Microfluidics for the treatment of hydrocephalus

The aim of this work consists in investigating how micro fluidic systems realized with different micro-electromechanical (MEMS) technologies and telemetry sensors can be applied in the treatment of the human disease called hydrocephalus. In particular we will evaluate system performances in terms of maximum allowable flowrate and valve efficiency

Research intelligence : bulletin of the British Educational Research Association

Thin detectors have been proposed to investigate the possibility to limit the full depletion voltage and the leakage current of heavily irradiated silicon devices. In this work we compare typical silicon detectors (p–n junctions over a $300 \mu \rm{m }$ thick substrate) with thinned devices ($50–100 \mu \rm{m}$ of thickness). In order to investigate the performances of these structures, simulations have been carried out using the ISE-TCAD DESSIS device simulator. The so called three-level model has been used to investigate the effects of the radiation fluence on charge collection efficiency of thin and thick silicon structures. For each thickness, we simulate the hit of a minimum ionizing particle and then we calculate the current at the diode's electrode. We consider a $7 \times 10^{11} \rm{cm}^{−3}$ n-doped substrate (a high resistivity substrate); all the structures are composed of a $40 \mu \rm{m}$ diode contact and a $15 \mu \rm{m}$ distant guard ring. The simulated collected charge of the $300 \mu \rm{m}$ diode is in agreement with the experimental results; the simulation of thinner structures ($50–100 \mu \rm{m}$) shows a saturation of the number of e–h pairs collected at the diode's electrodes. These results suggest that thin detectors may have a better performance at higher fluences than thick ones. They are maximizing the collected charge at lower depletion voltage

Thermo-mechanical analysis of microstructures for chemoresistive gas sensors

The thermo-mechanical behaviour of different bulk-micromachined microheater structures for chemoresistive gas sensors is investigated by means of 3D finite element simulation. Si3N4-SiO2-Si3N4 and SiO2-Si3N4-SiO2 stacked membranes are compared in terms of heat confinement and mechanical properties. The mechanical behaviour of the membrane and of two different suspended-bridge structures under applied external load is analysed. The present study served as a basis for the development of a microheater which hase shown excellent heating efficiency characteristics

Compact modeling of n-side interstrip resistance in p-stop and p-spray isolated double-sided silicon microstrip detectors

A compact, analytical model is derived for the n-side interstrip resistance of double-sided silicon microstrip detectors, allowing for fast and accurate prediction of the minimum p-stop (or p-spray) implant dose ensuring adequate interstrip isolation. The basic idea on which the proposed model relies is that the portion of the detector between two adjacent n-strips can effectively be assimilated to an equivalent n-channel MOSFET. The interstrip resistance can be evaluated as the output resistance of such an equivalent MOSFET using standard SPICE-like models. The influence of radiation-induced oxide charge and p-stop (or p-spray) voltage can be incorporated into the model by simply including in the threshold voltage expression the induced flat-band voltage shift and body-effect term, respectively

Numerical simulation of radiation damage effects in p-type and n-type FZ silicon detectors

In the framework of the CERN-RD50 Collaboration, the adoption of p-type substrates has been proposed as a suitable mean to improve the radiation hardness of silicon detectors up to fluencies of $1 \times 10^{16} \rm{n}/cm^2$. In this work two numerical simulation models will be presented for p-type and n-type silicon detectors, respectively. A comprehensive analysis of the variation of the effective doping concentration ($N_{\rm{eff}}$), the leakage current density and the charge collection efficiency as a function of the fluence has been performed using the Synopsys T-CAD device simulator. The simulated electrical characteristics of irradiated detectors have been compared with experimental measurements extracted from the literature, showing a very good agreement. The predicted behaviour of p-type silicon detectors after irradiation up to $10^{16} \rm{n}/cm^2$ shows better results in terms of charge collection efficiency and full depletion voltage, with respect to n-type material, while comparable behaviour has been observed in terms of leakage current density

Two-dimensional numerical simulation of edge-generated currents in type-inverted, single-sided silicon microstrip detectors

A theoretical study is presented showing that the reverse leakage current thermally generated at the cutting edge of type-invertedp+/n single-sided silicon microstrip detectors is limited. Such behavior is shown to be related to a self-limiting mechanism acting on the edge surface generation, which prevents the net generation rate of electron-hole pairs at the detector edge from exceeding a saturation value, as the local hole density approaches its equilibrium value

Si-PIN X-Ray detector technology

PIN diodes and other test structures have been fabricated on both n- and p-type, high-resistivity, Floating-Zone (FZ) silicon substrates. Different alternative extrinsic-gettering techniques have been adopted to the purpose of meeting the required specification of a detector leakage current density lower than 1 nA/cm2. Phosphorus-doped polysilicon gettering provided the best results on n-type Si with a leakage current density lower than 0.2 nA/cm2 at 100 um depletion width. On the contrary, devices made on p-type substrates exhibited a leakage current density two orders of magnitude higher. A proper control of the oxide charge at the silicon-silicon dioxide interface was found to be crucial in obtaining a predictable behavior of PIN diode detectors. Some degradation of the reverse leakage current has been observed after device dicing and bonding

Thermal and electrical characterization of silicon photomultiplier

Detection of low levels of light is one of the key aspects in medical and space applications. Silicon photomultiplier, a novel type of avalanche photodetector which operates in Geiger mode, shows promising results and offer superior design options. The performance characteristics of the SiPM realized in FBK-irst are studied and presented in this paper. The leakage current, dark rate and internal gain are characterized as a function of temperature. The investigation has been carried out in the framework of the DASiPM Collaboration and the INFN/FBK-irst MEMS project. © 2008 IEEE

Der @Apotheker-Berater : Apothekenführung, Recht, Steuern, Finanzen

In the framework of the CERN-RD50 and INFN-SMART collaboration, we have investigated the possibility of using thin devices as a solution to improve the reliability of silicon detectors after long-term irradiation at the Super-Large Hadron Collider (LHC). In this work, we compare conventional silicon detectors (p-on-n type diodes over a $300 \mu \rm{m}$ thick wafer substrates) with thinned devices ($50–100 \mu \rm{m}$ thick). The performance of these structures have been studied by means of a three defect level radiation damage model, implemented in the SYNOPSYS-TCAD device simulator. The effects of the radiation fluence on the effective doping concentration ($N_{\rm{eff}}$), leakage current and charge collection efficiency (CCE) have been investigated up to irradiation fluencies of $10^{16} \ 1$ MeV neutron-equivalent/cm$^2$. The simulations have been compared with experimental measurements carried out on similar test structures irradiated with neutrons and protons at high fluencies