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Nanovadi ir perspektīvi pielietojumiem vides sensoros, nanoelektromehāniskās (NEM) ierīcēs, saules baterijās u.c. Lai šādas ierīces varētu komercializēt, pašlaik tiek strādāts pie to sintēzes uzlabošanas un īpašību izpētes. Lai noteiktu, kuri nanovadi ir perspektīvi pielietošanai NEM slēdžos un sensoros, tika noteiktas to fizikālās īpašības. Darbā tika sintezēti Bi2Se3 nanovadi un izpētītas Bi2Se3, un Ge1-xSnx nanovadu un aerografīta tetrapodu fizikālās īpašības. Tika secināts, ka aerografīts nav piemērots lietošanai NEM slēdžos. Tika realizēti NEM slēdži ar Bi2Se3, Ge1-xSnx un Ge nanovadiem. Tiem tika izpētītas kontakta īpašības un tie tika optimizēti ar oscilējoša lauka palīdzību. Bi2S3 nanovadiem tika pētīta to iespējamā pielietošana vides mitruma sensoros. Atslēgvārdi: nanovadi, sensori, nanoelektromehāniski slēdži, aerografītsNanowires are perspective materials for applications in environment sensors, nanoelectromechanical (NEM) devices, solar batteries, etc. To commercialize these devices, work on optimizing synthesis and determination of their properties is carried out. To determine which nanowires are perspective for use in NEM switches and sensors, their physical properties were determined. Bi2Se3 nanowires were synthesized and the physical properties of Bi2Se3, Ge1-xSnx nanowires and aerographite tetrapods were investigated. NEM switches with Bi2Se3, Ge1-xSnx and Ge nanowires were realized. The contact properties of switches were investigated, and they were optimized by using oscillating electric field. Bi2S3 nanowires were investigated for their potential use in humidity sensors. Keywords: nanowires, sensors, nanoelectromechanical switches, aerographit

Review: Electrostatically actuated nanobeam-based nanoelectromechanical switches – materials solutions and operational conditions

Funding Information: This work was supported by the Latvian Council of Science (project No. 549/2012) and the University of Latvia project No. AAP2016/B043 and No. ZD2010/AZ19. Publisher Copyright: © 2018 Jasulaneca et al.; licensee Beilstein-Institut. License and terms: see end of document.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.publishersversionPeer reviewe

Fine-grained quartz from cryoconite holes of the Russell Glacier, southwest Greenland – a scanning electron microscopy study

Funding Information: Prof. Albertas Bitinas (Klaipėda) and Prof. Petras Šinkūnas (Vilnius) are thanked for valuable comments, which improve the final version of the manuscript. Research was supported by the SIA SunGIS (E. Kalińska-Nartiša), by the ERAF project No. 1.1.1.2/ VIAA/1/16/118 (K. Lamsters) and by University of Latvia project “Climate change and sustainable use of natural resources” (No. AAP2016/B041).We thank Reinis Pāvils for field assistance. Publisher Copyright: © Baltica 2017.The western ablation zone of the Greenland ice sheet is darker than the surrounding ice, because a higher amount of fine-grained particles, known as a cryoconite, occur. To date, biotic cryoconite components have gained a lot of attention, in contrast with mineral components, which have been studied to a limited extent. In this study, fine-grained quartz grains from the cryoconite holes of the Russell Glacier, southwest Greenland are, therefore, examined. Authors use scanning electron microscope to elucidate shape, surface character and origin of these mineral quartz particles. Triangular-faceted, sharp-edged grains dominate in most of the investigated samples, and originate from local sources, where grain-to-grain contact in the ice prevail. Grains with smooth corners and edges result from chemical weathering in meltwater of alkaline pH, in which quartz solubility significantly increases. However, part of these rounded grains is due to mechanical abrasion by wind action. Postsedimentary frost action is visible through grains entirely or partially covered by scaly-grained encrustation. Local processes and sources are largely responsible for aforementioned grain outlines. However, few grains with bulbous silica precipitation argue for a dry and warm climate, and distant, out-of-Greenland origin.publishersversionPeer reviewe

