Channel Length Research Articles

PHSOR06 Presentation Time: 9:25 AM: HDR Treatments with Automated Channel Length Adjustments: Verification of Treatment Dwell Positioning Accuracy for Gynecologic Brachytherapy

PHSOR06 Presentation Time: 9:25 AM: HDR Treatments with Automated Channel Length Adjustments: Verification of Treatment Dwell Positioning Accuracy for Gynecologic Brachytherapy

Modelling of Cut-off Frequency of Armchair Graphene Nanoribbon Tunnel Field Effect Transistor Using Transfer Matrix Method

Graphene is considered as a promising two-dimensional material for electronic device applications due to its high charge carrier mobility and it is extremely thin in size. As a material, graphene has great potential for the development of high-speed nano electric devices. Graphene can be used as a channel material in Tunnel Field Effect Transistor (TFET). In this study, the cut-off frequency of the armchair graphene nanoribbon tunnel field effect transistor (AGNR-TFET) device was modelled quantum mechanically. The solution of the Dirac-like Hamiltonian and Poisson equations self-consistently is used to determine the potential profile of device and the transmittance is calculated using the transfer matrix method (TMM). The Landauer formulation with the help of Gauss Legendre Quadrature Method (GLQM) is used to calculate the tunnelling current and the cut-off frequency of AGNR-TFET. The calculation results showed that the cut-off frequency increased as the drain voltage increased, while the increase in channel length and the N-index graphene made the cut-off frequency decreased. Moreover, the thicker the oxide layer could increase the cut-off frequency and the higher the temperature on the device would reduce the cut-off frequency.

Virtual Fabrication of 14nm Gate Length n-Type Double Gate MOSFET

Due to Moore's law, it is that predicted the channel length of a metal-oxide-semiconductor Field Effect Transistor (MOSFET) will tend to shrink from the submicron to the nanoscale size. Thus, precision in the manufacturing process has become crucial. This study describes the virtual fabrication as well as the electrical characteristics of a 14nm NMOS double gate with a bilayer graphene/high-K/metal gate. In this device, Hafnium Dioxide (HfO2) is employed as a high-k material, and Tungsten Silicide (WSix) is used as a metal gate. Several Silvaco TCAD Tools, including ATHENA and ATLAS, were utilized in the fabrication and simulation of the device, respectively. According to the simulation results, the optimal threshold voltage (VTH), drive current (ION), and leakage current (IOFF) and subthreshold slope (SS) values are 0.2059 V, 797.5650 μA/μm. 29.5794 nA/μm, and 89.1712x10-3 V respectively. The findings of this research showed that the efficiency of this 14nm double gate n-type MOSFET device is satisfactory because the threshold voltage and leakage current parameters are in accordance with ITRS 2013, and that it may have been utilized as a utility man in future modelling and optimization efforts.

Mechanically Stable PMMA‐Based Large‐Area Nano‐Channels with Sub‐10 nm Depth

AbstractArtificial sub‐microfluidic and nanofluidic devices allow for studying mass or ion transport effects under spatial confinement. It remains challenging to fabricate large‐scale, nanofluidic channels of well‐defined thickness for fundamental studies and practical applications, especially for extreme confinement conditions (e.g., with sub‐10 nm channel height). Here, a strategy is reported to fabricate large‐scale nano‐channels with the channel height down to 5.0 nm. The fabrication is enabled by developing ultra‐flat and ultra‐thin polymethylmethaacrylate (PMMA) layers as the spacer. The ease of scaling up the channel length to a millimeter in the lateral dimensions with high mechanical stability is demonstrated. Furthermore, experimental evidence is provided of the role of the mechanical coupling between the spacer and capping materials in determining the device's mechanical properties, and how controlling the channel width and the top graphite thickness can be employed to tailor the device's mechanical properties. Finally, employing near‐field IR experiments, the decay constant is established for the near‐field absorption intensity of PMMA molecules inside the channel by increasing the top layer thickness. This work develops a novel method for fabricating large‐area, mechanically stable nano‐channels for nanofluidic devices and lays the foundation for further in situ spectroscopic studies of electrochemistry within sub‐10 nm confinement.

