Is there ballistic transport in metallic nano-objects? Ballistic versus diffusive contributions

Abstract

When discussing the resistance of an atomic-or nanometre-size contact we should consider both its ballistic and its diffusive contributions. But there is a contribution of the leads to the resistance of the contact as well. In this context, the geometry and the roughness of the surfaces limiting the system will contribute to the resistance, and these contributions should be added to the ideal ballistic resistance of the nanocontact. We have calculated, for metallic materials, the serial resistance of the leads arising from the roughness, and our calculations show that the ohmic resistance is as important as the ballistic resistance of the constriction. The classical resistance is a lower limit to the quantum resistance of the leads. Many examples of earlier experiments show that the mean free path of the transport electrons is of the order of the size of the contacts or the leads. This is not compatible with the idea of ballistic transport. This result may put in serious difficulties the current, existing interpretation of experimental data in metals where only small serial resistances compared with the ballistic component of the total resistance have been taken into account. The two-dimensional electron gas (2DEG) is also discussed and the serial corrections appear to be smaller than for metals. Experiments with these last systems are proposed that may reveal new interesting aspects in the physics of ballistic and diffusive transport.

Transition from Ohmic to ballistic transport in oriented graphite: Measurements and numerical simulations

“…However when this ratio increases there are two corrections to the Maxwell spreading resistance: ͑i͒ the Ohmic value is corrected by a factor of the order of unity as pointed by Wexler 9 ͑ii͒ and more important, a dominant ballistic term appears when ᐉ / W տ 1. This was observed by Knudsen and Sharvin 7,9 and the value of R reads 8,9 R 3D = 4͑T͒ᐉ/3A + ␥͑k͒͑T͒/W, ͑1͒…”

Atomic configuration, conductance, and tensile force of platinum wires of single-atom width

“…The geometry and roughness of the contact surfaces including electrodes also contribute to the conductance. 15 In our observation, both the wire part and electrodes are observed at an atomic resolution.…”

“…At this zero wire length, electron inelastic scattering through the contact decreases to the minimum; the transmission probability in each channel increases. As shown by García et al, 15 in addition to the geometry of ASWs, the shape and roughness of the electrodes contribute to electron inelastic scattering. For the present ASWs, it has not been shown whether all d channels perfectly open in the limit of zero wire length.…”

“…19,[26][27][28] The geometry and roughness of the contact surfaces including electrodes also contribute to the conductance. 15 In conductance histograms of Pt and Ir NCs, peaks are not observed at quantized values, and the peaks are wider than those of Au NCs. 4,6,7,13,[29][30][31][32][33][34][35][36][37] The deviation from quantized values is interpreted on the basis of inelastic scattering of electrons at 5d orbitals.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] This artificial one-dimensional arrangement of single atoms is unstable; gold ͑Au͒ ASWs survive for up to 2 ms at a retraction speed of ϳ10 nm/ s. On the basis of similarity in surface reconstruction, it is proposed that ASWs of the single metallic elements, platinum ͑Pt͒ and iridium ͑Ir͒, also possess structural stability comparable to that of Au ASWs. The formation process of ASWs during thinning of NCs has been investigated in relation to their quantized conductance defined by a quantum ͑G 0 =2e 2 / h, where e is the electron charge and h is Planck's constant͒.…”