Memory switching effects in a-Si/c-Si heterojunction bipolarstructures

The authors report a three-terminal undoped amorphous silicon (a-Si)/p-n crystalline silicon (c-Si) structure, which exhibits OFF and ON states. An OFF state is characterized by a current in the structure in the low nanoampere range due to the large resistance of the undoped a-Si layer, while in the ON state the structure exhibits a large conductance and its current is determined in practice by the load resistance. Reversible switching between the two states with a rise time of about 40 ns and a fall time of about 200 ns was achieved by applying appropriate positive or negative current pulses to the base of the c-Si p-n junction. The structure can be integrated into a standard bipolar process, and, being of a size suitable for VLSI applications, may be useful as a basic three-terminal memory cell     

Multiple states and variable intensity in the plasma display panel

The plasma display panel, in its usual mode, retains information in the form of wall charges that determine whether or not a sequence of discharges will be maintained at a given cell. These discharges are stable in the sense that a perturbation in wall voltage at a particular discharge will damp out over the succeeding discharges. Recent work has shown that a cell in a plasma display panel can exist in one of several states, each with a unique set of wall voltages and each with a unique average intensity. As with the bistable case, each state is stable in the sense that perturbations damp out. Three states have been achieved simultaneously, with brightnesses that can be characterized as bright, medium, and dim. Within the constraints of a simple theoretical model, the conditions for stability can be stated in terms of the products of the slopes of charge transfer curves. This technique for achieving variable intensity retains the advantage, inherent in the plasma display technique, that the information, once imparted to the display, is retained as long as the sustaining signal is applied to the entire panel.     

Interfacial dipole in organic p–n junction to realize write-once–read-many-times memory

A new approach is exploited to realize nonvolatile organic write-once–read-many-times (WORM) memory based on copper phthalocyanine (CuPc)/hexadecafluoro-copper-phthalocyanine (F₁₆CuPc) p–n junction. The as-fabricated device is found to be at its ON state and can be programmed irreversibly to the OFF state by applying a negative bias. The WORM device exhibits a high ON/OFF current ratio of up to 2.6 × 10⁴. An interfacial dipole layer is testified to be formed and destructed at the p–n junction interface for the ON and OFF states, respectively. The ON state at positive voltage region is attributed to the efficient hole and electron injection from the respective electrodes and then recombination at the CuPc/F₁₆CuPc interface, and the transition of the device to the OFF state results from the destruction of the interfacial dipole layer and formation of an insulating layer which restricts charge carrier recombination at the interface.     

Ovonic Memory Switching in Multimaterial Fibers

We demonstrate the first rewritable memory in thermally drawn fibers. A high tellurium‐content chalcogenide glass, contacted by metallic electrodes internal to the fiber structure, is drawn from a macroscopic preform. An externally applied voltage is utilized to switch between a high resistance (OFF) and a low resistance (ON) state; this in turn allows the fibers to function as a memory device reminiscent of the ovonic switch. The difference between the ON and OFF states is found to be four orders of magnitude. The glass–crystal phase transition is localized to micrometer‐wide filaments, whose position can be optically controlled along the fiber axis. An architecture that enabled the encoding of multiple bits per fiber is described.     

A Smart Light‐Controlled Carrier Switch in an Organic Light Emitting Device

A real ON–OFF carrier switch based on a new ferrocenyl diarylethene compound (DTE‐FC) as the light‐sensitive and photoswitching layer in an organic light‐emitting device (OLED) with a multilayer sandwich structure has been prepared. This switch layer functions not only as a hole transporter but also as a good barrier block when needed, which arises from the light‐induced photochromic effect of the DTE‐FC. For the uncolored open‐ring form of DTE‐FC, no luminescence was observed despite the increase in applied voltage. On the contrary, for the colored photostationary state of DTE‐FC, which was obtained by irradiation with 365 nm light, the luminescence could be observed when the applied voltage reached 14.0 V and increased with applied voltage. Thus, the uncolored state corresponds to the OFF state of luminescence and the photostationary state corresponds to the ON state. The two states can be interconverted by control of the UV and visible light (>500 nm) irradiation.     

Design and performance of a polymer Mach-Zehnder interferometer electro-optic modulator at 1.55 μm

Based on poled guest-host electro-optic (EO) polymer DR1/SU-8, a Mach-Zehnder interferometer (MZI) EO modulator operated at 1.55 μm is proposed. For achieving high response speed and high EO modulation efficiency, both waveguide structure and electrode structure are especially optimized. The impedance match and less index mismatch are achieved. The final characteristic impedance of electrode is about 49.4 Ω, and the microwave index and the light-wave index are 1.5616 and 1.6006, respectively. The device is fabricated using wet-etching technique and inductively coupled plasma (ICP) etching technique, and its performance is measured at 1.55 μm. Experimental results show that when the applied voltage is tuned, the modulator can be changed from ON state to OFF state. The insertion loss at ON state is 12 dB and the extinction ratio between ON and OFF states is about 10 dB. The high response speed is in nano-second level for a square-wave signal. Therefore, the modulator possesses potential applications in high-speed optical networks on chip.     

