Gate Material Research Articles

Near-infrared light-controlled kartogenin delivery of multifunctional Prussian blue nanocomposites for cartilage defect repair.

Articular cartilage injury repair remains a challenge for clinicians and researchers. Mesenchymal stem cells (MSCs) have multiple differentiation potentials and can be induced to differentiate into the chondrogenic lineage for cartilage defect repair; however, the insufficient capacity of chondrogenic differentiation and excess reactive oxygen species (ROS)-mediated oxidative stress, which always lead to differentiation into hypertrophic chondrocytes, still need to be resolved. Accordingly, kartogenin (KGN), which can promote chondrogenic differentiation of MSCs, has shown promise in promoting infected cartilage repair. However, realizing controllable release to prolong its action time and avoid hypertrophic differentiation is critical. We herein developed a mesoporous Prussian blue nanoparticle (mPB)-based near-infrared (NIR) light-responsive controlled nanosystem. KGN was encapsulated in temperature-stimulated responsive phase change materials (PCMs), which were used as excellent gating materials (KGN-PCM@mPBs). In addition, the mPBs could efficiently scavenge ROS by their enzyme-like antioxidative activities. Our study demonstrates that the nanocomposites could efficiently promote chondrogenic differentiation and successfully inhibit the hypertrophic differentiation of MSCs. By intra-articular injection of KGN-PCM@mPBs and NIR-triggered precisely controlled release, satisfactory cartilage repair effects can be achieved in a rat chondral defect model. Thus, this constructed NIR-mediated KGN-PCM@mPB nanoplatform may represent an effective cartilage repair strategy with satisfactory biosafety in clinical applications.

A review on effect of various high-k dielectric materials on the performance of FinFET device

The scalability of bulk CMOS faced various possible issues due to inherent material and process innovation constraints. Alternatively, transistor devices with supplementary gates, such as the Fin Field-effect transistor (FinFET) structure has attracted developing interest during the last few generations of their emergence, attributable to the appropriate control of the gate electrode over subthreshold parameters and seem to be favorable for Ultra large-scale integration, resulting in excessive immune function to short-channel effects (SCEs). In this paper, we will see the effect of several types of high-k gate dielectrics materials i.e Hafnium oxide (HfO2), Lanthanum doped zirconium oxide (LaZrO2), Silicon dioxide (SiO2), crystalline-silicon (c-Si), and polycrystalline-silicon (poly-Si), etc. channels are characterized for the short channel effects (SCEs), leakage current, Ion/Ioff ratio, drain induced barrier lowering (DIBL), and subthreshold swing (SS). The effect of important device parameters is considered regarding SCEs. The variation of the materials indicates improvements for the SCEs in FinFETs device architecture and also enhanced effective carrier mobility. Hence, we can clearly see that the use of high-k gate material has allowed for effective control of the diminishing of short channel effects.

Qualitative Analysis of DG-TFET Structures with Gate Material Engineering

The paper largely focuses on enhancing device parameters of a Double Gate Tunnel Field Effect Transistor structure such as ON current, OFF Current,transconductance and ratio of ON current to OFF current (ION / IOFF) using hetero dielectric gate material. The paper presents three state of art of dual gate TFET i.e., Conventional Double Gate TFET (CDGTFET), horizontally placed Dual Material Double Gate TFET (HDMDGTFET), vertically placed Dual Material Double Gate TFET (VDMDGTFET). The dual material dielectric combinations used in the structures are (SiO2-TiO2), (HfO2-TiO2) and (SiO2-SiC). The Structures are being modeled using Silvaco Atlas tool. Simulations of these structures are carried out and various electrical parameters have been obtained. The results obtained from simulation of these structures are being presented and discussed in this paper. Comparison of the three structures is carried out and resulted in the reduction of ON Current and OFF Current is observed.

