Search

Heavy ion irradiation effects on charge trapping memory (CTM) capacitors with TiN/Al2O3/HfO2/Al2O3/HfO2/SiO2/p-Si structure have been investigated. The ion induced interface charges and oxide trap charges were calculated and analyzed by capacitance-voltage (C-V) characteristics. The C-V curves shifted towards negative direction after swift heavy ion irradiation, which is due to the net positive charges accumulate in trapping layer. Memory window decreases with the increase of ion fluences in high voltage, which results from the heavy ion induced structure damage in blocking layer. The mechanism of the heavy ion irradiation effects on CTM capacitors was discussed in detail with energy band diagrams. The result may help to better understand the physical mechanism of the heavy ion induced degradation of CTM capacitors.

The problem of three-dimensional (3D) acoustic scattering in complicated medium has been of considerable interest to researchers for many years. An ultrasonic scattered field calculating technique is proposed to study the scattering echo from strongly scattered materials in a two-layer medium. Firstly, with the high frequency stationary phase method, the Green's function of two-layer fluid media is derived. And then based on the idea of integral equation discretization, the Green’s function method is extended to two-layer fluid media to get the scattering field expression of defects in complicated medium. With this method, the scattering field of 3D defect in a two-layer medium is calculated and the characteristics of received echoes are studied. The results show that this method is able to solve the scattering P wave field of 3D defect with arbitrary shape at any scattering intensity in two-layer media. Considering the circumstance of water-immersion ultrasonic non-destructive test(NDT), the scattering sound field characteristics of different types of defects are analyzed by simulation, which will help to optimize the detection scheme and corresponding imaging method in practice, so as to improve the detection quality.

The high degree of freedom and novel nonlinear phenomena of multimode fiber are attracting attention. In this work, we demonstrate a spatiotemporal mode-locked multimode fiber laser, which relies on microfiber knot resonance (MKR) via dissipative four-wave-mixing (DFMW) to achieve high-repetition-rate pulses. Apart from that, DFMW mode locking with switchable central wavelengths can also be obtained. It was further found that high pulse energy induced nonlinear effect of the dominant mode-locking mechanism transforming from DFMW to nonlinear Kerr beam cleaning effect (NL-KBC). The experimental results are valuable for further comprehending the dynamic characteristics of spatiotemporal mode-locked multimode fiber lasers, facilitating them much more accessible for applications.

We investigate the nonequilibrium thermodynamics of a quenched XY spin chain with multi-spin interaction in a transverse field. The analytical expressions of both the average work and the relative entropy are obtained under different quenching parameters. The influences of the system parameters on the nonequilibrium thermodynamics are investigated. We find that at finite temperature the critical phenomenon induced by the multi-spin interaction and the external field can be revealed by the properties of the system nonequilibrium thermodynamics. In addition, our results indicate that the average work and the relative entropy can be used to detect both the existence and strength of the multi-spin interaction in the nonequlibrium system.

Trichel pulse is a kind of pulsed mode in negative DC corona discharge, which has attracted significant attention because of its considerable applications in industry. Over eighty years, plenty of effort including simulations and experiments has been spent to reveal the ionization and quenching mechanisms of Trichel pulse. By revisiting and summarizing the basic characteristics and well-accepted ionization and quenching mechanisms, this review provides a basic understanding and the current status of Trichel pulse.

Mg3Sb1.5Bi0.5-based alloys have received much attention, and current reports on this system mainly focus on the modulation of doping. However, there lacks the explanation for the choice of Mg3Sb1.5Bi0.5 as matrix. Here in this work, the thermoelectric properties of Mg3Sb2−x Bi x (0.4 ≤ x ≤ 0.55) compounds are systematically investigated by using the first principles calculation combined with experiment. The calculated results show that the band gap decreases after Bi has been substituted for Sb site, which makes the thermal activation easier. The maximum figure of merit (ZT) is 0.27 at 773 K, which is attributed to the ultra-low thermal conductivity 0.53 W·m−1·K−1 for x = 0.5. The large mass difference between Bi and Sb atoms, the lattice distortion induced by substituting Bi for Sb, and the nanoscale Bi-rich particles distributed on the matrix are responsible for the reduction of thermal conductivity. The introduction of Bi into Mg3Sb2-based materials plays a vital role in regulating the transport performance of thermoelectric materials.

