SiO2 Interface Research Articles

Direct Measurement of Enhanced Ion Conductivity at an Ionic Liquid Electrolyte (ILE)/SiO2 Interface with Interdigitated Electrode Array

Recently, our group reported a novel solid-state electrolyte material which is constituted of a nano-porous SiO2 monolith and an ionic liquid electrolyte (ILE) which occupies the pores. The unique feature of this solid nano-composite electrolyte (nano-SCE) is its ion conductivity which is higher than that of the ILE itself [1]. Here, we report a direct measurement of this enhanced ion conductivity by measuring the ion conductivity of a thin-film ILE on a planar SiO2 substrate. The enhanced ion conductivity is directly measured with interdigitated electrode arrays deposited on a planar SiO2 substrate, as shown in Figure 1. By depositing a thin-film ILE film on these electrodes, the impedance response of the ILE/SiO2 interface could be measured by impedance spectroscopy (IS). The ion conductivity on the ILE/SiO2 interface could subsequently be quantified by analysis of the equivalent circuit model and by measuring the ILE film thickness. The ILE film thickness is scaled down to the nanometer regime. This is the first time that such thin ILE films could be deposited using liquid processing techniques. The enhanced ion conductivity is revealed when the ILE film thickness is reduced to 20 nm thicknesses and below. The ion conductivity of the ILE films with a thickness around 80 nm have a similar conductivity compared to the bulk ILE. Enhanced ion conductivity along interfaces has been observed before and is typically referred to as heterogenous doping [2]. The mechanism that governs the enhanced conductivity in the nano-SCE are similar to those described by heterogenous doping. However, the ion conductivities measured in this work are many times higher compared to those reported before. In conclusion, for the first time ILE thin-films with thicknesses in the nanometer regime are deposited with liquid processing. Moreover, the ion conductivity at the ILE/SiO2 interface could be quantified and showed an increased conductivity compared to the bulk ILE value.

Analytical drain current model of stacked oxide SiO2/HfO2 cylindrical gate tunnel FETs with oxide interface charge

In this paper, we have developed an analytical drain current model of stacked oxide SiO2/HfO2 cylindrical gate tunnel field-effect transistor (CG TFET) by considering the effect of interface trap charge at Si–SiO2 interface nearby the source–channel junction. To model the channel potential, Poisson’s equation has been solved by using the parabolic approximation method in a cylindrical coordinate system with appropriate boundary conditions. The potential model has then been utilized for developing some expressions for minimum tunneling length, lateral electric field, and the drain current of stacked oxide SiO2/HfO2 CG TFET. The impact of the source/drain depletion region has been considered for improving the accuracy of the proposed model. The commercially available ATLAS™ 3D-based TCAD simulation data have been used to validate the proposed model results.

Defects induced by gamma-ray irradiation and post-irradiation annealing and its influence on the threshold voltage of p-channel power VDMOS transistors

ABSTRACTThe investigations presented here study the creation as well as passivation/neutralization of positive trapped charge in the oxide (fixed traps) and traps near and at the Si–SiO2 interface (switching traps) exposed to gamma-ray irradiation and subsequent annealing (at room temperature and late at 150°C) in commercial p-channel power Vertical Double Diffused Metal-Oxide-Semiconductor transistors. The separation of fixed and switching traps that contributes to the threshold voltage shift was carried out using the midgap-subthreshold method. It was shown that fixed traps creation is a dominant process during irradiation. Subsequent postirradiation annealing at room temperature, without gate bias, was performed for , i.e. 19.4 days and it further lead to a relatively small change in , induced by a decrease in fixed traps density and an increase in switching traps density. The experimental results have revealed the existence of latent switching traps build-up during continued annealing at 150°C with +10 V gate bias. At latter annealing times, the switching traps passivation becomes the dominant process. In order to explain these experimental results, we have used models that include processes of creation and passivation of fixed and switching traps during irradiation and annealing. The possible application of these components in gamma-ray dosimetry was also analysed.

