Search

Heterogeneous integration enables high-density integration to improve system functionality, but meanwhile brings reliability concerns due to the intensification of temperature and thermal stress. However, research on thermal stress effects in nanoscale transistors within heterogeneous integrated circuit is still very limited up to now. Multiphysics computation for the heterogeneous integration of nanoscale p-FinFET with GaN high electron mobility transistor (HEMT) on silicon substrate is performed. Firstly, self-heating of GaN HEMT induced thermal stress is simulated. Then, thermal stress effects induced by the GaN HEMT on quantum transport in the FinFET at different locations are compared and analyzed, including the hole effective mass, hole average velocity, on/off-state current, and on-off ratio. Moreover, the impacts of crystal orientation configurations are further discussed. Simulation results show that the impact of thermal stress on FinFET is highly dependent on the Si crystal orientation and its location relative to GaN HEMT. Taking the FinFET with (001)/[110] confinement/transport orientation, which is at a distance of R FET and an angle of φ from the GaN HEMT as an example, thermal stress induces the significant reductions in I on and I off of FinFET at φ = π/2 and φ = 3π/2, and the increases of I on and I off in FinFET at φ = 0 and φ = π, but has small impact on FinFETs located diagonally to the GaN HEMT. [ABSTRACT FROM AUTHOR]

Metal-Ferroelectric-Insulator-Semiconductor (MFIS) structure ferroelectric tunnel junction (FTJ) memristor becomes one of the most promising candidates for next-generation memories. Two numerical simulation methods have been developed and analyzed previously to calculate the tunneling current in the MFIS-FTJ, one by using the Wentzel–Kramers–Brillouin (WKB) method with the band profile obtained from Poisson's equation, the other by self-consistently solving Poisson's equation and the drift-diffusion transport equations with a tunneling-induced carrier generation rate. However, numerical methods can be computationally expensive, especially for device design with various parameters. In this work, an artificial neural network (ANN) model that can predict the device performance is proposed, the model can reduce computational cost while maintaining good accuracy. In addition, to further investigate the applicable conditions of the two simulation methods mentioned above, we also develop an ANN model to predict the relative differences between the two methods' results under different conditions, and the prediction results show good agreement with numerical results. [ABSTRACT FROM AUTHOR]

A type of broadband (325−980 nm) self-powered photodetector based on graphene/GaAs van der Waals heterojunction is reported. By simply spinning a layer of Ag nano-particles (Ag NPs) onto graphene/GaAs heterostructure, the responsivity and detectivity of our devices for the whole spectrum range are enhanced significantly. The maximum photocurrent responsivity of 210 mA W −1 (increased by 38%) and detectivity of 2.98 × 10 13 Jones (increased by 202%) are achieved at 405 nm, which is about two or three orders of magnitude larger than other graphene based self-powered photodetectors. The mechanism of the improvement originates from the overlap the depletion region of graphene/GaAs heterostructure, the surface plasmon enhanced light field region below the surface and the light absorption region of the GaAs layer. The external quantum efficiency (EQE) measurement, transient photoluminescence (PL) test and the comparative theoretical simulation show that the surface plasmon enhancement should only be applicable for graphene/direct band gap semiconductor heterostructure, where the semiconductor should have a high optical absorption coefficient. The obtained high performance broadband photodetector with excellent detectivity is a promising candidate for many important optoelectronic applications, such as ultrasensitive image sensor in charge coupled displayer field, which requires colour sensors not only with high photo responsivity but also in a wide spectral range. [ABSTRACT FROM AUTHOR]

