New Superionic Memory Devices Can Provide Clues to the Human Memory Structure and to Consciousness

Since the work of Penrose and Hameroff the possibility is discussed that the location of human memory and consciousness could be connected with tubulin microtubules. If one would use superionic nano-materials rolled up to microtubules with an electrolyte inside the formed channels mediating fast ionic exchange of protons respectively lithium ions, it seems to be possible to write into such materials whole image arrays (pictures) under the action of the complex electromagnetic spectrum that composes these images. The same material and architecture may be recommended for super-computers. Especially microtubules with a protofilament number of 13 are the most important to note. We connected such microtubules before with Fibonacci nets composed of 13 sub-cells that were helically rolled up to deliver suitable channels. Our recent Fibonacci analysis of Wadsley-Roth shear phases such as niobium tungsten oxide , exhibiting channels for ultra-fast lithium-ion diffusion, suggests to use these materials, besides super-battery main application, in form of nanorods or microtubules as effectively working superionic memory devices for computers that work ultra-fast with the complex effectiveness of human brains. Finally, we pose the question, whether dark matter, ever connected with ultrafast movement of ordinary matter, may be responsible for synchronization between interactions of human brains and consciousness.

Current Controlled Relaxation Oscillations in Ge_2Sb_2Te_5-Based Phase Change Memory Devices

The relaxation oscillation of the phase change memory （PCM） devices based on the Ge2Sb2Te5 material is investigated by applying square current pulses. The current pulses with different amplitudes could be accurately given by the independently designed current testing system. The relaxation oscillation across the PCM device could be measured using an oscilloscope. The oscillation duration decreases with time, showing an inner link with the shrinking threshold voltage Vth. However, the relaxation oscillation would not terminate until the remaining voltage Von reaches the holding voltage Vh. This demonstrates that the relaxation oscillation might be controlled by Von. The increasing current amplitudes could only quicken the oscillation velocity but not be able to eliminate it, which indicates that the relaxation oscillation might be an inherent behavior for the PCM cell.

Investigation of flux dependent sensitivity on single event effect in memory devices

Heavy-ion flux is an important experimental parameter in the ground based single event tests. The flux impact on a single event effect in different memory devices is analyzed by using GEANT4 and TCAD simulation methods. The transient radial track profile depends not only on the linear energy transfer （LET） of the incident ion, but also on the mass and energy of the ion. For the ions with the energies at the Bragg peaks, the radial charge distribution is wider when the ion LET is larger. The results extracted from the GEANT4 and TCAD simulations, together with detailed analysis of the device structure, are presented to demonstrate phenomena observed in the flux related experiment. The analysis shows that the flux effect conclusions drawn from the experiment are intrinsically connected and all indicate the mechanism that the flux effect stems from multiple ion-induced pulses functioning together and relies exquisitely on the specific response of the device.

Design of an Electrically Written and Optically Read Non-volatile Memory Device Employing BiFeO3/Au Heterostructures with Strong Absorption Resonance

Exploiting new concepts for dense, fast, and nonvolatile random access memory with reduced energy consump- tion is a significant issue for information technology. Here we design an ＇electrically written and optically read＇ information storage device employing BiFeO3/A u heterostruetures with strong absorption resonance. The electro- optic effect is the basis for the device design, which arises from the strong absorption resonance in BiFeO3/Au heterostructures and the electrically tunable significant birefringence of the BiFeO3 film. We first construct a sim- ulation calculation of the BiFeO3/Au structure spectrum and identify absorption resonance and electro-optical modulation characteristics. Following a micro scale partition, the surface reflected light intensity of different polarization units is calculated. The results depend on electric polarization states of the BiFeO3 film, thus BiFeO3/Au heterostructures can essentially be designed as a type of electrically written and optically read infor- mation storage device by utilizing the scanning near-field optical microscopy technology based on the conductive silicon cantilever tip with nanofabricated aperture. This work will shed light on information storage technology.

Effect of Pulse and dc Formation on the Performance of One-Transistor and One-Resistor Resistance Random Access Memory Devices

We investigate the effect of the formation process under pulse and dc modes on the performance of one transistor and one resistor （1 T1R） resistance random access memory （RRAM） device. All the devices are operated under the same test conditions, except for the initial formation process with different modes. Based on the statistical results, the high resistance state （FIRS） under the dc forming mode shows a lower value with better distribution compared with that under the pulse mode. One of the possible reasons for such a phenomenon originates from different properties of conductive filament （CF） formed in the resistive switching layer under two different modes. For the dc forming mode, the formed filament is thought to be continuous, which is hard to be ruptured, resulting in a lower HRS. However, in the case of pulse forming, the filament is discontinuous where the transport mechanism is governed by hopping. The low resistance state （LRS） can be easily changed by removing a few trapping states from the conducting path. Hence, a higher FIRS is thus observed. However, the HRS resistance is highly dependent on the length of the gap opened. A slight variation of the gap length will cause wide dispersion of resistance.

