bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Fabrication and Characterization of Copper-Silica-Metal Resistive Switching Devices
Authors: Chen Wenhao , Patadia Arshey , Kozicki Michael N 
Published: February 2020

Switching in metal-oxide-metal devices has been studied since the late 1960s. A number of mechanisms have been identified to explain the change in resistance in such structures, including the formation of metallic filaments which bridge the insulating layer and provide a low resistance pathway between the electrodes. The low power “cationic” switching of copper-silica-metal devices, where the metal is a relatively inert conductor (e.g., tungsten), has gained attention in recent times as these materials are already present in the back-end-of-line (BEOL) of integrated circuits, making device integration simpler and less expensive than in the case of more “exotic” resistive switching systems. This technology is a variant of programmable metallization cell (PMC) or conductive-bridging random access memory (CBRAM). The switching mechanism involves the transport of copper ions in the oxide and their subsequent reduction to form the conducting metallic pathway. The oxidizable electrode provides ions into the reaction environment to maintain the supply of copper for the growing filament. The switching process is bipolar, in that a bias opposite to that used for writing is required to reverse the filament formation process to return the device to its high resistance state. The copper-silica-metal structures exhibit similar switching characteristics to previously-commercialized devices based on higher chalcogenide glasses, albeit at somewhat lower switching speed for the same programming voltage, while possessing inherently greater CMOS compatibility. Devices have been fabricated using either physical vapor deposition (PVD) or chemical vapor deposition (CVD) of the silica under conditions that allow the film to have a slightly lower density than a typical deposited oxide to promote ion transport and facilitate filament formation. A forming step is required to form a switchable region in the oxide and following this, sub-µs switching at low voltage and current is readily attainable.
In this talk we will report on the operational characteristics of these copper-silica-metal devices and the effect of different processing approaches on individual structures as well as crossbar arrays. We will also show the results of impedance spectroscopy analysis as they pertain to the physical structure of the devices. The applications of this technology range from active and passive non-volatile memories to neuromorphic elements and physical unclonable functions (PUFs) for physical and cyber security and these uses will be highlighted in the talk.
In Operando Characterization of Pt-TaOx-Ta Bipolar Vacancy Change Memories
Authors: Jacobs-Gedrim Robin Bay , Kotula Paul , Mook William Moyer , Bondi Robert James , Lowery Lisa Marie , Goeke Ronald S. , Smith Carl L. , Hughart David R. , James Conrad D. , Marinella Matthew J. 
Published: February 2020

Clear and unambiguous experimental observation of the physical processes leading to resistance change during formation and switching of bipolar valence change memories (VCM) remains one of the main remaining challenges in the characterization and understanding of resistive memory devices[1]. Presented here is a Scanning Transmission Electron Microscopy (STEM) Electron Energy Loss Spectroscopy (EELS) study which reveals a valence change filamentary switching mechanism during low-current bipolar resistive switching operation in Pt-TaOx-Ta resistive memory devices. No change in the film stack is observed in High Angle Annular Dark Field (HAADF) STEM during SET or RESET operation, which is consistent with expectations for a low-current operation VCM. A ~50 nm wide filamentary region is observed in EELS maps analyzed with multivariate statistical analysis disappearing on RESET operation and reappearing during SET operation. In this filamentary region, the Ta O2,3 edge is consistent with oxidized Ta but there is a sharp metallic plasmon feature which is blue shifted in accordance with our previous ab initiopredictions for metallic oxides.
[1] Yang Y and Lu W D 2016 Progress in the Characterizations and Understanding of Conducting Filaments in Resistive Switching Devices IEEE Transactions on Nanotechnology
15 465-72
(Invited) Resistance Switching in Silicon-Rich Silica: Electronic, Structural and Photonic Perspectives
Authors: Kenyon Anthony Joseph , Mehonic Adnan , Munde Manveer , Ng Wing Hung , Buckwell Mark , Montesi Luca , Zarudnyi Konstantin , Bosman Michel , Gerard Thomas , Shluger Alex L 
Published: February 2020

