A. Tibuzzi

Polysilicon mesoscopic wires coated by Pd as high sensitivity H2 sensors

A new class of H2 sensors made up of mesoscopic polysilicon wires coated by palladium is presented. Using surface micromachining combined with an usual microelectronic planar process, polysilicon wires of the following dimensions have been constructed: from 250 nm up to 3.7 µm wide, from 100 µm up to 140 µm long, about 700 nm thick. Because of their high surface/volume ratio, these wires have shown a very high resistance percentage variation under hydrogen absorption. Enhanced resolution together with a low production cost are the most important feature of this device.

MOS-junction-based nanostructures by thermal oxidation of silicon wires for hydrogen detection

Heavily p-doped monocrystalline silicon wires have been fabricated by employing isotropic Si wet etch and thermal oxidation to achieve a nanometric cross section-a gate-oxide growth and a final palladium evaporation made up the MOS junction able to detect hydrogen concentration in air. Several types of wire dimensions have been designed and fabricated: length ranges from 5 to 70 /spl mu/m; the smallest widths obtained are around 250-300 nm, while the biggest are up to 7 /spl mu/m. Preliminary experimental results show a high signal/noise ratio sensor response to 100 ppm concentration of H/sub 2/ at room temperature, 1-atm air.

MOS junction based nanostructures by thermal oxidation of silicon wires for hydrogen detection

Heavily p-doped monocrystalline silicon wires have been fabricated by employing wet etch and thermal oxidation steps to achieve a nanometric cross-section; a gate oxide growth and a final palladium evaporation made up the MOS junction able to detect hydrogen concentrations in air.

Finger emitter/base bipolar junction phototransistors for optical gas sensing in the blue spectral region

In this work we report on the design, fabrication, electrical characterization and sensing tests of new silicon bipolar junction phototransistors, coated by Zn-(heptiloxy)-TPP. The finger-shaped emitter/base junction has been proved to enhance the responsivity in the blue spectral region with respect to the standard fully implanted detector (0.24A/W and 0.14A/W respectively at 5 V reverse bias). This effect has been experimentally tested in reverse biased E/B junction and, even though the phototransistor is operated with floating base, slightly forward biasing the E/B junction, this improvement in responsivity was still observed. The new transducers exhibit a beta current gain higher than 150 and were employed to detect ethanol concentrations down to 300ppm.

POLYSILICON MESOSCOPIC WIRES COATED BY Pd AS H2 SENSORS

In this work a novel monocrystalline silicon nanowires array has been investigated and presented as hydrogen sensor, designed and fabricated by employing high resolution microfabrication techniques ...

AN INTEGRATED ELECTRO-OPTICAL NOSE

A first prototype of an electro-optical nose has been designed, assembled and tested. This new system is made up of a matrix of silicon integrated photodiodes (the electro-optical transducers), coated by different thin films of metalloporphyrins (used as chemically interactive material -CIMwith a function of incident light filter), and of a blue LED source with an emission peak centred in the main absorption band of the CIM (the Soret Band, around 430 nm).