Analysis of the Reformulated Source to Drain Tunneling Probability for Improving the Accuracy of a Multisubband Ensemble Monte Carlo Simulator.

As an attempt to improve the description of the tunneling current that arises in ultrascaled nanoelectronic devices when charge carriers succeed in traversing the potential barrier between source and drain, an alternative and more accurate non-local formulation of the tunneling probability was suggested. This improvement of the probability computation might result of particular interest in the context of Monte Carlo simulations where the utilization of the conventional Wentzel-Kramers-Brillouin (WKB) approximation tends to overestimate the number of particles experiencing this type of direct tunneling. However, in light of the reformulated expression for the tunneling probability, it becomes of paramount importance to assess the type of potentials for which it behaves adequately. We demonstrate that, for ensuring boundedness, the top of the potential barrier cannot feature a plateau, but rather has to behave quadratically as one approaches its maximum. Moreover, we show that monotonicity of the reformulated tunneling probability is not guaranteed by boundedness and requires an additional constraint regarding the derivative of the prefactor that modifies the traditional WKB tunneling probability.

Comprehensive Analytical Modelling of an Absolute pH Sensor.

In this work, we present a comprehensive analytical model and results for an absolute pH sensor. Our work aims to address critical scientific issues such as: (1) the impact of the oxide degradation (sensing interface deterioration) on the sensor's performance and (2) how to achieve a measurement of the absolute ion activity. The methods described here are based on analytical equations which we have derived and implemented in MATLAB code to execute the numerical experiments. The main results of our work show that the depletion width of the sensors is strongly influenced by the pH and the variations of the same depletion width as a function of the pH is significantly smaller for hafnium dioxide in comparison to silicon dioxide. We propose a method to determine the absolute pH using a dual capacitance system, which can be mapped to unequivocally determine the acidity. We compare the impact of degradation in two materials: SiO2 and HfO2, and we illustrate the acidity determination with the functioning of a dual device with SiO2.

Simulation and Modeling of Novel Electronic Device Architectures with NESS (Nano-Electronic Simulation Software): A Modular Nano TCAD Simulation Framework.

The modeling of nano-electronic devices is a cost-effective approach for optimizing the semiconductor device performance and for guiding the fabrication technology. In this paper, we present the capabilities of the new flexible multi-scale nano TCAD simulation software called Nano-Electronic Simulation Software (NESS). NESS is designed to study the charge transport in contemporary and novel ultra-scaled semiconductor devices. In order to simulate the charge transport in such ultra-scaled devices with complex architectures and design, we have developed numerous simulation modules based on various simulation approaches. Currently, NESS contains a drift-diffusion, Kubo-Greenwood, and non-equilibrium Green's function (NEGF) modules. All modules are numerical solvers which are implemented in the C++ programming language, and all of them are linked and solved self-consistently with the Poisson equation. Here, we have deployed some of those modules to showcase the capabilities of NESS to simulate advanced nano-scale semiconductor devices. The devices simulated in this paper are chosen to represent the current state-of-the-art and future technologies where quantum mechanical effects play an important role. Our examples include ultra-scaled nanowire transistors, tunnel transistors, resonant tunneling diodes, and negative capacitance transistors. Our results show that NESS is a robust, fast, and reliable simulation platform which can accurately predict and describe the underlying physics in novel ultra-scaled electronic devices.

Self-Consistent Enhanced S/D Tunneling Implementation in a 2D MS-EMC Nanodevice Simulator.

The implementation of a source to drain tunneling in ultrascaled devices using MS-EMC has traditionally led to overestimated current levels in the subthreshold regime. In order to correct this issue and enhance the capabilities of this type of simulator, we discuss in this paper two alternative and self-consistent solutions focusing on different parts of the simulation flow. The first solution reformulates the tunneling probability computation by modulating the WKB approximation in a suitable way. The second corresponds to a change in the current calculation technique based on the utilization of the Landauer formalism. The results from both solutions are compared and contrasted to NEGF results from NESS. We conclude that the current computation modification constitutes the most suitable and advisable strategy to improve the MS-EMC tool.

Full-band quantum transport simulation in the presence of hole-phonon interactions using a mode-space k·p approach.