We introduce a new consensus pattern, named a successive lag cluster consensus (SLCC), which is a generalized pattern of successive lag consensus (SLC). By applying delay-dependent impulsive control, the SLCC of first-order and second-order multi-agent systems is discussed. Furthermore, based on graph theory and stability theory, some sufficient conditions for the stability of SLCC on multi-agent systems are obtained. Finally, several numerical examples are given to verify the correctness of our theoretical results.

The thermal stability of a vertical-cavity surface-emitting laser (VCSEL) array is enhanced by redesigning the mesa arrangement. Based on a thermoelectric coupling three-dimensional (3D) finite-element model, an optimized VCSEL array is designed. The effects of this optimization are studied experimentally. Power density characteristics of VCSEL arrays with different mesa configuration are obtained under different thermal stress in which the optimized device shows improved performance. Optimized device also shows better stability from measured spectra and calculated thermal resistances. The experimental results prove that our simulation model and optimization is instructive for VCSEL array design.

In this paper, stable single-mode operation at high temperatures is produced by the surface-relief-integrated vertical cavity surface emitting laser (VCSEL). The gain-cavity mode detuning technique is employed to realize high operating temperatures for the VCSEL. The surface relief is etched in the centre of the top side as a mode discriminator for the fundamental mode output, and the threshold current minimum is 1.94 mA at high temperatures by the gain-cavity mode detuning technique. Maximum single-fundamental-mode output power of 0.45 mW at 80 °C is obtained, and the side mode suppression ratios (SMSRs) are more than 30 dB with increasing temperature and current, respectively.

Metallic nanofilms are important components of nanoscale electronic circuits and nanoscale sensors. The accurate characterization of the thermophysical properties of nanofilms is very important for nanoscience and nanotechnology. Currently, there is very little specific heat data for metallic nanofilms, and the existing measurements indicate distinct differences according to the nanofilm size. The present work reports the specific heats of 40-nm-thick suspended platinum nanofilms at 80–380 K and ～5×10^ Pa using the 3w method. Over 80–380 K, the specific heats of the Pt nanofilms range from 166–304 J/(kg・K), which are 1.65–2.60 times the bulk values, indicating significant size effects. These results are useful for both scientific research in nanoscale thermophysics and evaluating the transient thermal response of nanoscale devices.

High-performance submicron-scaled NiCuZn ferrites are prepared by the solid-state reaction method through using CuO as additive. In the synthesis process, a mixture of superfine powder is sintered at 900 °C for 3 h, and the obtained product is NiZn-ferrite with spinel structure. We observe that the particle size increases with raising the sintering temperature. The NiCuZn ferrite with relatively uniform size and granular shape has the best performance: its coercivity is 14 Oe (1 Oe=79.5775 Am−1) and saturation magnetization is 48 emu/g. We also study the effects of particle size, magnetocrystalline anisotropy, and microstructure on coercivity. The method presented here is convenient and economical for producing the high-permeability ferrite powders.

A novel diode string-triggered gated-PiN junction device, which is fabricated in a standard 65-nm complementary metal-oxide semiconductor (CMOS) technology, is proposed in this paper. An embedded gated-PiN junction structure is employed to reduce the diode string leakage current to 13 nA/μm in a temperature range from 25 °C to 85 °C. To provide the effective electrostatic discharge (ESD) protection in multi-voltage power supply, the triggering voltage of the novel device can be adjusted through redistributing parasitic resistance instead of changing the stacked diode number.

Graphene is a new promising candidate for application in radio-frequency (RF) electronics due to its excellent electronic properties such as ultrahigh carrier mobility, large threshold current density, and high saturation velocity. Recently, much progress has been made in the graphene-based RF field-effect transistors (RF-FETs). Here we present for the first time the high-performance top-gated RF transistors using millimeter-scale single graphene domain on a SiO2/Si substrate through a conventional microfabrication process. A maximum cut-off frequency of 178 GHz and a peak maximum oscillation frequency of 35 GHz are achieved in the graphene-domain-based FET with a gate length of 50 nm and 150 nm, respectively. This work shows that the millimeter-scale single graphene domain has great potential applications in RF devices and circuits.

