A Backscattering Model Incorporating the Effective Carrier Temperature in Nano MOSFET

In this work we propose a channel backscattering model in which increased carrier temperature at the top of the potential energy barrier in the channel is taken into account. This model represents an extension of a previous model by the same authors which highlighted the importance of considering the partially ballistic transport between the source contact and the top of the potential energy barrier in the channel. The increase of carrier temperature is precisely due to energy dissipation between the source contact and the top of the barrier caused by the high saturation current. To support our discussion, accurate 2D full band Monte Carlo device simulations with quantum correction have been performed in double gate nMOSFETs for different geometries (gate length down to 10 nm), biases and lattice temperatures. Including the effective carrier temperature is especially important to properly treat the high inversion regime, where previous backscattering models usually fail

A microscopically accurate model of partially ballistic nanoMOSFETs in saturation based on channel backscattering

We propose a model for partially ballistic MOSFETs and for channel backscattering that is alternative to the well known Lundstrom model and is more accurate from the point of view of the actual energy distribution of carriers. The key point is that we do not use the concept of "virtual source". Our model differs from the Lundstrom model in two assumptions: i) the reflection coefficients from the top of the energy barrier to the drain and from top of the barrier to the source are approximately equal (whereas in the Lundstrom model the latter is zero), and ii) inelastic scattering is assumed through a ratio of the average velocity of forward-going carriers to that of backward-going carriers at the top of the barrier kv > 1 (=1 in the Lundstrom model). We support our assumptions with 2D full band Monte Carlo (MC) simulations including quantum corrections in nMOSFETs. We show that our model allows to extract from the electrical characteristics a backscattering coefficient very close to that obtained from the solution of the Boltzmann transport equation, whereas the Lundstrom model overestimates backscattering by up to 40%

Accurate QTF Sensing Approach by Means of Narrow Band Spectral Estimation

We propose a new approach for the extraction of the equivalent parameters of quartz tuning forks used as sensors by means of noise measurements. Noise is used as the test signal for the determination, by means of spectral analysis, of the frequency response of a circuit including the quartz tuning fork whose parameters need to be determined. A new approach for the analysis of strongly peaked noise spectra was developed in order to allow the correct measurement of the strongly peaked noise spectrum at the output of the system, which is the result of the high-quality factor of any quartz tuning fork-based sensor. With the approach we propose, the best compromise in terms of accuracy and measurement time can be obtained in a single measurement run. The performances of the approach we propose are discussed in comparison with those that can be obtained from a swept spectrum approach in the same operating conditions

Barrier Lowering and Backscattering Extraction in Short-Channel MOSFETs

In this work we propose a fully experimental method to extract the barrier lowering in short-channel saturated MOSFETs using the Lundstrom backscattering transport model in a one sub-band approximation and carrier degeneracy. The knowledge of the barrier lowering at the operative bias point in the inversion regime is of fundamental importance in device scaling. At the same time we obtain also an estimate of the backscattering ratio and of the saturation inversion charge. Respect to previously reported works on extraction of transport parameters based on the Lundstrom model, our extraction method is fully consistent with it, whereas other methods make a number of approximations in the calculation of the saturation inversion charge which are inconsistent with the model. The proposed experimental extraction method has been validated and applied to results from device simulation and measurements on short-channel poly-Si/SiON gate nMOSFETs with gate length down to 70 nm. Moreover we propose an extension of the backscattering model to the case of 2D geometries (e.g. bulk MOSFETs). We found that, in this case, the backscattering is governed by the carrier transport in a few nanometers close to the silicon/oxide interface and that the value of the backscattering ratio obtained with a 1D approach can be significantly different from the real 2D value

Serum Albumin Is Inversely Associated With Portal Vein Thrombosis in Cirrhosis

We analyzed whether serum albumin is independently associated with portal vein thrombosis (PVT) in liver cirrhosis (LC) and if a biologic plausibility exists. This study was divided into three parts. In part 1 (retrospective analysis), 753 consecutive patients with LC with ultrasound-detected PVT were retrospectively analyzed. In part 2, 112 patients with LC and 56 matched controls were entered in the cross-sectional study. In part 3, 5 patients with cirrhosis were entered in the in vivo study and 4 healthy subjects (HSs) were entered in the in vitro study to explore if albumin may affect platelet activation by modulating oxidative stress. In the 753 patients with LC, the prevalence of PVT was 16.7%; logistic analysis showed that only age (odds ratio [OR], 1.024; P = 0.012) and serum albumin (OR, -0.422; P = 0.0001) significantly predicted patients with PVT. Analyzing the 112 patients with LC and controls, soluble clusters of differentiation (CD)40-ligand (P = 0.0238), soluble Nox2-derived peptide (sNox2-dp; P < 0.0001), and urinary excretion of isoprostanes (P = 0.0078) were higher in patients with LC. In LC, albumin was correlated with sCD4OL (Spearman's rank correlation coefficient [r(s)], -0.33; P < 0.001), sNox2-dp (r(s), -0.57; P < 0.0001), and urinary excretion of isoprostanes (r(s), -0.48; P < 0.0001) levels. The in vivo study showed a progressive decrease in platelet aggregation, sNox2-dp, and urinary 8-iso prostaglandin F2 alpha-III formation 2 hours and 3 days after albumin infusion. Finally, platelet aggregation, sNox2-dp, and isoprostane formation significantly decreased in platelets from HSs incubated with scalar concentrations of albumin. Conclusion: Low serum albumin in LC is associated with PVT, suggesting that albumin could be a modulator of the hemostatic system through interference with mechanisms regulating platelet activation