We present results from a study of resistance switching in silicon-rich silica – ie silicon dioxide containing an excess of silicon. We demonstrate that changes in resistance are the result of field-driven movement of oxygen, and that this can result in large-scale changes in oxide structure and stoichiometry. While resistance switching in oxides has been studied for a number of years as a route to non-volatile electronic memories, the optical response of such systems has remained largely unknown. Here we demonstrate that simple two-terminal MIM devices can be switched between different resistance states using a combination of electrical bias and optical stimulation. This opens up intriguing possibilities for novel classes of sensors.
We also demonstrate neuromorphic behaviour in our devices. Our electrical measurements show that, under the right conditions, the devices can be made to emulate some of the important behaviours of biological neurons – plasticity, for example. Taken together with the light sensitivity of these resistance switches, this opens up further possibilities for the development of light-triggered neural networks for such applications as pattern recognition and image classification.
(Invited) Optoelectronic Components Based on Semiconducting Transition Metal Dichalcogenides
Authors: Balicas Luis 
Published: February 2020

Transition metal dichalcogenides (TMDs) are layered compounds which display a wide range of electronic ground states, ranging from superconductivity, to semi-metallicity to wide gap semiconducting behavior. Here, we will discuss our previous studies on exfoliated semiconducting compounds, which indicate, for example, that field-effect transistors (FETs) based on few atomic layers of these materials (i.e. MoSe2 or WSe2), and their heterostructures, display a great potential for photo-sensing [1,2,3] and photovoltaic applications [4], since these compounds are prone to a particularly strong interaction with light. Other compounds like ReS2 display a gate-voltage controlled metal to insulator transition at room temperature, with the metallic state surviving down to quite low temperatures [5]. Ambipolar FETs based on ReSe2 show promise as voltage inverters [6]. Meanwhile, we find through a detailed structural analysis reveals that it is possible to produce solid solutions of, for example, Mo1-xWxTe2 which leads to a sharp phase-boundary between the semiconducting 2H- and the semi-metallic T
d- phases [7]. Based on a series of recent theoretical predictions, we argue that it might be possible to tune this phase-boundary through a gate voltage perhaps leading to phase change memory elements. Furthermore, given that 2H-MoTe2 display a band gap comparable to Si (≈ 1 eV) and that its semi-metallic counterpart is claimed to display topological properties, we argue that it might possible to produce optoelectronic components characterized by low dissipation if one is capable to harvest the topological nature of its semi-metallic phase.
[1] N. Pradhan et al., ACS Appl. Mater. & Interfaces 7, 22, 12080 (2015).
[2] N. Pradhan et al., 2D Mater. 3, 041004 (2016).
[3] N.R. Pradhan et al., Adv. Electron. Mater. 1, 10, 1500215 (2015)
[4] S. Memaran et al., Nano Lett. 15, 7532 (2015)
[5] N. Pradhan et al., Nano Lett. 15, 8377 (2015)
[6] N. R. Pradhan (unpublished)
[7] D. Rhodes et al., Nano Lett. 17, 1616 (2017)
(Invited) Novel Electronic Transport in Topological Semimetals
Authors: Yu Wenlong , Jiang Yuxuan , Yang Jeremy , Dun Zhiling , Zhou Haidong , Jiang Zhigang , Lu Ping , Pan Wei 
Published: February 2020

Since the discovery of graphene, Dirac systems have attracted considerable attention due to their extraordinary properties. Recently, Dirac semimetals (DSs)-a new quantum state of matter-have been proposed. DSs can be viewed as an analogue of graphene but with linear energy dispersion in all three momentum directions. Due to the distinct electronic properties, DSs have been a fertile playground in discovering novel phenomena. In addition, it is possible to realize topological superconductivity in DSs, which plays a key role in next generation quantum computation. Shortly after theoretical predictions, several materials have been experimentally confirmed to be DSs, such as Cd3As2 and ZrTe5. Here, we report magneto-transport studies on Cd3As2 and ZrTe5. Shubnikov–de Haas oscillations were observed in both materials. A non-trivial Berry’s phase of π was obtained indicating the existence of Dirac fermions. However, angular dependence measurement shows different results in these two materials. Dirac fermions in ZrTe5 show a two-dimensional nature while in Cd3As2 they behave like three-dimensional particles. In addition, we observed supercurrent in superconductor (Al)–DS (Cd3As2)–superconductor (Al) junctions. Realizing topological superconductivity is an essential step towards finding Majorana fermions which are believed to be building blocks for quantum computers.
Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
Aluminum Intercalation and High Capacity of Two-Dimensional (2D) Vanadium Carbide (MXene) Cathode in Rechargeable Aluminum Batteries
Authors: VahidMohammadi Armin , Beidaghi Majid 
Published: February 2020