Design and analysis of graphene–MoS2 hybrid layer based SPR biosensor with TiO2–SiO2 nano film for formalin detection: numerical approach

In this paper, a Surface Plasmon Resonance (SPR) biosensor has been numerically developed that used Graphene–MoS2–Au–TiO2–SiO2 hybrid structure for the detection of formalin. This developed sensor has been sensed the presence the formalin based on attenuated total reflection (ATR) method by observing the change of “surface plasmon resonance angle-the change of minimum reflectance attributor” and “the resonance frequency characteristics (RFC)-maximum transmittance attributor”. Chitosan has been used as probe sensing medium to accelerate particular reaction with the formalin. Here, graphene is used as biomolecular recognition element because of its high adsorption ability and optical characteristics which helps to improve sensor sensitivity, MoS2 used for it has larger band gap, high fluroscence quenching ability, higher optical absorption efficiency, TiO2–SiO2 bilayer as the improvement of sensitivity and Gold (Au) as the sharp SPR curve. Numerical results give the impression that the variation of RFC and SPR angle for improper sensing of formalin is quiet negligible that confirms no formalin is detected whereas for proper sensing these change are considerably countable that confirms the detection of formalin. From the sensor sensitivity analysis, owing to add TiO2–SiO2 bilayer with Graphene–MoS2 Hybrid layer, maximum sensitivity of 85.375% has been numerically resulted. This high sensor performance is for taking advantages of Graphene surface high selectively which detect bio molecular compounds through pi-stacking force, larger work function (5.1 eV) of MoS2 which allows the high sensitive detection of bio targets and Rich plasmon happens at the TiO2–SiO2 interface.

Fabrication of Top-Gate MoS2 FET with Transferred Al2O3 Gate Dielectric

This study describes the fabrication of top-gate molybdenum disulfide (MoS2) field-effect transistor (FET) using transfer printing of an Al2O3 gate dielectric. Semiconducting MoS2 has been considerable attention for applications as channel materials of FETs because a two-dimensional (2D) crystal is free from dangling bonds at the surface [1]. On the other hand, atomic layer deposition (ALD) of high-k gate dielectric is incompatible with MoS2 since an ALD precursor cannot be chemisorbed onto the surface of MoS2 due to the absence of dangling bonds [2]. Furthermore, ALD disrupts the surface structure and induces the oxidation of the channel layer [2], leading to the degradation of FET characteristics or the failure of devices. This study addresses these issues by utilizing the transfer printing of a high-k gate dielectric on a MoS2 layer [2], [3]. Transfer printing can avoid the deposition of a high-k gate dielectric directly on a fragile MoS2 surface. An abrupt and sharp interface can be anticipated by implementing the transfer printing of high-k gate dielectric.A key component for developing the transfer printing of the Al2O3 gate dielectric is to find out an appropriate sacrificial layer on the handling substrate. In this study, nickel (Ni) metal was adopted as the sacrificial layer for the transfer printing of the Al2O3 gate dielectric. It was revealed that the adhesion strength at Ni and thermally grown SiO2 interface is reduced by immersion in deionized water (DIW) [3]. The penetration of water into the interface results in the separation of Ni from the SiO2 surface. This Ni layer can be etched by using dilute nitric acid (HNO3). On the other hand, HNO3, which is an oxidizing agent, cannot etch an oxide gate dielectric.A 50-nm-thick Ni layer was deposited on the SiO2 (400 nm)/Si substrate by thermal evaporation (Fig. 1 (a)). The Al2O3 gate dielectric was deposited on the Ni layer by ALD with trimethylaluminum (TMA) and a H2O oxidant at a substrate temperature of 300 oC. Polymethyl methacrylate (PMMA) was prepared on Al2O3 by spin-coating as a protective layer. Next, a thermal release tape was attached to the PMMA layer. Then, the entire substrate was immersed in DIW for 5 min to weaken the adhesion strength between Ni and SiO2. The laminated structure was peeled off from the SiO2 surface in DIW. After the etching of Ni layer with dilute HNO3 (60% HNO3 : H2O = 1 : 10), the Al2O3 gate dielectric was transferred on MoS2 flakes. The Al2O3 gate dielectric and PMMA bilayer can be released from the thermal release tape by baking on a hot plate. After the removal of PMMA by oxygen plasma ashing, Al (40 nm) for the gate and Au (40 nm)/Ti (10 nm) for the source/drain were fabricated by the lift-off process. Finally, forming gas annealing (FGA) was performed in ambient (H2 : N2 = 3% : 97%) at 300 oC for 30 min to improve the electrical contacts at source/drain.The fabricated FET has small hysteresis, low leakage current, a subthreshold slope of 120 mV/dec, and a carrier mobility of 7.3 cm2/Vs (Fig. 1 (b)). The abrupt and sharp interface was demonstrated for transfer printing of the Al2O3 gate dielectric on the MoS2 channel layer. Process mismatches including temperature and chemical compatibility are avoidable by adopting the transfer printing method. The use of transferred high-k gate dielectrics is not restricted to MoS2 FETs. It is also applicable to various 2D layered materials. This study opens up the interesting direction for the research and development of 2D material-based functional devices. AcknowledgmentsThe authors would like to thank Professor Y. Kawano, Professor T. Hoshii, Professor I. Muneta, Professor K. Kakushima, Professor K. Tsutsui, and Professor H. Wakabayashi of Tokyo Institute of Technology for their continuous support in the experiments. This study was supported by JST CREST (Grant No. JPMJCR16F4) and a JSPS Grant-in-Aid for Young Scientists (B) (Grant No. 17K14662).

