Physical Origins of Universal Mobility in MOSFET Inversion Layers: Conservation Laws

The salient properties of charge flow (or current) along the MOSFET’s inversion layer are shown to be consilient with a river’s flow in a gravitational potential field, insofar as both are fundamentally governed by energy conservation principles, and their laminar and turbulent conditions determined by friction losses at shallow depths. We establish analytically that the low-field, "universal" effective mobility, μ_eff<b>, </b>long reported to vary as ~(E*_T)^-1/3 for transversal fields below 0.5 MV/cm, is manifestation and consequence of both energy and momentum conservation under laminar flow conditions and quantum mechanical effects, in which case the inversion layer’s mean thickness also varies as ~(E*_T)^-1/3 up to a maximum value E*_T ≈ 0.35 MV/cm at 300K, determined only by interface "terrain" amplitude and fundamental constants.

Modeling the MOSFET's Inversion Layer and Its Universal Mobility: A New Experimental Method

<div>We formulate a simple, yet accurate, model for a non-uniform mobile charge density ρ(z) giving rise to a mean potential Ψ* across an inversion layer of finite extent, which we measure by means of a novel, sensitive, experimental method involving nulls of harmonic distortion components (D2 ≈ D3 ≈ 0) of the drain current under sinusoidal excitation below saturation. We thus establish analytically and experimentally, that the low-field, "universal" effective mobility µ_eff varies as ~(E*_T)^-1/3for transversal fields E_T*= <b>-</b>(1/ε_si)<b>·</b>[ɳQ_i + Q_b] <b>≤ </b>0.5 MV/cm, wherein ɳ varies continuously between 1/2 and 1/3. We also establish and observe that the higher order, derivative, parameter θ_T quantifying µ_eff’s modulation by E*_T varies as ~(E*_T)^-5/3 under laminar flow conditions, thereby further corroborating the foregoing effects and interpretations thereof.</div>

Modeling the MOSFET's Inversion Layer and Its Universal Mobility: A New Experimental Method

<div>We formulate a simple, yet accurate, model for a non-uniform mobile charge density ρ(z) giving rise to a mean potential Ψ* across an inversion layer of finite extent, which we measure by means of a novel, sensitive, experimental method involving nulls of harmonic distortion components (D2 ≈ D3 ≈ 0) of the drain current under sinusoidal excitation below saturation. We thus establish analytically and experimentally, that the low-field, "universal" effective mobility µ_eff varies as ~(E*_T)^-1/3for transversal fields E_T*= <b>-</b>(1/ε_si)<b>·</b>[ɳQ_i + Q_b] <b>≤ </b>0.5 MV/cm, wherein ɳ varies continuously between 1/2 and 1/3. We also establish and observe that the higher order, derivative, parameter θ_T quantifying µ_eff’s modulation by E*_T varies as ~(E*_T)^-5/3 under laminar flow conditions, thereby further corroborating the foregoing effects and interpretations thereof.</div>

Physical Origins of Universal Mobility in MOSFET Inversion Layers: Conservation Laws

The salient properties of charge flow (or current) along the MOSFET’s inversion layer are shown to be consilient with a river’s flow in a gravitational potential field, insofar as both are fundamentally governed by energy conservation principles, and their laminar and turbulent conditions determined by friction losses at shallow depths. We establish analytically that the low-field, "universal" effective mobility, μ_eff<b>, </b>long reported to vary as ~(E*_T)^-1/3 for transversal fields below 0.5 MV/cm, is manifestation and consequence of both energy and momentum conservation under laminar flow conditions and quantum mechanical effects, in which case the inversion layer’s mean thickness also varies as ~(E*_T)^-1/3 up to a maximum value E*_T ≈ 0.35 MV/cm at 300K, determined only by interface "terrain" amplitude and fundamental constants.

Synthesis and Effect of the Structure of Bithienyl-Terminated Surfactants for Dielectric Layer Modification in Organic Transistor

A series of bithienyl-terminated surfactants with various alkyl chain lengths (from C8 to C13) and phosphono or chlorodimethylsilyl anchoring groups were synthesized by palladium-catalyzed hydrophosphonation, or platinum-catalyzed hydrosilylation as a key step. Surfactants were tested in pentacene or α-sexithiophene-based organic field-effect transistors (OFETs) for the modification of the dielectric surface. The studied surfactants increased the effective mobility of the α-sexithiophene-based device by up to one order of magnitude. The length of alkyl chain showed to be significant for the pentacene-based device, as the effective mobility only increased in the case of dielectric modification with bithienylundecylphosphonic acid. AFM allowed a better understanding of the morphology of semiconductors on bare SiO2 and surfaces treated with bithienylundecylphosphonic acid.

Cross-Border Transport and Mobility in the EU Issues and State of the Art

“In addressing the issues of cross-border transport and mobility, the CROSSMOBY project and this book make a significant contribution to what the European Union has been calling for several years: to achieve a seamless mobility system in order to strengthen European cohesion and integration. Creating the conditions for structuring an effective mobility system is also a prerequisite for regional economic growth, territorial cohesion and the development of the potential of cross-border regions. Economic development and job creation in the border regions also depend on the benefits that border regions derive from cross-border trade. Improving the supply and quality of rail, road and water links and services also contributes to improving the quality of life of the inhabitants and making these areas more attractive for tourism”. From the preface by Massimiliano Angelotti

Fine-grained data reveal segregated mobility networks and opportunities for local containment of COVID-19

Deriving effective mobility control measures is critical for the control of COVID-19 spreading. In response to the COVID-19 pandemic, many countries and regions implemented travel restrictions and quarantines to reduce human mobility and thus reduce virus transmission. But since human mobility decreased heterogeneously, we lack empirical evidence of the extent to which the reductions in mobility alter the way people from different regions of cities are connected, and what containment policies could complement mobility reductions to conquer the pandemic. Here, we examined individual movements in 21 of the most affected counties in the United States, showing that mobility reduction leads to a segregated place network and alters its relationship with pandemic spread. Our findings suggest localized area-specific policies, such as geo-fencing, as viable alternatives to city-wide lockdown for conquering the pandemic after mobility was reduced.

TCAD Modeling of Nanoscale Bulk FinFET Structures with Account of Radiation Exposure

Transition from planar MOSFET structures to FinFET 3D structures ensures various radiation type resistance. However, the characteristics of radiation-exposed devices made at different factories vary considerably and it is hard to explain FinFET structures’ radiation resistance dependence on variations of their physical and topological parameters and electrical modes. In this work, a RAD-TCAD model of FinFET on bulk silicon was developed. Additional semi-empirical radiation dependences specific to FinFET structures were introduced into the basic model of a nanometer MOSFET: the charge carrier effective mobility, the traps concentration in the SiO2 and HfO2 oxides and at the Si / SiO2 interface. The model was implemented in the Sen-taurus Synopsys TCAD environment. The model was validated on a test set of FinFET structures with a channel length from 60 nm to 7 nm before and after exposure to gamma irradiation in the dose range up to 1 Mrad. Comparison of the modeled and experimental I-V characteristics has shown an error of no more than 15 %.