SOI MOSFET with an insulator region (IR-SOI): A novel device for reliable nanoscale CMOS circuits

Device performance in the electronic circuits degrades with elapsed time. Therefore it is important to design a new device to have a reliable performance. In this paper, we present the unique features exhibited by a novel nanoscale silicon-on-insulator (SOI) metal-oxide-semiconductor field effect transistor (MOSFET) in which the silicon active layer consists of an insulator region (IR-SOI). The high-K dielectric HfO₂ as an insulator material is located in the silicon active layer and drain region. Our simulation results demonstrate that this leads to improve the hot electron reliability of the IR-SOI in comparison with the conventional SOI-MOSFET (C-SOI). The insulator region HfO₂ considerably decreases the electric field in the channel and drain regions. Therefore, the degradation mechanism in the proposed structure is lower than that in the C-SOI structure because of reduction of hot carrier effect (HCE). Also using two-dimensional and two-carrier device simulation, we have investigated the improvement in device performance focusing on the HCE, off current, gate current and gate induced drain leakage (GIDL) which can effect on the reliability of the CMOS devices.     

A novel SET/MOSFET hybrid static memory cell design

In this paper, a single electron transistor (SET)/metal-oxide-semiconductor field effect transistor (MOSFET)-based static memory cell is proposed. The negative differential conductance (NDC) characteristics of the SET block help us establish the static memory cell circuits more compactly than those in conventional technologies. The proposed memory cell consists of one MOSFET and two back-to-back connected SET blocks exhibiting the NDC. The peak-to-valley current ratio of the SET block is above four with C/sub G/=5.4C/sub T/ (C/sub T/=0.1 aF) at T=77K. The read and write operations of the proposed memory cell were validated with SET/MOSFET hybrid simulations at T=77 K. Even though the fabrication process that integrates MOSFET devices and SET blocks with NDC is not yet available, these results suggest that the proposed SET/MOSFET hybrid static memory cell is suitable for a high-density memory system.     

A novel technique for fabrication of near-net-shape CMCs

A sol-gel vacuum infiltration technique has been developed for the fabrication of near-net-shape ceramic matrix composites (CMCs) using discontinuous mullite fibre preform with 15 vol.% of fibre content and ZrO₂.10 wt.% Y₂O₃ sol as the infiltrant. Effect of sol viscosity, number of infiltration and calcination temperature on physico-mechanical properties of fabricated CMCs were examined. Characterization of the fibre preform, matrix material (in the form of ceramic specimen without fibre) and the developed CMCs were performed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD indicated the presence of cubic (c) and tetragonal (t) zirconia in both the CMCs and the ceramic specimens calcined even at 1400°C. Flexural strength of the CMCs and the ceramic specimens (calcined at 1400°C), determined by the three-point bending test, was found to be about 14 mPa and 1.40 mPa, respectively. SEM indicated multiple fracture of the matrix which gave rise to pseudo elasticity. This is also evident from the load-displacement curve of the three-point bend test. SEM studies also indicated fibre pull-out in the fracture surface of the CMCs.     

A novel Ag/graphene composite: facile fabrication and enhanced antibacterial properties

In this work, a novel Ag/graphene composite was synthesized as a promising antibacterial agent. The high-quality graphene was prepared from the expandable graphite first and silver nanoparticles (Ag NPs) were then supported on the graphene sheets by a facile chemical reduction. TEM, SEM, and XPS characterizations show the crystalline of Ag NPs with a typical diameter of 45–50 nm are homogeneously decorated onto graphene sheets without aggregation. Furthermore, the antibacterial activity of composite is investigated using the agar well diffusion method. Results reveal the Ag/graphene composites exhibit outstanding and stable antibacterial activity against E. coli due to good dispersibility of Ag NPs and high-quality of graphene substrate.     