Immobilised humic substances as low-cost sorbents for emerging contaminants

Funding Information: Funding: This research was supported by the Latvian Council of Science, Fundamental and Applied Research Project No. lzp-2018/1-0009 “Properties and structure of peat humic substances and possibilities of their modification”. Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Environmental pollution with contaminants of emerging concern (CECs) is a worldwide problem that is receiving increasing attention. Although these substances have been released in the aquatic environment for a long time, wastewater treatment plants are still incapable of removing emerging contaminants completely. Consequently, trace metals, metalloids and pharmaceuticals, as well as surfactant leftovers, are often found in environmental samples. Environmentally friendly and cost-effective sorbents such as humic substances can be used for purification if their sorption properties are increased by immobilization. To our knowledge, immobilized humic substances have not been widely studied as sorbents up to now. In this study, humic substances were immobilized to obtain low-cost sorbents. The chosen methods for characterization of the obtained sorbents showed successful immobilization. Traditional pollutants, such as Cr(III) (a metal), As(V) (a metalloid) and chlorpromazine (a pharmaceutical), were used as representative contaminants. Sorption experiments were conducted using the batch system, and sorption was also studied based on the sorbent dosage, initial concentration of the studied element or substance, solution pH and sorption time. The results show that all the obtained immobilized humic substances in this study can be used as sorbents to remove contaminants from water. At the same time, from these humic substances, only those immobilized using iron compounds are suitable for the removal of arsenic.publishersversionPeer reviewe

Relative Humidity Dependent Resistance Switching of Bi2S3 Nanowires

Funding Information: This work was done within Latvian National Research Program IMIS 2 and University of Latvia Base/Performance Funding Projects nos. AAP2016/B043 and ZD2010/AZ19. Publisher Copyright: © 2017 Raimonds Meija et al.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.publishersversionPeer reviewe

Application of Ge nanowire for two-input bistable nanoelectromechanical switch

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.publishersversionPeer reviewe

Determination of Young's modulus of Sb2S3 nanowires by in situ resonance and bending methods

Publisher Copyright: © 2016 Jasulaneca et al.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.publishersversionPeer reviewe

Bi2Se3 Nanostructured Thin Films as Perspective Anodes for Aqueous Rechargeable Lithium-Ion Batteries

Funding Information: This research was funded by the European Regional Development Fund Project (ERDF) No. 1.1.1.1/19/A/139. Y.R. acknowledges the support of post-doctoral ERDF project No. 1.1.1.2/VIAA/4/20/694. V.L. also acknowledges the support of “Strengthening of the capacity of doctoral studies at the University of Latvia within the framework of the new doctoral model”, identification No. 8.2.2.0/20/I/006. A.S. acknowledges the support from the Institute of Solid State Physics, University of Latvia, which, as the Center of Excellence, has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2. Publisher Copyright: © 2022 by the authors.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.publishersversionPeer reviewe

Fabrication and Characterization of Double- and Single-Clamped CuO Nanowire Based Nanoelectromechanical Switches

Funding Information: This research was funded by the European Regional Development Fund (project no. 1.1.1.1/16/A/256, ?Creation of nanoelectromechanical switches?). Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.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.publishersversionPeer reviewe

Extra tension at electrode-nanowire adhesive contacts in nano-electromechanical devices

We report a strong tangential component of the reaction force at electrode to nanowire adhesive contact which was previously established using electrostatic attraction. The reaction force tangential component absolute value was found to be comparable to or even bigger than the corresponding normal component. This effect is important for understanding of the mechanics of nano-electromechanical devices. Both the experiment and the corresponding theory are presented. Fitting of the obtained analytical solutions to experimental data was used to measure the reaction force acting at the contact for several nanowire-electrode configurations