Nanoscale two-bit/cell NAND silicon-oxide-nitride-oxide-silicon memory device with different tunneling oxide thicknesses

Nanoscale two-bit/cell NAND-type silicon-oxide-nitride-oxide-silicon (SONOS) flash memory devices with different tunneling oxide thicknesses were designed to reduce the short channel effect and the coupling interference. The process step and the electrical characteristics of the proposed SONOS memory devices were simulated by using SUPREM-4 and MEDICI, respectively. The short channel effect in the nanoscale two-bit/cell SONOS devices was decreased than that of the conventional devices due to a larger effective channel length. The drain current at the on-state of the proposed NAND SONOS memory devices decreased than that of the conventional NAND SONOS devices due to the high channel resistivity. The I on/I off ratio of the proposed NAND SONOS memory devices was larger than that of the conventional memory devices due to the dramatic decrease in the subthreshold current of the proposed devices. The electrical characteristics of the NAND SONOS memory devices with different tunneling oxide thicknesses were better than those of the conventional NAND SONOS devices.     

Flexible molecular-scale electronic devices

Flexible materials and devices could be exploited in light-emitting diodes, electronic circuits, memory devices, sensors, displays, solar cells and bioelectronic devices. Nanoscale elements such as thin films, nanowires, nanotubes and nanoparticles can also be incorporated into the active films of mechanically flexible devices. Large-area devices containing extremely thin films of molecular materials represent the ultimate scaling of flexible devices based on organic materials, but the influence of bending and twisting on the electrical and mechanical stability of such devices has never been examined. Here, we report the fabrication and characterization of two-terminal electronic devices based on self-assembled monolayers of alkyl or aromatic thiol molecules on flexible substrates. We find that the charge transport characteristics of the devices remain stable under severe bending conditions (radius?≤?1?mm) and a large number of repetitive bending cycles (≥1,000). The devices also remain reliable in various bending configurations, including twisted and helical structures.     

Impedance spectroscopy of manganite films prepared by metalorganic chemical vapor deposition

Polycrystalline Pr(1-x)CaxMnO3 (PCMO) films were prepared by liquid source metalorganic chemical vapor deposition using in situ infrared spectroscopic monitoring. The electric properties of the PCMO-based devices with Ni and Al electrodes (Ni-PCMO-Ni and Al-PCMO-Al devices) were studied by dc current-voltage (I-V) measurements and ac impedance spectroscopy. The current varied linearly with the applied voltage in Ni-PCMO-Ni devices, while nonlinear behavior was observed in I-V curves for Al-PCMO-Al devices. Impedance spectra were also different between Ni-PCMO-Ni and Al-PCMO-Al devices. The Cole-Cole plots for the Ni-PCMO-Ni devices showed only a single semicircular arc, which was assigned to the PCMO bulk impedance. Impedance spectra for the Al-PCMO-Al devices had two distinct components, which could be attributed to the PCMO bulk and to the interface between the PCMO film and the Al electrode, respectively. The bias dependence of the impedance spectra suggested that the resistance switching in the Al-PCMO-Al devices was mainly due to the resistance change in the interface between the film and the electrode. The metal electrode plays an important role in the resistance switching in the PCMO-based devices. The choice of the optimum metal electrodes is essential to the ReRAM application of the manganite-based devices.     

Load bearing capacity of bone anchored fiber-reinforced composite device

The purpose of this study was to evaluate the push-out load-bearing capacity of threaded fiber-reinforced composite (FRC) devices for use as bone-anchored devices. The purpose was also to evaluate the possibility to use bioactive glass (BAG) granules on the experimental FRC devices in terms the mechanical behavior. Three experimental FRC devices (n = 15) were fabricated for the study: (a) threaded device with smooth surface; (b) threaded device with BAG granules (S53P4, Vivoxid Ltd, Turku, Finland) and supplementary retention grooves, and (c) unthreaded device with BAG granules. Threaded titanium devices were used as controls. The FRC devices were prepared from a light-polymerized dimethacrylate resin reinforced with preimpregnated unidirectional and bidirectional E-glass fibers (EverStick, StickTech Ltd, Turku, Finland). Experimental and control devices were embedded into dental plaster to simulate bone before the mechanical push-out test was carried out. ANOVA and Weibull analysis were used for the statistical evaluation. Threaded FRC devices had significantly higher push-out strength than the threaded titanium device (p < .001). The push-out forces exceeding 2,500 N were measured for threaded FRC devices with supplementary grooves and BAG coating. No thread failures were observed in any FRC devices. The unthreaded FRC devices with BAG lost 70% of glass particles during the test, while no BAG particles were lost from threaded FRC devices. It can be concluded that threaded FRC devices can withstand high push-out forces in the dental plaster without a risk of thread failure under physiological load.     

