Browsing by Author "Erts, Donats"

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    Application of Ge nanowire for two-input bistable nanoelectromechanical switch
    (2013) Andzane, Jana; Prikulis, Juris; Meija, Raimonds; Kosmaca, Jelena; Biswas, Subhajit; Holmes, Justin D.; Erts, Donats
    Recently, several research groups presented bistable two-terminal nanoelectromechanical switches based on individual single-clamped active element. All presented devices had one input electrode. Similar devices having two or more input electrodes have not been yet investigated. In this work we present the two-input bistable controlled nanoelectromechanical switch based on an individual single-clamped Ge nanowire. The switch is realised using in-situ SEM technique and operating due to balancing of electrostatic, adhesion and elastic forces. The operation conditions of the device are investigated and presented. The advantages and drawbacks of the device are discussed.
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    Bi2Se3 Nanostructured Thin Films as Perspective Anodes for Aqueous Rechargeable Lithium-Ion Batteries
    (2022-10) Lazarenko, Vitalijs; Rublova, Yelyzaveta; Meija, Raimonds; Andzane, Jana; Voikiva, Vanda; Kons, Artis; Sarakovskis, Anatolijs; Viksna, Arturs; Erts, Donats
    In recent years, aqueous rechargeable lithium-ion batteries (ARLIBs) have attracted attention as an alternative technology for electrical storage. One of the perspective battery anode materials for application in ARLIBs is Bi2Se3, which has already shown good perspectives in the application of conventional lithium-ion batteries (LIBs) that use organic electrolytes. In this study, the electrochemical properties of Bi2Se3 thin films with two different layers on the electrode surface—the solid electrolyte interphase (SEI) and the Bi2O3 layer—were investigated. The results of this work show that the formation of the SEI layer on the surface of Bi2Se3 thin films ensures high diffusivity of Li+, high electrochemical stability, and high capacity up to 100 cycles, demonstrating the perspectives of Bi2Se3 as anode material for ARLIBs.
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    Determination of Young's modulus of Sb2S3 nanowires by in situ resonance and bending methods
    (2016) Jasulaneca, Liga; Meija, Raimonds; Livshits, Alexander I.; Prikulis, Juris; Biswas, Subhajit; Holmes, Justin D.; Erts, Donats
    In this study we address the mechanical properties of Sb2S3 nanowires and determine their Young's modulus using in situ electricfield- induced mechanical resonance and static bending tests on individual Sb2S3 nanowires with cross-sectional areas ranging from 1.1·104 nm2 to 7.8·104 nm2. Mutually orthogonal resonances are observed and their origin explained by asymmetric cross section of nanowires. The results obtained from the two methods are consistent and show that nanowires exhibit Young's moduli comparable to the value for macroscopic material. An increasing trend of measured values of Young's modulus is observed for smaller thickness samples.
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    Distribution of Iron Nanoparticles in Arrays of Vertically Aligned Carbon Nanotubes Grown by Chemical Vapor Deposition
    (2022-10) Okotrub, Alexander V.; Gorodetskiy, Dmitriy V.; Guselnikov, Artem V.; Kondranova, Anastasiya M.; Bulusheva, Lyubov G.; Korabovska, Mariya; Meija, Raimonds; Erts, Donats
    Arrays of aligned carbon nanotubes (CNTs) are anisotropic nanomaterials possessing a high length-to-diameter aspect ratio, channels passing through the array, and mechanical strength along with flexibility. The arrays are produced in one step using aerosol-assisted catalytic chemical vapor deposition (CCVD), where a mixture of carbon and metal sources is fed into the hot zone of the reactor. Metal nanoparticles catalyze the growth of CNTs and, during synthesis, are partially captured into the internal cavity of CNTs. In this work, we considered various stages of multi-walled CNT (MWCNT) growth on silicon substrates from a ferrocene–toluene mixture and estimated the amount of iron in the array. The study showed that although the mixture of precursors supplies evenly to the reactor, the iron content in the upper part of the array is lower and increases toward the substrate. The size of carbon-encapsulated iron-based nanoparticles is 20–30 nm, and, according to X-ray diffraction data, most of them are iron carbide Fe3C. The reasons for the gradient distribution of iron nanoparticles in MWCNT arrays were considered, and the possibilities of controlling their distribution were evaluated.
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    Fabrication and Characterization of Double- and Single-Clamped CuO Nanowire Based Nanoelectromechanical Switches
    (2021-01) Jasulaneca, Liga; Livshits, Alexander I.; Meija, Raimonds; Kosmaca, Jelena; Sondors, Raitis; Ramma, Matiss M.; Jevdokimovs, Daniels; Prikulis, Juris; Erts, Donats
    Electrostatically actuated nanoelectromechanical (NEM) switches hold promise for operation with sharply defined ON/OFF states, high ON/OFF current ratio, low OFF state power consumption, and a compact design. The present challenge for the development of nanoelectromechanical system (NEMS) technology is fabrication of single nanowire based NEM switches. In this work, we demonstrate the first application of CuO nanowires as NEM switch active elements. We develop bottom-up and top-down approaches for NEM switch fabrication, such as CuO nanowire synthesis, lithography, etching, dielectrophoretic alignment of nanowires on electrodes, and nanomanipulations for building devices that are suitable for scalable production. Theoretical modelling finds the device geometry that is necessary for volatile switching. The modelling results are validated by constructing gateless double-clamped and single-clamped devices on-chip that show robust and repeatable switching. The proposed design and fabrication route enable the scalable integration of bottom-up synthesized nanowires in NEMS.