Performance Analysis and Comparison of Different High-K Materials Used as Gate Dielectrics in DH-TMSG MOSFET

Abstract: To overcome SCEs and provide better packing density and performance a device called Double Halo Triple Material Surround Gate MOSFET is introduced. The device is designed by the combination of gate engineering and channel engineering. The device uses a surround gate MOSFET with triple material gate employing gate material engineering which improves the gate transport efficiency by modifying electric field pattern and surface potential along channel, resulting in higher carrier transport efficiency and SCEs. To extend the use of CMOS technology beyond 14 nm node technology, new device materials are required that can enhance the performance of MOSFETs. The use of high-k materials in double gate (DG) MOSFET can triumph over the problem of power dissipation and leakage current. The further mitigation in device dimension becomes a challenging task due to the existence of unavoidable short channel effects. The introduction of gate stack and channel engineering in MOSFET devices open a new window for future generation devices. The gate dielectric materials have played a significant role in the design of novel and high performances at nanoscale of electrical devices. It can be observed that when approaching a higher value of dielectric constant, the on current increases while the subthreshold slope (SS) threshold voltage (Vth) and leakaga current reduced. The scaling of complementary metal oxide semiconductor (CMOS) transistors has led to the silicon dioxide layer used as a gate dielectric becoming so thin that the gate leakage current becomes too large.

Simulation Analysis of Noise Components in NCTFET with Ferroelectric Layer in Gate Stack

Tunnel FETs (TFETs) are a strong contender for replacing conventional MOSFETs in lower power applications due to their low off-state current and sub-threshold swing being much lower than 60 mV/decade. The major trade-off is the shortcomings of TFET, which are ambipolar behaviour, low on-state current and large miller capacitance. The various novel structures of TFETs have been proposed by researchers. This work presents one such structure of heterojunction negative capacitance TFET with raised source and gate material overlapping. With the intervention of the ferroelectric layer in the gate stack of TFET, the overall performance of the device has been improved. Further AC DC analysis and electrical noise analysis are carried out for the proposed device to see the impact of improvisations being done in the structure on the input–output characteristics of the device. Synopsys TCAD tool is used to carry out the simulations at low and high frequencies. As per the results obtained, the raised source device using Ge as source material exhibits a high ION of 4.295 × 10−5 A/μm, low IOFF of 6.01 × 10−15 A/μm and sub-threshold slope of 53.75 mV/decade. The proposed device structure is having least ambipolarity and can be used in ultra-low power circuits.

Free Vibration Analysis of Stiffened Lock Gate Coupled with Reservoir Fluid considering Linearised Free Surface Condition

The effect of surrounding reservoir fluid on the stiffened lock gate structure is investigated using the finite element method. A single stiffener is used to stiffen the plate, which is placed edge to edge along the height on the plate's center nodal line. Mindlin’s plate bending and Euler’s beam theories are used to formulate plate and stiffener, respectively. The stiffened lock gate material is assumed to be isotropic, homogeneous, uniformly thick and elastic in nature. The fluid is assumed to be incompressible and inviscid, resulting in an irrotational flow field. The fluid domain's top free surface is assumed to be linear based on Airy’s linear wave theory. The far boundary of the fluid domain is truncated numerically close to the lock gate to control the size of computation without influencing the results, very much. It is truncated by solving the Laplace equation using Fourier half range cosine series expansion in the finite element formulation. Pressure and displacement are considered as nodal variables for the fluid domain and the lock gate, respectively. The interaction between the fluid domain and the lock gate is established by finite element formulation and transformed into a computer code, written in FORTRAN. The natural frequencies of clamped and simply supported stiffened lock gates are evaluated by the varying extent of the fluid. Both stiffened and unstiffened gates are compared. The results are beneficial to the engineers/designers when the gate structure is subjected to cataclysmic events.

