System of nano-silver inkjet printed memory cards and PC card reader and programmer

This work describes the development of inkjet printed, low-cost memory cards, and complementary pair of memory card reader and card reader/programmer for PCs. This constitutes a complete system that can be used for various applications. The memory cards are manufactured by inkjet printing nano-silver ink on photo paper substrate. The printed memory structures have an initial high resistance that can later be programmed to specific values representing data on the cards, the so called Write Once Read Many (WORM) memories. The memory card reader measures the resistance values of the memory cells and reads it back to the computer by USB connection. Using multiple resistance levels that represent different states it is possible to have a larger number of selectable combinations with fewer physical bits compared to binary coding. This somewhat counters one of the limitations of resistive memory technology that basically each cell needs one physical contact. The number of possible states is related to the resolution of the reader and the stability of the WORM memory.     

Design of an integrated low-noise read-out system for DNA capacitive sensors

This paper presents an electronic system for a fast DNA label-less detection. The sensitivity of the capacitive sensor in use is improved by depositing an insulating self-assembled monolayer (SAM) over the golden electrodes. The capacitance shift due to the hybridization effect is monitored by means of a charge-sensitive amplifier and digitalized by means of a comparator and a counter. The read-out solution demonstrates the ability to identify a 0.01% variation on the capacitive value of the sensor. Results from measurements with the optimized sensor show the reliability of the electronics. The investigated solution is suitable for monolithic systems or for a micro-fabricated array of sensors. An example of the integrated front-end is described and performances and noise evaluation are reported here.     

Design and characterization of novel read-out systems for a capacitive DNA sensor

This paper presents novel read-out electronic systems for a fast DNA label-less detection. The capacitive shift due to the hybridization effect is monitored by means of a charge sensitive amplifier and a differential stage. The systems provide an A/D conversion and an evaluation of the capacitive shift amount with a resolution of 11 bit. The read-out solutions demonstrate the ability to identify a 0.01% variation on the capacitive value of the sensor. The investigated techniques are suitable for monolithic systems or for a micro-fabricated array of sensors.     

System-level impacts of persistent main memory using a search engine

Computer memory systems traditionally use distinct technologies for different hierarchy levels, typically volatile, high speed, high cost/byte solid state memory for caches and main memory (SRAM and DRAM), and non-volatile, low speed, low cost/byte technologies (magnetic disks and flash) for secondary storage. Currently, non-volatile memory (NVM) technologies are emerging and may substantially change the landscape of memory systems. In this work we assess system-level latency and energy impacts of a computer with persistent main memory using PCRAM and Memristor, comparing the development and execution of a search engine application implementing both a traditional file-based approach and a memory persistence approach (Mnemosyne). Our observations show that using memory persistence on top of NVM main memory, instead of a file-based approach on top DRAM/Disk, produces less than half lines of code, is more than 4× faster to develop, consumes 33× less memory energy, and executes search tasks up to 33× faster.     

Non-volatile memory with zinc oxide nanoparticles embedded in a hybrid polymethylsilsesquioxane layer

In this article the electrical characteristics of zinc oxide nanoparticles (ZnO NP) embedded in polymethylsilsesquioxane (PMSSQ) film have been studied. PMSSQ film with embedded ZnO NP was sandwiched between aluminium and ITO coated glass as a capacitor-based memory device. Charge transport mechanism in this device has been investigated. The device can be programmed and erased similar to a flash-memory. Programming the device causes the trapping of electrons transported from the aluminium into the ZnO NP via trapped-charge-limited current mechanism. The erasing of the memory device is via the Fowler-Nordheim tunneling of electrons in the opposition direction towards the aluminium electrode.     

ZnO as a dielectric for organic thin film transistor-based non-volatile memory

This paper demonstrates the novel application of d.c. sputtered zinc oxide (ZnO) as a charge trapping dielectric material for the application of an organic thin film transistor (OTFT) based non-volatile memory (NVM). The motivation of using ZnO as a dielectric is due to its chemical stability and optical transparency, enabling future development of transparent electronic devices. Unbalanced magnetron d.c. sputtering with Ar:O₂ ratio of 80:20 was used to obtained a ZnO dielectric of 50 nm thick. The ZnO has an optical band gap of 3.23 eV, resistivity and k-value of 5 × 10⁷ Ω-cm and 50, respectively. The ZnO sandwiched between two layers of low-k methyl-silsesquioxane (MSQ) sol–gel dielectric creates a triple layer dielectric structure for charge storage. A solution-processable pentacene, 13,6-N-Sulfinylacetamodipentacene, was used as an active layer of an OTFT-NVM. It has been successfully demonstrated that this OTFT-NVM can be electrically programmed and erased at a low voltage.     