Transport in a Two-Channel Nanotransistor Device with Lateral Resonant Tunneling.

We study field effect nanotransistor devices in the Si/SiO2 material system which are based on lateral resonant tunneling between two parallel conduction channels. After introducing a simple piecewise linear potential model, we calculate the quantum transport properties in the R-matrix approach. In the transfer characteristics, we find a narrow resonant tunneling peak around zero control voltage. Such a narrow resonant tunneling peak allows one to switch the drain current with small control voltages, thus opening the way to low-energy applications. In contrast to similar double electron layer tunneling transistors that have been studied previously in III-V material systems with much larger channel lengths, the resonant tunneling peak in the drain current is found to persist at room temperature. We employ the R-matrix method in an effective approximation for planar systems and compare the analytical results with full numerical calculations. This provides a basic understanding of the inner processes pertaining to lateral tunneling transport.

Performance comparison of different intensity modulation formats for FSO systems

Abstract Intensity modulation (IM) formats are the legacy formats which are continuing to act as modulation formats of interest in fiber optic communication systems and optical networks. The IM formats have become formats of interest in free space optic communication (FSO) systems due to its simple generation and detection principle, thus making FSO system economical and easier to handle/operate under adverse and random characteristics of atmospheric channel. This paper compares the performance of different IM formats (with memory and without memory or memoryless). The IM formats considered here are non return to zero (NRZ), return to zero (RZ), carrier suppressed RZ (CSRZ), vestigial side band CSRZ (VSB-CSRZ), duobinary RZ (DRZ) and modified duobinary RZ (MDRZ). The comparative analysis investigates the effect of launch power and length of FSO channel at different data rates of 10 Gb/s and 40 Gb/s for single channel FSO system, with the help of simulations. The results discussed, depicts that VSB-CSRZ outperforms other modulation formats at 10 Gb/s and duobinary format has shown lesser degradation in system performance when bit rate increases from 10 Gb/s to 40 Gb/s.

Electromagnetic Model of K‐Changes

AbstractK‐changes are observed as step‐like increases in the thundercloud electric fields. The K‐changes occur in the late part of intra‐cloud lightning or during negative cloud‐to‐ground lightning between return strokes. It has been shown that the processes leading to K‐changes initiate in the decayed part of a positive leader channel and propagate toward the flash origin. They are often accompanied by microsecond‐scale electric field pulses. We introduce a new model to simulate processes leading to the K‐changes in cloud‐to‐ground lightning. Our method is based on the full solution of Maxwell's equations coupled to Poisson's equation for the thundercloud charge structure. To model the K‐changes, we gradually increase the decayed channel conductivity. The modeled current wavefront propagates due to the K‐processes downward along a vertical channel and completely attenuates before reaching the ground. We derive the evolution of the linear charge densities and the scalar electric potential along the channel leading to K‐changes. We model electrostatic step‐like changes in the measured electric field together with the approximate rates and amplitudes of the microsecond scale pulses. Step‐like changes increase their amplitudes with the length of the simulated channel and with a higher conductivity of the channel. The microsecond‐scale pulse waveshapes depend mainly on the propagation velocity of the current wave, and the time scale of the conductivity increase. We show that our modeled waveforms are in a good agreement with observations conducted in Florida.