Carrier transport mechanism in aluminum nanoparticle embedded AlQ3 structures for organic bistable memory devices

Electrical bistability is demonstrated in organic memory devices based on tris-(8-hydroxyquinoline)aluminum (AlQ₃) and aluminum nanoparticles. The role of the thickness of middle aluminum layer and the size of the nanoparticles in device performance is investigated. Above a threshold voltage, the device suddenly switches from a low conductivity OFF state to a high conductivity ON state with a conductivity difference of several orders of magnitude. The OFF state of the device could be recovered by applying a relatively high voltage pulse. The electronic transition is attributed to an electric field induced transfer of charge between aluminum nanoparticles and AlQ_3. The type of charge carriers responsible for conductance switching is investigated. The charge carrier conduction mechanism through the device in ON and OFF states is studied by temperature dependent current–voltage characteristics and analyzed in the framework of existing theoretical models. The conduction mechanism in the OFF state is dominated by field-enhanced thermal excitation of charge carriers from localized centers, whereas it changes to Fowler–Nordheim tunneling of charge carriers in the ON state. The device exhibited excellent stability in either conductivity states. The results indicate the strong potential of the device towards its application as a nonvolatile electronic memory.     

Photovoltaic-p-i-n diodes for RF control-switching application

A photovoltaic-p-i-n diode switch, consisting of two back-to-back p-i-n diodes which can be forward biased to the ON state by photovoltaic cell photocurrents, is introduced for optically controlling RF signals. Without light, the switch is in the OFF state and isolation is determined by the diode junction capacitance. We report a device operating in the VHF range and handling 25 W. With 40 mA photocurrent injected into each diode, the measured insertion loss at 25-W input power is ≈0.08 dB, mainly limited by the diode series resistance; its capacitance was 380 fF. Experiments indicate that low insertion loss requires the signal period ≪ carrier lifetime so that carrier sweep out in the I-region does not reduce conductivity     

基于MDT数据优化小区空闲态与连接态 覆盖一致性的方法

本文提出了利用最小化路测数据(MDT)判断小区空闲态、连接态覆盖一致性的优化方法。根据最小化路测中的Logged和Imm数据分别判断某一地理栅格的RRC空闲态和连接态用户归属主服小区否一致。针对空闲态和连接态存在大量不一致栅格的小区,提出通过修改小区参数修改调整不同状态下覆盖区域,最终保证RRC空闲态、RRC连接态覆盖一致以达到降低发起业务后的非必要切换次数,提高户初始业务阶段速率,提升用户感知。     

Design model for bulk CMOS scaling enabling accurate latchup prediction

The integration density of advanced bulk CMOS structures heavily depends on SCR type of latch up. Depending on the technology chosen the n-p-n-p-n-p interaction, which can be fired by noise, destroys tile stored information or even the chip itself. This paper presents the first complete two-dimensional numerical analysis for a typical CMOS structure including latchup path in the "OFF," "ON," "firing" and "sustaining" mode. Results and experimental data are discussed and used to develop a simplified, yet accurate CMOS design model. This allows the calculation of the firing and sustaining edge depending on geometrical and processing data.     

Memory effect in the current-voltage characteristic of 8-hydroquinoline aluminum salt films

This letter investigated the reproducible bistable resistance switching characteristics of a single-layer organic device based on 8-hydroquinoline aluminum (Alq3) fabricated by spin coating. By controlling the ON-state current through the Alq3 films, it has been possible to achieve various resistance states of the films. In addition, the resistance of the ON-state Alq3 films also affects the threshold current and voltage to switch off the device. The independence of the current-injected direction to erase the ON state implies that the filament theory could elucidate the observed phenomenon. The ratio between low- and high-resistance states can reach five orders of magnitude, which will be a potential material for nonvolatile memory application.     

Chemical linkage functions of poly(ether imide)s on the resistive switching memory effects

A series of aromatic poly(ether imide)s, AZTA-PEIs containing triphenylamine and 1,2,4-triazole moieties are prepared and characterized. All the polymers with inherent viscosity from 0.58 to 1.1 dL/g show glass transition temperatures in the range of 250–278 °C. Resistive switching memory devices are constructed based on the processable poly(ether imide) (AZTA-PEIa). The device can be switched from the initial OFF state to the ON state under either positive or negative electrical sweep at about ±3.2 V. The ON state is nonvolatile and can maintain the high conducting state even turning off the electrical power and applying a reverse bias. The device fulfills the requirements of a write-once read-many times memory (WORM) with a high ON/OFF current ratio up to 10⁵ and a long retention time in both ON and OFF states. The bistable switching effects of the polymer result from the conformation-coupled charge transfer from electron donors (triazole-substituted triphenylamine moieties) to electron acceptors (phthalimide moieties). By comparing with the memory behaviors of analogue polymers, the functions of ether and imide in the chemical polymer structure on the memory behaviors are discussed.     