Fabrication techniques at the nanometer scale offer potential opportunities to access single-dopant features in nanoscale transistors. Here, we report full-band quantum transport simulations with hole-phonon interactions through a device consisting of two gates-all-around in series and a p-type Si nanowire channel with a single dopant within each gated region. For this purpose, we have developed and implemented a mode-space-based full-band quantum transport simulator with phonon scattering using the six-band k · p method. Based on the non-equilibrium Green's function formalism and self-consistent Born's approximation, an expression for the hole-phonon interaction self-energy within the mode-space representation is introduced.

Unidades especializadas de cefalea, una alternativa viable en España / Specialised headache units, a feasible alternative in Spain

INTRODUCCIÓN: Las consultas por cefalea son el motivo más frecuente de demanda de atención de causa neurológica en la atención primaria y en los servicios de neurología. Las unidades de cefalea mejoran la calidad asistencial, reducen las listas de espera, facilitan el acceso a nuevos tratamientos de eficacia contrastada y optimizan el gasto sanitario. No obstante, la implantación de estas unidades no está extendida en España debido a la relativa importancia atribuida a la patología y a la suposición de que su coste es elevado. OBJETIVO: Definir la estructura y los requerimientos mínimos de una unidad de cefalea con la intención de contribuir a su extensión en los hospitales de España. SUJETOS Y MÉTODOS: Estudio de consenso entre profesionales tras la revisión de la bibliografía sobre la estructura, las funciones y los recursos de una unidad de cefalea para un área de 350.000 habitantes. RESULTADOS: Se tomaron como referencia ocho publicaciones para la identificación de recursos mínimos necesarios de una unidad de cefalea. El panel de expertos estuvo integrado por 12 profesionales de diferentes especialidades. El principal recurso para la implementación de estas unidades son profesionales (superiores y técnicos), lo que puede suponer un coste adicional para el primer año de alrededor de 107.287,19 euros. CONCLUSIONES: Si consideramos los costes directos e indirectos debidos a las pérdidas por productividad laboral por paciente y los comparamos con los costes estimados de implantación de estas unidades y su expectativa de resultados, todo apunta a que es necesaria la generalización de unidades de cefalea en España

INTRODUCTION: Visits due to headaches are the most frequent cause of demand for neurological treatment in primary care and neurology services. Headache units improve the quality of care, reduce waiting lists, facilitate access to new treatments of proven efficacy and optimise healthcare expenditure. However, these units have not been implemented on a widespread basis in Spain due to the relatively low importance attributed to the condition and also the assumption that such units have a high cost. AIM: To define the structure and minimum requirements of a headache unit with the intention of contributing to their expansion in hospitals in Spain. SUBJECTS AND METHODS: We conducted a consensus study among professionals after reviewing the literature on the structure, functions and resources required by a headache unit designed to serve an area with 350,000 inhabitants. RESULTS: Eight publications were taken as a reference for identifying the minimum resources needed for a headache unit. The panel of experts was made up of 12 professionals from different specialties. The main resource required to be able to implement these units is the professional staff (both supervisory and technical), which can mean an additional cost for the first year of around 107,287.19 euros. CONCLUSIONS: If we bear in mind the direct and indirect costs due to losses in labour productivity per patient and compare them with the estimated costs involved in implementing these units and their expected results, everything points to the need for headache units to become generalised in Spain

Low-value care practice in headache: a Spanish mixed methods research study.

