Direct Imaging of Atomic Scale Structure and Electronic Properties of GaAs Wurtzite and Zinc Blende Nanowire Surfaces

Hjort, Martin; Lehmann, Sebastian; Knutsson, Johan; Timm, Rainer; Jacobsson, Daniel; Lundgren, Edvin; Dick, Kimberly A.; Mikkelsen, Anders

doi:10.1021/nl402424x

Cited by 64 publications

(115 citation statements)

References 58 publications

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“…For bulk GaAs, the Zinc blende phase is the only phase possible and thus essentially all Schottky barrier height studies to date (except perhaps a recent report where the phase influence is not discussed 13 ) were done for this crystal phase. However, as recently shown by different groups 41,42 , the difference in band gap alignment and band gap size is below 0.1 eV, which is much smaller than the Schottky barrier reduction observed in our case and comparable to the measurement errors. To the best of our knowledge, the effect of different crystal phases on interface properties and the Schottky barrier height has not been studied so far.…”

Section: Experimental Designsupporting

confidence: 89%

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Strong Schottky barrier reduction at Au-catalyst/GaAs-nanowire interfaces by electric dipole formation and Fermi-level unpinning

et al. 2014

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Nanoscale contacts between metals and semiconductors are critical for further downscaling of electronic and optoelectronic devices. However, realizing nanocontacts poses significant challenges since conventional approaches to achieve ohmic contacts through Schottky barrier suppression are often inadequate. Here we report the realization and characterization of low n-type Schottky barriers (B0.35 eV) formed at epitaxial contacts between Au-In alloy catalytic particles and GaAs-nanowires. In comparison to previous studies, our detailed characterization, employing selective electrical contacts defined by high-precision electron beam lithography, reveals the barrier to occur directly and solely at the abrupt interface between the catalyst and nanowire. We attribute this lowest-to-date-reported Schottky barrier to a reduced density of pinning states (B10 17 m À 2 ) and the formation of an electric dipole layer at the epitaxial contacts. The insight into the physical mechanisms behind the observed lowenergy Schottky barrier may guide future efforts to engineer abrupt nanoscale electrical contacts with tailored electrical properties.

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Section: Experimental Designsupporting

confidence: 89%

“…It is known that GaAs NWs often have two crystal phases with different band gap alignment and sizes 41,42 . In our samples the presence of two crystal phases is manifested by stacking faults (Supplementary Fig.…”

Section: Experimental Designmentioning

confidence: 99%

Strong Schottky barrier reduction at Au-catalyst/GaAs-nanowire interfaces by electric dipole formation and Fermi-level unpinning

et al. 2014

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“…In our case, we assumed that crystalline InP nanowires were mechanically deposited from their growth substrate onto a Si 3 N 4 membrane. Nanowires normally have quite smooth surfaces, but still show roughness and facets on the nanometer scale (Hjort et al, 2013). We therefore used a value of 10 MW m À2 K À1 for the nanowire-substrate interface.…”

mentioning

confidence: 99%

Simulated sample heating from a nanofocused X-ray beam

Wallander

Wallentin

2017

J Synchrotron Radiat

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Recent developments in synchrotron brilliance and X-ray optics are pushing the flux density in nanofocusing experiments to unprecedented levels, which increases the risk of different types of radiation damage. The effect of X-ray induced sample heating has been investigated using time-resolved and steadystate three-dimensional finite-element modelling of representative nanostructures. Simulations of a semiconductor nanowire indicate that the heat generated by X-ray absorption is efficiently transported within the nanowire, and that the temperature becomes homogeneous after about 5 ns. The most important channel for heat loss is conduction to the substrate, where the heat transfer coefficient and the interfacial area are limiting the heat transport. While convective heat transfer to air is significant, the thermal radiation is negligible. The steady-state average temperature in the nanowire is 8 K above room temperature at the reference parameters. In the absence of heat transfer to the substrate, the temperature increase at the same flux reaches 55 K in air and far beyond the melting temperature in vacuum. Reducing the size of the X-ray focus at constant flux only increases the maximum temperature marginally. These results suggest that the key strategy for reducing the X-ray induced heating is to improve the heat transfer to the surrounding.

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“…Although this procedure was successfully used to remove the native oxides from homogeneous InAs NWs, 8 in the present case, the temperature was too low for a complete removal of native oxides from GaAs NWs. 6 Unfortunately, a higher temperature could not be used in order to avoid InAs surface degradation and the formation of In droplets. All samples were cleaned by an identical cleaning process.…”

Section: Methodsmentioning

confidence: 99%

“…5. The electronic properties of such high-mobility devices can be correlated with structural properties [6][7][8] and with the quality of the heterointerface. A better understanding of such correlations requires a detailed analysis of the effective band confinement of these structures, using highly surface-and interfacesensitive techniques.…”

Section: Introductionmentioning

confidence: 99%

Band bending at the heterointerface of GaAs/InAs core/shell nanowires monitored by synchrotron X-ray photoelectron spectroscopy

Khanbabaee

Bussone

Knutsson

et al. 2016

Journal of Applied Physics

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Unique electronic properties of semiconductor heterostructured nanowires make them useful for future nano-electronic devices. Here, we present a study of the band bending effect at the heterointerface of GaAs/InAs core/shell nanowires by means of synchrotron based X-ray photoelectron spectroscopy. Different Ga, In, and As core-levels of the nanowire constituents have been monitored prior to and after cleaning from native oxides. The cleaning process mainly affected the Asoxides and was accompanied by an energy shift of the core-level spectra towards lower binding energy, suggesting that the As-oxides turn the nanowire surfaces to n-type. After cleaning, both As and Ga core-levels revealed an energy shift of about À0.3 eV for core/shell compared to core reference nanowires. With respect to depth dependence and in agreement with calculated strain distribution and electron quantum confinement, the observed energy shift is interpreted by band bending of core-levels at the heterointerface between the GaAs nanowire core and the InAs shell. Published by AIP Publishing. [http://dx

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Direct Imaging of Atomic Scale Structure and Electronic Properties of GaAs Wurtzite and Zinc Blende Nanowire Surfaces

Cited by 64 publications

References 58 publications

Strong Schottky barrier reduction at Au-catalyst/GaAs-nanowire interfaces by electric dipole formation and Fermi-level unpinning

Strong Schottky barrier reduction at Au-catalyst/GaAs-nanowire interfaces by electric dipole formation and Fermi-level unpinning

Simulated sample heating from a nanofocused X-ray beam

Band bending at the heterointerface of GaAs/InAs core/shell nanowires monitored by synchrotron X-ray photoelectron spectroscopy

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