A novel one-time-programmable memory unit based on Schottky-type p-GaN diode

In this work,a novel one-time-programmable memory unit based on a Schottky-type p-GaN diode is proposed.During the programming process,the junction switches from a high-resistance state to a low-resistance state through Schottky junction breakdown,and the state is permanently preserved.The memory unit features a current ratio of more than 10^(3),a read voltage window of 6 V,a programming time of less than 10^(−4)s,a stability of more than 108 read cycles,and a lifetime of far more than 10 years.Besides,the fabrication of the device is fully compatible with commercial Si-based GaN process platforms,which is of great significance for the realization of low-cost read-only memory in all-GaN integration.

Zirconia quantum dots for a nonvolatile resistive random access memory device

We propose a nonvolatile resistive random access memory device by employing nanodispersion of zirconia(ZrO2) quantum dots(QDs) for the formation of an active layer. The memory devices comprising a typical sandwich structure of Ag(top)/ZrO2(active layer)/Ti(bottom) are fabricated using a facile spin-coating method. The optimized device exhibits a high resistance state/low resistance state resistance difference(about 10 Ω), a good cycle performance(the number of cycles larger than 100), and a relatively low conversion current(about 1 μA). Atomic force microscopy and scanning electron microscope are used to observe the surface morphology and stacking state of the ZrO2 active layer. Experimental results show that the ZrO2 active layer is stacked compactly and has a low roughness(Ra=4.49 nm) due to the uniform distribution of the ZrO2 QDs. The conductive mechanism of the Ag/ZrO2/Ti device is analyzed and studied, and the conductive filaments of Ag ions and oxygen vacancies are focused on to clarify the resistive switching memory behavior. This study offers a facile approach of memristors for future electronic applications.

Resistive switching performance improvement of In GaZnO-based memory device by nitrogen plasma treatment

With the demand of flat panel display development,utilizing the non-volatile memory devices based on indium-gallium-zinc-oxide(IGZO)film may be integrated with IGZO thin film transistors(TFTs)to accomplish system-on-panel applications.In this work,1×1μm^2 via hole structure IGZO based memory device was fabricated and the resistive switching(RS)behavior was investigated.By inserting a nitrogen doping layer IGZO:N by plasma treatment in Pt/IGZO/Ti N device,highly improved RS performance including lower forming voltage,remarkable uniformity,large memory window of 102,retention property of 10^4 s at 125℃,excellent pulse endurance of 10^7 cycles were achieved.The X-ray photoelectron spectroscopy analysis indicates that plasma doping method can evenly dope nitrogen and induce more non-lattice oxygen in the IGZO film.It is deduced that the N atoms of the inserting layer can influence the random formation of oxygen vacancy type conducting filaments,which results in more stable and uniform performance.

The Effect of Substrate on the Properties of Non-volatile Ferroelectric P(VDF-TrFE)/P3HT Memory Devices

Ferroelectric poly(vinylidene fluoride-trifluoroethylene)(P(VDF-TrFE))/semiconducting poly(3-hexyl thiophene)(P3HT)blend systems have drawn great attention with their potential use for electronic applications,particularly non-volatile memory devices.It is essential to grasp a full understanding of the crystallization habits of the two polymers on different substrates for purposeful control of the structures of the blend and therefore the properties of the devices.Here,the effects of structure and morphology of the blend films generated at different substrate surfaces on the ferroelectric and switching properties of related devices are reported.It is identified that P(VDF-TrFE)/P3HT blend films prepared on graphene substrate show not only an obvious optimization in the ferroelectric behavior of P(VDF-TrFE),but also an enhancement of the charge transport within P3HT domains.By employing sandwich structure constructed by silver electrode and P3HT/P(VDF-TrFE)blend film on graphene substrate,high-performance ferroelectric memory devices have been obtained,which exhibit a great electrical switching behavior with high ON/OFF ratio of about 1000 and low coercive voltage of approximately 5 V.These findings provide useful guidance for fabricating highperformance ferroelectric memory devices.