High-performance InGaZnO power transistors: Effect of device structural parameters

In this work, the effect of offset channel length (Loffset) and the dielectric layer thickness (d) on the InSnO/InGaZnO (ITO/IGZO) dual-active-layer (DAL) high-voltage thin-film transistors (HV-TFTs) is systematically investigated. The characteristics of the DAL HV-TFTs resemble that of GaN high electron mobility transistors, wherein the breakdown voltages (VBD) reach saturation at a certain Loffset, and the on-resistance (Ron) linearly increases with Loffset. The linear fitting of Ron vs Loffset indicates that d has a multifaceted impact on the performance of HV-TFTs. In addition to its theoretical role in transistor models, d also influences the channel doping concentration and sidewall deposition issues in practical devices. The DAL HV-TFT with a 30-nm Al2O3 gate dielectric achieves a remarkable VBD of 450 V, the highest figure of merit of 118.2 kW/cm2, and a positive threshold voltage of 3.65 V. Both experiments and simulations indicate that the breakdown occurs within the semiconductor channel, paving the way for further improvement of the performance.

Methane Adsorption and Transport in Tortuous Slit-like Nanochannels: A Molecular Simulation Study.

Tortuosity is a crucial characteristic of porous materials, such as the shale matrix where shale gas is stored. The presence of tortuous nanochannels significantly affects the adsorption and transport of nanoflows. In this research, we use molecular dynamics simulation (MD) to study the adsorption and transport properties of shale gas (methane) in a curved slit-like nanochannel constructed from bent graphene sheets. Our findings reveal that the curvature of the tortuous channel influences methane adsorption: convex surfaces exhibit stronger adsorption, while concave surfaces exhibit weaker adsorption; the discrepancy is amplified by the nanoflow. Additionally, nanoflow velocity is heterogeneously distributed within the curved channel, with higher tangential flow velocities observed near the entrance and the outer surface. We also identify a "bouncing effect", where the nanoflow not only moves tangentially along the channel but also bounces between the inner and outer walls. Furthermore, methane in narrower channels exhibits higher tangent flow velocity and higher bouncing frequency but smaller flux, whereas larger curvature results in shorter channel length and smaller tortuosity, but the transport tangent velocity and flux are both reduced. The findings of this study can help in the better understanding of shale gas nanoflow properties in tortuous media and provide insights for simulating more general nonstraight nanoflows.

A Two-Step Dry Etching Model for Non-Uniform Etching Profile in Gate-All-Around Field-Effect Transistor Manufacturing.

The Gate-All-Around Field-Effect Transistor (GAAFET) is proposed as a successor to Fin Field-Effect Transistor (FinFET) technology to increase channel length and improve the device performance. The GAAFET features a complex multilayer structure, which complicates the manufacturing process. One of the most critical steps in GAAFET fabrication is the selective lateral etching of the SiGe layers, essential for forming the inner-spacer. Industry commonly encounters a non-uniform etching profile during this step. In this paper, a continuous two-step dry etching model is proposed to investigate the mechanism behind the formation of the non-uniform profiles. The model consists of four modules: anisotropic etching simulation, Ge atom diffusion simulation, Si/SiGe etch selectivity calculation and SiGe selective etching simulation. By calibrating and verifying this model with experimental data, the edge rounding and gradient etching rates along the sidewall surface are successfully simulated. Based on further examination of the influence of chamber pressure on the profile using this model, the inner-spacer shape is improved experimentally by appropriately reducing the chamber pressure. This work aims to provide valuable insights for etching process recipes in advanced GAAFETs manufacturing.

New tunneling source follower with low 1/f noise and high voltage gain

We have designed a tunneling source follower (TSF) for image sensors that achieves high voltage gain (Av) and low 1/f noise simultaneously. The TSF is composed of N-P-N-N, especially the p-doped grounded area, which serves to amplify the insufficient tunneling current, allowing the source follower (SF) to utilize band-to-band tunneling (BTBT). Compared to thermionic emission, tunneling based structures contribute to increasing Av through lower channel length modulation and lower body effect. As a result, TSF achieves a higher Av (~ 1.0 V/V) than conventional SF (~ 0.9 V/V). Moreover, the n-doped channel makes the buried conductive channel farther from the interface, lowering the noise. The input-referred voltage noise spectral density (SV) is approximately 10 times lower in TSF than that of in conventional SF. Therefore, our TSF can be a possible candidate for High Av and low 1/f noise image sensors.

