Low-Vacuum Catalyst-Free Physical Vapor Deposition and Magnetotransport Properties of Ultrathin Bi2Se3 Nanoribbons

In this work, a simple catalyst-free physical vapor deposition method is optimized by adjusting source material pressure and evaporation time for the reliable obtaining of freestanding nanoribbons with thicknesses below 15 nm. The optimum synthesis temperature, time and pressure were determined for an increased yield of ultrathin Bi2Se3 nanoribbons with thicknesses of 8–15 nm. Physical and electrical characterization of the synthesized Bi2Se3 nanoribbons with thicknesses below 15 nm revealed no degradation of properties of the nanoribbons, as well as the absence of the contribution of trivial bulk charge carriers to the total conductance of the nanoribbons

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

Properties of semiconductor nanowires and their applications in nanoelectromechanical systems

Nanovadi ir viendimensionāli nanomateriāli ar rādiusu nanometros un garumu mikrometros. Nanovadi ir vēlamas komponentes nanoelektromehāniskās (NEM) ierīcēs, piemēram, slēdžos. Šajās ierīces nanovadi kalpo kā aktīvie elementi, kas, mehāniski pārslēdzoties, spēj pārslēgt elektriskās ķēdes, tāpēc ir svarīgas nanovadu mehāniskās un elektriskās īpašības. Darbā tika pētīti CuO, GeSn un Bi2Se3 nanovadi ar mērķi tos pielietot NEM ierīcēs. Tika veikta CuO nanovadu sintēze ar termiskās oksidācijas metodi. Izanalizēta dažādu sintēzes parametru, piemēram, ūdens tvaika un elektriskā lauka, ietekme uz nanovadu morfoloģiju. Tika izpētītas CuO nanovadu mehāniskās īpašības. GeSn nanovadu Junga modulis tika noteikts ar rezonanses metodi in-situ skenējošajā elektronu mikroskopā (SEM). Demonstrētas perspektīvas CuO un Bi2Se3 nanovadu integrēšanai NEM slēdžos.Nanowires (NWs) are one-dimensional nanomaterials with radii in the scale of nanometers and lengths in the scale of micrometers. NWs are desirable components in nanoelectromechanical (NEM) devices, such as switches. NWs are the active element in these devices, diverting current by altering their position, thus their mechanical and electrical properties are important. CuO, GeSn and Bi2Se3 NWs were investigated for use in NEM devices. CuO NWs were synthesized via thermal oxidation method. Various synthesis parameters, such as the presence of water vapor or an applied electric field, were investigated for their effect on NW morphology. Mechanical properties of CuO NWs were investigated. Young’s modulus of GeSn NWs was determined via in-situ SEM resonance method. Perspective integration of CuO and Bi2Se3 NWs in to NEM switches was demonstrated

Size Distribution, Mechanical and Electrical Properties of CuO Nanowires Grown by Modified Thermal Oxidation Methods

Size distribution, Young’s moduli and electrical resistivity are investigated for CuO nanowires synthesized by different thermal oxidation methods. Oxidation in dry and wet air were applied for synthesis both with and without an external electrical field. An increased yield of high aspect ratio nanowires with diameters below 100 nm is achieved by combining applied electric field and growth conditions with additional water vapour at the first stage of synthesis. Young’s moduli determined from resonance and bending experiments show similar diameter dependencies and increase above 200 GPa for nanowires with diameters narrower than 50 nm. The nanowires synthesized by simple thermal oxidation possess electrical resistivities about one order of magnitude lower than the nanowires synthesized by electric field assisted approach in wet air. The high aspect ratio, mechanical strength and robust electrical properties suggest CuO nanowires as promising candidates for NEMS actuators

Synthesis of CuO and Bi2Se3 nanowires with controlled properties for applications as active elements of nanodevices