Enhancement of carrier mobility in metal-oxide semiconductor field-effect transistors using negative thermal expansion gate electrodes

Strained-Si technology is crucial to improving the performance of metal-oxide-semiconductor field-effect transistors (MOSFETs). To introduce large strain into the channel, we proposed a structure for the negative thermal expansion gate electrode. In this study, we used manganese nitride as the gate material, which is a negative thermal expansion material. The fabricated MOSFETs with the manganese nitride gate showed a 10% increase in electron mobility compared to the MOSFET with the Al gate. The results show that the negative thermal expansion gate technology is promising as a technology booster for MOSFET scaling.

Chemically Sensitive Field‐Effect Transistors, Past, Present and Future

AbstractHistory, failures, successes and potential of Chemically Sensitive Field Effect Transistors (CHEMFET) are presented, based on fifty years of Author's personal experience working in this field. This article is divided into operation of devices in the liquid phase and in the gas phase. The recognition step in the first is based on ion partitioning. It requires a macroscopic reference electrode, which becomes the principal limiting factor. The CHEMFETs for dry operation rely on selective chemical modulation of work function of the electronically conducting gate material. They do not require an external reference and offer the possibility of miniaturization and multivariate sensing. Fabrication and economic aspects of both types of CHEMFETs are also discussed.

Defect structures and dopant solution states of Hf‐doped Si3N4 ceramics

AbstractTransition‐metal‐doped silicon nitride ceramics have attracted much attention as gate materials for semiconductors because of their electrical properties as well as chemical and thermal stability. The present study aims to clarify the defect structures of Hf‐doped β‐Si3N4 by theoretical calculations and scanning transmission electron microscopy (STEM). First‐principles calculations based on a hybrid functional method were performed. It was found that Hf dopants are mainly substituted for the Si sites and can be occasionally located at interstitial sites in the lattice of β‐Si3N4. The substitution sites of Hf dopants predicted by the first‐principles calculations were also confirmed by the high‐resolution STEM images.

(Invited) Advances in Atomic Layer Processing of Hafnia-Zirconia Ferroelectrics

The limits of integrating ferroelectric materials on commercial semiconductor chips were demolished the moment ferroelectricity in hafnia and zirconia films was reported in 2011. This breakthrough moment in the history of ferroelectric materials was made possible by the fortuitous interplay between advances in atomic layer processing and the strong surface energy dependence of crystal phases in HfO2 and ZrO2. Aided by commercial investment in using both materials as high-k gate and DRAM dielectric materials, atomic layer deposition (ALD) processes are beginning to take full advantage of the completely solid-soluble hafnia-zirconia (Hf1-xZrxO2) ferroelectric system with new precursors and new insights obtained by systematically evaluating film growth conditions. The capability to precisely adjust the compositional profile and to alter oxidation conditions during atomic layer deposition film growth are giving an unprecedented level of control to engineer Hf1-xZrxO2 and doped HfO2 thin films for ferroelectric applications.The latest advances in atomic layer processing of Hf1-xZrxO2 and doped-HfO2 are presented where the dynamic interaction between composition and film growth conditions provide an engineering roadmap to adjust the physical and structural properties of the dielectric films. Metal precursors play a crucial role in the ensuing film properties. The adjustability of the electrical and structural properties of Hf1-xZrxO2 with ozone exposure during ALD film growth is discussed with respect to the important role oxygen and oxygen vacancies have in the overall phase stability of these novel ferroelectric materials, as well as C incorporation caused by ALD precursors. Just as atomic layer deposition has proven to be instrumental in the discovery and stabilization of the ferroelectric phase in HfO2-based thin films, atomic layer etching (ALE) of HfO2/ZrO2-based layers is now being used to preserve ferroelectricity while pushing the thickness dimension to new limits, yielding high performance films for ferroelectric tunnel junction applications. Further innovations in atomic layer processing will continue to be a harbinger of high performance ferroelectrics in the coming years based on the current status and future outlook for ferroelectric Hf1-xZrxO2 and other emerging ferroelectric materials.

