1,721,009 research outputs found
Negative effect of cations out-diffusion and auto-doping on switching mechanisms of transparent memristor devices employing ZnO/ITO heterostructure
No full textAn excessive unintentional out-diffuses In atoms into the switching layer is a potential threat to the switching stability of memristor devices having indium tin oxide (ITO) as the electrode. We suggest that the physical factor (bombardment of Ar ions and bombardment induced localized heat during ZnO deposition) and chemical factor (bonding dissociation energy, point defects, and bond length of atoms) responsible for promoting the out-diffusion. The In atom acts as dopant in the ZnO lattice that degenerates the ZnO insulative behavior. Furthermore, the In ions take part in the conduction mechanism where they may compete with other mobile species to form and rupture the filament, and hence, deteriorate the switching performance. We propose a facile UV/O3 (UVO) treatment to mitigate such damaging effects. The device fabricated on the UVO-treated ITO substrate exhibits significant switching parameter improvement than that of the device manufactured on untreated ITO. This work delivers an insight into the damaging effect of out-diffusion and auto-doping processes on the reliability of memristor devices
Dataset: Conduction channel configuration controlled digital and analog response in TiO2-based inorganic memristive artificial synapses
No full textDataset for manuscript titled "Conduction channel configuration controlled digital and analog response in TiO2-based inorganic memristive artificial synapses" for journal APL materials. The dataset contains the electrical and materials data in Origin file format.</span
Film-nanostructure-controlled inerasable-to-erasable switching transition in ZnO-based transparent memristor devices: sputtering-pressure dependency
No full textWe found that the write-once-read-many-times (WORM, inerasable)-to-rewritable (erasable) transition phenomenon results from the different structures of the filament, which is determined by the grain orientations of the deposited films. The conduction mechanism of this switching transition and its impact on the synaptic behavior in various ZnO nanostructures are also discussed. Furthermore, our WORM devices have a programmable physical damage function that can be exploited for use in security systems against data theft, hacking, and unauthorized use of software/hardware. This work proposes ZnO-based nonvolatile memory for invisible electronic applications and gives valuable insight into the design of WORM and rewritable memories
Conduction channel configuration controlled digital and analog response in TiO<sub>2</sub>-based inorganic memristive artificial synapses
No full textThe operating current regime is found to play a key role in determining the synaptic characteristic of memristor devices. A conduction channel that is formed using high current compliance prior to the synaptic operation results in digital behavior; the high current stimulus forms a complete conductive filament connecting the cathode and anode, and the high electric field promotes abrupt redox reactions during potentiation and depression pulsing schemes. Conversely, the conduction can be reconfigured to produce a filamentary-homogeneous hybrid channel by utilizing the low current stimulus, and this configuration enables the occurrence of analog behavior. The capabilities of memristors showing programmable digital-to-analog or analog-to-digital transformation open a wide range of applications in electronics. We propose a conduction mechanism to explain this phenomenon.Analog memristor technologies offer promising potential for in-memory computing applications.1 In-memory computing is a state-of-the-art computer architecture that envisages data processing in the memory unit and thus overcomes data latency between memory and central processing units.1 A memristor device has a facile top-electrode/metal oxide (switching layer)/bottom-electrode sandwiched architectonic rendering ultra-high-density circuits;2 the recent effort has successfully fabricated cross-bar arrays having sub-15 nm cells.3 Moreover, such a small dimension and its low power operation could realize memristor–neuron coupling to enable the silicon–brain interface.4,5Several physical and chemical mechanisms have been proposed to explain the electron conduction in the memory cell, such as those based on metallic diffusion (electrochemical metallization), valence change, thermo-chemical, and interfacial coupling.6–8 A valence change memristor is controlled by an electric field that induces the formation and rupture of oxygen vacancy filaments to switch the device On (state 1) and Off (state 0), respectively, also called memristive behavior.9 The formation of the filament is initiated by the creation of oxygen vacancies by ionizing the oxygen from the lattice of the oxide switching layer, and these vacancies grow from the cathode to anode while the oxygen ions drift to and are oxidized at the anode/switching layer interface; the electrons, then, can easily flow through this filament, enabling the device in a low resistance state (LRS, state 1).10 Conversely, the filament can be ruptured by re-ionizing the oxygen at the anode/switching layer interface to recombine with the vacancies, creating a conduction gap between the electrode and remnant of the filament and, hence, switching the device to a high resistance state (HRS, state 0).10Furthermore, the formation and rupture of the filaments can be used by an electric stimulus having short pulses and small amplitude to exhibit multiple states (states beyond 1 and 0); consequently, the device can perform an analogous gradual rise and fall of conductance.11 The gradual rise and fall of the conductance are called potentiation and depression, respectively, mimicking the mammalian brain's analogous synaptic weight response.12 However, the fabrication of analog memristors requires careful design and optimization, which makes the manufacturing process greatly challenging; this is because memristor devices often show digital behavior instead of analog, where the conductance change occurs abruptly.13Various designs have been proposed to achieve a reliable synaptic response but mostly focus on programming the pulse scheme11 and engineering the switching materials such as bi-layering,14 doping,15 embedding with nanocrystals,16 and surface modification.17 These methods could indeed improve the synaptic response; however, the fundamental question of the relationship between