Facile fabrication and photoluminescent characteristics of La(OH)3:Eu nanobelts

Large area La(OH)₃:Eu³⁺ nanobelts were synthesized in aqueous solution containing La(NO₃)₃, Eu(NO₃)₃, and CH₃COONH₄ with a current density of 2.0 mA cm⁻² at 343 K via a simple and efficient electrochemical deposition. The nanobelts typically have an average diameter of 100–200 nm, and length of up to hundreds nanometers. The surface morphologies of La(OH)₃:Eu³⁺ can be well controlled by changing the concentration of CH₃COONH₄ and the current densities. CH₃COONH₄ plays a key role in the formation of nanostructures. The gas bubbles functioning as a dynamic template were firstly utilized in our research for the synthesis of nanobelts. The photoluminescence properties of the as-prepared and annealed nanobelts were also investigated.     

A novel submicron-gap electrode fabrication technology using thermal oxidation

A novel and reproducible method to fabricate submicron-gap electrodes using thermal oxidation has been presented. In this method, oxidation process determines the gap distance. The micron-level silicon electrode gaps with different shapes were first generated on the silicon wafer by conventional photolithography followed by deep reactive ion etching process. Then thermal oxidation was conducted to realize the transition from silicon to silicon dioxide, i.e. reduce the gap width. Finally, the planar electrodes with sub-micron spacing were formed by metallization and photolithography. Scanning electron microscopy (SEM) was used to examine the electrode configuration and the electrical properties of as-prepared electrode pairs were also characterized. The results showed that using the method investigated in this work, Au electrodes with a submicron-sized gap could be easily fabricated, with good uniformity and reproducibility.     

A novel fabrication method for titania resistive switching device

The titania showing reversible resistive switching are attractive for today's semiconductor technology in nonvolatile random-access memories. A novel fabrication method for titania resistive switching device with vertical structure is proposed. First, the Pt electrode was fabricated the bottom using conventional photolithography and chemical etching technique. Next, the titania thin films with the thickness about 50 nm was deposited on the bottom electrode by electron beam evaporation (EBE). Then, the trench of photoresist for electrode deposit was etched with mild chemical process to preserve the original structure of titania layer. After that, the platinum was deposited in the trench of photoresist using ion sputter. A final lift-off process to define the Pt top electrodes was performed with acetone in an ultrasonic bath to remove the resist. The resistive bistability was observed in this device. The on-threshold voltage is +1.5 V and the off-threshold voltage is -0.6 V. The resistance ratio between the two stable states of the device including Al electrode is approximately 1 x 10(3), the state is nonvolatile and the retention-time test performed over an hour in sweeping mode measurement. The results indicate the forming and rupture of conductive channel relate to the defects and distributing of oxygen vacancy. This method is low-cost, high-yielding, and easy to implement, which is applicable to the fabrication of nonvolatile memories.     

三维超材料制造技术现状与趋势

三维超材料是具有三维空间特定排布的亚波长人工周期结构,具有自然材料不具备的超常规物理性能。本文以三维超材料的电磁调控技术为线索,简要论述了近年来三维超材料在基础研究和制造工艺方面的研究现状;梳理了目前三维超材料的制造方法,包含印刷电路板及组装的方法、机械加工方法、3D打印技术、微纳制造工艺;选取电磁隐身罩、透镜天线、吸波器、柔性超材料等代表性应用类别,简述了三维超材料器件的电磁调控方法与实现手段,所涉及的超材料种类包括左手超材料、渐变折射率超材料、智能超材料等。基于目前三维超材料研究领域待解决的问题,对今后三维超材料的发展趋势进行了探讨。

     

A novel non-catalytic approach for fabrication of bamboo-like carbon nanotubes

Bamboo-like carbon nanotubes (BCNTs) were synthesized via pyrolysis of PMMA@PDVB core-shell spheres in argon atmosphere at 900 °C without any metallic catalyst. TEM and HRTEM observations show the carbon nanotubes with bamboo-like structure. The content of polymerized divinylbenzene (PDVB) in the core-shell nanostructures plays a very important role for the formation of BCNTs. The possible growth mechanism for BCNTs is proposed.     