Analytical modelling and sensitivity analysis of Gallium Nitride-Gate Material and, dielectric engineered- Schottky nano-wire fet(GaN-GME-DE-SNW-fet) based label-free biosensor

An analytical model of nanogap embedded Gallium Nitride Gate- Material and Dielectric Engineered- Schottky Nano-Wire Field Effect Transistor (GaN-GME-DE-SNW-FET) for implementation as a label-free biosensor is introduced. An expression for the surface potential is attained by resolving the 1-D Poisson equation and 2-D Laplace equation utilizing a superposition method. A Model for the threshold voltage is also developed to analyze the sensitivity of the biosensor. The projected model also contains the repercussion of barrier height dropping at the metal-semiconductor intersection along with Dielectric Engineering (DE) using high-k (HfO2) material and Gate Material Engineering (GME) using metal m1with workfunctionφm1and m2with workfunctionφm2. The sensitivity of biosensor's has been studied for diverse dielectric constant and charge densities immobilized within the nanogap cavity. A comparative study has also been done between Gallium nitride-based (GaN- GME-DE-SNW-FET) and Silicon-based (Si-GME-DE-SNW-FET) Label-free biosensors. The developed analytical model is verified and validated using ATLAS- TCAD device simulations.

Study the impact of graphene channel over conventional silicon on DC/analog and RF performance of DG dual-material-gate VTFET

In this article, using a Silvaco TCAD simulator, the impact of Graphene Channel Double Gate Dual Gate Material Vertical tunnel FET on the analog and RF application is studied. We observed better results in DC characteristics such as drain current (ION), leakage current (IOFF), subthreshold swing (SS), DIBL as well as On current Off current ratio (ION/IOFF). Graphene Vertical tunnel FET proves that the structure is a magnificent candidate for analog and high-frequency range applications. The important figures of merit (FOMs) illustrated in this article are analog performance such as transconductance (gm), second-order transconductance (gg2), output conductance (gd), and VIP2. Due to the dual effect of the high mobility/ controllable band gap of graphene channel and band-to-band tunnel, the proposed structure greatly impacts the result.

Electrical properties of cerium hexaboride gate hydrogen-terminated diamond field effect transistor with normally-off characteristics

Fabrication of hydrogen-terminated (H-terminated) diamond field effect transistor (FET) with low work function cerium hexaboride (CeB6) gate material has been successfully performed. For the 8 μm gate length device, the threshold voltage (VTH) is extracted to be −0.46 V, demonstrating a normally-off characteristics. The maximum drain source current density (IDmax) is −83.8 mA/mm, and the competitive IDmax may be ascribed to the undamaged two-dimensional hole gas channel. The interface state density (Dit) is evaluated to be 1.93 × 1012 cm−2·eV−1, and the relatively low value may be attributed to the uncontaminated interface in gate material. This work provides a promising strategy to realize normally-off H-terminated diamond FET for fail-safety and energy-efficient power electronic devices.

Physics-based 2D analytical potential model with disorder effects for scaling a-IGZO TFT via dual material gate engineering

A dual material gate (DMG) amorphous indium gallium zinc oxide (a-IGZO) thin-film transistor (TFT) is proposed, which has a gate structure of lateral-contact-metals with two work functions. In view of multiple gate materials and localized/delocalized states, the potential calculations using Poisson’s equation are complicated and without analytical solution, which complicates the gate controllability analysis and future compact modeling methodology. Therefore, we have developed an analytical 2D potential model, that shows a great agreement with the numerical solution, taking into account asymmetry effects and scaling behavior. It can be used to tune potential or electric-field profiles by DMG engineering, increase the average channel electric-field, reduce the electric-field at the Drain side, and thus improve the performance of short-channel a-IGZO TFT with immunity to drain-induced-barrier-lowing (DIBL) and hot carrier effect (HCE).

