSi optical microcavities show an increase of about 5 orders of magnitude in electric current with respect to the same bare device. This feature can be used to sense volatile substances.
In this work we have investigated the photoluminescence signal emitted by graphene oxide (GO) nanosheets infiltrated in silanized porous silicon (PSi) matrix. We have demonstrated that a strong enhancement of the PL emitted from GO by a factor of almost 2.5 with respect to GO on crystalline silicon can be experimentally measured. This enhancement has been attributed to the high PSi specific area. In addition, we have observed a weak wavelength modulation of GO photoluminescence emission, this characteristic is very attractive and opens new perspectives for GO exploitation in innovative optoelectronic devices and high sensible fluorescent sensors.
In this paper the realization and the characterization of a resonant cavity enhanced photodetector (RCE), completely
silicon compatible and working at 1.55 micron, is reported. The detector is a RCE structure incorporating a Schottky
diode and its working principle is based on the internal photoemission effect. In order to obtain a fabrication process
completely compatible with standard CMOS silicon technology, a photodetector having copper (Cu) as Schottky metal
has been realized. Performances devices in terms of responsivity, free spectral range, finesse are reported.
In the last few years, silicon photonics has been characterized by a wide range of applications in several fields, from
communications to sensing, from biophotonics to the development of new artificial materials. In this communication,
we report a review of the main results obtained in our laboratories in design, fabrication and characterization of new
silicon-based optical structures and devices, including metamaterials, photodetectors, raman light amplifiers, and
porous silicon based bio-chemical sensors and biochips. Future perspectives in integration of silicon based MEMS
and MOEMS are also presented.
In this paper, the design of resonant cavity enhanced photodetectors, working at 1.55 micron and based on silicon
technology, is reported. The photon absorption is due to internal photoemission effect over the Schottky barrier at the
metal-silicon interface. A comparison is presented among three different photodetectors having as Schottky metal: gold,
aluminium or copper respectively. In order to quantify the performance of photodetector, quantum efficiency including
the image force effect, as a function of bias voltage is calculated.
In this paper, a methodology for the analysis of a resonant cavity enhanced (RCE) photodetector, based on internal
photoemission effect and working at 1.55 &mgr;m, is reported. In order to quantify the performance of photodetector, quantum
efficiency including the image force effect, bandwidth and dark current as a function of bias voltage are calculated.
We propose a comparison among three different Schottky barrier Silicon photodetectors, having as metal layers gold, silver
or copper respectively. We obtain that the highest efficiency (0.2%) but also the highest dark current is obtained with metal
having the lowest barrier, while for all devices, values of order of 100GHz and 100MHz were obtained, respectively, for the
carrier-transit time limited 3-dB bandwidth and bandwidth-efficiency.
In this work we investigate the possibility to use Zinc Oxide (ZnO) thin films, deposited by RF magnetron sputtering, for
the realization of integrated optical structures working at 1550 nm. Structural properties of sputtered zinc oxide thin
films were studied by means of X-ray Diffraction (XRD) measurements, while optical properties were investigated by
spectrophotometry and Spectroscopic Ellipsometry (SE). In particular, ellipsometric measurements allowed to determine
the dispersion law of the ZnO complex refractive index (see manuscript) = n - jk through the multilayer modeling using Tauc-Lorentz
(TL) dispersion model. We have found a preferential c-axis growth of ZnO films, with slightly variable deposition rates
from 2.5 to 3.8 Å/s. Conversely, the refractive index exhibits, from UV to near IR, a considerable and almost linear
variation when the oxygen flux value in the deposition chamber varies from 0 to 10 sccm. In order to realize a waveguide
structure, a 3-&mgr;m-thick ZnO film was deposited onto silicon single crystal substrates, where a 0.5-&mgr;m-thick thermal SiO<sub>2</sub>
buffer layer was previously realized, acting as lower cladding. Dry and wet chemical etching processes have been
investigated to achieve controllable etching rate and step etching profile, with the aim to realize an optical rib waveguide.
The etched surfaces were inspected using scanning electron microscopy (SEM) and optical microscopy. Moreover, we
carried out the experimental measurements of the fringes pattern and Free Spectral Range (FSR) of an integrated Fabry-
Perot etalon, obtained by cleaving of a single mode rib waveguide.
In this paper we present a general methodology for the design of resonant cavity enhanced (RCE) photodetectors based on the internal photoemission effect. In order to estimate the theoretical quantum efficiency we take advantage of the analytical formulation of the internal photoemission effect (Fowler theory), and its extension for thin films. In particular, the absorptance is numerically determined by means of an approach based on the transfer matrix method. Finally, we apply the proposed methodology to the design of a silicon RCE photodetector operating at 1.55μm, based on the internal
photoemission effect at an Au-Si schottky barrier.
Silicon optical receivers, operating at the optical communication wavelengths in the 1.3-1.55 μm range, have attracted much research effort. Unfortunately, the performance of the devices proposed in literature are poor because this wavelength range is beyond the absorption edge of silicon. In order to extend the maximum detectable wavelength, the most common approach, in the realization of Si-based detectors, is the use of silicon-germanium layers on silicon, anyway, requiring processes non compatible with standard CMOS technology. In this paper, with the aim to extend the operation of silicon-based photo-detectors up to the 1.3-1.55 μm range, an alternative approach is investigated: we propose the design of a resonant cavity enhanced Schottky photodetector based on the internal photoemission effect. The device fabrication is completely compatible with standard silicon technology.