We present a method for the production of polycrystalline Si (poly-Si) photonic micro-structures based on laser writing. The method consists of local laser-induced crystallization of amorphous ...silicon (a-Si) followed by selective etching in chemical agents that act preferentially on the a-Si material, consequently revealing the poly-Si content of the film. We have studied the characteristics of these structures as a function of the laser processing parameters and we demonstrate their potential photonic functionality by fabricating polycrystalline silicon ridge optical waveguides. Preliminary waveguide transmission performance results indicated an optical transmission loss of 9 dB/cm in these unrefined devices.
The field of surgical interventions emphasizes knowledge and experience; explicit and detailed models of surgical processes are hard to obtain by observation or measurement. However, in medical ...engineering and related developments, such models are highly valuable. Surgical process modeling deals with the generation of complex process descriptions by observation. This places high demands on the observers, who have to use a sizable terminology to denominate surgical actions, instruments, and patient anatomies, and to describe processes unambiguously. Here, we present a novel method, employing an ontology-based user interface that adapts to the actual situation and describe the principles of the system. A validation study showed that this method enables observers with little recording experience to reach a recording accuracy of >90%. Furthermore, this method can be used for live and video observation. We conclude that the method of ontology-supported recording for complex behaviors can be advantageously employed when surgical processes are modeled.
Low-field leakage current has been measured in thin oxides after exposure to ionising radiation. This Radiation Induced Leakage Current (RILC) can be described as an inelastic tunnelling process ...mediated by neutral traps in the oxide, with an energy loss of about 1 eV. The neutral trap distribution is influenced by the oxide field applied during irradiation, thus indicating that the precursors of the neutral defects are charged, likely to be defects associated with trapped holes. The maximum leakage current is found under zero-field condition during irradiation, and it rapidly decreases as the field is enhanced, due to a displacement of the defect distribution across the oxide towards the cathodic interface. The RILC kinetics are linear with the cumulative dose, in contrast with the power law found on electrically stressed devices.
This paper presents the radiation testing of a commercial-off-the-shelf SRAM-based field-programmable gate arrays (FPGAs) with heavy ions. Test experiments have been conducted to identify and to ...classify the single-event upsets (SEUs) in the configuration memory that induce single-event functional interrupt for the user-implemented circuit. Moreover the paper presents a new approach for assessing the effects of SEUs based on the combination of radiation testing and simulation-based fault injection tool. First experimental results show the FPGA look-up table (LUT) resources (used to implement combinatorial logic) are the most sensitive to SEUs, whereas interconnect resources are the most critical for the device cross section because they use the largest number of configuration bits. The analysis of experimental data underlines that the most probable error affecting interconnections is the shorting of two nets. This observation indicates that new fault models should be considered along with the classic stuck-at one model designing fault-tolerant architectures, which are intended for implementation in FPGA devices.
SRAM-based field programmable gate arrays (FPGAs) are particularly sensitive to single event upsets (SEUs) that, by changing the FPGA's configuration memory, may affect dramatically the functions ...implemented by the device. In This work we describe a new approach for predicting SEU effects in circuits mapped on SRAM-based FPGAs that combines radiation testing with simulation. The former is used to characterize (in terms of device cross section) the technology on which the FPGA device is based, no matter which circuit it implements. The latter is used to predict the probability for a SEU to alter the expect behavior of a given circuit. By combining the two figures, we then compute the cross section of the circuit mapped on the pre-characterized device. Experimental results are presented that compare the approach we developed with a traditional one based on radiation testing only, to measure the cross section of a circuit mapped on an FPGA. The figures here reported confirm the accuracy of our approach.