Phase change materials and their application to random access memory technology

Phase change materials can exist in two different phases, the amorphous and the crystalline phase, which exhibit distinctly different physical properties. It is possible to repeatedly switch the state of these materials, from the amorphous phase to the crystalline phase by heating the material above its crystallization temperature, and from the crystalline to the amorphous phase by melt-quenching. Phase change materials have been utilized very successfully in all modern optical re-writable storage media such as CDs, DVDs and Blu-ray disks. Recently, they have also been applied to solid-state memory devices where their large difference in electrical resistivity is used to store information. This paper reviews the unique properties of phase change materials in particular as they are important for their application to these devices.     

Studies on Inkjet-Printed Conducting Lines for Electronic Devices

Inkjet printing is considered one of the most promising methods for patterning and materials deposition. The feasibility of employing inkjet technology for the creation of conductive pathways on printed circuit boards is addressed herein. Prediction of the width, length, and thickness of printed lines as a function of the dot diameter, resolution, and volume fraction of the particles in the ink is presented. Surface treatment of the substrate to promote desirable adhesion and wetting properties as well as the adjustment of the curing process to reduce the surface roughness of the printed traces were studied. In a sintering study, samples sintered at 250°C for 20 min showed a resistivity of 4.2 μΩ cm, which is approximately 2.6 times that of bulk silver. A low-temperature sintering method through the reduction of a metal salt is presented. The resistivity of printed samples sintered at 140°C for 30 min in the presence of silver nitrate with N,N-dimethylformamide showed a resistivity of 22.5 μΩ cm.     

非接触式电能传输综述

非接触式电能传输是一种利用电磁感应耦合技术、电力电子技术和现代控制技术实现的电源侧与负载侧完全分离的电能传输技术,它克服了传统电能传输方式在一些特殊环境如易燃、易爆、水下等场合存在的弊端,实现了电能安全可靠地传送。文中简单介绍了非接触式电能传输的工作原理和方式,归纳总结了电磁感应式、电磁共振式及辐射式三种不同传输方式的特点,分析了该技术的应用前景。     

A benchmark study of commercially available copper nanoparticle inks for application in organic electronic devices

A set of three commercial copper nanoparticle based inkjet inks has been benchmarked with respect to their potential to form conducting printed structures for future applications in organic electronic devices. Significant differences were observed in terms of jetting properties, spreading behaviour and line formation on a number of relevant substrates. The inks' stabilities against oxidation were investigated, inkjet printed patterns were subjected to photonic flash sintering and their electrical properties characterized. As a result, optimized conditions for printing and post-deposition processing were determined. Photonic flash sintering, which is a roll-to-roll compatible manufacturing process, allowed a significant reduction in sintering time. Flash sintering was performed in the presence of air, thereby excluding the necessity for processing under inert atmosphere. One product was identified which showed satisfactory performances regarding all tested features: stable jet formation, well-defined definition of the printed structures and high electrical conductivity (20% of the value of bulk Cu). The obtained results can be considered as a promising step towards the future application of Cu inks in organic electronic devices.     

Organic small-molecule heterointerface for use in transistor-type non-volatile memory

A chargeable layer is an essential element for charge transfer and trapping in a transistor-based non-volatile memory device. Here we demonstrate that a heterointerface layer comprising of two different small molecules can show electrical memory characteristics. The organic heterointerface layer was fabricated with a pentacene and tris(8-hydroxyquinoline) aluminum (Alq3) layers by sequential vapor deposition without breaking the vacuum state. Pentacene was adopted as the active layer on the top, and Alq3 was used as the bottom layer for charge trapping. The bottom-gate top-contact transistor with an organic heterointerface layer showed distinct non-volatile memory behaviors and showed high air stability and reliability. We investigated the energy structure of the pentacene/Alq3 heterointerface layer to reveal the operation mechanism of the non-volatile memory and suggested that the writing/erasing gate bias-dependent energy barrier originating from the difference between the energy levels of the pentacene and Alq3 layers controls the charge transfer at the heterointerface layer. Our approach suggests a simple way to fabricate heterointerface layers for organic non-volatile memory applications with high air stability and reliability.     

非接触式识别卡通信方案的比较分析

本文对非接触式识别卡的国际标准（ＩＳＯ１４４４３）草案中互不兼容的两种通信方案进行了比较分析。在功率传输，频带占用，信号通信接口和防碰撞协议几方面对比两种方案的优劣，给出了量化结果。     

Role of tunneling layer in graphene-oxide based organic nonvolatile memory transistors

This paper demonstrates non-volatile memory transistor using solution processable graphene oxide (GO) as charge storage nodes in the configuration, p⁺⁺Si/SiO₂/GO/Tunneling layer/Pentacene/Au. The tunneling layers are polymethylmethacrylate (PMMA) and polyvinylphenol (PVP). GO film could be deposited as single layered flakes with a uniform distribution using spin coating technique. The devices with PMMA as charge tunneling layer exhibited higher mobility and on/off ratio than PVP based devices. The devices show a large positive threshold voltage shift (∼24 V for PMMA and ∼15 V for PVP) from initial value during programming at gate voltage of +80 V kept for 10 s. The transfer curves can be restored approximately to its initial condition by applying an erasing voltage of −30 V for 10 s for both the devices. Since such a large shift is not observed without GO layer, we consider that memory effect was due to electron trapping in GO. Further, retention of the initial memory window was measured to be 63% and 37% after 3000 s for PMMA and PVP based devices, respectively.     