基片集成波导技术的研究现状和展望

综述了基片集成波导(SIW)技术研究的现状和热点,首先分析了SIW的基本理论,包括SIW结构设计、损耗机制和频带宽度等;然后详细分析了基于SIW的微波和毫米波器件,包括无源器件、有源器件、天线和可调谐器件;接着对基于SIW技术的器件模拟和制作进行了详细论述;最后对SIW技术应用于太赫兹器件的设计进行了展望.     

Microchannel-Based Refractive Index Sensors Monolithically Integrated With Silica Waveguides: Structures and Sensitivities

Refractive index sensors using self-forming microchannels embedded in borophosphosilicate glass and monolithically integrated with silica waveguides are presented. Fabricated devices presented include solid-core and liquid-core directional couplers, liquid-core modal interferometers, Mach-Zehnder interferometers, segmented waveguides, and microchannel grating devices. Sensitivities of these devices are calculated and compared with each other and to other well-known devices. Experimental characterizations show that the performance of fabricated devices agrees well with calculations.     

Endovascular Metal Devices for the Treatment of Cerebrovascular Diseases

Cerebrovascular disease involves various medical disorders that obstruct brain blood vessels or deteriorate cerebral circulation, resulting in ischemic or hemorrhagic stroke. Nowadays, platinum coils with or without biological modification have become routine embolization devices to reduce the risk of cerebral aneurysm bleeding. Additionally, many intracranial stents, flow diverters, and stent retrievers have been invented with uniquely designed structures. To accelerate the translation of these devices into clinical usage, an in‐depth understanding of the mechanical and material performance of these metal‐based devices is critical. However, considering the more distal location and tortuous anatomic characteristics of cerebral arteries, present devices still risk failing to arrive at target lesions. Consequently, more flexible endovascular devices and novel designs are under urgent demand to overcome the deficiencies of existing devices. Herein, the pros and cons of the current structural designs are discussed when these devices are applied to the treatment of diseases ranging broadly from hemorrhages to ischemic strokes, in order to encourage further development of such kind of devices and investigation of their use in the clinic. Moreover, novel biodegradable materials and drug elution techniques, and the design, safety, and efficacy of personalized devices for further clinical applications in cerebral vasculature are discussed.     

CMOS-compatible fabrication of room-temperature single-electron devices

Devices in which the transport and storage of single electrons are systematically controlled could lead to a new generation of nanoscale devices and sensors. The attractive features of these devices include operation at extremely low power, scalability to the sub-nanometre regime and extremely high charge sensitivity. However, the fabrication of single-electron devices requires nanoscale geometrical control, which has limited their fabrication to small numbers of devices at a time, significantly restricting their implementation in practical devices. Here we report the parallel fabrication of single-electron devices, which results in multiple, individually addressable, single-electron devices that operate at room temperature. This was made possible using CMOS fabrication technology and implementing self-alignment of the source and drain electrodes, which are vertically separated by thin dielectric films. We demonstrate clear Coulomb staircase/blockade and Coulomb oscillations at room temperature and also at low temperatures.     

Rashba Effect in Functional Spintronic Devices

Exploiting spin transport increases the functionality of electronic devices and enables such devices to overcome physical limitations related to speed and power. Utilizing the Rashba effect at the interface of heterostructures provides promising opportunities toward the development of high-performance devices because it enables electrical control of the spin information. Herein, the focus is mainly on progress related to the two most compelling devices that exploit the Rashba effect: spin transistors and spin–orbit torque devices. For spin field-effect transistors, the gate-voltage manipulation of the Rashba effect and subsequent control of the spin precession are discussed, including for all-electric spin field-effect transistors. For spin–orbit torque devices, recent theories and experiments on interface-generated spin current are discussed. The future directions of manipulating the Rashba effect to realize fully integrated spin logic and memory devices are also discussed.     