the electron conduction and the structure of the filaments determining such analog and digital behavior in memristor devices is still less examined. In this work, we investigate the conduction channel configuration at the interface responsible for dictating the analog and digital response of the memristors. We explain the occurrence of digital-to-analog transformation in the device, and the conduction mechanism is also proposed by studying the phenomenon observed in devices having different thicknesses.The device architecture and measurement setup are depicted in Figs. 1(a) and 1(b), respectively. A 15 nm TiN bottom electrode (BE) was deposited onto a Pt/Ti-coated Si-wafer substrate employing the atomic layer deposition technique. TiO2 switching layer films with thicknesses of 16 and 25 nm were deposited onto the bottom electrode. Hereafter, TiN/Ti bilayer top electrodes (TEs) having a diameter of 250 µm were patterned onto the TiO2 films using a metal shadow mask. The sheet resistance of the TiN electrodes is found to be less than 19 Ω/sq. The thicknesses of TiN and Ti are 50 and 15 nm, respectively. The TiO2, TiN, and Ti films were deposited using a DC sputtering system from a Ti target in a mixture of Ar/O2, Ar/N2, and Ar ambience, respectively. The devices made with 16 and 25 nm thick TiO2 films were denoted as D16 and D25, respectively. The electrical characteristics were investigated using an Agilent B1500A semiconductor analyzer. A voltage bias was applied to the top electrode while the bottom electrode was grounded; a current compliance (CC) was used during the positive bias voltage sweep to avoid permanent breakdown. For DC sweep, a negative bias of −1.4 V was used for all devices to switch the device Off. In the case of synaptic measurement, AC pulse schemes were used to induce the response by applying pulse amplitudes of −1.2 and 1 V for depression and potentiation, respectively, with a pulse width of 20 µs. Meanwhile, the pulse read was conducted using an amplitude of 0.1 V with a width of 1 ms. An epoch consists of 500 pulses of depression (D) and 500 pulses of potentiation (P). Note that the synaptic response test was conducted after several switching cycles. The element profile and defect were measured by x-ray photoelectron spectroscopy (XPS, PHI Quantera SXM)
Band tailoring by annealing and current conduction of Co-doped ZnO transparent resistive switching memory
No full textThe switching characteristics of ITO/Zn1-xCoxO/ITO transparent resistive random access memories were studied. 5 mol% cobalt doped ZnO resistive layer improves bipolar switching properties. In addition, the redshift in band energy caused by doping of cobalt (Co) was studied. The doped memory device also showed a change in band energy by 0.1 eV when subjected to annealing of 400 °C. Annealing below 400 °C temperature did not show any characteristic changes. The film morphology analysis suggested the increase in roughness with annealing temperature, which can be seen from FESEM and AFM images. In this study annealing and Co doping effect on ZnO based non-volatile memory device is presented. Moreover, transparent memory devices with 90% transmittance at 550 nm wavelength have been reported. At low field and high field region Schottky emission and ionic conduction are dominated respectively
Low-power electronic technologies for harsh radiation environments
No full textElectronic technologies that can operate in harsh radiation environments are important in space, nuclear and avionic applications. However, radiation-hardened (rad-hard) integrated circuits often require additional processing and more complex configurations than conventional systems. Here we review the development of low-power, rad-hard electronics, examining the underlying phenomena of radiation-induced electronic failure and the design methodologies available with conventional complementary metal–oxide–semiconductor (CMOS) technologies to mitigate the problem. We also explore the potential use and applications of various emerging memory technologies in rad-hard electronics
Transparent ZnO resistive switching memory fabricated by neutral oxygen beam treatment
No full textIn this work, a Cu/ZnO/ITO resistive random access memory (RRAM) structure in which ZnO films are irradiated with neutral oxygen beams was employed to investigate the effect of neutral oxygen beams as a surface treatment. It was confirmed that the treatment reduced the defect concentration in the sputtered-ZnO film and improved the resistance change characteristics of the device. These results indicate the great potential of neutral oxygen beams in the development of RRAM devices using ZnO films
Conduction mechanism of Co-doped ZnO transparent memristive devices
No full textThe Co dopant substitutes the Zn atomic position in the hexagonal crystal lattice and generates acceptor defects. These defects play significant role in modulating the conduction mechanism of the memristive device. The devices without Co dopant have high concentration of donor defects so that the electron can flow easily through hopping these donor defects; henceforth, only weak filaments can be formed during the set process. Meanwhile, the increase of the acceptor defects in the films enhances the film resistivity. This acceptor defects also contribute to an increase of barrier height at the electrode/dielectric interface where the electrons require higher energy to overcome this barrier and, eventually, induce the formation of strong filaments during the set process
Enhanced synaptic linearity in ZnO-based invisible memristive synapse by introducing double pulsing scheme
No full textThe synaptic plasticity of indium tin oxide (ITO)/ZnO/ITO highly transparent (more than 88%) analog switching resistive memory device is investigated. Highly stable analog switching behavior for more than 2500 cycles with a good memory window of approximately two orders makes it suitable for synapse application. The synaptic response is investigated by applying identical electrical pulses. The potentiation and depression of the device used the conventional identical single-pulse scheme to perform high nonlinearity (0.83) and decaying training epochs. However, the linearity and the training epochs are improved to 0.44 by implementing the identical double-pulse scheme. The proposed double-pulse scheme offers a broad dynamic range (200) having 320 conductance states. This invisible structure and double-pulse scheme can be highly suitable for the neuromorphic computing devices
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