Wide-band and wide-angle, visible- and near-infrared metamaterial-based absorber made of nanoholed tungsten thin film

In this paper, the absorptivity of a tungsten ($W$W) based metamaterial absorber has been studied. The paper revolves around the spectral characteristics of the nano-holed $W$W film coated over silicon oxide (SiO${_2}$2) substrate. The anisotropic effective permittivity of the nanoholed W film has been deduced by employing the effective medium theory. The light-plasmon coupling at $W$W-$SiO_{2}$SiO2 interface has been investigated by the eigenvalue equation. The effect of the nanoholed radii on coupling and absorptivity has been analyzed. As such, absorption features of the absorber have been studied in the visible and near-infrared (NIR) regimes by finite difference time domain(FDTD) simulation under the excitation of fundamental transverse electric(TE)- and transverse magnetic (TM)-mode. It has been observed that absorptivity can be altered by tailoring the holes radii of tungsten nanolayer. Further, the effects of the incidence angle of the light on the absorptivity have been studied. Observations reveal that absorptivity depends on the nanohole radius of $W$W, and angle of incidence of excited light. Also, wideband absorptivity has been attained using $W$W thin film. Such an absorber would be useful for solar cell, solar heating and integrated optics related applications.

Behavior of SiNx/SiO2 Double Layer for Surface Passivation of Compensated p-Type Czochralski Silicon Wafers

Surface passivation of Czochralski (Cz) p-type compensated silicon using a hydrogenated silicon nitride/silicon oxide (SiNx-H/SiO2) double layer (hereinafter called SiNx/SiO2) has been investigated. The characteristics of the deposited films depended strongly on surface preparation, deposition process, and annealing parameters. Fourier-transform infrared (FTIR) spectroscopy was used to analyze the chemical bonds in the Si–SiNx/SiO2 structure, and quasi-steady-state photoconductance (QSSPC) measurements were used to evaluate the minority-carrier lifetime (τeff), to check the quality of the passivation. The results showed that, after SiNx/SiO2 double-layer deposition, τeff remained rather poor (13.29 μs). This low degree of passivation is principally due to the appearance of an inversion layer after oxidation, inducing switching of the semiconductor type at the surface. This inversion layer is due to the segregation properties of both boron and phosphorus impurities. This phenomenon was highlighted by secondary-ion mass spectrometry (SIMS) characterization, revealing a substantial phosphorus concentration near the Si–SiO2 interface and penetration of boron inside the oxide, with concentration of 1 × 1018 cm−3 and 4 × 1018 cm−3, respectively. Annealing at 400°C under low pressure of 3.34 × 10−3 kPa improved the minority-carrier lifetime to τeff = 15.94 μs, leading to enhanced surface passivation related to the reduced interface state density and improved statistical distribution of different bonding environments.

