1,720,998 research outputs found
Modelling of current percolation channels in emerging resistive switching elements
No full textMetallic oxides encased within Metal-Insulator-Metal (MIM) structures can demonstrate both unipolar and bipolar switching mechanisms, rendering them the capability to exhibit a multitude of resistive states and ultimately function as memory elements. Identifying the vital physical mechanisms behind resistive switching can enable these devices to be utilized more efficiently, reliably and in the long-term. In this paper, we present a new approach for analysing resistive switching by modelling the active core of two terminal devices as 2D and 3D grid circuit breaker networks. This model is employed to demonstrate that substantial resistive switching can only be supported by the formation of continuous current percolation channels, while multi-state capacity is ascribed to the establishment and annihilation of multiple channels
Resistive switching of oxygen enhanced TiO<sub>2</sub> thin-film devices
No full textIn this work, we investigate the effect of oxygen-enhanced TiO2 thin films on the switching dynamics of Pt/TiO2/Pt memristive nanodevices. We demonstrate that such devices can be used as resistive random access memory (RRAM) cells without required electroforming. We experimentally demonstrate that devices based on TiO2 films fabricated via sputtering with partial pressures of Ar/O2 6/6 sccm and 2/10 sccm show OFF/ON ratios of six and two orders of magnitude, respectively. Additionally, it was found that a lower O2 flow during sputtering of TiO2 allows for lower energy requirements for switching the devices from a high to low resistive state
Correlated resistive/capacitive state variability in solid TiO<sub>2</sub> based memory devices
No full textIn this work, we experimentally demonstrated the correlated resistive/capacitive switching and state variability in practical TiO2 based memory devices. Based on filamentary functional mechanism, we argue that the impedance state variability stems from the randomly distributed defects inside the oxide bulk. Finally, our assumption was verified via a current percolation circuit model, by taking into account of random defects distribution and coexistence of memristor and memcapacitor
Stochastic switching of TiO<sub>2</sub>-based memristive devices with identical initial memory states
Full text linkIn this work, we show that identical TiO2-based memristive devices that possess the same initial resistive states are only phenomenologically similar as their internal structures may vary significantly, which could render quite dissimilar switching dynamics. We experimentally demonstrated that the resistive switching of practical devices with similar initial states could occur at different programming stimuli cycles. We argue that similar memory states can be transcribed via numerous distinct active core states through the dissimilar reduced TiO2-x filamentary distributions. Our hypothesis was finally verified via simulated results of the memory state evolution, by taking into account dissimilar initial filamentary distribution
Digital printing of functional materials: a step forward to green electronics - invited talk
Full text linkHow can we fabricate more ecological friendly functional materials and electronic devices?
Nowadays, the environmental issues of electronics from both the perspectives of used materials and manufacturing process is a major concern. The usage, storage, disposal protocol and the volume of waste material continues to increase the environmental footprint of our increasingly “throw away society”. Almost ironically, that society is increasingly involved in pollution prevention, resources consumption issues and post-consumer waste management. Clearly, there exists a dichotomy between environmentally aware usage and consumerism. The current technology to manufacture functional materials and electronic devices requires heat generation in a deposition process and hence generation of harmful chemicals/radiation. Additionally, there are environmental limitations, for example, high vacuum equipment requires enormous amounts of electricity to run, thus creating a larger carbon footprint.
With this background, it is imperative to explore new electronic functional materials but as well as new manufacturing pathways.
This talk will encompass the potential of inkjet printing technology as an innovative manufacturing pathway for functional materials, and electronic devices as an reliable alternative to traditional manufacturing protocols
Electrical bistability in a composite of polymer and barium titanate nanoparticles.
Full text linkGrowth in the use of organic materials in the fabrication of electronic devices is on the rise.
Recently, some attempts have been undertaken to manufacture polymer memory devices. Such devices
are fabricated by depositing a blend (an admixture of organic
polymer, small organic molecules and nanoparticles) between two metal electrodes. These
devices show two electrical conductivity states (“high” and “low”) when a voltage is applied,
thus rendering the structures suitable for data retention. In this paper, we describe an attempt to fabricate memory devices using ferroelectric nanoparticles embedded in an organic
polymer. This paper also discusses issues related to the observed memory effectThe authors would like to thank EPSRC (Grant #EP/E047785/1) for supporting this work
Non-volatile memory device- using a blend of polymer and ferroelectric nanoparticles.
Full text linkIn recent years, the interest in the application of organic materials in electronic devices (light emitting diodes, field effect
transistors, solar cells), has shown a rapid increase. A new family of organic electronic device is organic memory device.
These devices, based on a thin film of nano-sized particles and small molecules embledded in an organic layer attracted
considerable attention. This work presents the polymer memory device which is made of a blend of poly(vinyl acetate) and
ferroelectric barium titanate nanoparticles. A polymer blend of polyvinyl acetate and barium titanate (BaTiO3) nanoparticles
was prepared in methanol and spin coated onto a glass substrate marked with thin Al tracks and top contacts were
evaporated onto the blend after drying - this resulted in a metal-organic-metal (MOM) structure. The current-voltage (I-V)
behaviour of MOM devices shows that the devices can be switched from a high conductivity state to a low conductivity
state, by applying an external electric field - this property can be exploited to store data bits. The working mechanism, in
these devices is based on ferroelectric properties of barium titanate.The authors would like to thank EPSRC (Grant # EP/E047785/1) for supporting this work
Bistability in electrically writable non-volatile polymer memory devices.
Full text linkIn recent years, interest in applications of organic materials in electronic devices (light
emitting diodes, field effect transistors, solar cells), has increased rapidly. The advantages of
organic materials are the ease of processing, lower production costs and structural flexibility
allowing achievement of the desired electrical and mechanical characteristics. Very recently,
there have been demonstrations of blends of polymer and metal nanoparticles and/or small
organic molecules in memory devices; such memory devices are called polymer memory devices
(PMDs). These devices show two electrical conductance states (“high” and “low”) when voltage
is applied, thus rendering the structures suitable for data retention.
These two states can be viewed as the realisation of non-volatile electrical memory. There is
always growing need to look for inexpensive, fast, high-density memory devices with longer
retention times and PMDs do possess some of these aforesaid criteria. Albeit, there is a rapid
development in this area, the memory mechanism is still unclear. This work attempts to analyse
the memory effect in PMDs and proposes a theory based on experimental data. The thin film
polymer blends (polyvinyl acetate, polyvinyl alcohol and polystyrene) and small organic
molecules were deposited by spin coating onto a glass substrate marked with thin metal tracks. A
top contact was evaporated onto the blend after drying - this resulted in a metal-organic-metal
(MOM) structure. MOM devices with different metal electrodes (a series of metals with different
work functions Al, In,Cu,Cr, Ag and Au) were used to understand the exact electrical transport
mechanism through the blend and the individual polymers. An in-depth electrical analysis of
these MOM devices was carried out using an HP4140B picoammeter (current-voltage) and an
LCR HP4192 bridge. FTIR and UV-VIS spectroscopy were also conducted in order to
understand blend properties and the effect of the same, if any, on the electrical charging
mechanism in the PMDs.The authors would like to thank EPSRC (Grant # EP/E047785/1) for supporting this work
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