A large-scale Si nanowire array (SiNWA) is fabricated with gold (Au) nanoparticles by simple metal-assisted chemical etching and metal reduction processes. The three-dimensional nanostructured Au/SiNWA is evaluated as an active substrate for surface-enhanced Raman scattering (SERS). The results show that the detection limit for rhodamine 6G is as low as 10−7 M, and the Raman enhancement factor is as large as 105 with a relative standard deviation of less than 25%. After the calibration of the Raman peak intensities of rhodamine 6G and thiram, organic molecules could be quantitatively detected. These results indicate that Au/SiNWA is a promising SERS-active substrate for the detection of biomolecules present in low concentrations. Our findings are an important advance in SERS substrates to allow fast and quantitative detection of trace organic contaminants.

In this paper, oxidation of Ge surface by N2O plasma is presented and experimentally demonstrated. Results show that 1.0-nm GeO2 is achieved after 120-s N2O plasma oxidation at 300 °C. The GeO2/Ge interface is atomically smooth. The interface state density of Ge surface after N2O plasma passivation is about ~ 3 × 1011 cm−2eV−1. With GeO2 passivation, the hysteresis of metal—oxide—semiconductor (MOS) capacitor with Al2O3 serving as gate dielectric is reduced to ~ 50 mV, compared with ~ 130 mV of the untreated one. The Fermi-level at GeO2/Ge interface is unpinned, and the surface potential is effectively modulated by the gate voltage.

In this paper, we investigate the performance of the bulk fin field effect transistor (FinFET) through a three-dimensional (3D) full band Monte Carlo simulator with quantum correction. Several scattering mechanisms, such as the acoustic and optical phonon scattering, the ionized impurity scattering, the impact ionization scattering and the surface roughness scattering are considered in our simulator. The effects of the substrate bias and the surface roughness scattering near the Si/SiO2 interface on the performance of bulk FinFET are mainly discussed in our work. Our results show that the on-current of bulk FinFET is sensitive to the surface roughness and that we can reduce the substrate leakage current by modulating the substrate bias voltage.

The via interconnects are key components in ultra-large scale integrated circuits (ULSI). This paper deals with a new method to create single-walled carbon nanotubes (SWNTs) via interconnects using alternating dielectrophoresis (DEP). Carbon nanotubes are vertically assembled in the microscale via-holes successfully at room temperature under ambient condition. The electrical evaluation of the SWNT vias reveals that our DEP assembly technique is highly reliable and the success rate of assembly can be as high as 90%. We also propose and test possible approaches to reducing the contact resistance between CNT vias and metal electrodes.

As a connection between the process and the circuit design, the device model is greatly desired for emerging devices, such as the double-gate MOSFET. Time efficiency is one of the most important requirements for device modeling. In this paper, an improvement to the computational efficiency of the drain current model for double-gate MOSFETs is extended, and different calculation methods are compared and discussed. The results show that the calculation speed of the improved model is substantially enhanced. A two-dimensional device simulation is performed to verify the improved model. Furthermore, the model is implemented into the HSPICE circuit simulator in Verilog-A for practical application.

This paper mainly reports the permanent impact of displacement damage induced by heavy-ion strikes on the deep-submicron MOSFETs. Upon the heavy ion track through the device, it can lead to displacement damage, including the vacancies and the interstitials. As the featured size of device scales down, the damage can change the dopant distribution in the channel and source/drain regions through the generation of radiation-induced defects and thus have significant impacts on their electrical characteristics. The measured results show that the radiation-induced damage can cause DC characteristics degradations including the threshold voltage, subthreshold swing, saturation drain current, transconductance, etc. The radiation-induced displacement damage may become the dominant issue while it was the secondary concern for the traditional devices after the heavy ion irradiation. The samples are also irradiated by Co-60 gamma ray for comparison with the heavy ion irradiation results. Corresponding explanations and analysis are discussed.