A novel method for massive fabrication of β-SiC nanowires

Silicon carbide nanowires (NWs), that were over 200 μm in length and 20–200 nm in diameter, were prepared by high-pressure reaction from SiBONC powder tablets. Annealing temperatures between 1,500 °C and 1,600 °C and Si/B molar ratios between 70:30 and 60:40 were suitable for the growth of the nanowires. The nanowires were fabricated by in situ chemical vapor growth process on the tablets. The SiC nanowires were identified as single crystal β-SiC. The analysis of X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed the single crystalline nature of nanowires with a growth direction of <111>. Massive growth of single crystalline SiC nanowires is important to meet the requirements of the fabrication of SiC nanowire-based nanodevices.     

A novel porous scaffold fabrication technique for epithelial and endothelial tissue engineering

Porous scaffolds have the ability to minimize transport barriers for both two- (2D) and three-dimensional tissue engineering. However, current porous scaffolds may be non-ideal for 2D tissues such as epithelium due to inherent fabrication-based characteristics. While 2D tissues require porosity to support molecular transport, pores must be small enough to prevent cell migration into the scaffold in order to avoid non-epithelial tissue architecture and compromised function. Though electrospun meshes are the most popular porous scaffolds used today, their heterogeneous pore size and intense topography may be poorly-suited for epithelium. Porous scaffolds produced using other methods have similar unavoidable limitations, frequently involving insufficient pore resolution and control, which make them incompatible with 2D tissues. In addition, many of these techniques require an entirely new round of process development in order to change material or pore size. Herein we describe “pore casting,” a fabrication method that produces flat scaffolds with deterministic pore shape, size, and location that can be easily altered to accommodate new materials or pore dimensions. As proof-of-concept, pore-cast poly(ε-caprolactone) (PCL) scaffolds were fabricated and compared to electrospun PCL in vitro using canine kidney epithelium, human colon epithelium, and human umbilical vein endothelium. All cell types demonstrated improved morphology and function on pore-cast scaffolds, likely due to reduced topography and universally small pore size. These results suggest that pore casting is an attractive option for creating 2D tissue engineering scaffolds, especially when the application may benefit from well-controlled pore size or architecture.     

Simulation and fabrication of attenuated phase-shifting masks: CrF(x)

To acquire the required resolution for 248- and 193-nm lithography, a study of attenuated phase-shifting mask (Att-PSM) technology is in progress. We performed a simulation study using a matrix method to calculate relative transmittance and the amount of phase shift of light through the PSM. However, we found that the average film composition changed with deposition time. Accordingly, optical constants were found to be a strong function of film thickness. Therefore we rearranged the relationship between deposition parameters (e.g., deposition time or gas flow rate ratio) and optical constants (e.g., refractive index and extinction coefficient) to extract the empirical formula for the optical constants with respect to film composition. To verify our simulation study, we fabricated a phase shifter based on our simulation result, which was found to have a transmittance of 8.3% and a phase shift of 179.5 degrees . Consequently, we obtained a reliable optimum condition for the deep-ultraviolet Att-PSM.     

A novel technique for fabrication of rod-like shape zeolite LTA and hydroxysodalite by extrusion of bentonite powder: Effects of technical factors on structural characteristics

The current investigation proposes a novel method for the fabrication of zeolite-based packed beds by extrusion of a paste, containing Ca-bentonite, boehmite, and sodium hydroxide, as rod-like shape. The formed precursor was heated at 800 °C to reinforce the extrudates, aged at different times, 3–24 h, and converted to the zeolite structure by recrystallization in the hydrothermal condition, 3–9 h. The obtained results showed that aging, and recrystallization times affect the crystalline phase structure, morphology of particles, textural properties, and cation exchange capacity (CEC) as characterized by X-ray diffractometry, field emission electron microscopy, and N₂ adsorption–desorption isotherms. The thermally treated extrudates could be converted to zeolite LTA, and or hydroxysodalite (HS), depending on aging, and recrystallization times. It is necessary to age the treated extrudates in 9 h, and control the recrystallization time within 3 h to achieve zeolite LTA with a proper CEC, 232 mg g⁻¹. Contrarily, the choice of inverse conditions, leads to create a mesoporous HS with a broad pore size distribution, 2–50 nm.     