BACKGROUND: Headache is one of the most prevalent diseases. The Global Burden of Disease Study ranks it as the seventh most common disease overall and the second largest neurological cause of disability in the world. The "Do Not Do" recommendations are a strategy for increasing the quality of care and reducing the cost of care for headache. This study aimed to identify specific low-value practices in headache care, determine their frequency, and estimate the cost overrun that they represent, in order to establish "Do not Do" recommendations specifically for headache by consensus and according to scientific evidence. METHODS: This was a mixed methods research study that combined qualitative consensus-building techniques, involving a multidisciplinary panel of experts to define the "Do Not Do" recommendations in headache care, and a retrospective observational study with review of a randomized set of patient records from the past 6 months in four hospitals, to quantify the frequency of these "Do Not Do" practices. We calculated the sum of direct costs of medical consultations, medicines, and unnecessary diagnostic tests. RESULTS: Seven "Do Not Do" recommendations were established for headache. In total, 3507 medical records were randomly reviewed. Low-value practices had a highly variable occurrence, depending on the hospital and type of headache. Overall, 34.1% of low-value practices were related to treatment, 21% were related to overuse of imaging in consultation, and 19% were related to emergency care. The estimated cost of low-value practices in the four hospitals was 203,520.47 euros per 1000 patients. CONCLUSIONS: This study identified low-value headache practices that need to be eradicated and provided data on their frequency and cost overruns.

Quantum Enhancement of a S/D Tunneling Model in a 2D MS-EMC Nanodevice Simulator: NEGF Comparison and Impact of Effective Mass Variation.

As complementary metal-oxide-semiconductor (CMOS) transistors approach the nanometer scale, it has become mandatory to incorporate suitable quantum formalism into electron transport simulators. In this work, we present the quantum enhancement of a 2D Multi-Subband Ensemble Monte Carlo (MS-EMC) simulator, which includes a novel module for the direct Source-to-Drain tunneling (S/D tunneling), and its verification in the simulation of Double-Gate Silicon-On-Insulator (DGSOI) transistors and FinFETs. Compared to ballistic Non-Equilibrium Green's Function (NEGF) simulations, our results show accurate I D vs. V G S and subthreshold characteristics for both devices. Besides, we investigate the impact of the effective masses extracted Density Functional Theory (DFT) simulations, showing that they are the key of not only the general thermionic emission behavior of simulated devices, but also the electron probability of experiencing tunneling phenomena.

Simulation of the Impact of Ionized Impurity Scattering on the Total Mobility in Si Nanowire Transistors.

Nanowire transistors (NWTs) are being considered as possible candidates for replacing FinFETs, especially for CMOS scaling beyond the 5-nm node, due to their better electrostatic integrity. Hence, there is an urgent need to develop reliable simulation methods to provide deeper insight into NWTs' physics and operation, and unlock the devices' technological potential. One simulation approach that delivers reliable mobility values at low-field near-equilibrium conditions is the combination of the quantum confinement effects with the semi-classical Boltzmann transport equation, solved within the relaxation time approximation adopting the Kubo⁻Greenwood (KG) formalism, as implemented in this work. We consider the most relevant scattering mechanisms governing intraband and multi-subband transitions in NWTs, including phonon, surface roughness and ionized impurity scattering, whose rates have been calculated directly from the Fermi's Golden rule. In this paper, we couple multi-slice Poisson⁻Schrödinger solutions to the KG method to analyze the impact of various scattering mechanisms on the mobility of small diameter nanowire transistors. As demonstrated here, phonon and surface roughness scattering are strong mobility-limiting mechanisms in NWTs. However, scattering from ionized impurities has proved to be another important mobility-limiting mechanism, being mandatory for inclusion when simulating realistic and doped nanostructures, due to the short range Coulomb interaction with the carriers. We also illustrate the impact of the nanowire geometry, highlighting the advantage of using circular over square cross section shapes.

Variability Predictions for the Next Technology Generations of n-type SixGe1-x Nanowire MOSFETs.

Using a state-of-the-art quantum transport simulator based on the effective mass approximation, we have thoroughly studied the impact of variability on Si x Ge 1 - x channel gate-all-around nanowire metal-oxide-semiconductor field-effect transistors (NWFETs) associated with random discrete dopants, line edge roughness, and metal gate granularity. Performance predictions of NWFETs with different cross-sectional shapes such as square, circle, and ellipse are also investigated. For each NWFETs, the effective masses have carefully been extracted from s p 3 d 5 s ∗ tight-binding band structures. In total, we have generated 7200 transistor samples and performed approximately 10,000 quantum transport simulations. Our statistical analysis reveals that metal gate granularity is dominant among the variability sources considered in this work. Assuming the parameters of the variability sources are the same, we have found that there is no significant difference of variability between SiGe and Si channel NWFETs.