Rechargeable aluminum batteries that utilize aluminum metal as the anode are one of the most promising alternative energy storage systems for current Li-ion batteries that suffer from flammability, safety issues, high cost, and limited lithium resources. Aluminum is the most abundant metal in Earth’s crust, offers three-electron redox reactions in electrochemical systems, and has the highest theoretical volumetric capacity of 8040 mAh cm-3 among all metals and reasonably high theoretical gravimetric capacity of 2980 mAh g-1. Also, aluminum metal can be handled in the open air; thus, aluminum batteries benefit from high safety and facile cell fabrication and operation compared to lithium and sodium battery systems [1]. However, development of these battery systems is mostly hindered by a lack of cathode materials that can host aluminum cations and offer high capacities and insertion potentials.
In this presentation, we show reversible intercalation of aluminum in two-dimensional (2D) vanadium carbides (V2C), a member of MXene family of materials, as a potential high-performance cathode material for rechargeable aluminum batteries. MXenes with a general formula of Mn+1Xn (n=1,2, and 3, M is a transition metal, and X is carbon and/or nitrogen) are a family of 2D transition metal carbides and/or carbonitrides that are produced by selective etching of the A layer elements (i.e. Al) from MAX phases (i.e. V2AlC), a large group of layered ternary carbides, nitrides, and carbonitrides [2-4]. The Aluminum battery cells incorporating V2C MXene as cathode operates by electrochemical deposition and dissolution of aluminum at the anode and intercalation/de-intercalation of Al3+ ions in between the layers of 2D nanosheets of MXene cathode. Our study shows that through a careful and proper fabrication of electrode structure, V2C cathodes can deliver reversible capacities more than ~ 200 mAh g-1 at a high charge and discharge rate of 100 mA g-1, comparable to current cathode materials for lithium and sodium-ion batteries. V2C cathode exhibits a high Coulombic efficiency of above 95% and delivers a good rate capability in a 1.7 V potential window. We also show that change in the oxidation state of the transition metal in the MXene structure plays an important role in charge storage mechanism of MXenes as cathode materials for Aluminum batteries.

Keywords: 2D, Vanadium carbide, MXenes, Aluminum battery

References

1. G. A. Elia, et al., Adv. Mater. 28, 7564-7579 (2016).
2. M. Naguib, et al., ACS Nano. 6, 1322–1331 (2012).
3. B. Anasori, M. R. Lukatskaya, Y. Gogotsi, Nat. Rev. Mater.2, 16098 (2017).
4. M. R. Lukatskaya et al., Science. 341, 1502–5 (2013).
Solid State Batteries and the Mechanical Properties of Lithium
Authors: Masias Alvaro , Sakamoto Jeff 
Published: February 2020

The current revival of electrified vehicles seen in recent years has been enabled by significant advances in lithium ion batteries. This technology has progressed steadily at approximately 8% per year improvement in specific energy (Wh/kg). The achievement and maintenance of this specific energy growth rate is the result of massive, global progress in battery research, development and manufacturing. However, to promote the rapid displacement of petroleum fuels from the transportation sector, the current evolutionary growth in battery energy may be insufficient.
Amongst candidate next generation battery approaches, solid state (SS) is one of the most versatile and promising technologies. SS batteries can enable improvements in specific energy mainly by allowing for the use of high energy (due to its low electronegativity and high capacity) lithium metal anodes. A SS separator of comparable dimensions as a conventional polyolefin separator could lead to ~50% improvement in cell energy density by enabling metallic lithium anodes [1]. However, elemental lithium is pyrophoric & difficult to stabilize owing to its strongly reactive nature, and as a result its use as a reliable rechargeable battery electrode has proven challenging despite research efforts for more than 50 years. The development of a SS electrolyte material that could introduce lithium metal anodes would provide rechargeable batteries with a step change improvement in specific energy, leading to longer range EVs due to lighter/smaller batteries.
The research and selection of a solid state material requires balancing many different and often competing requirements simultaneously, which no one material can satisfy currently. Additionally, some SS electrolytes have shown a tendency to allow for lithium dendrites to penetrate their structure once a critical charge density (CCD) has been reached [2]. The role lithium's mechanical properties play in the dendrite growth mechanism is poorly understood and is the focus of this work. The literature features limited reports of lithium's elastic modulus, with tension values as low as 1.9, commonly referencing bending values of 5.0 and single crystal calculations as high as 11.5 GPa [3,4,5]. This work will explore further the mechanical properties of lithium in context of the actual SS battery environment where additional properties such as creep may dominate.
REFERENCES
[1] McCloskey, B. et al. J Phys. Chem. Lett. 6 (2015) 4581-4588.
[2] Sharafi, A. et al. J. Power Sources, 302 (2016) 135-139.
[3] Schultz, R. Technical Report FERMILAB-TM-2191. (2002).
[4] Bridgeman, P. Proc Am Acad Arts Sci., 57 (1922) 41-66.
[5] Robertson, W. et al. Phys. Rev., 117 (1960) 440-442.
Synergistic Effects from Substrate and Electrolytes on Li Deposition
Authors: Lochala Joshua Andrew , Wu Bingbin , Tarverne Tyler , Xiao Jie 
Published: February 2020