A New Capacitorless 1T DRAM Cell: Surrounding Gate MOSFET With Vertical Channel (SGVC Cell)

We propose a surrounding gate MOSFET with vertical channel (SGVC cell) as a 1T DRAM cell. To confirm the memory operation of the SGVC cell, we simulated its memory effect and fabricated the highly scalable SGVC cell. According to simulation and measurement results, the SGVC cell can operate as a 1T DRAM having a sufficiently large sensing margin. Also, due to its vertical channel structure and common source architecture, it can readily be made into a 4F² cell array     

Design and fabrication of a novel reflection filter

Reflection filters are useful in optical communication, display, and other systems. A novel reflection filter is designed and fabricated. Analytical design formulas have been put forward and show good agreement with the measured maximum reflectance as well as with the bandwidth at the central wavelength. The effective admittance and distribution of the electrical field intensity are also calculated to analyze the properties of the filter. This novel filter with high peak reflectance, narrow bandwidth, and deep cutoff, is simple to design, easy to fabricate and convenient to integrate, compared with the conventional dielectric multilayer reflection filters.     

A novel method for fabrication of CdS quantum dot-sensitized solar cells

In this report, a novel and facile in situ gas–solid reaction method has been developed for the deposition of CdS quantum-dots (QDs) on a mesoscopic TiO₂ film. In the approach, cadmium nitrate solution was first coated on mesoporous TiO₂ films, and subsequently transformed into CdS QDs (with size about 2–3 nm) by reaction with hydrogen sulfide (H₂S) gas generated in a closed container at room temperature. Different from the conventional solution techniques, this method offers new opportunities for rapid and facile deposition of CdS QD-coated TiO₂ films without the introduction of the by-products. With the CdS QDs-decorated TiO₂ active electrodes, the liquid and solid solar cells were fabricated with power conversion efficiencies (PCEs) of 1.90 and 0.80%, respectively.     

A novel fabrication method for the nanoscale tunneling field effect transistor

Tunneling Field Effect Transistors (TFETs) are considered as a candidate for low power applications. However, most of TFETs have been researched on only for long channels due to the misalignment problem that occurs during the source/drain doping process in device fabrication. Thus, a new method is proposed for the fabrication of TFETs in nanoscale regions. This proposed fabrication process does not need an additional mask to define the source/drain regions, and makes it possible to form a self-aligned source/drain doping process. In addition, through TCAD simulation, the electrical characteristics of a TFET with dopant engineering and a rounded gate edge shape for a higher on/off current ratio were investigated. As a result, the TFET showed the properties of a larger on-current, a lower average subthreshold swing (58.5 mV/dec), and a 30-fold smaller leakage current compared to the conventional TFET The TFET with dopant engineering and a rounded gate edge shape can also be fabricated simply through the proposed fabrication process.     

A novel systematic method to evaluate computer-supported collaborative design technologies

Selection of suitable computer-supported collaborative design (CSCD) technologies is crucial to facilitate successful projects. This paper presents the first systematic method for engineering design teams to evaluate and select the most suitable CSCD technologies comparing technology functionality and project requirements established in peer-reviewed literature. The paper first presents 220 factors that influence successful CSCD. These factors were then systematically mapped and categorised to create CSCD requirement statements. The novel evaluation and selection method incorporates these requirement statements within a matrix and develops a discourse analysis text processing algorithm with data from collaborative projects to automate the population of how technologies impact the success of CSCD in engineering design teams. This method was validated using data collected across 3 years of a student global design project. The impact of this method is the potential to change the way engineering design teams consider the technology they use and how the selection of appropriate tools impacts the success of their CSCD projects. The development of the CSCD evaluation matrix is the first of its kind enabling a systematic and justifiable comparison and technology selection, with the aim of best supporting the engineering designers collaborative design activity.