Role of boundary roughness in the electronic transport of Bi nanowires

Abstract

We present a study of electronic transport in 200 nm diameter bismuth nanowire arrays embedded in an alumina matrix where the nanowires are oriented preferentially with the trigonal crystalline axis parallel to the wire length. The study is based on measurements of the resistance and thermopower over a wide range of temperatures (4–300 K) as well as of magnetoresistance for fields of up to 9 T. The Fermi energies are obtained from the Landau level spectrum; results show that the wires have the intrinsic electron and hole concentrations. At high temperatures, the mobilities are temperature dependent and the electron mobility is several orders of magnitude larger than that of holes. This nanowire mobility behavior, which is also observed in the bulk, is attributed to carrier-phonon scattering. At low temperatures, the mobilities are temperature independent and roughly the same for electrons and holes. An interpretation in terms of boundary roughness scattering is proposed.

Reflection resonances in surface-disordered waveguides: strong higher-order effects of the disorder

“…nn and compare it to the corresponding analytical predictions in equations ( 17) and (18). The corresponding results for 1/L (b) nn as a function of ∆ are shown in figure 3(a).…”

“…Following this analysis we extract from the disorder-averaged transmission the numerical values for L ( ) (17) and (18). The corresponding results for L 1 ( ) nn b as a function of Δ are shown in figure 3(a).…”

“…The corresponding results for 1/L (b) nn as a function of ∆ are shown in figure 3(a). We also plot the theoretical predictions given by equations ( 17) and (18), respectively, as well as the AGS terms 1/L (b,AGS) 11 alone. The agreement we find between the AGS terms and the numerical calculations is already remarkably good for most of the chosen parameters, such that the SGS contributions can be easily identified to be dominant at those specific parameter values where deviations from the AGS predictions occur (see vertical arrows in figure 3(a)).…”

“…The corresponding resonances are very pronounced and robust with respect to ensemble averaging, and lead to an enhancement of wave reflection by more than one order of magnitude.The problem of scattering off a rough surface is a central topic in physics which occurs for many different types of waves and on considerably different length scales [1][2][3][4]. Phenomena induced by surface corrugations play a major role in the study of acoustic, electromagnetic, and matter waves alike and appear in macroscopic domains such as acoustic oceanography and atmospheric sciences [5,6], but also emerge on much smaller length scales, e.g., for photonic crystals [7], optical fibers and waveguides [8,9], surface plasmon polaritons [10], metamaterials [11], thin metallic films [12-14], layered structures [15], graphene nanoribbons [16,17], nanowires [18][19][20], and confined quantum systems [21,22]. While having a detrimental effect on the performance of many of the above systems, surface roughness can also be put to use, e.g., for the fabrication of high-performance thermoelectric devices [23,24] and for light trapping in silicon solar cells [25]; rough surfaces cause anomalously large persistent currents in metallic rings [26] and provide the necessary scattering potential to manipulate ultra-cold neutrons which are bound by the earthʼs gravity potential [27].In view of this sizeable research effort, it might come as a surprise that even quite fundamental effects emerging in surface-disordered systems are still not fully understood.…”

Surface scattering and band gaps in rough waveguides and nanowires

“…The coherent scattering through systems with surface roughness is a ubiquitous phenomenon which occurs on vastly different length and time scales. 1,2 The effects induced by surface scattering often are the key for the understanding both of natural phenomena, like the scattering of underwater waves at a rough ocean seabed, 3 as well as of man-made devices like optical fibers and waveguides, [4][5][6][7] photonic crystal devices, 8-10 metamaterials, 11 thin metallic films, 12,13 layered structures, 14,15 nanowires, [16][17][18] in optical diffraction tomographs, 19 and confined quantum systems in general. 20 For some devices, like quantum cascade lasers 21 and gated graphene nano-ribbons [22][23][24] the scattering at rough boundaries was identified as one of the dominant factors that limits the device performance.…”