High-power semiconductor edge-emitting light-emitting diodes foroptical low coherence reflectometry

A new semiconductor source was designed for optical low coherence reflectometry, increasing the sidelobe-free dynamic range by three to five orders of magnitude compared to conventional EELED's. Reflectivities internal to an optical fiber circuit separated by as much as eight orders of magnitude can now be detected at wavelengths of 1.3 and 1.55 μm, using compact semiconductor sources. For applications not requiring sidelobe-free operation, the same devices can be operated at high current (200 mA) and low temperatures (near 0°C) to produce nearly 1 mW of 1.5 μm emission coupled into single-mode fiber. The resulting wavelength spectrum is smooth, enabling fiber-based absorption spectral measurements     

A Two-Dimensional Model for Interface Coupling in Triple-Gate Transistors

The influence of the fin width on substrate-to-gate coupling in long-channel silicon-on-insulator triple-gate transistors is investigated. A complementary analysis, taking into account both the "front coupling" (variation of the front-channel threshold voltage V_T1, as a function of the substrate bias V_G2) and "back coupling" (variation of the back-channel threshold voltage V_T2) as a function of the front-gate bias V_G1) characteristics has been carried out. It is shown that the back coupling, as opposed to the front coupling, is highly sensitive to the fin width in narrow-channel devices and can even be used in fin width extraction. Simple analytical 2-D models for the body potential, V_T1, and V_T2 have been developed to clarify the experimental data, showing in particular the gradual control of the back interface potential by the lateral gates in narrow fins. The model stands as a 2-D generalization of the Lim and Fossum's well-known 1-D interface coupling model     

Iso-shaping rigid bodies for estimating their motion from image sequences

In many medical imaging applications, due to the limited field of view of imaging devices, acquired images often include only a part of a structure. In such situations, it is impossible to guarantee that the images will contain exactly the same physical extent of the structure at different scans, which leads to difficulties in registration and in many other tasks, such as the analysis of the morphology, architecture, and kinematics of the structures. To facilitate such analysis, we developed a general method, referred to as iso-shaping, that generates structures of the same shape from segmented image sequences. The basis for this method is to automatically find a set of key points, called shape centers, in the segmented partial anatomic structure such that these points are present in all images and that they represent the same physical location in the object, and then trim the structure using these points as reference. The application area considered here is the analysis of the morphology, architecture, and kinematics of the joints of the foot from magnetic resonance images acquired at different joint positions and load conditions. The accuracy of the method is analyzed by utilizing ten data sets for iso-shaping the tibia and the fibula via four evaluative experiments. The analysis indicates that iso-shaping produces results as predicted by the theoretical framework.     

CNTs in Optoelectronic Devices: New Structural and Photophysical Insights on Porphyrin‐DWCNTs Hybrid Materials

The preparation and physical characterization of diverse porphyrin‐derived double‐walled carbon nanotubes (DWCNTs) conjugates are described. A porphyrin molecule is covalently linked and physically adsorbed to COOH‐derived DWCNTs. The photophysical properties of all porphyrin‐CNTs derivatives are studied in solution and in polymeric matrices. Definitive experimental evidence for photoinduced electron and/or energy transfer processes involving the porphyrin chromophores and the CNT wall is not obtained, but solid‐state UV‐vis absorption profiles display electronic transitions fingerprinting J‐ and H‐ type aggregates, where porphyrin molecules intermolecularly interact “head‐to‐tail” and “face‐to‐face”, respectively. In parallel, molecular modeling based on force‐field simulations is performed to understand the structure of the porphyrin‐CNTs interface and the nature of the interactions between the porphyrins and the DWCNTs. Finally, multilayered ‐ type devices are fabricated with the aim of investigating the interaction of the porphyrin‐derived DWCNTs with poly(3‐hexylthiophene)‐pyrene matrices containing small amounts of 1‐[3‐(methoxycarbonyl)propyl]‐1‐phenyl‐[6.6]C₆₁.     