Amorphous Structure and Bonding Chemistry of Aluminium Antimonide（AISb） Alloy for Phase-change Memory Device

With the help of first-principles molecular dynamics calculations, we obtained the atomic picture of amorphous A1Sb（a-A1Sb） for phase-change memory application. Generally, a-A1Sb shows sp3 bonding network, which is the intrinsic characteristic for its good thermal stability. Significant wrong（homogenous） AI-AI bonds can also be observed from the pair correlation function. This hints the amorphous phase may consist of A1 cluster and Sb-rich A1-Sb alloy. Recent experiment has observed the Sb-rich region of AISb alloy can be switched to crystal, on the basis of which, combined with our calculations, we thus propose that on the one hand such a Sb-rich region in a-A1Sb can retain the rapid crystallization like pure Sb solid and on the other hand some AI atoms play the important role of stabilizing Sb rich network with sp3 bonding. The present study offers a microscopic view to understand the phase change mechanism of AlSb alloy for information storage device.

Performance improvement of charge trap flash memory by using a composition-modulated high-k trapping layer

A composition-modulated （HfO2）x（Al2O3）1-x charge trapping layer is proposed for charge trap flash memory by controlling the A1 atom content to form a peak and valley shaped band gap. It is found that the memory device using the composition-modulated （HfO2）x（Al2O3）l-x as the charge trapping layer exhibits a larger memory window of 11.5 V, improves data retention even at high temperature, and enhances the program/erase speed. Improvements of the memory characteristics are attributed to the special band-gap structure resulting from the composition-modulated trapping layer. Therefore, the composition-modulated charge trapping layer may be useful in future nonvolatile flash memory device application.

Dynamic resistive switching in a three-terminal device based on phase separated manganites

A three-terminal device based on electronic phase separated manganites is suggested to produce high performance resistive switching. Our Monte Carlo simulations reveal that the conductive filaments can be formed/annihilated by reshaping the ferromagnetic metal phase domains with two cross-oriented switching voltages. Besides, by controlling the high resistance state（HRS） to a stable state that just after the filament is ruptured, the resistive switching remains stable and reversible, while the switching voltage and the switching time can be greatly reduced.

Advances in MoS_2-Based Field Effect Transistors(FETs)

This paper reviews the original achievements and advances regarding the field effect transistor(FET) fabricated from one of the most studied transition metal dichalcogenides: two-dimensional Mo S2. Not like graphene, which is highlighted by a gapless Dirac cone band structure, Monolayer Mo S2 is featured with a 1.9 e V gapped direct energy band thus facilitates convenient electronic and/or optoelectronic modulation of its physical properties in FET structure. Indeed,many Mo S2 devices based on FET architecture such as phototransistors, memory devices, and sensors have been studied and extraordinary properties such as excellent mobility, ON/OFF ratio, and sensitivity of these devices have been exhibited. However, further developments in FET device applications depend a lot on if novel physics would be involved in them. In this review, an overview on advances and developments in the Mo S2-based FETs are presented. Engineering of Mo S2-based FETs will be discussed in details for understanding contact physics, formation of gate dielectric, and doping strategies. Also reported are demonstrations of device behaviors such as low-frequency noise and photoresponse in Mo S2-based FETs, which is crucial for developing electronic and optoelectronic devices.

ADDITIVE-INDUCED ENHANCEMENT OF OPTICAL CLARITY OF POLYACRYLAMIDE HYDROGEL

The aqueous polymerization of acrylamide and crosslinking with N,N-methylenebisacrylamide afforded hydrogelsdisplaying high levels of light scattering (poor optical clarity). Enhancement of the optical clarity within a polyacrylamide(PAm) hydrogel was accomplished through the implementation of 'refractive index matching'. Water-soluble additives wereutilised to better match the refractive index inhomogeneities throughout a given hydrogel. This resulted in lower lightscattering within the system and hence improved clarity. Amino acids, sugars, polymers, and other water-soluble additivessuch as glycerol were investigated by this methodology. Most additives investigaed displayed potential for effectivelyreducing the light scattering within a PAm hydrogel as a function of increased additive concentration. On increasing therefractive index of the water medium, the overall refractive index of a PAm hydrogel was also observed to increase. Thisprovided a quantitative means of determining the effectiveness of a given additive for improving the optical clarity within ahydrogel.

Comparison between Pt/TiO_2/Pt and Pt/TaO_X/TaO_Y/Pt based bipolar resistive switching devices

Nonvolatile memories have emerged in recent years and have become a leading candidate towards replacing dynamic and static random-access memory devices.In this article,the performances of T1O_2 and TaO_2nonvolatile memristive devices were compared and the factors that make TaO_2 memristive devices better than T1O_2 memristive devices were studied.TaO_2 memristive devices have shown better endurance performances（10~8times more switching cycles） and faster switching speed（5 times） than TiO_2 memristive devices.Electroforming of TaO_2 memristive devices requires ~ 4.5 times less energy than TiO_2 memristive devices of a similar size.The retention period of TaO_2 memristive devices is expected to exceed 10 years with sufficient experimental evidence.In addition to comparing device performances,this article also explains the differences in physical device structure,switching mechanism,and resistance switching performances of TiO_2 and TaO_2 memristive devices.This article summarizes the reasons that give TaO_2 memristive devices the advantage over TiO_2 memristive devices,in terms of electroformation,switching speed,and endurance.