Microwave assisted rapid synthesis of Fe2O3@SiO2 core-shell nanocomposite for the persistence of magnetic property at high temperature

Fe2O3 nanoparticles (NPs) coated by the SiO2 shell with a thickness up to ˜6.5 nm were synthesized by a fast and facile microwave irradiation approach. The thickness of the SiO2 shell around Fe2O3 NPs could be controlled by varying tetraethoxysilane (TEOS) concentration as well as avoiding individual SiO2 particle formation. The synthesized Fe2O3@SiO2 core-shell nanocomposites (NCs) were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive X-ray (EDX) spectroscopy. The bigger particle size compared to the uncoated Fe2O3 NPs and SiOSi asymmetric stretching vibrational band at 1101 cm−1 in the prepared NCs obtained by FE-SEM and FT-IR study, respectively anticipated the successful SiO2 coating on Fe2O3 NPs. The presence of homogeneous silica layer was authenticated by TEM observation. The change in binding energy of Fe 2p3 and Si 2p in the synthesized NCs compared to the uncoated Fe2O3 and pure SiO2 NPs corroborated the formation of FeOSi bond at the interface of Fe2O3 (core) and SiO2 (shell). The existence of magnetic property in the prepared NCs, even above the Curie temperature of Fe2O3, was assured by vibrating sample magnetometer (VSM) study. This observation will undoubtedly inspire to design and fabricate novel heterostructures of iron oxide to retain its magnetization at high temperature.

Influence of the W Content on the Characteristics of MoxW1−xSi2 Heating Elements Fabricated by Self-Propagating High-Temperature Synthesis

MoSi2-based composites are promising structural materials for high-temperature applications. MoxW1−xSi2 (x = 1, 0.9, 0.8, and 0.7) powders were successfully synthesized by self-propagating high-temperature synthesis. These powders were used to fabricate heating elements, which were then subjected to a post-annealing process to improve the structural quality. To determine the influence of the W content (0–30 mol%) on the characteristics of MoxW1−xSi2 composites, the surface morphologies, densities, and bending strengths of the MoxW1−xSi2 heating elements were investigated. Moreover, to validate the durability of the MoxW1−xSi2 heating elements, an accelerated degradation test (ADT) was conducted at temperatures up to 1700°C (heating rate = 5°C/min). The MoxW1−xSi2 heating element with 30 mol% of W exhibited a high density, a high bending strength, and superior durability after the ADT test. In contrast, the MoxW1−xSi2 heating element with 0 mol% of W showed inferior durability owing to the formation of bubbles at the MoxW1−xSi2 /SiO2 interface. Thus, the addition of W enhances the reliability and durability of MoxW1−xSi2 composites as heating elements.