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    Gold nanowire synthesis by semi-immersed nanoporous anodic aluminium oxide templates in potassium dicyanoaurate-hexacyanoferrate electrolyte
    (2014-11-01) Baitimirova, Margarita; Pastare, Anita; Katkevics, Juris; Viksna, Arturs; Prikulis, Juris; Erts, Donats
    The synthesis reaction of potassium dicyanoaurate-hexacyanoferrate electrolyte and the pertinence of this electrolyte for gold nanowire synthesis are reported. Gold nanowires were synthesised in anodic aluminium oxide (AAO) nanopores using an improved design of the electrochemical cell. AAO templates with thick gold layers were placed on the surface of the electrolyte, thus the ends of the nanopores were opened, allowing the electrolyte to freely diffuse into the nanopores, extruding gases. The presented procedure simplifies the preparation before nanowire synthesis: AAO templates before synthesis do not need to degas and isolate themselves from contact with the electrolyte by a parafilm or a non-conductive adhesive. A considerably faster nanowire growth in the given conditions in the case of a semi-immersed AAO template when compared with the complete immersion method is reported. For comparison with literature data, gold nanowires were synthesised by the classical electrochemical cell using potassium dicyanoaurate-citrate electrolyte. Long, smooth and high purity nanowires were obtained using semi-immersed templates.
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    Nanomechanics of individual aerographite tetrapods
    (2017-04-12) Meija, Raimonds; Signetti, Stefano; Schuchardt, Arnim; Meurisch, Kerstin; Smazna, Daria; Mecklenburg, Matthias; Schulte, Karl; Erts, Donats; Lupan, Oleg; Fiedler, Bodo; Mishra, Yogendra Kumar; Adelung, Rainer; Pugno, Nicola M.
    Carbon-based three-dimensional aerographite networks, built from interconnected hollow tubular tetrapods of multilayer graphene, are ultra-lightweight materials recently discovered and ideal for advanced multifunctional applications. In order to predict the bulk mechanical behaviour of networks it is very important to understand the mechanics of their individual building blocks. Here we characterize the mechanical response of single aerographite tetrapods via in situ scanning electron and atomic force microscopy measurements. To understand the acquired results, which show that the overall behaviour of the tetrapod is governed by the buckling of the central joint, a mechanical nonlinear model was developed, introducing the concept of the buckling hinge. Finite element method simulations elucidate the governing buckling phenomena. The results are then generalized for tetrapods of different size-scales and shapes. These basic findings will permit better understanding of the mechanical response of the related networks and the design of similar aerogels based on graphene and other two-dimensional materials.
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    Relative Humidity Dependent Resistance Switching of Bi2S3 Nanowires
    (2017) Meija, Raimonds; Kunakova, Gunta; Prikulis, Juris; Varghese, Justin M.; Holmes, Justin D.; Erts, Donats
    Electrical properties of Bi2S3 nanowires grown using a single source precursor in anodic aluminum oxide templates are sensitive to the relative humidity in an inert gas environment. Dynamic sensing dependency is obtained and shows presence of spontaneous resistance switching effect between low and high relative humidity states. Employing the thermionic field emission theory, heights of Schottky barriers are estimated from the current-voltage characteristics and in relation to the humidity response. The change of Schottky barrier height is explained by local changes in physically adsorbed water molecules on the surface of the nanowire.
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    Review: Electrostatically actuated nanobeam-based nanoelectromechanical switches – materials solutions and operational conditions
    (2018-01-25) Jasulaneca, Liga; Kosmaca, Jelena; Meija, Raimonds; Andzane, Jana; Erts, Donats
    This review summarizes relevant research in the field of electrostatically actuated nanobeam-based nanoelectromechanical (NEM) switches. The main switch architectures and structural elements are briefly described and compared. Investigation methods that allow for exploring coupled electromechanical interactions as well as studies of mechanically or electrically induced effects are covered. An examination of the complex nanocontact behaviour during various stages of the switching cycle is provided. The choice of the switching element and the electrode is addressed from the materials perspective, detailing the benefits and drawbacks for each. An overview of experimentally demonstrated NEM switching devices is provided, and together with their operational parameters, the reliability issues and impact of the operating environment are discussed. Finally, the most common NEM switch failure modes and the physical mechanisms behind them are reviewed and solutions proposed.
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    Surface structure promoted high-yield growth and magnetotransport properties of Bi2Se3 nanoribbons
    (2019-12-01) Kunakova, Gunta; Meija, Raimonds; Andzane, Jana; Malinovskis, Uldis; Petersons, Gvido; Baitimirova, Margarita; Bechelany, Mikhael; Bauch, Thilo; Lombardi, Floriana; Erts, Donats
    In the present work, a catalyst-free physical vapour deposition method is used to synthesize high yield of Bi2Se3 nanoribbons. By replacing standard glass or quartz substrates with aluminium covered with ultrathin porous anodized aluminium oxide (AAO), the number of synthesized nanoribbons per unit area can be increased by 20–100 times. The mechanisms of formation and yield of the nanoribbons synthesized on AAO substrates having different arrangement and size of pores are analysed and discussed. It is shown that the yield and average length of the nanoribbons can base tuned by adjustment of the synthesis parameters. Analysis of magnetotransport measurements for the individual Bi2Se3 nanoribbons transferred on a Si/SiO2 substrate show the presence of three different populations of charge carriers, originating from the Dirac surface states, bulk carriers and carriers from a trivial 2DEG from an accumulation layer at the Bi2Se3 nanoribbon interface with the substrate.