Point-contact pseudo-MOSFET for in-situ characterization ofas-grown silicon-on-insulator wafers

A pseudo-MOS transistor can be activated in as-grown silicon-on-insulator (SOI) structures without any device processing by using point-contact probes. The measurement setup for in-situ operation and typical transistor characteristics are presented. Parameters are extracted which relate to minority and majority carriers, buried oxide, and the Si-SiO₂ interface     

Application of an objective method for localizing bilateral cortical FDG PET abnormalities to guide the resection of epileptic foci

PURPOSE: In order to improve the objective localization of bilateral cortical abnormalities in positron emission tomography (PET) image volumes, we developed a new three-dimensional image processing technique. The accuracy of this approach with respect to invasive subdural electroencephalography (EEG) data was assessed in a group of children with neocortical epilepsy. METHODS: Glucose PET image volumes were obtained from 12 epileptic children (mean age 5.2 +/- 4.3 years). Bilateral cortical areas of abnormal glucose metabolism were objectively determined using two conditional criteria assessed against a normal database. The normal database was derived from a group of 15 adult controls (mean age 27.6 years). The spatial relationship between seizure onset electrodes and PET abnormalities was assessed using a conventional receiver operating characteristic (ROC) analysis as well as using a newly defined spatial proximity index (SPI), which characterizes the association between adjacent, but not coincident, abnormalities. RESULTS: ROC analysis at the 2 standard deviation (SD) threshold, revealed an accuracy of 65% to detect seizure onset areas with a sensitivity of 64 +/- 17% and a specificity of 66 +/- 24%. Sensitivity decreased to 46 +/- 24% at the 3-SD threshold with a specificity of 80 +/- 21% (accuracy 75%). The average value for the SPI was determined as 3.82 +/- 1.65 which was 20% lower than the SPI value calculated using a simple in-plane two-dimensional asymmetry between homotopic cortical segments (4.52 +/- 3.82). CONCLUSION: The presented image processing technique improves localization of cortical abnormalities and provides valuable imaging clues for placement of subdural EEG grids prior to surgical resection.     

Transport profiles,the influence of internal stress and potential fluctuations in thin silicon films on sapphire

Gate-controlled and temperature-dependent measurements of the Hall voltage and capacitance were performed on thin (0.65 μm) slightly n-doped silicon on sapphire (SOS). New results are presented on mobility and donor impurity profiles, as well as on carrier scattering mechanisms at all depths inside the film and for different temperatures from 77 to 300 K. The particular configuration of the conduction band in SOS, resulting from both internal stress and potential fluctuations, is considered for a complete interpretation of the experimental results.     

Hot-electron-induced degradation of front and back channels inpartially and fully depleted SIMOX MOSFETs

The characteristics of the front and back channels of 1-μm-long SIMOX MOSFETs were measured before and after various types of periods of hot-electron stress, and a comparison between the induced degradations was made. The back channel degrades much more severely than the front channel for both partially depleted and fully depleted devices. Fully depleted MOSFETs (140-nm-thick) are favorably contrasted with partially depleted ones (300-nm-thick) as to their vulnerability to hot-carrier-induced damage. Although defects are always located at and/or near the interface of the stressed channel, they may influence the properties of the opposite channel (via interface coupling) in fully depleted MOSFETs     

Uniaxial alignment of nanoconfined columnar mesophases

By confining discotic phthalocyanines in a network of crisscrossed nanogrooves, we obtain a uniaxial alignment of the columnar mesophase. The alignment process is based on the anisotropy of interface tension between the mesophase and the nanogrooves' walls. Preferential mesophase alignment results from this nonhomogeneity combined with the anisotropy of the network cell dimensions. A simple model is proposed to explain the experimental observations.     

Experimental investigation of ESD design window for fully depleted SOI N-MOSFETs

In this article, the impact in FDSOI technology, of ground plane and buried oxide (BOX) size on the robustness and on the NMOS triggering voltage (Vt1) is shown. We show experimentally that firstly thin BOX devices are more robust than thick BOX devices and secondly with a higher Vt1, thin BOX device purposes a larger range to trigger ESD network and to optimize design.