Silicon surface passivation by transparent conductive zinc oxide

Surface passivation is essential for high-efficiency crystalline silicon (c-Si) solar cells. Despite the common use of transparent conductive oxides (TCOs) in the field of solar cells, obtaining surface passivation by TCOs has thus far proven to be particularly challenging. In this work, we demonstrate outstanding passivation of c-Si surfaces by highly transparent conductive ZnO films prepared by atomic layer deposition. Effective surface recombination velocities as low as 4.8 cm/s and 11 cm/s are obtained on 3 Ω cm n- and p-type (100) c-Si, respectively. The high levels of surface passivation are achieved by a novel approach by using (i) an ultrathin SiO2 interface layer between ZnO and c-Si, (ii) a sacrificial Al2O3 capping layer on top of the ZnO film during forming gas annealing, and (iii) the extrinsic doping of the ZnO film by Al, B, or H. A combination of isotope labeling, secondary-ion mass spectrometry, and thermal effusion measurements showed that the sacrificial Al2O3 capping layer prevents the effusion of hydrogen from the crystalline ZnO and the underlying Si/SiO2 interface during annealing, which is critical in achieving surface passivation. After annealing, the Al2O3 capping layer can be removed from the ZnO film without impairing the high levels of surface passivation. The surface passivation levels increase with increased doping levels in ZnO, which can be attributed to field-effect passivation by a reduction in the surface hole concentration. The ZnO films of this work are suitable as a transparent conductor, an anti-reflection coating, and a surface passivation layer, which makes them particularly promising for simplifications in future solar cell manufacturing.

Promoted chemoselective crotonaldehyde hydrogenation on zirconia-doped SiO2 supported Ag catalysts: Interfacial catalysis over ternary Ag–ZrO2–SiO2 interfaces

In gas-phase chemoselective hydrogenation of crotonaldehyde on Ag-based catalysts, zirconia doping on silica supports was found to improve catalytic performance in terms of unsaturated alcohol selectivity, hydrogenation activity, and stability. The surface modification of silica by zirconia doping favors the fine dispersion of Ag species due to the enhanced quantity and strength of surface acid sites, which enable construction of abundant catalytic sites effective for CO bond hydrogenation. High crotyl alcohol selectivity, exceeding 80%, and significant inhibition of monohydrogenation on the CC bond were observed on the optimal Ag/Zr–SiO2 catalyst. Dynamic O2 chemisorption measurement revealed that the pure Ag powders did not chemisorb O2 irreversibly under 323 K, but SiO2 or Zr–SiO2 supported Ag catalysts did. The amounts of Ag active for O2 chemisorption, which are at least one order of magnitude lower than that of surface Ag derived from TEM and XRD characterizations, match well with the perimeter interface Ag of hemispherical particles. A strong correlation between hydrogenation activity and O2 uptake on those Ag/SiO2 and Ag/Zr–SiO2 catalysts with different Ag dispersions and deactivation degrees was observed, implying that the effective catalytic sites for crotonaldehyde chemoselective hydrogenation may originate from accessible interface sites with unique redox properties. Catalyst induction and deactivation were observed on both Ag/SiO2 and Ag/Zr–SiO2 catalysts in real catalytic operation. Changes in metal stable interface structure, rather than metal aggregation and coagulation, are assumed to be the main cause of irreversible catalyst deactivation, because the apparent Ag particle sizes changed slightly, but the oxygen chemisorption ability deteriorated considerably. Electropositive Ag sites interacting with neighboring oxygen from oxide supports at the ternary Ag–ZrO2–SiO2 interface are proposed to account for highly selective CO bond hydrogenation to produce the desired unsaturated alcohol.

Reduction of interface state density in SiC (0001) MOS structures by low-oxygen-partial-pressure annealing

We report that annealing in low-oxygen-partial-pressure (low-pO2) ambient is effective in reducing the interface state density (DIT) at a SiC (0001)/SiO2 interface near the conduction band edge (EC) of SiC. The DIT value at EC − 0.2 eV estimated by a high (1 MHz)-low method is 6.2 × 1012 eV−1 cm−2 in as-oxidized sample, which is reduced to 2.4 × 1012 eV−1 cm−2 by subsequent annealing in O2 (0.001%) at 1500 °C, without interface nitridation. Although annealing in pure Ar induces leakage current in the oxide, low-pO2 annealing does not degrade the oxide dielectric property (breakdown field ∼10.4 MV cm−1).