Single JFET Front-End Amplifier for Low Frequency Noise Measurements with Cross Correlation-Based Gain Calibration

We propose an open loop voltage amplifier topology based on a single JFET front-end for the realization of very low noise voltage amplifiers to be used in the field of low frequency noise measurements. With respect to amplifiers based on differential input stages, a single transistor stage has, among others, the advantage of a lower background noise. Unfortunately, an open loop approach, while simplifying the realization, has the disadvantage that because of the dispersions in the characteristics of the active device, it cannot ensure that a well-defined gain be obtained by design. To address this issue, we propose to add two simple operational amplifier-based auxiliary amplifiers with known gain as part of the measurement chain and employ cross correlation for the calibration of the gain of the main amplifier. With proper data elaboration, gain calibration and actual measurements can be carried out at the same time. By using the approach we propose, we have been able to design a low noise amplifier relying on a simplified hardware and with background noise as low as 6 nV/√Hz at 200 mHz, 1.7 nV/√Hz at 1 Hz, 0.7 nV/√Hz at 10 Hz, and less than 0.6 nV/√Hz at frequencies above 100 Hz

On the design of an automated system for the characterization of the electromigration performance of advanced interconnects by means of low-frequency noise measurements

Low-frequency noise measurements have long been recognized as a valuable tool in the examination of quality and reliability of metallic interconnections in the microelectronic industry. While characterized by very high sensitivity, low-frequency noise measurements can be extremely time-consuming, especially when tests have to be carried out over an extended temperature range and with high temperature resolutionas it is required by some advanced characterization approaches recently proposed in the literature. In order to address this issue we designed a dedicated system for the characterization of the low-frequency noise produced by a metallic line vs temperature. The system combines high flexibility and automation with excellent background noise levels. Test temperatures range from ambient temperature up to 300°C. Measurements can be completely automated with temperature changing in pre-programmed steps. A ramp temperature mode is also possible that can be used, with proper caution, to virtually obtain a continuous plot of noise parameters vs temperature

Portable and Highly Versatile Impedance Meter for Very Low Frequency Measurements

Electrical Impedance Spectroscopy (EIS) is a characterization technique that is gaining more and more importance in various fields of research and applications. The frequency range of investigation varies according to the type of application. In some fields (biology, medicine, energy) it is useful to be able to perform measurements at very low frequency values (down to a few mHz or even below). While impedance meters operating at frequencies in the range from a few tens of Hz up to a few MHz can be regarded as quite standard pieces of instrumentation commonly available in many laboratories, instrumentation for measurements at very low frequencies, although commercially available, is less common. The subject of this work is the design, realization and testing of a low frequency impedance measurement platform that has the advantage of being portable, rather inexpensive, and yet highly versatile. In our approach, we exploit a personal computer and a soundboard as a powerful system for digital signal generation and analysis that, with the help of low complexity and low-cost external hardware and a public domain software for the implementation of the core system, allow to tailor the platform for targeting specific applications with minimal effort. As an example, we will demonstrate the application of the system to the investigation of polypyrrole-based supercapacitor structures

Portable Knee Health Monitoring System by Impedance Spectroscopy Based on Audio-Board

Knee injuries are among the most common health problems in the world. They not only affect people who practice sports, but also those who lead a rather sedentary life. Factors such as age, weight, working and leisure activities can affect the health of the knees, causing disorders such as inflammation, edema, deterioration of cartilage and osteoarthritis. Although for the diagnosis and treatment of the various pathologies it is always advisable to contact orthopedists and specialized structures, it would often be useful to monitor the state of health of the knees in order to evaluate the healing (or worsening) process and the effects of sport/motion activities or rehabilitation. In this perspective, a portable knee health monitoring system was developed to be used at home or in gyms and sports environments in general. Besides requiring a simple custom front end, the system relies on a PC audio board capable of a sampling rate of 192 kHz to perform bioimpedance measurements at frequencies in excess of 50 kHz. A simple numerical calibration procedure allows to obtain high accuracy while maintaining low hardware complexity. The software developed for the operation of the system is freely available to any researcher willing to experiment with the bioimpedance measurement approach we propose, ensuring the conditions of portability and low complexity. Primary (intracellular and extracellular resistances and cell membrane capacitance) and secondary (real and imaginary parts of the total impedance) bioimpedance parameters can be obtained and analyzed through direct measurements with reference to an equivalent circuit model. The functionality of the system has been tested on nine subjects with different well-known health conditions, providing encouraging results in terms of the ability to correlate bioimpedance measurements to the health status of the knees. If proper clinical trials were to confirm our preliminary results, a system such as the one we propose could be used for fast and frequent monitoring of knee joints, thus possibly reducing the frequency at which complex and expensive medical exams, sometimes involving long waiting lists, must be performed