Variable Learning-Memory Behavior fromπ-Conjugated Ligand to Ligand-Containing Cobalt(II)Complex

In the information-explosion era,developing novel algorithms and memristive devices has become a promising concept for next-generation capacity enlargement technology.Organic small molecule-based devices displaying superior learning-memory performance have attracted much attention,except for the existence of poor heat-resilience and mediocre conductivity.In this paper,a strategy of transforming an organic-type data-storage material to metal complex is proposed to resolve these intrinsic issues.A pristine NDI-derivative(NIPy)and its corresponding Co(II)complex(CoNIPy)are synthesized for the purpose of electrical property investigation.CoNIPy complex-based memristive device exhibits superior ternary WORM memory performance compared with the binary behavior of NIPy,including>104 s of reading,lower threshold voltage(V_(th)),1:10^(2):10^(5)of OFF/ON1/ON2 current ratio,and long-term stability in heating environment.The variable learning-memory behavior can be attributed to the enhanced ligand-to-metal charge transfer(LMCT)and improved redox activity after the introduction of central metal atom and coordination bond.These studies on material innovation and optimal performance are of great importance not only for environmentally-robust memristive devices but also for practical application of a host of organic electronic devices.

Metal nanocluster-based devices:Challenges and opportunities

Atomically precise nanoclusters(NCs)with fascinating physicochemical characteristics different from their nanoparticles(NPs)counterparts have gained increasing attention in diverse fields of applications.The foremost outcome of such NC-based applications is leading to transform them into devices.In fact,there are already some reports on the development of NC-based devices.For instance,NCs exhibit their potential in solar cells,showing high light-harvesting efficiency comparable to traditional semiconductor solar cells.Further,recent progress in characterizing Au NCs films and micro-crystals shows semiconductor-like properties such as field effect and photoresponse.These successes indicate that metal NCs possess a high potential for application in multidisciplinary areas for advancing the development in fundamental and practical purposes.However,no such comprehensive review is available to highlight recent advances and new applicable devices based on noble metal NCs.Herein,we reviewed the recent development in this area,including synthesis challenges of metal NCs and related applications of NC-sensitized solar cells,strain sensors,chemo-/biosensors,transistors,floating memory,and other devices.Furthermore,the future opportunities such as modifying synthetic methods to make other metal NCs,enhancing the efficiency of solar cells,and exploring more NCbased devices alternative to semiconductors are pointed out.We hope that rapidly increasing interest in NC-based devices will stimulate the research in this area and inspire the advances in combined devices accordingly.

Synthesis of halide perovskite microwires via methylammonium cations reaction

Low-dimensional halide perovskites(HPs)have received considerable attention in recent years due to their novel physical properties such as compositional flexibility,high quantum yield,quantum size effects and superior charge transport.Here we show room temperature solution synthesis of 1D organic-inorganic lead bromide perovskite microwires(MWs).Our method uses acetone as a reactant,and when CH3NH3PbBr3 is immersed,acetone reacts with CH3NH3+cations in the CH3NH3PbBr3 single crystal by the dehydration condensation.The reaction generates a large(CH3)2C=NHCH3+A-site which cannot be accommodated by the cuboctahedron formed by the corner-sharing[PbBr6]4−octahedral,leading to the transition of corner-sharing octahedra to face-sharing triangular prism and the crystal structure transformation from 3D to 1D.The formation process of(CH3)2C=NHCH3PbBr3 MWs does not involve any ligands,templates or catalysts.A two-terminal memory device was constructed using the(CH3)2C=NHCH3PbBr3 MWs,showing great potential of the method in fabrication of electronic and optoelectronic devices.

MAGNETOELECTRIC RESPONSES IN MULTIFERROIC COMPOSITE THIN FILMS

Multiferroic composite thinfilms of ferroelectrics and magnets have attracted ever-increasing interest in most recent years.In this review,magnetoelectric(ME)responses as well as their underlying ME coupling mechanisms in such multiferroic composite thinfilms are discussed,oriented by their potential applications in novel ME devices.Among them,the direct ME response,i.e.,magnetic-field control of polarization,can be exploited for micro-sensor applications(sensing magneticfield,electric current,light,etc.),mainly determined by a strain-mediated coupling interaction.The converse ME response,i.e.,electric-field modulation of magnetism,offers great opportunities for new potential devices for spintronics and in data storage applications.A series of prototype ME devices based on both direct and converse ME responses have been presented.The review concludes with a remark on the future possibilities and scientific challenges in thisfield.