A comprehensive study on the interface states in the ECR-PECVD SiO2/p-Si MOS structures analyzed by different method

The electrical properties of SiO2/p-Si films deposited by ECR-PECVD s were studied at different frequencies (100-1 MHz) and gate voltages (−6–3 V). Results showed a frequency dispersion of C-Vg and G/ω-Vg. With increasing frequency, the capacitance and conductance are strongly decreased. An apparent peak in the depletion regime of the G/ω-Vg plots can be attributed to the existence of density Nss at Si/SiO2. The (Nss)value vary from 1.5 × 1012 to 0.5 × 1011 eV−1 cm−2, it has been determined by High-Low frequency capacitance technic. The Nss- Vg curve presents a peak at about −3 V, suggesting the presence Nss between the (Si)/SiO2 interface. Hill and Coleman method shows that the Nss decreases with increasing frequency which explains the high value of capacitance at low frequency. The Nss and their relaxation time τ by the conductance method ranged from 1.8 × 1013 to 1.37 × 1011 eV−1 cm−2 and 5.17 10−7 to 8 × 10−6 s, in the range (0.189-Ev) and (0.57- Ev) eV, respectively. The Nss was responsible for the non-ideal behavior of C-Vg and G-Vg leading to the breakdown of such device. Comparing the three method results show that parallel conductance is very precise and accurate.

Strong interfacial perpendicular anisotropy and interfacial damping in Ni0.8Fe0.2 films adjacent to Ru and SiO2

We report detailed investigations of a strong perpendicular magnetic anisotropy in Ni0.8Fe0.2 thin films originating from interfaces with adjacent Ru and SiO2 layers. The anisotropy is quantified using broadband ferromagnetic resonance measurements for three types of layered heterostructures, namely an asymmetric structure of SiO2/Ni0.8Fe0.2/Ru and symmetric structures of Ru/Ni0.8Fe0.2/Ru and SiO2/Ni0.8Fe0.2/SiO2. The results show a stronger perpendicular anisotropy at the Ni0.8Fe0.2/SiO2 interface than at the Ni0.8Fe0.2/Ru interface and a lower interfacial damping contribution for the Ni0.8Fe0.2/SiO2 interface compared to the Ni0.8Fe0.2/Ru interface.

Effect of the Electric Mode and γ Irradiation on Surface-Defect Formation at the Si–SiO2 Interface in a MOS Transistor

The results of experimental investigation into surface-defect formation under the effect of gamma-radiation with a dose rate P = 0.1 rad(Si)/s on MOS (metal-oxide-semiconductor) transistors with the n-type channel in the passive and active modes are presented. Two stages of surface-defect formation are observed. A qualitative model is proposed to explain the effect of the the drain transistor voltage on the defect formation process.

Annealing-induced evolution in interface stability and electrical performance of sputtering-driven rare-earth-based gate oxides

Annealing temperature-dependent ultrathin Dy2O3 gate dielectric films, grown on Si substrates by reactive sputtering, were characterized in terms of structural, optical and electrical properties using x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), UV–Vis transmission spectroscopy and electrical measurements of Dy2O3/Si gate stack. Additionally, the thickness of the interfacial SiO2 layer during the deposition and annealing process has been calculated using the Si 2p XPS spectra to exclude its influence on the electrical parameter of Dy2O3 films. XPS analyses for all the samples have shown the abrupt growth of the Dy-silicate for 700°C-annealed sample, which is identified as the primary reason for the dramatic reduction in its electrical performance. In addition, optimized Dy2O3 sample with annealed temperature at 600 °C exhibits the lowest equivalent oxide thickness of 1.6 nm, the highest dielectric constant 16.8, the lower leakage current density 4.45 × 10−8 A/cm2 and the lower frequency dispersion of 6.21%. Based on the experimental analysis, the optimized annealing temperature has been obtained to achieve Dy2O3 gate dielectric thin films as deposition of high-k with high-quality on Si substrates.