Li metal has been considered the “holy grail” anode materials. Li metal has the most negative potential with an extremely high theoretical specific capacity of 3860 mA h g−1.[1] It is, however, plagued with multiple challenges which need solutions before the realization of this material. Li metal has two main failure mechanisms, one is the random growth of detrimental dendrites, which can lead to rapid thermal runoff, i.e. Galaxy Note 7.[2] The other issue that arises upon cycling is pulverization of lithium metal through none uniform plating, leading to an increase in solid electrolyte formation(SEI) and thereby the increase in voltage polarization within the cell.[3] Both Li failure mechanisms are rooted in the uneven distribution of SEI layers whose properties vary depending on the location of SEI formed.[4] The initial surface chemistry on Li metal influences SEI formation in the very beginning. In this work, electrochemical deposition of Li metal on specific substrate has been performed to understand the nucleation and growth of Li crystals. Electrolyte and substrate have been identified to have synergistic effects on the morphology and efficiency of deposited Li. The fundamental mechanisms that dictates the smooth Li deposition will be discussed.

References:

1) Xu, W., Wang, J., Ding, F., Chen, X., Nasybulin, E., Zhang, Y. and Zhang, J.G., 2014. Lithium metal anodes for rechargeable batteries. Energy & Environmental Science, 7(2), pp.513-537.
2) Cohen, Y.S., Cohen, Y. and Aurbach, D., 2000. Micromorphological studies of lithium electrodes in alkyl carbonate solutions using in situ atomic force microscopy. The Journal of Physical Chemistry B, 104(51), pp.12282-12291.
3) Lu, D., Shao, Y., Lozano, T., Bennett, W.D., Graff, G.L., Polzin, B., Zhang, J., Engelhard, M.H., Saenz, N.T., Henderson, W.A. and Bhattacharya, P., 2015. Failure mechanism for fast‐charged lithium metal batteries with liquid electrolytes. Advanced Energy Materials, 5(3).
4) Aurbach, D., Zinigrad, E., Cohen, Y. and Teller, H., 2002. A short review of failure mechanisms of lithium metal and lithiated graphite anodes in liquid electrolyte solutions. Solid state ionics, 148(3), pp.405-416.
(Invited) Band Gap Engineering and Optoelectronic Performance of Indium Gallium Arsenide Nanobelts
Authors: Zhang Xuehong , Yang Tiefeng , Pan Anlian 
Published: February 2020