自校准技术在多通道测试设备中的应用

着眼于解决多通道设备的校准问题。多通道设备的校准通过在设备设计之初内装自校准模块来实现,并使用外接设备来校准自校准模块中的基准源。输出参量采用内部自校准模块自动校准,可以大大减少设备的校准工作量。     

新型集成电路器件与中、高档B超诊断仪的研制开发

本文扼要地介绍了新型器件在中、高档B超研制开发中的重要地位。首先介绍了PLD、GA、SC等ASIC器件的简单原理、设计思想,指出了采用ASIC替代传统的SSI/MSI器件的优点以及在我国推广应用的困难。其后,文章又介绍了数字信号处理、图象处理及计算机专用芯片的基本情况。最后提出了对PLD、SC、GA等ASIC器件和DSP、图象处理以及计算机专用芯片在中、高档B超中进行应用研究的建议和设想。     

Polymer coating behavior of Rayleigh-SAW resonators with gold electrode structure for gas sensor applications

Results from systematic polymer coating experiments on surface acoustic wave (SAW) resonators and coupled resonator filters (CRF) on ST-cut quartz with a corrosion-proof electrode structure entirely made of gold (Au) are presented and compared with data from similar SAW devices using aluminium (Al) electrodes. The recently developed Au devices are intended to replace their earlier Al counterparts in sensor systems operating in highly reactive chemical gas environments. Solid parylene C and soft poly[chlorotrifluoroethylene-co-vinylidene fluoride] (PCFV) polymer films are deposited under identical conditions onto the surface of Al and Au devices. The electrical performance of the Parylene C coated devices is monitored online during film deposition. The PCVF coated devices are evaluated after film deposition. The experimental data show that the Au devices can stand up to 40% thicker solid films for the same amount of loss increase than the Al devices and retain better resonance and phase characteristics. The frequency sensitivities of Au and Al devices to parylene C deposition are nearly identical. After coating with soft PCFV sensing film, the Au devices provide up to two times higher gas sensitivity when probed with cooling agent, octane, or tetrachloroethylene.     

Numerical analysis of wave generation and propagation in a focused surface acoustic wave device for potential microfluidics applications

We develop a 3-D finite element model of a focused surface acoustic wave (F-SAW) device based on LiNbO/sub 3/to analyze the wave generation and propagation characteristics for devices operating at MHz frequencies with varying applied input voltages. We compare the F-SAW device to a conventional SAW device with similar substrate dimensions and transducer finger periodicity. SAW devices with concentrically shaped focused interdigital transducer fingers (F-IDTs) are found to excite waves with high intensity and high beam-width compression ratio, confined to a small localized area. F-SAW devices are more sensitive to amplitude variations at regions close to the focal point than conventional SAW devices having uniform IDT configuration. We compute F-SAW induced streaming forces and velocity fields by applying a successive approximation technique to the Navier-Stokes equation (Nyborg's theory). The maximum streaming force obtained at the focal point varies as the square of the applied input voltage. Computed streaming velocities at the focal point in F-SAW devices are at least an order of magnitude higher than those in conventional SAW devices. Simulated frequency response indicates higher insertion losses in F-SAW devices than in conventional devices, reflecting their greater utility as actuators than as sensors. Our simulation findings suggest that F-SAW devices can be utilized effectively for actuation in microfluidic applications involving diffusion limited transport processes.     

Switching mechanisms in flexible solution-processed TiO₂ memristors

Memristors are emerging as unique electrical devices with potential applications in memory, reconfigurable logic and biologically inspired computing. Due to the novelty of these devices, the complete details of their switching mechanism is not yet well established. In this work, the switching mechanism of our solution-processed titanium dioxide-based memristor is investigated by studying how variations in the device area and film thickness affect electrical behavior and correlating these behavioral changes to proposed switching mechanisms. The conduction path of the switching is also investigated through electrical characterization of devices both before and after physically cutting the devices in half, as well as through infrared imaging of the devices during operation. The results suggest that the electrical behavior of these devices is dominated by a localized, charge-based phenomenon that exhibits a dependence on device area.     

Fabrication of arrayed Si nanowire-based nano-floating gate memory devices on flexible plastics

Arrayed Si nanowire (NW)-based nano-floating gate memory (NFGM) devices with Pt nanoparticles (NPs) embedded in Al2O3 gate layers are successfully constructed on flexible plastics by top-down approaches. Ten arrayed Si NW-based NFGM devices are positioned on the first level. Cross-linked poly-4-vinylphenol (PVP) layers are spin-coated on them as isolation layers between the first and second level, and another ten devices are stacked on the cross-linked PVP isolation layers. The electrical characteristics of the representative Si NW-based NFGM devices on the first and second levels exhibit threshold voltage shifts, indicating the trapping and detrapping of electrons in their NPs nodes. They have an average threshold voltage shift of 2.5 V with good retention times of more than 5 x 10(4) s. Moreover, most of the devices successfully retain their electrical characteristics after about one thousand bending cycles. These well-arrayed and stacked Si NW-based NFGM devices demonstrate the potential of nanowire-based devices for large-scale integration.     

