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Scaling of High-Performance Organic Permeable Base Transistors
摘要： Organic permeable-base transistors (OPBTs) show potential for high-speed, flexible electronics. Scaling laws of OPBTs are discussed and it is shown that OPBT performance can be increased by reducing their effective device area. Comparing the performance of optimized OPBTs with state-of-the-art organic field-effect transistors (OFETs), it is shown that OPBTs have a higher potential for an increased transit frequency. Not only do OPBTs reach higher transconductance values without the need for sophisticated structuring techniques, but they are also less sensitive to parasitic contact resistances. With the help of a 2D numerical model, the reduced contact resistances of OPBTs are explained by a homogeneous injection of current across the entire emitter electrode, compared to injection in a small area along the edge of the source of OFETs.
关键词： scaling,injection,organic permeable-base transistors,contact resistance,transit frequency
更新于2025-10-22 19:50:37
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Scaling effects on the optical properties of patterned nano-layered shape memory films
摘要： Nano-layered films of PVAc/PU systems were fabricated by forced assembly coextrusion method. The bulk shape memory properties of PVAc/PU systems were utilized to program nanoscale patterns such as diffraction grating which exhibit iridescence after patterning. A hot embossing process has been utilized to imprint diffraction grating patterns as nano-scale information onto the surface of the thin multilayer films. Three levels of hierarchy i.e. layer thickness, spacing and heights of patterns, governs the functionality of the patterned multilayer film. The time and temperature dependent viscoelastic shape memory behavior determines the opto-mechanical tunability of the film. Mechanical switching of the patterns also leads to optical switching of the films which corresponds to their efficiency of information retrieval. The recovery of patterns as well as the diffractive property depends on the layer thickness (l) of films and heights of patterns (h0). The results illustrate that the higher ratio of h0/l better is the recovery of the grating patterns and the corresponding diffractive properties. This scaling effect enables versatile applications in information security by tuning the layer structure of the multilayer shape memory films.
关键词： scaling effect,shape memory film,pattern programming,hot embossing,multilayer film,information security,diffractive optical element,thermal responsive optics
更新于2025-10-22 19:40:53
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Scaling behavior in on-chip field-amplified sample stacking
摘要： Field amplified sample stacking (FASS) uses differential electrophoretic velocity of analyte ions in the high-conductivity background electrolyte zone and low-conductivity sample zone for increasing the analyte concentration. The stacking rate of analyte ions in FASS is limited by molecular diffusion and convective dispersion due to non-uniform electroosmotic flow (EOF). We present a theoretical scaling analysis of stacking dynamics in FASS and its validation with a large set of on-chip sample stacking experiments and numerical simulations. Through scaling analysis, we have identified two stacking regimes that are relevant for on-chip FASS, depending upon whether the broadening of the stacked peak is dominated by axial diffusion or convective dispersion. We show that these two regimes are characterized by distinct length and time scales, based on which we obtain simplified non-dimensional relations for the temporal growth of peak concentration and width in FASS. We first verify the theoretical scaling behavior in diffusion and convection dominated regimes using numerical simulations. Thereafter, we show that the experimental data of temporal growth of peak concentration and width at varying electric fields, conductivity gradients, and EOF exhibit the theoretically predicted scaling behavior. The scaling behavior described in this work provides insights into the effect of varying experimental parameters, such as electric field, conductivity gradient, electroosmotic mobility, and electrophoretic mobility of the analyte on the dynamics of on-chip FASS.
关键词： dispersion,scaling analysis,on-chip electrophoresis,field-amplified sample stacking
更新于2025-09-23 15:23:52
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Focusing of Spaceborne Bistatic SAR Data Based on Time-Domain Perturbation
摘要： Spaceborne bistatic synthetic aperture radar (BiSAR) system with an inclined geosynchronous (GEO) illuminator and a low-earth-orbit (LEO) receiver is capable of providing higher signal-to-noise ratio (SNR), finer resolution and vast area of surveillance. However, spatial-variant characteristics of the echo signal caused by the complex bistatic formation raise technical challenges in data focusing. To address the issue, an improved chirp scaling (CS) algorithm based on time-domain perturbation is proposed. Firstly, the signal model of GEO-LEO bistatic SAR is derived based on the geometry. Then, two-dimension (2-D) perturbation functions are employed to correct the spatial-variant characteristics of the echo signal. Finally, the phase compensation functions are generated to compensate for the residual phase. The proposed algorithm is able to implement wide-swath and high-resolution imaging. Simulation results of point targets show the validity of the presented method.
关键词： chirp scaling,spatial-variant,imaging,bistatic SAR,time-domain perturbation
更新于2025-09-23 15:22:29
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[IEEE 2018 Conference on Design and Architectures for Signal and Image Processing (DASIP) - Porto, Portugal (2018.10.10-2018.10.12)] 2018 Conference on Design and Architectures for Signal and Image Processing (DASIP) - Low Power Image Processing Applications on FPGAs Using Dynamic Voltage Scaling and Partial Reconfiguration
摘要： The TULIPP project aims to facilitate the development of embedded image processing systems with real-time and low-power constraints. In this paper, several adaptive dynamic runtime techniques for reconfigurable SoCs are described. These methods are used for low power image processing applications on high-performance embedded platforms. Dynamic voltage scaling and dynamic partial reconfiguration target the low-power requirements of the embedded systems while debugging supports the fast development on the hardware side of the system. The proposed techniques were tested and verified using an own developed custom SDSoC image processing library.