First Principle Study of Spin Tunneling Current Under Field Effect in Magnetic Tunnel Junction for Possible Application in STT-RAM

A first principle analysis of Fe/MgO/Fe magnetic tunnel junction (MTJ) having gate voltage over insulated barrier region (MgO) is presented. Because of different work functions of gate and barrier materials, transfer of density of states (DOS) in forbidden energy gap of MgO is found above Fermi energy due to Schottky effect. It is reported that diffused DOS allows high tunneling of majority channel current because of less interference of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\Delta _{{1}}}$ </tex-math></inline-formula> symmetry of Bloch states with evanescent states in barrier. It shows high spin injection efficiency 0.9928, 0.9959, and 0.9871 with tunnel magneto resistance (TMR) ratios 1743.30%, 1450.06%, and 572.62% at gate voltages 1–3 V, respectively, with left and right electrodes at 0.5 V. Present work gives a basis for using MTJs as three terminal devices in magnetic random access memory (MRAM) applications.

Poly(ionic liquid) Gating Materials for High-Performance Organic Thin-Film Transistors: The Role of Block Copolymer Self-Assembly at the Semiconductor Interface.

The widespread realization of wearable electronics requires printable active materials capable of operating at low voltages. Polymerized ionic liquid (PIL) block copolymers exhibit a thickness-independent double-layer capacitance that makes them a promising gating medium for the development of organic thin-film transistors (OTFTs) with low operating voltages and high switching speed. PIL block copolymer structure and self-assembly can influence ion conductivity and the resulting OTFT performance. In an OTFT, self-assembly of the PIL gate on the semiconducting polymer may differ from bulk self-assembly, which would directly influence electrical double-layer formation. To this end, we used poly{[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} (P(NDI2OD-T2)) as a model semiconductor for our OTFTs, on which our PILs exhibited self-assembly. In this study, we explore this critical interface by grazing-incidence small-angle X-ray scattering (GISAXS) and atomic force microscopy (AFM) of P(NDI2OD-T2) and a series of poly(styrene)-b-poly(1-(4-vinylbenzyl)-3-butylimidazolium-random-poly(ethylene glycol) methyl ether methacrylate) (poly(S)-b-poly(VBBI+[X]-r-PEGMA)) block copolymers with varying PEGMA/VBBI+ ratios and three different mobile anions (where X = TFSI-, PF6-, or BF4-). We investigate the thin-film self-assembly of block copolymers as a function of device performance. Overall, a mixed orientation at the interface leads to improved device performance, while predominantly hexagonal packing leads to nonfunctional devices, regardless of the anion present. These PIL gated OTFTs were characterized with a threshold voltage below 1 V, making understanding of their structure-property relationships crucial to enabling the further development of high-performance gating materials.

Effect of the gate electrodes/water interface on the performance of ZnO-based water gate field-effect transistors

Field-effect transistors can be gated with water as the dielectric due to the formation of electrical double layers at water interfaces, which results in high specific capacitance and low voltage operation. The incorporation of analytes in aqueous suspension influences the water's electrical properties changing the water-gated field-effect transistors (WGFETs) performance and allowing it to be used as sensor and biosensor platforms. However, the material used as a gate electrode can affect the transistor's performance due to several factors, as the metal work function, its electrochemical range, and the presence of physicochemical reactions. Here, we evaluated the performance of WGFETs using spray-deposited zinc oxide (ZnO) as the active layer and five different gate electrodes: graphite pencil (GP), gold (Au), indium tin oxide (ITO), tungsten (W), and tin (Sn). The threshold voltage (VTH) values found were 0.41, 0.44, 1.12, 1.21 and 1.74 V for the Sn, W, Au, GP and ITO electrodes, respectively. The field-effect mobility was strongly influenced by the gate material, varying in the range from 0.07 to 0.46 cm2/Vs. The WGFETs operating with W and Sn gates showed the highest Ion/Ioff ratio and the lowest VTH when compared to the other electrodes. However, this characteristic may be associated with the formation of a natural oxide layer at its interface with water, which could be undesirable from the stability view. The use of ITO as the gate electrode resulted in a large hysteresis and two orders of magnitude smaller current in the output curve compared to Au and GP. Among the materials used as the gate electrode, GP stands out mainly because it gives the lowest subthreshold swing (SS = 90 mV/dec) and the highest transconductance (gm = 0.40 mS). Also, the GP matches with ZnO as biocompatible material for low-cost, eco-friendly, and metal-free electronics. In summary, the results showed that the gate electrode significantly influences the main parameters of the device and, therefore, should be an analysis factor when aiming to use WGFETs as sensors.

