Conductance through atomic point contacts between fcc(100) electrodes of gold

Abstract

Electrical conductance through various nanocontacts between gold electrodes is studied by using the density functional theory, scalar-relativistic pseudopotentials, generalized gradient approximation for the exchange-correlation energy and the recursion-transfer-matrix method along with channel decomposition. The nanocontact is modeled with pyramidal fcc(100) tips and 1 to 5 gold atoms between the tips. Upon elongation of the contact by adding gold atoms between the tips, the conductance at Fermi energy E F evolves from G ≈ 3G 0 to G ≈ 1G 0 (G 0 = 2e/h 2 ). Formation of a true one-atom point contact, with G ≈ 1G 0 and only one open channel, requires at least one atom with coordination number 2 in the wire. Tips that share a common vertex atom or tips with touching vertex atoms have three partially open conductance channels at E F , and the symmetries of the channels are governed by the wave functions of the tips. The long 5-atom contact develops conductance oscillations and conductance gaps in the studied energy range −3 ≤ E − E F ≤ 5 eV, which reflects oscillations in the local density of electron states in the 5-atom linear "gold molecule" between the electrodes, and a weak coupling of this "molecule" to the tips.

Role of Polytetrahedral Structures in the Elongation and Rupture of Gold Nanowires

“…G is reported in units of G 0 = 2 e 2 / h , where e is the charge of an electron and h is Planck’s constant. We validated our conductance measurements by investigating single-point atom contacts, finding good agreement with previous theoretical calculations. ,, Further details of the implementation and its accuracy can be found in ref .…”

“…We validated our conductance measurements by investigating single point atom contacts, finding good agreement with previous theoretical calculations. 20,21,34 Further details of the implementation and its accuracy can be found in Ref. 48…”

“…The observation of conductance quantization in atomic-scale junctions [1][2][3][4][5] has fueled much interest in understanding their formation in mechanically deformed metallic nanowires (NWs), [6][7][8][9][10][11][12][13][14][15][16][17] in large part due to potential applications in nano-and molecular-electronic devices. To this extent, quantifying the structural changes that occur as a NW elongates is important for understanding how and why parameters such as initial crystal structure, 7,8 temperature, 14 and rate of elongation 11,14 affect the material properties (e.g., conductance, [18][19][20][21] mechanical stability, 11,22 or the opening of a bandgap 23 ). Many studies have been performed that focus on identifying changes to the crystalline structure, such as slipping and reorientation of the crystalline lattice, 6,13,14,17,24 and under what conditions single-atom wide monatomic chains are likely to form.…”

“…The observation of conductance quantization in atomic-scale junctions − has fueled much interest in understanding their formation in mechanically deformed metallic nanowires (NWs), − in large part due to potential applications in nano- and molecular electronic devices. To this extent, quantifying the structural changes that occur as a NW elongates is important for understanding how and why parameters such as initial crystal structure, , temperature, and rate of elongation , affect the material properties, such as conductance, − mechanical stability, , or the opening of a band gap . Many studies have been performed that focus on identifying changes to the crystalline structure, such as slipping and reorientation of the crystalline lattice, ,,,, and under what conditions single-atom-wide monatomic chains are likely to form. ,,,, However, to date, there has only been limited emphasis on quantifying the formation and structure of the “amorphous” or, more generally, noncrystalline domains that often appear within NWs. ,,, The formation of these noncrystalline structures is likely to result in significant changes to the properties of the NWs.…”