An analytical model of Radiation Induced Leakage Current (RILC) has been developed for ultra-thin gate oxides submitted to high dose ionizing radiation. The model is based on the solution of the ...Schrodinger equation for a simplified oxide band structure, where RILC occurs through electron trap-assisted tunneling. The values of the model parameters have been calibrated by comparing the transmission probabilities obtained in this model with those obtained through the WKB method in the actual oxide band structure. No free fitting parameter has been introduced, and all physical constant values have been selected within the values found in literature. Different trap distributions have been considered as candidates, but the comparison between simulated and experimental curves have indicated that a double gaussian distribution in space and in energy grants the best fit of the experimental results for different ionizing particles, oxide fields during irradiation, radiation doses, and oxide thickness. Excellent matching has been found for both positive and negative RILC by using a single trap distribution. The trap density linearly increases with the radiation dose and decreases with the oxide field during irradiation. The trap distribution is spatially symmetrical in the oxide, centered in the middle of the oxide thickness, and is not modified as the cumulative dose increases.
We have investigated new aspects of the gate leakage current due to radiation-induced soft breakdown (RSB) of thin oxides subjected to heavy-ion irradiation. Temperature and noise characteristics of ...RSB on MOS capacitors with 3- and 4- nm MOS oxides have been experimentally investigated. We have developed an empirical law to describe quantitatively the temperature dependence of the RSB current. A small activation energy has been found by using an Arrhenius relation, in agreement with the RSB tunneling conduction mechanism. The RSB variation at high temperature has been only estimated, as measurements of RSB oxides easily produced catastrophic breakdown. We have studied the RSB noise and identified different contributions to the characteristic random telegraph noise, correlated with the trapping and conduction characteristics of the RSB spots. An original model has been developed that successfully describes the different probability distributions of the current fluctuations that cannot be simulated by using previous models, such as those based on Levy or Gaussian distributions. Finally, a correlation was established between the shape of the fluctuation distribution and the degradation level of the oxide.
The excess leakage current across ultrathin dielectrics is studied for different ionizing radiation sources. Namely, X-rays, 8-MeV electrons, and three-ion beams with different LETs values are used ...on large-area MOS capacitors with 4-nm thick oxides. Small oxide fields were applied during irradiation, reaching 3 MV/cm at most. For ionizing radiation with relatively low LET (less than 10 MeV sq cm/mg), only radiation-induced leakage current (RILC) was observed, due to the formation of neutral defects mediating electron tunneling via a single oxide trap. For high LET values, instead, the gate leakage current could be described by an empirical relation proper to soft breakdown (SB) phenomena detected after electrical stress. Moreover, the typical random telegraph signal noise feature of this radiation-induced soft breakdown (RSB) currents was observed during and after irradiation. RSB can be attributed to conduction through a multidefect path across the oxide, produced by the residual damage of dense ion tracks. The oxide field applied during irradiation enhances the RSB intensity, but RSB can be achieved even for irradiation at zero field. We also study the effect of modifying the angle of incidence of the ion beam on the intensity of the gate leakage current. (Author)
Recently it has been shown in a fluidodynamic simulation, that a wing-profiled structure of rather small size placed in the vicinity of a wind turbine augments the power of the wind turbine. In this ...paper we present the first experimental results from a prototype.
Heavy ion irradiation of thin gate oxides Ceschia, M.; Paccagnella, A.; Turrini, M. ...
IEEE transactions on nuclear science,
12/2000, Letnik:
47, Številka:
6
Journal Article
Recenzirano
We have studied the gate leakage current after heavy ion irradiation of MOS capacitors with thin gate oxides. In 3-nm and 4-nm oxides radiation-induced soft breakdown (RSB) occurs even after ion ...fluences as small as 100 ion hits on the device surface. The RSB conductive paths likely reproduce the ion hit distribution: some of them can drive a substantial fraction of the whole gate leakage current. The bias applied during irradiation enhances the RSB current intensity but no critical field exists to ignite the RSB, which is observed also under flat-band. The irradiated 3-nm oxides show smaller current variations and random telegraph signal (RTS) noise than the 4-nm oxides, owing to the higher current driven in fresh devices by direct tunneling conduction. The RTS noise increases with the radiation dose; it can be described successfully neither by a Levy nor by a Gaussian distribution. In 6.5-nm and 10-mn thick oxides the defect clusters generated by heavy ion irradiation can produce RSB and RILC (radiation induced leakage current), which have not been observed after low LET irradiation or electrical stresses.
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