Quantum transport properties of ultrathin silver nanowires

Abstract

The quantum transport properties of the ultrathin silver nanowires are investigated. For a perfect crystalline nanowire with four atoms per unit cell, three conduction channels are found, corresponding to three s bands crossing the Fermi level. One conductance channel is disrupted by a single-atom defect, either adding or removing one atom. Quantum interference effect leads to oscillation of conductance versus the inter-defect distance. In the presence of multiple-atom defect, one conduction channel remains robust at Fermi level regardless the details of defect configuration. The histogram of conductance calculated for a finite nanowire (seven atoms per cross section) with a large number of random defect configurations agrees well with recent experiment.PACS: 73.63. Nm, 61.46.+w In recent years, metallic nanowires are of great interest as building blocks for nanoelectronic devices. Since the dimension of the metallic nanowires is comparable to the electron Fermi wavelength, the conductance is quantized in units ofThe number of conductance channels is determined by the number of electronic bands crossing the Fermi level (E F ) and sensitively depends on the nanowire geometry. The effect of conductance quantization and the related high sensitivity lead to potential applications such as single-atom switch [4], conductor [5,6], and chemical sensor [7].Most earlier works on the quantum conductance of metallic nanowires are based on the point contacts formed between metal electrodes [1]. With mechanically controllable break junctions [8,9] or tip-surface contact [10,11,12,13] techniques, the statistical histograms of the conductance value for large number of contacts have been recorded. However, the metallic nanowires obtained from nanoscale contact are limited by the short length and structural instability for practical applications. Other fabricating methods, such as reduction of metal compounds [14], ions irradiation [15], carbon nanotubes capillary growth [16,17,18], and template-aid synthesis [19,20] have been introduced to generate much longer nanowires with well-defined structures. Understanding the transport properties of these long and nearly freestanding metallic nanowires are important for their future applications in nanoelectronics. Recently, Kim's group has successfully obtained ultrathin single-crystalline silver nanowire arrays [20]. The silver nanowires with 0.4 nm width (only four atoms on the cross section) and µm-scale length are grown inside the pores of organic templates. In this letter, we investigate the transport properties of the ultrathin silver nanowires and discussed the effect of defects on the conductances.The geometry optimization for the silver nanowires are performed by using ab initio plane-wave ultrasoft pseudopotential method [21]. Both atomic positions and cell parameters for the nanowires (perfect crystalline or with structural defects) were fully relaxed at level of local density approximation (LDA). We adopt the initial configurations proposed in Ref. [20], that is, fcc-like...

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“…Conductance, G(2e 2 /h) of silver nanowires with single-atom defects: Adatom (dotted line) and for perfect nanowires (solid curve) (Zhao et al 2003). Dresselhaus 2003), nanobarcodes , nanolasers , one-dimensional waveguide and resonant tunneling diodes (Björk et al 2002a, b).…”

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