Crystalline Silicon Solar Cells With Coannealed Electron- and Hole-Selective SiC x Passivating Contacts

We present electron- and hole-selective passivating contacts based on wet-chemically grown interfacial SiO x and overlying in-situ doped silicon carbide (SiC x ) deposited by plasma-enhanced chemical vapor deposition. After annealing at 850 °C, excellent surface passivation on the p -type planar crystalline silicon wafer is obtained for both electron- and hole-selective contacts. Their potential is demonstrated at the device level by employing a simple process flow, in which the junction formation of the two polarities is achieved with a single coannealing step. Both-side-contacted patterning-free planar p -type cells with an area of 4 cm2 and screen-printed metallization reach a fill factor of 83.4% and a open-circuit voltage of 726 mV. Zirconium-doped indium oxide with excellent optoelectrical properties is used as a front electrode. The decrease in the parasitic absorption in the front electrode results in higher photogenerated current. By realizing front-side-textured and rear-side-planar p -type cells, an efficiency of up to 22.6% is achieved.

Plasmonic router based on spin–orbital interaction

Abstract All-optical devices have wide application in computing and communicating, among whom, all-optical router plays important role in it. In this letter, we build up a plasmonic router based on spin–orbital interaction. The spin–orbital interaction is generated by a metasurface, which is an array of air-slit resonator. The resonator is enclosed by four Archimedes spirals etched on 300 nm thick Au film. The metasurface have two interfaces, Au–Air interface and Au–SiO2 interface, each interface processes two output ports. And at 1064 nm, the ports on Au–SiO2 interface are activated and spin can control one of them open. And at 1500 nm, the ports on Au–Air interface are activated and also, spin can control the states of them. Besides, the metasurface can be cladded with liquid crystal, which can tune the optimal frequency of specific ports by changing the optical axis. This result may contribute to the application of all-optical devices.

Analytical Modeling of Gate-Stack DG-MOSFET in Subthreshold Regime by Green’s Function Approach

An accurate analytical model of the gate-stack symmetric double-gate (DG) MOSFET using Green's function approach is developed in this brief. An exact analytical solution to 2-D Poisson's equation is derived in the subthreshold regime of operation, considering 2-D mixed boundary conditions and multizone techniques. It is observed that the Green's function approach of solving 2-D Poisson's equation in both oxides (t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ox1</sub> and t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ox2</sub> ) and silicon region can accurately predict channel potential and subthreshold current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sub</sub> ) of gate-stack DG-MOSFET. We further extend our model to mitigate the fringe-induced barrier lowering (FIBL) effect in the gate-stack device, by optimizing the interfacial layer thickness. It is observed that selection of interfacial SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layer as ~0.75 times of equivalent oxide thickness is necessary to completely mitigate the FIB' effect of SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -based gate-stack DG-MOSFET.

Enhanced Thermal Boundary Conductance in Few‐Layer Ti3C2 MXene with Encapsulation

Van der Waals interactions in 2D materials have enabled the realization of nanoelectronics with high-density vertical integration. Yet, poor energy transport through such 2D-2D and 2D-3D interfaces can limit a device's performance due to overheating. One long-standing question in the field is how different encapsulating layers (e.g., contact metals or gate oxides) contribute to the thermal transport at the interface of 2D materials with their 3D substrates. Here, a novel self-heating/self-sensing electrical thermometry platform is developed based on atomically thin, metallic Ti3 C2 MXene sheets, which enables experimental investigation of the thermal transport at a Ti3 C2 /SiO2 interface, with and without an aluminum oxide (AlOx ) encapsulating layer. It is found that at room temperature, the thermal boundary conductance (TBC) increases from 10.8 to 19.5 MW m-2 K-1 upon AlOx encapsulation. Boltzmann transport modeling reveals that the TBC can be understood as a series combination of an external resistance between the MXene and the substrate, due to the coupling of low-frequency flexural acoustic (ZA) phonons to substrate modes, and an internal resistance between ZA and in-plane phonon modes. It is revealed that internal resistance is a bottle-neck to heat removal and that encapsulation speeds up the heat transfer into low-frequency ZA modes and reduces their depopulation, thus increasing the effective TBC.