Modeling and characterization of low frequency noise in self-aligned top-gate coplanar IGZO thin-film transistors

Abstract A modified low-frequency noise (LFN) model was proposed to accurately estimate the quality of the gate dielectric in self-aligned top-gate (SA TG) coplanar structure indium–gallium–zinc oxide (IGZO) thin-film transistors (TFTs). The proposed LFN model was derived by modifying the conventional carrier number with correlated mobility fluctuation model considering the peculiar characteristics of SA TG coplanar IGZO TFTs such as the channel length reduction due to the diffusion of hydrogen atoms or oxygen vacancies from the source/drain to the channel, as well as the relatively large source/drain parasitic resistance. The proposed model was validated by demonstrating that the measured LFN values were in good agreement with the predicted values from the proposed model for all SA TG coplanar IGZO TFTs with SiO2 gate dielectrics deposited under different plasma-enhanced chemical vapor deposition (PECVD) power densities. The near-interface gate dielectric trap densities extracted from each TFT using the proposed LFN model revealed a clear increase as the PECVD power increased, which is considered a major cause of poor positive-bias-temperature-stress stability of the SA TG coplanar IGZO TFT with SiO2 gate dielectric deposited under high PECVD power conditions.

A Study on the Production-Inventory Problem with Omni-Channel and Advance Sales Based on the Brand Owner’s Perspective

This study explores a supply chain product-inventory problem with advance sales under the omni-channel strategies (physical and online sales channels) based on the brand owner’s business model and develops corresponding models that have not been proposed in previous studies. In addition, because the brand owner is a member of the supply chain, and has different handling methods for defective products or products returned by customers in various retail channels, defective products or returned products are included in the supply chain models to comply with actual operating conditions and fill the research gap in the handling of defective/returned products. Regarding the mathematical model’s development, we first clarify the definition of model parameters and relevant data collection, and then establish the production-inventory models with omni-channel strategies and advance sales. The primary objective is to determine the optimal production, delivery, and replenishment decisions of the manufacturer, physical agent, and online e-commerce company in order to maximize the joint total profits of the entire supply chain system. Further, this study takes the supply chain system of mobile game steering wheel products as an example, uses data consistent with the actual situation to demonstrate the optimal solutions of the models, and conducts sensitivity analysis for the proposed model. The findings reveal that increased demand shortens the replenishment cycle and raises order quantity and shipment frequency in the physical channel, similar to the online channel during normal sales. However, during the online pre-order period, higher demand reduces order quantity and cycle length but still increases shipment frequency. Rising ordering or fixed shipping costs lead to higher order quantity and cycle length in both channels, but variable shipping costs in the online channel reduce them. Market price increases boost order quantity and frequency in the online channel, while customer return rates significantly impact inventory decisions.

Unveiling gas transport mechanisms in tunable MXene nanochannels: Insights from molecular dynamics simulations

MXene-based membranes have shown tremendous potential in gas separation applications. Here, molecular dynamics (MD) simulations are used to investigate the effects of varying the structural parameters of Ti₃C₂O₂ nanochannels on the permeation and separation performance of H₂, CO₂, N₂, and CH₄ gases. The results demonstrate that the interlayer spacing significantly influences gas permeability, with wider channels generally exhibiting higher permeance. Channel length, however, has a relatively minor impact on permeability, varying by gas species. Potential of mean force (PMF) analysis reveals that CO₂ molecules face a notable energy barrier at the channel entrance and have the strongest interactions with the MXene interface within the channel, potentially leading to blockage. Spatial density analysis further confirms this CO₂ blockage phenomenon, which diminishes as the interlayer spacing increases. In terms of gas separation selectivity, H₂/CH₄ and H₂/CO₂ mixtures exhibit high selectivity, with maximum values of 41.08 and 27.06, respectively. Notably, the H₂/CO₂ system exhibits a positive correlation between permeability and selectivity, breaking the traditional permeability-selectivity trade-off. This anomalous behavior can be attributed to the CO₂ blockage effect. This study provides theoretical guidance for the design and optimization of MXene-based membrane materials in practical applications.