Controlled growth of a graphene charge-floating gate for organic non-volatile memory transistors

We report memory application for graphene as a floating gate in organic thin-film transistor (OTFT) structure. For graphene floating gate, we demonstrate a simpler synthesis method to form a discrete graphene layer by controlling the growth time during a conventional CVD process. The resulting organic memory transistor with the discrete graphene charge-storage layer is evaluated. The device was demonstrated based on solution-processed tunneling dielectric layers and evaporated pentacene organic semiconductor. The resulting devices exhibited programmable memory characteristics, including threshold voltage shifts (∼28 V) in the programmed/erased states when an appropriate gate voltage was applied. They also showed an estimated long data retention ability and program/erase cycles endurance more than 100 times with reliable non-volatile memory properties although operated without encapsulation and in an ambient condition.     

一种非接触式IC卡控制器的设计

介绍了ＩＳＯ／ＩＥＣ１４４３中ＴｙｐｅＢ类型非接触式ＩＣ卡实现抗冲突的算法，设计了一种适用于非接触式ＩＣ卡的具有抗冲突功能控制逻辑的ＶＬＳＩ结构，并用ＶＨＤＬ语言进行了仿真。电路中提出了确定时间片的伪随机算法来实现抗冲突功能。用１μｍＣＭＯＳ单元库进行综合，在２０ＭＨｚ时钟频率下，电路的规模为７０００门左右，并键路径延时为４６ｎｓ。该电路可应用于实际的非接触工ＩＣ卡控制器，具有一定的实用价值。     

Focused ion beam contact to non-volatile memory cells

Electrical characterization of non-volatile memory cells has been performed. A focused ion beam (FIB) contact procedure is presented that allows to contact the floating gate.Calculations and measurement results on an exemplary floating gate memory cell show intact cell structure with limited retention time after FIB modification. The presented procedure allows the measurement and control of the previously unavailable floating gate current and voltage.     

一种多码率非接触式智能卡解码器设计

在0.18μm 2P4M CMOS工艺上实现了一种符合ISO/IEC 14443 TYPE A(2008)协议的多码率非接触式智能卡专用集成电路解码器。解码器通过两个同步计数器的状态组合恢复单位编码时钟,引进中间变量输出不归零码。采用上升沿触发计数器,优化凹槽容差性能,避免因凹槽信号导致的电源毛刺对数据的影响。测试结果表明,该解码器支持106 kb/s,212 kb/s,424 kb/s和848kb/s四种码率的改进Miller编码数据解码,对应不同码率均有高凹槽容差性能,满足非接触式智能卡性能要求。     

Incorporation of non-conjugated polymer chain in conjugated polymer matrix: A new single step strategy for free standing non-volatile polymer memory

A new single step strategy for polymer memory materials has been explored using free-standing polypyrrole (PPy) film in which non-conjugated polymer chains are incorporated as trap states during synthesis. The PPy film was synthesized by the acidic oxidation of 2,2′:5′,2′′-terpyrrole at the air/water interface. The free-standing PPy films show large hysteresis along with current peaks in opposite directions during current voltage (I–V) characteristics. Hysteric behavior has been utilized to show rewritable memory effect. Furthermore, once electrical state (high or low conduction state) is set, the state is stable for months in ambient condition unless the state is reset by applying a voltage of opposite polarity. Thus the PPy film can be used as read once memory. The memory effect of the film is due to the conformational changes of non-conjugated polymer chains in the PPy matrix. The changes in conformation were confirmed from UV–Vis and FTIR spectra. This new strategy leads free-standing film based all organic polymer memory devices at ultra low cost.     

Charge storage and memory effect in graphene quantum dots – PEG600 hybrid nanocomposite

We report an easy, one step, low cost method to obtain a hybrid composite material consisting in graphene quantum dots (GQDs) embedded in a polymeric – poly(ethylene glycol) bis (carboxymethyl) ether – matrix. Optical measurements show the excitation wavelength dependent photoluminescence of the GQDs – PEG₆₀₀. In comparison with self-passivated GQDs, the composite exhibits a blue shifted photoluminescence, as well as additional emission peaks in the range of 570–600 nm. These features are explained by the presence of new electronic surface states induced by the polymeric matrix as it was demonstrated by the electrochemical measurements. The transport properties consist in a large clockwise hysteresis presenting high and low resistance states, also two distinctive regions of negative differential resistance. The photocurrent decay and the transient currents indicate a large charge storage and confirm the existence of trap charge levels. The experimental findings suggest that the leading mechanism underling the transport is Simmons Verderber. We demonstrated the switching properties of GQDs – PEG₆₀₀ for applications in non-volatile memory by performing standard sequence memory tests.