Graphene based van der Waals heterostructure has attracted wide attention recently, especially for graphene/semiconductor Schottky junction. Herein, through delicately designing and engineering the van der Waals heterostructure between graphene and indium phosphide (InP), which has a suitable bandgap of 1.34 eV for solar energy conversion, we have achieved graphene/p-InP solar cells with power conversion efficiency (PCE) of 3.3% under AM 1.5G illumination. The chemical doping or electrical field modulation has been used to tune the Fermi level of graphene, which leads to a PCE of 5.6% for the device under gating effect. Furthermore, the interface recombination rate could be reduced while graphene is doped or gated, as evidenced by transient photoluminescence measurements. Considering the stability of cell performance under illumination and the high resistance to space irradiation damage of InP, graphene/InP heterojunction may be promising for special applications such as space solar cells. [ABSTRACT FROM AUTHOR]

Microwave absorption materials or structures show great application prospects in the design of 5 G systems. A graphene-assisted wideband metamaterial microwave absorber with polarization insensitivity and wide incidence angle is proposed based on the round-with-square-hole (RSH) shaped monolayer graphene structure in this paper. The calculation results of the device over an ultra-wideband (16–100 GHz) yields good absorption above 90% when the chemical potential of graphene is 0.1 eV. The fractional bandwidth is 145% for both transverse electric and transverse magnetic polarizations with normal incidence. The influences of the geometry structure parameters and graphene chemical potential on absorption characteristics have been investigated. The structure exhibits polarization independent and wide incidence angle properties since the geometrical symmetry structure. In addition, the structure provides excellent performance when the whole thickness of the device is less than 1 mm. Mechanism of the wideband operation is deciphered based on the normalized relative impedance, surface current and electric field distributions. The novel microwave absorber demonstrates great potential in various fields of electromagnetic stealth, electromagnetic interference shielding, 5 G systems, and so on. [ABSTRACT FROM AUTHOR]

Abstract Vehicle emissions have become the major source of air pollution as well as heavy metals pollution accompanied with unprecedented economic development and urbanization in China. Yunnan province, the congruity area of undeveloped region with high vehicle population increasing, as well as special natural conditions, was taken as the study area. We estimated the vehicle emissions during 2003–2015 with COPERT IV model, including private cars (PC), buses (BUS), light duty vehicles (LDV) and heavy duty trucks (HDT), then analyzed the vehicle emission characteristics, involving CO, CO 2 , SO 2 , NO x , NO, NO 2 , N 2 O, NH 3 , Volatile organic compounds (VOC), Ambient Air Non-Methane Volatile Organic compound (NMVOC), CH 4 , PM 2.5 , PM 10 , PM (exhaust), Cadmium and Zinc. The results indicated that all pollutants as well as heavy metals were increased at different growth trends except SO 2 although more stringent emission standard implementation, the rising of vehicle population become the main contributor to the vehicle emission growth, and CO 2 emission was the major vehicle emissions accounted for one third of total CO 2 emissions in Yunnan. PC was the main contributor to the rising of CO, VOC, NMVOC, CH 4 , NH 3 , CO 2 , Cadmium and Zinc, which was also the major vehicle growth type; HDT and LDV brought to the emissions of N 2 O, NO x , NO, PM 10 , NO 2 , PM 2.5 , and PM (exhaust) respectively. At last, uncertainty of emission estimation was analyzed based on the Monte Carlo simulation. The vehicle emission become one critical field of emission reduction in Yunnan which should be given greater emphasis to environmental concerns. Highlights • The vehicle emission inventory in Yunnan province during 2003–2015 was estimated. • Around one third of total CO 2 emissions came from vehicle emissions in Yunnan (2015). • Only SO 2 shown continuous downward trend during after 2010. • PC total emissions were in the top including heavy metals for its population. [ABSTRACT FROM AUTHOR]

This paper presents a novel scheme to incorporate quantum effect in classical hydrodynamic model. The scheme can be applied to multi-dimensional and transient conditions and no additional equations are required to solve quantum potential, so complexity of equations is drastically reduced. Simulation results show consistent with that of Monte Carlo simulation. This technology provides an efficient method for investigating quantum effect in small size semiconductor devices. A new guess method for hydrodynamics model has also been proposed in this paper and a 2D hydrodynamic simulator based on quantum correction and new initial guess method has been developed. The solution obtained from DD model gives a good initial guess of HD model. Its advantage is it can achieve convergence after a few iterations because initial guess is closed to final solution. Two-dimensional simulations have been carried out on a few nanoscale devices. The results have been compared with that of other initial guess methods and the significant differences have been found, especially in numerical stability. [Copyright &y& Elsevier]