Field‐effect modulated water‐splitting by photoinduced charge carriers on BiFeO3 film

AbstractIn this study, the field‐effect generated by illuminated p‐type ferroelectric bismuth ferrite (BiFeO3 or BFO) semiconductor film is utilized to modulate the water‐splitting performance of a system with a macroscopic spatial separation between the anode and cathode. When the BFO film in contact with an electrolyte is illuminated with a light of sufficiently high frequency, an electrolytic conducting channel is formed due to the field effect induced by photoexcited charge carriers in the BFO film, which in turn alters the water‐splitting pathway and the reaction mechanism. The field effect can be modulated by changing the orientation of the ferroelectric polarization in the BFO film. With a BFO film of 4.5 mm channel length and an overall upward ferroelectric polarization direction, a ∼30% increase in water‐splitting performance in a neutral‐pH electrolyte is achieved in the presence of field‐effect induced by a 20 mW 405 nm light source. The mechanism behind the field‐effect modulation is also further verified by monitoring the pH of the electrolyte during the water‐splitting process and conducting thresholding analysis on the recorded data. The field‐effect modulation described in this study can potentially be used to enhance the performance of a photoelectrochemical water‐splitting system by taking advantage of the presence of light illumination in the system or be utilized in electrochemical sensing applications.

Grit size effect on HydroFlex polishing dynamics and performance

Controllable, adaptable internal polishing is critical to metal additive manufactured (MAM) complex channels. Conventional fluid-based internal polishing methods are challenging to control the material removal, resulting in varied surface roughness (Sa) depending on channel length, aspect ratio (AR), and complexity. HydroFlex is an internal polishing method which drives a fixed-abrasive grinding wheel via a flexible spindle to navigate complex, high AR channels controllably and predictably removing material. Key to HydroFlex performance is the orbital motion of the grinding wheel governed by the hydrodynamic and cutting forces to achieve uniform polishing. Effect of grit size on orbital motion, and corresponding performance was experimentally evaluated. 46 µm, 76 µm, and 91 µm grit sizes were tested at a rotational speed of 50,000 rpm and a channel to wheel (C/W) ratio of 0.54 and orbital frequency and consistency, grinding force, Sa, material removal rate (MRR), and wheel wear were compared. Orbital frequency was found to directly correlate with increasing grit size and consistency of orbit shown to be highest at moderate grinding forces. Sa and MRR were inversely proportional with sub-micron roughness achieved at 0.15 g/min and 0.34 g/min corresponding to 2.2 µm Sa. Wheel wear was effected by grain pullout, attrition, and capping with all grit sizes experiencing similar wear. These findings suggest that orbital motion can be controlled through manipulation of wheel kinetics enabling precise control of grinding dynamics essential to adaptable performance in complex, non-uniform MAM channels.

Kinetic investigation of the energy storage process in graphene fiber supercapacitors: Unraveling mechanisms, fabrications, property manipulation, and wearable applications

AbstractGraphene fiber supercapacitors (GFSCs) have garnered significant attention due to their exceptional features, including high power density, rapid charge/discharge rates, prolonged cycling durability, and versatile weaving capabilities. Nevertheless, inherent challenges in graphene fibers (GFs), particularly the restricted ion‐accessible specific surface area (SSA) and sluggish ion transport kinetics, hinder the achievement of optimal capacitance and rate performance. Despite existing reviews on GFSCs, a notable gap exists in thoroughly exploring the kinetics governing the energy storage process in GFSCs. This review aims to address this gap by thoroughly analyzing the energy storage mechanism, fabrication methodologies, property manipulation, and wearable applications of GFSCs. Through theoretical analysis of the energy storage process, specific parameters in advanced GF fabrication methodologies are carefully summarized, which can be used to modulate nano/micro‐structures, thereby enhancing energy storage kinetics. In particular, enhanced ion storage is realized by creating more ion‐accessible SSA and introducing extra‐capacitive components, while accelerated ion transport is achieved by shortening the transport channel length and improving the accessibility of electrolyte ions. Building on the established structure–property relationship, several critical strategies for constructing optimal surface and structure profiles of GF electrodes are summarized. Capitalizing on the exceptional flexibility and wearability of GFSCs, the review further underscores their potential as foundational elements for constructing multifunctional e‐textiles using conventional textile technologies. In conclusion, this review provides insights into current challenges and suggests potential research directions for GFSCs.