A flexible polymer memory device

A flexible polymer memory device is demonstrated in a sandwich structure of polypyrrole/P6FBEu/Au. Conductance switching at a voltage of about 4 V, with an ON/OFF current ratio up to 200, was observed in this flexible memory device. At the low-conductivity state, current density–voltage (J–V) characteristics of the device were dominated by a charge injection current. At the high conductivity state, J–V characteristics were dominated by a space-charge-limited current. Both the ON and OFF states are stable up to 10⁶ read cycles at a read voltage of 1 V. The device can be used as a write-once read-many-times (WORM) memory with good electronic stability.     

Exact fluid-flow analysis of single on/off source feeding an ATMbuffer

A formula is developed to calculate the cell loss probability for an ATM buffer fed by a single ON/OFF source. This fluid-flow method uses balance equations to give a geometric progression for the state probabilities. Results show better accuracy than fluid-flow analysis based on differential equations. This cell loss formula can be applied as a more accurate component in connection admission control and bandwidth management algorithms for ATM networks     

Switching control of accommodation: experimental and simulationresponses to ramp inputs

The irregular staircase appearance of the accommodation response to a ramp stimulus, slow movement of a target towards the subject's eye, suggests a switching between different states of control. Experiments and model simulations indicate that blur processing by retina and cortex underlies threshold triggering of the switch. The ON state consists of a fairly high gain, closed-loop control system that minimizes error. The OFF state provides for a quasi-open-loop state and a slow drift to a bias level, under the influence of a leaky integrator.     

Characterization of PI:PCBM organic nonvolatile resistive memory devices under thermal stress

In this study, we fabricated nonvolatile organic memory devices using a mixture of polyimide (PI) and 6-phenyl-C61 butyric acid methyl ester (PCBM) (denoted as PI:PCBM) as an active memory material with Al/PI:PCBM/Al structure. Upon increasing the temperature from room temperature to 470 K, we demonstrated the good nonvolatile memory properties of our devices in terms of the distribution of ON and OFF state currents, the threshold voltage from OFF state to ON state transition, the retention, and the endurance. Our organic memory devices exhibited an excellent ON/OFF ratio (I_ON/I_OFF > 10³) through more than 200 ON/OFF switching cycles and maintained ON/OFF states for longer than 10⁴ s without showing any serious degradation under measurement temperatures up to 470 K. We also confirmed the structural robustness under thermal stress through transmission electron microscopy cross-sectional images of the active layer after a retention test at 470 K for 10⁴ s. This study demonstrates that the operation of PI:PCBM organic memory devices could be controlled at high temperatures and that the structure of our memory devices was maintained during thermal stress. These results may enable the use of nonvolatile organic memory devices in high temperature environments.     

Novel radiation pattern reconfigurable antenna with six beam choices

This article presents a novel radiation pattern reconfigurable antenna with six beam choices,which works in 5.2 GHz wireless local area network (WLAN) frequency band.The designed antenna has good imped...     

Numerical simulation of a dual-branch laser/amplifier switch basedon a thyristor-like structure

We present stationary simulations of a dual-branch heterostructure laser/optical-amplifier switch. The simulations of the thyristor-like structure show that the state of each anode branch can be maintained and controlled by small gate currents between ON and OFF. The switching approach employed here exhibits an extinction ratio of about 30 dB between the ON- and OFF-branch currents, with nearly symmetric rise and fall times of 5.1 and 6.1 ns, respectively. The device can be utilized as either a dual-branch laser or as an optical-amplifier space-division switch, e.g., in 2×2 switch matrices     

A successive approximation technique for displaying gray shades in liquid crystal displays (LCDs).

A successive approximation technique that is based on the conventional line-by-line-addressing is proposed. A large number of gray shades can be displayed without flicker by using low-cost liquid crystal display drivers that are designed to drive the pixels to either ON or OFF states in bilevel displays.     

Interface Modifications of InAs Quantum‐Dots Solids and their Effects on FET Performance

InAs nanocrystals field‐effect transistors with an ON/OFF ratio of 10⁵ are reported. By tailoring the interface regions in the active layer step‐by‐step, the evolution of the ON/OFF ratio can be followed from approximately 5 all the way to around 10⁵. The formation of a semiconducting solid from colloidal nanocrystals is achieved through targeted design of the nanocrystal–nanocrystal interaction. The manipulation characteristics of the nanocrystal interfaces include the matrix surrounding the inorganic core, the interparticle distance, and the order of nanocrystals in the 3D array. Through careful analysis of device characteristics following each treatment, the effect of each on the physical properties of the films are able to be verified. The enhanced performance is related to interparticle spacing, reduction in sub‐gap states, and better electronic order (lower σ parameter). Films with enhanced charge transport qualities retain their quantum‐confined characteristics throughout the procedure, thus making them useful for optoelectronic applications.