43 research outputs found
Electrical Re-Writable Non-Volatile Memory Device based on PEDOT:PSS Thin Film
open access articleIn this research, we investigate the memory behavior of poly(3,4 ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) cross bar structure memory cells. We demonstrate that Al/PEDOT:PSS/Al cells fabricated elements exhibit a bipolar switching and
reproducible behavior via current–voltage, endurance, and retention time tests. We ascribe the physical origin of the bipolar switching to the change of the electrical conductivity of PEDOT:PSS due to electrical field induced dipolar reorientation
Inkjet Printing of Functional Electronic Memory Cells: A Step Forward to Green Electronics
open access journalNowadays, the environmental issues surrounding the production of electronics, from the
perspectives of both the materials used and the manufacturing process, are of major concern. The
usage, storage, disposal protocol and volume of waste material continue to increase the environmental
footprint of our increasingly “throw away society”. Almost ironically, society is increasingly involved
in pollution prevention, resource consumption issues and post-consumer waste management. Clearly,
a dichotomy between environmentally aware usage and consumerism exists. The current technology
used to manufacture functional materials and electronic devices requires high temperatures for material
deposition processes, which results in the generation of harmful chemicals and radiation. With such
issues in mind, it is imperative to explore new electronic functional materials and new manufacturing
pathways. Here, we explore the potential of additive layer manufacturing, inkjet printing technology
which provides an innovative manufacturing pathway for functional materials (metal nanoparticles
and polymers), and explore a fully printed two terminal electronic memory cell. In this work, inkjetable
materials (silver (Ag) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS))
were first printed by a piezoelectric Epson Stylus P50 inkjet printer as stand-alone layers, and secondly
as part of a metal (Ag)/active layer (PEDOT:PSS)/metal (Ag) crossbar architecture. The quality of the
individual multi-layers of the printed Ag and PEDOT:PSS was first evaluated via optical microscopy
and scanning electron microscopy (SEM). Furthermore, an electrical characterisation of the printed
memory elements was performed using an HP4140B picoammeter
Emulating long-term synaptic dynamics with memristive devices
The potential of memristive devices is often seeing in implementing
neuromorphic architectures for achieving brain-like computation. However, the
designing procedures do not allow for extended manipulation of the material,
unlike CMOS technology, the properties of the memristive material should be
harnessed in the context of such computation, under the view that biological
synapses are memristors. Here we demonstrate that single solid-state TiO2
memristors can exhibit associative plasticity phenomena observed in biological
cortical synapses, and are captured by a phenomenological plasticity model
called triplet rule. This rule comprises of a spike-timing dependent plasticity
regime and a classical hebbian associative regime, and is compatible with a
large amount of electrophysiology data. Via a set of experiments with our
artificial, memristive, synapses we show that, contrary to conventional uses of
solid-state memory, the co-existence of field- and thermally-driven switching
mechanisms that could render bipolar and/or unipolar programming modes is a
salient feature for capturing long-term potentiation and depression synaptic
dynamics. We further demonstrate that the non-linear accumulating nature of
memristors promotes long-term potentiating or depressing memory transitions
Comparative Study of Silicon Nanowires Grown From Ga, In, Sn, and Bi for Energy Harvesting
The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.A high density of silicon nanowires for solar cell applications was fabricated on a single crystalline silicon wafer, using low eutectic temperature metal catalysts, namely, gallium, indium, tin, and bismuth. The use of silicon nanowires is exploited for light trapping with an aim to enhance the efficiency of solar cells. Additionally, we have optimized the deposition parameters so that there is merely deposition of amorphous silicon along with the growth of silicon nanowires. Thus, it may improve the stability of silicon-based solar cells. The different catalysts used are extensively discussed with experimental results indicating stable growth and
highly efficient silicon nanowires for photovoltaic applications. To test the stability, we measured the open-circuit voltage for
four hours and the change in voltage was ±0.05 V. The fabrication of all-crystalline silicon solar cells was demonstrated using the conventional mature industrial manufacturing process that is presently used for the amorphous silicon solar cells. To summarize,
this research compares various post-transition metals as a catalyst for the growth of nanowires discussing their properties, and such silicon nanowires can be utilized in several other applications not only limited to photovoltaic research
Modelling of Current Percolation Channels in Emerging Resistive Switching Elements
Metallic 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
Stochastic switching of TiO2 based memristive devices with identical initial memory states
In 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
Additive manufacturing of heat-sensitive polymer melt using a pallet-fed material extrusion
The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link
Creating Electrical Bistability Using Nano-bits – Application in 2-Terminal Memory Devices
This is an Open Access article.Intensive research is currently underway to exploit the highly interesting properties of nano-bits (“nano-sized particles and molecules”) for optical, electronic and other applications. The basis of these unique properties is the small-size of these structures which result in quantum mechanical phenomena and interesting surface properties. The small molecules and/or nano-particles are selected in such a way so that it can create an internal electric in the nano-composite. We define a nanocomposite is an admixture of small molecules and/or nano-particles and a polymer. We have demonstrated the internal electric field in our devices, made from nano-bits (nano-particles and/or molecules) and insulating materials, can contribute to the electrical bistability i.e. two conductive states
Digital Printing of Titanium Dioxide for Dye Sensitized Solar Cells
Silicon solar cell manufacturing is an expensive and high energy consuming process. In contrast, dye sensitized solar cell production is less
environmentally damaging with lower processing temperatures presenting a viable and low cost alternative to conventional production. This
paper further enhances these environmental credentials by evaluating the digital printing and therefore additive production route for these
cells. This is achieved here by investigating the formation and performance of a metal oxide photoelectrode using nanoparticle sized titanium
dioxide. An ink-jettable material was formulated, characterized and printed with a piezoelectric inkjet head to produce a 2.6 ÎĽm thick layer. The
resultant printed layer was fabricated into a functioning cell with an active area of 0.25 cm2 and a power conversion efficiency of 3.5%. The
binder-free formulation resulted in a reduced processing temperature of 250 °C, compatible with flexible polyamide substrates which are stable
up to temperatures of 350 ËšC. The authors are continuing to develop this process route by investigating inkjet printing of other layers within dye
sensitized solar cells