Pusvadītāju nanovadi ir perspektīvi materiāli pielietojumiem nanoelektromehāniskās (NEM) ierīcēs. Lai nanovadi būtu piemēroti industriāliem pielietojumiem, nepieciešams izstrādāt tādas sintēzes metodes, kas nodrošinātu paredzamu iznākumu, morfoloģiju, elektriskās un mehāniskās īpašības sintezētajiem nanovadiem. Lai nodrošinātu NEM slēdžu darbību ekstrēmos apstākļos, nepieciešams iegūt plašā temperatūru diapazonā pielietojamus nanovadus. Pielietojumiem istabas temperatūrā tika pētīti CuO un ar Sn dopēti Ge nanovadi. CuO nanovadi tika sintezēti ar pārveidotu termiskās oksidācijas metodi. Tika izpētīts, kā, papildinot termisko oksidāciju ar elektrisko lauku un ūdens tvaiku klātbūtni, iespējams kontrolēt sintezēto CuO nanovadu ģeometrisko parametru sadalījumu un elektriskās īpašības. Tika izpētītas ar Sn dopētu Ge nanovadu mehāniskās īpašības. Darbā ar fizikālās tvaiku nogulsnēšanas metodi tika sintezēti Bi2Se3 nanovadi. Tika izpētīta Au katalizatora ģeometrijas ietekme uz sintezēto Bi2Se3 nanovadu iznākumu, morfoloģiju un elektriskajām īpašībām. Sintezētie nanovadi tika sekmīgi izmantoti NEM slēdžu izveidē. Parādīta CuO nanovada NEM slēdža darbība istabas temperatūrā. Parādīta Bi2Se3 nanovada NEM slēdža darbība 5 K temperatūrā.Semiconductor nanowires are promising materials for applications in nanoelectromechanical (NEM) devices. For nanowires to be suitable for industrial applications, it is necessary to develop synthesis that provide a predictable yield, morphology, electrical and mechanical properties of the synthesized nanowires. To ensure the operation of NEM switches in extreme conditions, it is necessary to obtain nanowires that can be used in a wide temperature range. CuO and Sn doped Ge nanowires were studied for applications at room temperature. Control of the distribution of geometric parameters and electrical propertias via applying an electric field and adding water vapor during synthesis was investigated. The mechanical properties of Sn doped Ge nanowires were investigated. Bi2Se3 nanowires were synthesized with the physical vapor deposition method. The influence of Au catalyst geometry on the yield, morphology and electrical properties of the synthesized Bi2Se3 nanowires was investigated. The as-synthesized nanowires were successfully employed in NEM switches. The operation of a CuO nanowire NEM switch in room temperature was demonstrated. The operation of a Bi2Se3 nanowire NEM switch in 5 K temperatura was demonstrated

Enhanced thermoelectric properties of self-assembling ZnO nanowire networks encapsulated in nonconductive polymers

Abstract The near-room temperature thermoelectric properties of self-assembling ZnO nanowire networks before and after encapsulation in nonconductive polymers are studied. ZnO nanowire networks were synthesized via a two-step fabrication technique involving the deposition of metallic Zn networks by thermal evaporation, followed by thermal oxidation. Synthesized ZnO nanowire networks were encapsulated in polyvinyl alcohol (PVA) or commercially available epoxy adhesive. Comparison of electrical resistance and Seebeck coefficient of the ZnO nanowire networks before and after encapsulation showed a significant increase in the network's electrical conductivity accompanied by the increase of its Seebeck coefficient after the encapsulation. The thermoelectric power factor (PF) of the encapsulated ZnO nanowire networks exceeded the PF of bare ZnO networks by ~ 5 and ~ 185 times for PVA- and epoxy-encapsulated samples, respectively, reaching 0.85 μW m−1 K−2 and ZT ~ 3·10–6 at room temperature, which significantly exceeded the PF and ZT values for state-of-the-art non-conductive polymers based thermoelectric flexible films. Mechanisms underlying the improvement of the thermoelectrical properties of ZnO nanowire networks due to their encapsulation are discussed. In addition, encapsulated ZnO nanowire networks showed excellent stability during 100 repetitive bending cycles down to a 5 mm radius, which makes them perspective for the application in flexible thermoelectrics