The synthesis of photocatalysts with controlled facets has become an important approach to enhance the H 2 evolution activity. However, the relationship between different exposed facets of heterojunctions and photocatalytic performance still needs to be further investigated. In this study, three types of CdS@ZnO core-shell architectures with tunable heteroinnerfaces were fabricated. Hexagonal wurtzite ZnO samples with different percentages of exposed (001) facet showed up as rod-like, short rod-like and disk-like morphologies, respectively, subsequently, self-assembled flower-like CdS coated on the whole facet of ZnO, constructing a core-shell nanostructure with the corresponding tunable heterointerfaces. Under visible-light irradiation, it was discovered that the performance of hydrogen evolution is proportional to the ratio of (001) facet of ZnO in CdS@ZnO core-shell structures. Further photoelectric tests indicated that the (001) facet of ZnO by CdS modification can form a more perfect combination than that of (100) facet of ZnO, which exhibits higher electron conduction and separation performance. Image 1 • CdS@ZnO core-shell structures with tunable heterointerfaces were successfully synthesized. • The disk-like CdS@ZnO sample displays the highest H 2 production rate, which is nearly 6 times than that of pure CdS. • The H 2 evolution performance is proportional to the ratio of (001) facet of ZnO in CdS@ZnO core-shell structures. [ABSTRACT FROM AUTHOR]

This study presents a theoretical and experimental investigation on the power-law response to oxygen in the presence of reducing gases for metal oxide semiconductor gas sensors. In the presence of reducing gases, the exponents of power-law response to oxygen are derived, which allow us an effective probe to reveal the basic sensing mechanism. In order to obtain the power-law exponent, the transducer and receptor functions have been calculated in the presence of reducing gases. The transducer functions is built on two different conduction mechanisms, namely, Schottky barrier model and grain model. The receptor functions have been calculated by using the law of mass action for oxygen with different concentrations of reducing gases. The power response of SnO 2 to oxygen has been characterized in the presence of CO and found to be well consistent with theoretical expectation. [ABSTRACT FROM AUTHOR]

In this paper, WO 3 nanoparticles in a lamellar-structured were fabricated via an acidification method and the surface of nanoparticles were catalytically modified by Ru through a modified impregnation method based on an electronic adsorption mechanism. Gas sensors based on neat and Ru-loaded WO 3 nanoparticles were fabricated based on screen printing and sensor responses of acetone were evaluated under a dry and humid ambient, respectively. Experimental results clearly indicated that most of Ru was removed from the WO 3 during the washing process, however, a strong sensitization effect of Ru was achieved with a very few loading amount. Accordingly, the basic sensitization mechanism of Ru was investigated based on TPR results and oxygen adsorption behaviors. It is revealed that Ru is loaded on the surface with an oxidized state contributing to an electronic sensitization effect. In addition, Ru on the surface of WO 3 as a catalyst significantly enhanced the activity of surface lattice oxygens. As a consequence, surface lattice oxygens could also react with acetone and reduce sensor resistance leading to a sensitization effect. However, we do not expect that reactions of lattice oxygens dominate the sensing process. [ABSTRACT FROM AUTHOR]

We study analytically the plasmonic modes in the graphene-coated dielectric nanowire, based on the explicit form of nonlinear surface conductivity of graphene. The propagation constants of different plasmonic modes can be tuned by the input power at the order of a few tenths of mW. The lower and upper mode bifurcation branches are connected at the limitation value of the input power. Moreover, due to the nonlinearity of graphene, the dispersion curves of plasmonic modes at different input powers form an energy band, which is in sharp contrast with the single dispersion curve in the limit of zero input power. [ABSTRACT FROM AUTHOR]