Low dimensional III-V compound semiconductors, such as GaAs, InAs, and their ternary alloys, exhibit unique optical and electronic properties. Their abilities of efficient carrier transport, light emission, and detection means they can be used in integrated transistors, lasers, light-emitting diodes, and detectors for infrared communications [1-3]. Very recently, intense research has been directed toward the fabrication and application of the III-V nanoplates/sheets owing to their realization of multiterminal electronic devices such as Hall bars, quantum point contacts, and so forth. However, the influence of growth condition on the formation of these nanostructures is still unclear. Furthermore, these nanoplates/sheets generally suffer from small and irregular morphology, demonstrating the difficulties in the controlled growth. Importantly, realizing the continuously tunable composition and heterojunction of these nanostructures remains great challenges, particularly for the technologically important InGaAs. It's well known that InGaAs is of great interest for high-performance device in electronics and optoelectronics [4,5]. Unfortunately, the transistors and photodetectors based on low dimensional InGaAs nanostructures still need improvement due to their low on/off ratio, poor photoresponsivity, and so on. To address these problems, we have realized the controlled growth of high-quality single-crystal InGaAs nanobelts with fully tunable composition/bandgap via an orientation selective vapor growth. Density functional theory calculations reveal that the surface energy variation induced by the chemical potential of arsenic (μ
As) is critical for the formation of these nanobelts. When configured into transistors, the InGaAs nanobelt devices exhibit impressive electrical properties with the turn on/off ratio of 2×107, better than any value reported for a InGaAs nanowire device to date. The broadband phototransistor (covering 405-1,550 nm) were further fabricated with an ultrahigh photoresponsivity of >8000 A/W and an external quantum efficiency of >106 %, both of which are much higher than those of all the reported InGaAs nanowire photodetectors. These results suggest that the novel InGaAs nanobelts may open up new opportunities for various applications in integrated electronics, optoelectronics, and quantum electronics.
References:
[1] Xuehong Zhang, Xiao Wang, Anlian Pan et

al
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Mater., 2017, 1604431.
[2] Xinliang Chen, Xuehong Zhang, Anlian Pan et al., Nanotechnology, 2016, 27, 50.
[3] Huang Tan, Xuehong Zhang, Anlian Pan et al., Nano-Micro Lett., 2016, 8, 29-35.
[4] Liang Ma, Xuehong Zhang, Anlian Pan et al., Semicond. Sci. Technol., 2015, 30, 105033.
[5] Liang Ma, Xiujuan Zhuang, Anlian Pan et al., Nano Lett., 2014, 14，694–698.
[6] Pinyun Ren, Qinglin Zhang, Anlian Pan et al., Adv. Mater., 2014, 26, 7444-7449.
(Invited) Rectifiers, Mos Diodes and LEDs Made of Fully Porous GaN Produced by Chemical Vapor Deposition
Authors: Carvajal Joan J. , Mena Josue , Aixart Jordi , Díaz Francesc , Aguiló Magdalena 
Published: February 2020

GaN is an important wide band-gap semiconductor in electronics and optoelectronics. In its porous form is particularly interesting for developing optoelectronic devices with improved efficiency, such as LEDs with enhanced efficiency and sensors with enhanced sensitivity.
Through chemical vapour deposition (CVD) [1], we have shown that it is possible to produce nanoporous GaN without any etching or chemical post-growth treatment, with the porosity being present only on the (0001) face of the material. Low resistivity ohmic Pt and Au metallic contacts were demonstrated on porous n-type GaN by the formation of intermetallic seed layers through the vapour-solid-solid (VSS) mechanism [2]. Also, we have been able to develop p-type porous GaN by doping with Mg, with a charge carrier concentration of the order of 1018 cm-3 [3]. By tuning the concentration of Mg, introduced as Mg2N3 in the CVD system, it has been possible to form a polycrystalline high-k oxide between an ohmic metallic alloy interlayer contact and the porous GaN, while maintaining a clean interface, that allowed to fabricate a MOS-type diode on silicon in a single growth regime [4].
Through the careful selection of the substrate it has also been possible to produce porous GaN epitaxial layers [5] that allow for the fabrication of high quality partially and fully porous GaN rectifying p-n junctions, through a two step CVD process, and show their behaviour as diodes with effective uniform conduction under a green technology [6]. Here, we will also present the recent results we obtained in the light emission of these structures. Thus, these porous junctions have potential applications in high brightness unencapsulated LEDs with enhanced light emitting properties and high surface area sensors with improved sensitivity.
[1] Carvajal & Rojo, Crystal Growth Des., 9 (2009) 320
[2] Bilousov et al., ACS Appl. Mater. Interfaces 4 (2012) 6927
[3] Bilousov et al., Appl. Phys. Lett. 103 (2013) 112103
[4] Bilousov et al., Chem. Mater. 26 (2014) 1243
[5] Bilousov et al., CrystEngComm 16 (2014) 10255; Bilousov et al., ACS Appl. Mater. Interfaces 6 (2014) 17954
[6] Carvajal et al., ECS Transactions 66 (2015) 163

Figure 1