Probing molecules in integrated silicon-molecule-metal junctions by inelastic tunneling spectroscopy

Molecular electronics has drawn significant attention for nanoelectronic and sensing applications. A hybrid technology where molecular devices are integrated with traditional semiconductor microelectronics is a particularly promising approach for these applications. Key challenges in this area include developing devices in which the molecular integrity is preserved, developing in situ characterization techniques to probe the molecules within the completed devices, and determining the physical processes that influence carrier transport. In this study, we present the first experimental report of inelastic electron tunneling spectroscopy of integrated metal-molecule-silicon devices with molecules assembled directly to silicon contacts. The results provide direct experimental confirmation that the chemical integrity of the monolayer is preserved and that the molecules play a direct role in electronic conduction through the devices. Spectra obtained under varying measurement conditions show differences related to the silicon electrode, which can provide valuable information about the physics influencing carrier transport in these molecule/Si hybrid devices.     

A system architecture solution for unreliable nanoelectronic devices

The shrinking of electronic devices will inevitably introduce a growing number of defects and even make these devices more sensitive to external influences. It is, therefore, likely that the emerging nanometer-scale devices will eventually suffer from more errors than classical silicon devices in large scale integrated circuits. In order to make systems based on nanometer-scale devices reliable, the design of fault-tolerant architectures will be necessary. Initiated by von Neumann, the NAND multiplexing technique, based on a massive duplication of imperfect devices and randomized imperfect interconnects, had been studied in the past using an extreme high degree of redundancy. In this paper, this NAND multiplexing is extended to a rather low degree of redundancy, and the stochastic Markov nature in the heart of the system is discovered and studied, leading to a comprehensive fault-tolerant theory. A system architecture based on NAND multiplexing is investigated by studying the problem of the random background charges in single electron tunneling (SET) circuits. It might be a system solution for an ultra large integration of highly unreliable nanometer-scale devices.     

Control of local ion transport to create unique functional nanodevices based on ionic conductors

The development of nanometer-scale devices operating under a new principle that could overcome the limitations of current semiconductor devices has attracted interest in recent years. We propose that nanoionic devices that operate by controlling the local transport of ions are promising in this regard. It is possible to control the local transport of ions using the solid electrochemical properties of ionic and electronic mixed conductors. As an example of this concept, here, we report a method of controlling the transport of silver ions of the mixed-conductor silver sulfide (Ag₂S) crystal and basic research on nanoionic devices based on this mixed conductor. These devices show unique functions such as atom deposition, resistance switching, and quantum point contact switching. The switches operate through the formation and dissolution of an atomic bridge between the electrodes, and the behavior is realized by control of the local solid-state electrochemical reaction. Potential nanoionic devices utilizing the unique functions and characters that do not exist in conventional semiconductor devices are discussed.     

Control of local ion transport to create unique functional nanodevices based on ionic conductors

The development of nanometer-scale devices operating under a new principle that could overcome the limitations of current semiconductor devices has attracted interest in recent years. We propose that nanoionic devices that operate by controlling the local transport of ions are promising in this regard. It is possible to control the local transport of ions using the solid electrochemical properties of ionic and electronic mixed conductors. As an example of this concept, here, we report a method of controlling the transport of silver ions of the mixed-conductor silver sulfide (Ag₂S) crystal and basic research on nanoionic devices based on this mixed conductor. These devices show unique functions such as atom deposition, resistance switching, and quantum point contact switching. The switches operate through the formation and dissolution of an atomic bridge between the electrodes, and the behavior is realized by control of the local solid-state electrochemical reaction. Potential nanoionic devices utilizing the unique functions and characters that do not exist in conventional semiconductor devices are discussed.     

Fabrication of high sensitivity ZnO thin film ultrasonic devices byelectrochemical etch techniques

In this experiment, high quality thin film acoustic devices were constructed utilizing zinc oxide (ZnO) thin film deposition, integrated circuit (IC), and electrochemical etch techniques. The bridge type ZnO thin film ultrasonic devices produced showed acute high frequency response sensitivity, with the high frequency response at 600 KHz attaining -124 dBV μBar. The highest response was near 8 MHz. Sensitivity increased in direct proportion to frequency, indicating that the bridge-type ZnO thin film acoustic devices were suitable for application as ultrasonic wave sensors at high operating frequencies. Further experimentation verified that the bridge-type ZnO thin film acoustic devices fabricated also had ultrasonic signal transmitting capability and signal bidirectional devices having both transmission and reception functions were successfully constructed. Therefore, bridge-type ZnO thin film acoustic devices will continue to be developed in the future due to the reliable control possible over the structural transformations involved; and, since IC fabrication techniques can be readily adopted in the process, the manufacturing of such devices will be greatly assisted