3770
J. Phys. Chem. C 2010, 114, 3770–3775
Conductance Response of Tin Nanowires to the External Axial Pressure Load F. Gao,† H. Li,*,†,‡ X. Q. Zhang,† Y. F. Li,‡ and K. M. Liew§ Key Laboratory for Liquid-Solid Structural EVolution and Processing of Materials, Ministry of Education, Shandong UniVersity, Jinan 250061, China, Physics Department, Ocean Uniυersity of China, Qingdao, China, and Department of Building and Construction, City UniVersity of Hong Kong, Hong Kong ReceiVed: September 25, 2009; ReVised Manuscript ReceiVed: December 14, 2009
Five different optimized Sn nanowires embedded in single-walled carbon nanotubes (SWCNTs) are obtained by means of molecular dynamics (MD) simulation. Growth of Sn nanowires follows a helical or parallel pattern in confined space. Optimized Sn nanowires subject to compression are investigated. Results reveal that a four-strand-parallel nanowire can resist the highest pressure load among these five kinds of nanowires studied. The growth pattern of a nanowire determines its conductance response to the pressure load. Interestingly, conductance of double-helical and four-strand-parallel nanowires (which have an even number of atomic chains) increases with pressure load, while the conductance of three-strand-helical and five-strandhelical nanowires (which have an odd number of atomic chains) is found to decrease with pressure load. On the basis of the conductance response of the nanowire to the external pressure load, nanosensors can be fabricated to detect the stress and strain of nanostructured materials. I. Introduction Over the past decade, considerable effort has been made to explore various heterostructures with a combination of carbon nanotubes (CNTs) and nanowires (NWs) because of their unique structures. NWs, encapsulated inside the multiwalled CNTs are promising materials for applications in electrode materials, field emitters, nanoelectronic devices, and nanosensors.1–3 Sn, in bulk or powdered form, is also widely used as solder material due to its good conductance and the need for lead-free electronics packaging applications.4 Furthermore, Sn nanostructured materials have been shown to exhibit enhanced capacity and cycling stability when alloyed with lithium for secondary battery applications.5 An example of Sn-based nanostructure is small Sn particles (100 nm) contained in carbon hollow spheres, which were suggested as a potential solution to the capacity fading problem of Sn-based lithium storage compounds.6 Metallic nanowires can be used as interconnecting materials in nanoelectronic devices in the future. In such interconnects, interfacial transport and reactions at nanojunctions will be very significant due to the increased surface area and will strongly affect the quality and lifetime of the nanodevices.7 Onedimensional Sn wires with diameters smaller than the phase coherence lengths have been demonstrated to have superconducting features far below the superconducting transition temperature.8 Superconducting low dimensional systems are the natural choice for fast and sensitive infrared detection because of their quantum nature and the low noise.9 Superconducting tin nanowires10 have been already synthesized but are not suitable for handling since they are sensitive to oxidation. It is extremely difficult to fabricate an electronic device with a single monocrystalline Sn nanowire with the help of electron beam lithography, since the wires undergo strong oxidation when released from the porous membrane.11 Furthermore, Sn wires with diameters smaller than 70 nm are very unstable at room * Corresponding author,
[email protected]. † Shandong University. ‡ Ocean University of China. § City University of Hong Kong.
temperature, resulting in fragmentation within a few hours during sample fabrication under condition of external pressure load.12 Therefore, electronic measurements on a single very thin (
