The stability of polar oxide surfaces: The interaction of H2O with ZnO(0001) and ZnO(0001̄)

Wander, A.; Harrison, N. M.

doi:10.1063/1.1384030

Cited by 105 publications

(118 citation statements)

References 22 publications

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“…If ZnO is truncated in the (0001) and (0001) directions, a Zn ion layer will be exposed at one end while an O ion layer will be exposed at the opposite surface. 17 The two exposed surfaces are strongly polarized, and thus are unstable unless stabilized through one of several possible mechanisms. In clean environments, the polar surfaces prefer a shell-like reconstruction by outward relaxation of the outermost ion layers.…”

Section: Introductionmentioning

confidence: 99%

“…18,19 In another stabilization mechanism, the polar (0001) surfaces can become stable with the saturation of the surface bonds. 17,20,21 A third stabilization mechanism is to transfer some negative charge from the (0001)-O polar surface to the (0001)-Zn polar surface, which results in the reduction of the charges on the polar surfaces by a factor of 0.75. 16,22,23 Recently, the thermoelectric properties of ZnO NWs have received much attention due to the increasing global energy crisis.…”

Section: Introductionmentioning

confidence: 99%

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Polar surface effects on the thermal conductivity of ZnO nanowires: a shell-like surface reconstruction-induced preserving mechanism

2013

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We perform molecular dynamics (MD) simulations to investigate the effect of polar surfaces on the thermal transport in zinc oxide (ZnO) nanowires. We find that the thermal conductivity in nanowires with free polar (0001) surfaces is much higher than in nanowires that have been stabilized with reduced charges on the polar (0001) surfaces, and also hexagonal nanowires without any transverse polar surfaces, where the reduced charge model has been proposed as a promising stabilization mechanism for the (0001) polar surfaces for ZnO nanowires. From normal mode analysis, we show that the higher thermal conductivity is due to a shell-like reconstruction that occurs for the free polar surfaces. This shell-like reconstruction suppresses twisting motion in the nanowires such that the bending phonon modes are not scattered by the other phonon modes, and leads to substantially higher thermal conductivity in the ZnO nanowire with free polar surfaces. Furthermore, the autocorrelation function of the normal mode coordinate is utilized to extract the phonon lifetime, which leads to a concise explanation for the higher thermal conductivity in ZnO nanowires with free polar surfaces. Our work demonstrates that ZnO nanowires without polar surfaces, which exhibit low thermal conductivity, are more promising candidates for thermoelectric applications than nanowires with polar surfaces (and also high thermal conductivity).

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Polar surface effects on the thermal conductivity of ZnO nanowires: a shell-like surface reconstruction-induced preserving mechanism

2013

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“…The average diameter evolution as a function of ZnCl 2 is summarized in Fig. 2 ] increases, the oxygen reduction becomes important, being probably determined by the preferential adsorption of OH -ions on (0001) ZnO face due to its polar nature (30). The nanowire length was measured from cross section SEM images (not shown here).…”

Section: Morphology Of Zno Nanowire Arraysmentioning

confidence: 99%

Electrochemical Deposition and Characterization of ZnO Nanowire Arrays with Tailored Dimensions

et al. 2007

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A systematic study of the deposition of single crystal ZnO nanowire arrays from the oxygen electroreduction was performed. The influence of deposition parameters such as the concentrations of zinc precursor (ZnCl 2 ) and supporting electrolyte (KCl) on the formation of ZnO nanowire arrays, as well as on the dimensions of the nanowires was analyzed. Mean nanowire diameters from 25 to 80 nm were obtained by only modifying the [ZnCl 2 ] in solution, while high [KCl] allowed to reach diameters as high as 300 nm. The influence of [KCl] on the donor density determined from electrochemical impedance spectroscopy of ZnO nanowires was also shown. Carrier densities from 10 17 to 10 20 cm -3 were obtained depending on the deposition and annealing conditions. The results show that electrodeposition is a cost-effective technique which allows not only to grow ZnO single crystal nanowire arrays with tailored dimensions, but also to act on their electrical properties in a controlled way.

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“…The sensing mechanism is the polarization-induced bound surface charge by interaction with the polar molecules in the liquids. ZnO is a material for which significant progress in understanding its surface properties was achieved recently [58][59][60][61][62][63][64][65][66][67][68], stimulated by its importance for a number of applications ranging from cosmetics and medicine to heterogeneous catalysis. ZnO is a polar crystal whose polar axis is the c-axis, and it belongs to the C For our case the polar and nonpolar surfaces of the hexagonal single-crystal ZnO nanowire act as a direct detector without the need for a bioreceptor.…”

Section: Optical Properties Of Zno Nano-structuresmentioning

confidence: 99%

ZnO nanowires: chemical growth, electrodeposition, and application to intracellular nano‐sensors

Willander

Klason

Yang

et al. 2008

Phys. Status Solidi (c)

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In this paper we present our results on growth, characterization, and nano‐devices based on ZnO nano‐structures. The ZnO nano‐structures were grown by mainly two methods, the catalytic Vapor Liquid Solid (VLS) and the low temperature chemical growth. We show that by multiple coating combined with low temperature chemical growth, well aligned with size controlled ZnO nanowires on silicon substrates can be achieved. The dissolution, due to its important on the stability of ZnO nano‐structures in aqueous medium, is then discussed and some preliminary experimental results are shown. Basic Optical characteristics of ZnO nano‐rods are briefly discussed. Finally, electrochemical intracellular nano‐sensors based on ZnO nano‐wires are demonstrated as efficient nano‐sensors for monitoring the human cell activity with minute pH changes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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The stability of polar oxide surfaces: The interaction of H2O with ZnO(0001) and ZnO(0001̄)

Cited by 105 publications

References 22 publications

Polar surface effects on the thermal conductivity of ZnO nanowires: a shell-like surface reconstruction-induced preserving mechanism

Polar surface effects on the thermal conductivity of ZnO nanowires: a shell-like surface reconstruction-induced preserving mechanism

Electrochemical Deposition and Characterization of ZnO Nanowire Arrays with Tailored Dimensions

ZnO nanowires: chemical growth, electrodeposition, and application to intracellular nano‐sensors

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