Tuning the dielectric characteristics and energy storage properties of Ni-ZnO/rGO nanocomposite

In the present study, pure and Ni-doped ZnO/rGO nanocomposites (NCs) are reported using the cost-effective wet chemical route to explore their dielectric characteristics. The structural examinations using X-ray diffraction (XRD) exposed the hexagonal wurtzite structure in both pure and Ni doped ZnO samples. The presence of an additional secondary phase accredited to NiO was also observed in Ni doped sample. The microstructural investigations using scanning electron microscope (SEM) revealed that Ni addition in ZnO modified particle size, shape, and distribution. Using tunneling electron microscope (TEM), it demonstrated that nanoparticles are well distributed in rGO sheets. The dielectric constant and dielectric loss of NCs increased with rGO addition at low frequency region. The relatively higher observed value of the dielectric constant while lower loss is explained on the basis of oxygen vacancies generated. The ac conductivity of NCs increased gradually with frequency due to the tunneling and hopping mechanisms. These results demonstrated that the higher carrier generations at the interface between rGO and ZnO grains are due to the increased mobility of charge carriers. Thus, the synergetic effect among them has the potential for use in advanced microelectronic devices, for instance, a gate material in transistors, capacitance-based energy storage devices etc.

Simulation of Molybdenum Disulfide based MOSFET Device using COMSOL Multiphysics software

In this work, 2D physical modeling and simulation of Molybdenum disulfide based MOSFET device using COMSOL multiphysics software is carried out. The impact of dielectric materials such as SiO2 and Al2O3 on the performance of FET are investigated. Threshold voltage (VT), sub-threshold swing and on/off ratio are some of the electrical parameters studied in this work. The values of channel doping concentration, choice of metal work function and dielectric material, and the corresponding thickness of the gate material, are systematically varied to arrive at the device threshold voltage. FET device with 50nm thick Al2O3 gate insulator exhibits a threshold voltage of 1V and an on/off ratio of 107, whereas the device with SiO2 as the gate material with the same thickness exhibited higher threshold voltage of 2.8V and lower on/off ratio of 106. The polynomial first order technique in the MATLAB curve fitting tool is utilized to determine the relation between VT and gate oxide thickness.

Transport Spectroscopy of Ultraclean Tunable Band Gaps in Bilayer Graphene

AbstractThe importance of controlling both the charge carrier density and the band gap of a semiconductor cannot be overstated, as it opens the doors to a wide range of applications, including, for example, highly‐tunable transistors, photodetectors, and lasers. Bernal‐stacked bilayer graphene is a unique van‐der‐Waals material that allows tuning of the band gap by an out‐of‐plane electric field. Although the first evidence of the tunable gap is already found 10 years ago, it took until recent to fabricate sufficiently clean heterostructures where the electrically induced gap can be used to fully suppress transport or confine charge carriers. Here, a detailed study of the tunable band gap in gated bilayer graphene characterized by temperature‐activated transport and finite‐bias spectroscopy measurements is presented. The latter method allows comparing different gate materials and device technologies, which directly affects the disorder potential in bilayer graphene. It is shown that graphite‐gated bilayer graphene exhibits extremely low disorder and as good as no subgap states resulting in ultraclean tunable band gaps up to 120 meV. The size of the band gaps are in good agreement with theory and allow complete current suppression making a wide range of semiconductor applications possible.