Comparison of Patent Foramen Ovale Sizing by Transesophageal Echocardiography and Balloon Sizing in Patients Undergoing Percutaneous Closure

BackgroundA patent foramen ovale (PFO) has a complex anatomy, and evaluating the size before closure may be challenging. We aimed to investigate the correlation between preprocedural transesophageal echocardiography (TEE) and balloon sizing of PFO in patients undergoing percutaneous PFO closure. MethodsA retrospective single-center study with analysis of 100 patients who, due to paradox thromboembolism in the left circulation, underwent percutaneous PFO closure. The PFO sizing was compared to measures attained by TEE and balloon sizing using linear regression analysis. ResultsPFO size measured by TEE occurred smaller than balloon sizing (2.19 mm [95% CI: 1.91 to 2.46] vs. 8.51 mm [95% CI: 8.02 to 9.00], p < 0.001). Additionally, neither the PFO channel length nor the atrial septal mobility measured by TEE correlated to the PFO size attained by balloon sizing, respectively (slope ?0.018 [95% CI: ?0.117 to 0.081], R = 0.036, p = 0.719) and (slope 0.049 [95% CI: ?0.043 to 0.141], R = 0.105, p = 0.297). Statistically significant difference in regression analysis but poor correlation was found between both TEE attained PFO and shunt size when compared to balloon sizing. Diverting patients according to the size of the PFO shunt was not statistically significant between PFO of moderate size compared, respectively, to a large and small PFO size. However, a difference was observed between a small and large PFO shunt size. ConclusionsPFO defect and shunt size measured by TEE showed a poor correlation with balloon sizing. Neither PFO channel length nor septal mobility were correlated to the PFO size measured by balloon sizing.

Principle Study of MoS2 FET at lower Channel Lengths

Principle Study of MoS2 FET at lower Channel Lengths

Study of the Flow Characteristics of Pumped Media in the Confined Morphology of a Ferrofluid Pump With Annular Microscale Constraints

Abstract The driving mechanism of ferrofluid micropumps under the constraints of an annular microscale morphology is not fully understood. The gap between microfabrication technology and the fundamental theory of microfluidics has become a substantial obstacle to the development and application of ferrofluid micropumps. In this study, we first theoretically analyzed the Knudsen numbers of millimeter-scale microfluids using Jacobson's molecular hard sphere model, obtaining the initial conclusion that liquid flow conforms to the continuum hypothesis in geometric morphologies with characteristic dimensions greater than 7 × 10−8 m. Subsequently, using a microscopic lens combined with the particle image velocimetry optical measurement method, the flow patterns in millimeter-scale annular flow channels were captured and we observed wall slip phenomena in which the slip length of the millimeter-scale channel approached the micron level. The slip velocity and flowrate through the cross section of the microscale channel followed a logarithmic function relationship and could be divided into rapid growth, slow growth, and stable stages. As the characteristic scale of the channel was further reduced, the linear relationship between the slip velocity and cross-sectional flowrate in the rapid growth stage was broken, and the nonlinear relationship approximated an exponential function. Finally, a theoretical model for the flow behavior of the driving fluid in a ferrofluid micropump was established using slip boundary conditions. The flow patterns in microscale ring flow under slip conditions conformed to a quadratic function.