关键词： low power,FPGA,image processing,Debugging,Embedded systems,reconfigurable,real-time,Dynamic Voltage Scaling,Dynamic Partial Reconfiguration
更新于2025-09-23 15:22:29
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Graphene field-effect transistors with high extrinsic fT and fmax
摘要： In this work, we report on the performance of graphene field-effect transistors (GFETs) in which the extrinsic transit frequency (fT) and maximum frequency of oscillation (fmax) showed improved scaling behavior with respect to the gate length (Lg). This improvement was achieved by the use of high-quality graphene in combination with successful optimization of the GFET technology, where extreme low source/drain contact resistances were obtained together with reduced parasitic pad capacitances. GFETs with gate lengths ranging from 0.5 μm to 2 μm have been characterized, and extrinsic fT and fmax frequencies of up to 34 GHz and 37 GHz, respectively, were obtained for GFETs with the shortest gate lengths. Simulations based on a small-signal equivalent circuit model are in good agreement with the measured data. Extrapolation predicts extrinsic fT and fmax values of approximately 100 GHz at Lg=50 nm. Further optimization of the GFET technology enables fmax values above 100 GHz, which is suitable for many millimeter wave applications.
关键词： field-effect transistor,scaling,graphene,maximum frequency of oscillation,transit frequency
更新于2025-09-23 15:22:29
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Assessment of Self-Heating Effects Under Lateral Scaling of GaN HEMTs
摘要： The impact on self-heating mechanisms observed in GaN HEMTs fabricated on Si substrates is studied by means of a cellular Monte Carlo particle-based device simulator. Within this framework, the thermal effects are included through an energy-balance equation for phonons allowing for self-consistently coupling the charge and heat transport. First, the advanced electrothermal model of an experimental device is developed and calibrated to measured dc characteristics, showing an accurate description throughout the IDS(VGS?VDS) space, as a result of capturing the temperature dependence of the scattering processes that modify the charge transport. Then, the model is used to assess the effect of lateral scaling, i.e., reducing the source-to-gate LSG and gate-to-drain LGD dimensions, in terms of detailed temperature maps obtained for the acoustic and optical phonon modes as well as the electric field and carrier velocity profiles. It is found that the hot spot in the channel is not located at the peak electric field as predicted by previous methods, but instead, it is shifted toward the drain up to 32 nm. Furthermore, it is shown that, while scaled devices offer improved dc and small-signal ac performance, they are subjected to temperatures up to 15% higher in the channel as compared to the original nonscaled device when dissipating the same dc power, and the temperature distribution throughout the device shows a strong correlation with the scaled layout.
关键词： reliability,HEMTs,Monte Carlo methods,self-heating,scaling,GaN
更新于2025-09-23 15:22:29
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Generalized optimization method for energy conversion and storage efficiency of nanoscale flexible piezoelectric energy harvesters
摘要： The energy conversion and storage efficiency was commonly ignored in experimental studies on nanoscale flexible piezoelectric energy harvesters (PEHs). In this study, we develop a generalized theoretical method to optimize the energy conversion and storage efficiencies of nanoscale flexible PEHs. The results are validated by comparisons with experimental measurements for various ambient excitations. A simple scaling law is established to reveal the intrinsic correlation between the efficiency of energy conversion/storage and various system parameters of the PEHs. For either the energy conversion or storage circuit, the output power density may be maximized by properly designing an intrinsic normalized parameter. Furthermore, we demonstrate that an independent optimization criterion is indispensable for standard storage circuits since including a storage module into the conversion circuit redefines the electromechanical behavior of the PEH system. The results may be used as guidelines for optimizing the energy conversion and storage efficiencies of nanoscale flexible PEHs that have promising applications in harvesting biomechanical energies.
关键词： Scaling law,Optimization,Nanoscale flexible piezoelectric energy harvesters,Energy conversion,Energy storage
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE 3rd International Conference on Signal and Image Processing (ICSIP) - Shenzhen, China (2018.7.13-2018.7.15)] 2018 IEEE 3rd International Conference on Signal and Image Processing (ICSIP) - An Analytical Imaging Algorithm for Parallel Invariant SAR
摘要： This paper discusses the processing method for parallel invariant SAR, and an analytical imaging algorithm based on GLBF is proposed. The bulk focusing is performed by reference function multiplication (RFM), then the range scaling factor is derived and further corrected by Chirp-z transform (CZT). The algorithm can be applied to wide scene imaging with the derived data blocking rules. The proposed imaging algorithm is verified by simulations.
关键词： chirp-z transform (CZT),parallel invariant SAR,range scaling factor
更新于2025-09-23 15:22:29
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Scaling Procedures and Post-Optimization for the Design of High-Efficiency Klystrons
摘要： A semianalytical parametric scaling procedure (PSP) for klystron design has been developed. The PSP allows existing klystron designs to be scaled to different operating frequencies, beam power, and perveance, while maintaining the electron bunching and deceleration processes. For the fixed layout of a klystron RF circuit, the PSP provides parameters of the scaled klystron which are nearly optimal. The theoretical background and step by step derivation of the scaling principles are presented. The effectiveness of the PSP is shown through a generic five-cavity L-band klystron.
关键词： optimization,High-efficiency klystron,scaling method
更新于2025-09-23 15:22:29