Abstract : Plasmonic waveguides are proposed to transmit information optically from one electronic component to another in integrated nanoelectronic circuits. A metal–insulator–metal (MIM) plasmonic waveguide, rather than a traditional dielectric waveguide or an electric wire, is used for data transmission. The MIM plasmonic waveguide confines plasmonic (electromagnetic) waves to a dielectric slot with a cross-section of 50nm×50nm, and propagates them close to the speed of light. Two nanorods that form a nanoantenna are employed to receive the optical power from the waveguide, and localize as well as concentrate the received power in the proximity around the two nanorods. The localized optical power is converted to electric signals by a nanoscale plasmonics-to-electronics converter, which has a nanosized active volume and a bandwidth of up to 1THz. Both the plasmonic waveguide and the converter have nanoscale dimensions comparable to those of modern nanoelectronic counterparts. The proposed method could be used to improve the performance of existing nanoelectronic systems by exploiting the strength of optics. [Copyright &y& Elsevier]

Abstract: The ballistic regime gives the upper limit of an electron device performance. This paper proposes a fast and efficient model for calculating the current–voltage characteristic of a cylindrical nanowire within the framework of the non-equilibrium Green''s function. Under certain assumptions, the calculation is simplified to a one-dimensional problem and the modes due to the radial confinement are given by an analytical equation. We further derive an analytical expression for the current–voltage characteristic at temperature approaching 0K. The relationship between the radius of the nanowire and the electrical current is clearly shown in this expression. The effects of the radius on the current–voltage characteristic curve are also studied. Furthermore, we plot the trend of the saturation current as the radius is increased as predicted by both the numerical result and our analytical model. Our proposed model can be further used to include electron–photon interaction in the calculation of nanoscale optoelectronic devices. [Copyright &y& Elsevier]

The accumulation of hazardous arsenic-alkali slag poses a great threat to the environment and human health due to the high content of soluble sodium arsenate. In this paper, a novel process scheme is proposed for the comprehensive utilization and safe disposal of arsenic-alkali slag by the combination of beneficiation and metallurgy. The new technology is novel since every procedure of high arsenic content is run at room temperature, which guarantees good occupational health. The valuable alkali and antimony were recovered efficiently without any secondary pollution. The separation of arsenic and alkali is the most difficult and critical section of the process, where magnesium salt and ammonium salt were added to the arsenic alkali solution in certain manner to selectively precipitate arsenic in the form of MgNH 4 AsO 4 ·6H 2 O (magnesium ammonium arsenate) and Mg 3 (AsO 4) 2 ·8H 2 O (magnesium arsenate). By controlling the addition of ammonium salt and magnesium salt, arsenic slag with high arsenic content, good sedimentation performance, and high crystallinity was produced. The arsenic slag can be stored by rigid landfill for the future development. The whole process is relatively simple and safer than existing approaches, providing an alternative solution for the treatment of hazardous arsenic-alkali slag. [ABSTRACT FROM AUTHOR]

To implement the circular polarization antenna on the airborne electronic platform, a new technique of polarization change is investigated in this paper. A metasurface structure consisting of a 5 × 5 array has been designed. Each unit of the metasurface structure is a stack circular ring, and two orthogonal dipoles in a ring can convert the linear polarization wave into circular one. An ultra-wideband (UWB) antenna is designed combining with the metasurface structure. To filter some interference signals from special frequency bands such as WLAN and WiMAX, dual notched-bands have been designed on the UWB antenna. Therefore, dual circular polarization radiation character at two bands of 4 GHz–7.9 GHz and 8.1 GHz−12.4 GHz is achieved. The antenna with metasurface is operated at 2.6 GHz–13.6 GHz excepting for two notched-bands of 3.15 GHz–4.3 GHz and 5.5 GHz–5.75 GHz. Fabricated sample has been verified by experiment, and the results indicate that the design is available. [ABSTRACT FROM AUTHOR]