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Zhe Ren1 Jovana Colvin1 Thomas Cornelius2 Stephane Labat2 Danial Bahrami3 Ali Al Hassan3 Olivier Thomas2 Ulrich Pietsch3 Anders Mikkelsen1 Rainer Timm1

1, Lund University, Lund, , Sweden
2, Aix Marseille University, Marseille, , France
3, University of Siegen, Siegen, , Germany

Semiconductor nanowires offer a large flexibility in combining different materials, and are thus highly promising candidates for next generation (opto)-electronic devices [1, 2]. For understanding and improving the performance of these future nano-devices, it is crucial to correlate the strain and defects to the electrical properties at the individual nanostructure level. Since device operation itself might also influence the structural properties of the materials due to heating or piezoelectricity, both ex situ and in situ experiments are needed to further explore the influence of the strain and defects distribution on the electrical properties of the nanowires.
X-ray diffraction as a non-destructive technique is suitable for experiments in operando. With recent advances at third generation synchrotron light sources, X-ray diffraction techniques, such as coherent Bragg diffraction imaging (CBDI) now provide information about the strain and defects distribution within individual nanostructures [3]. On the other hand, scanning tunneling microscopes (STM) are dedicated for measuring the electrical properties of individual nanostructures without any process steps [4]. Here we will present recent experiments where we combined these two techniques both ex situ and in situ.
In the ex situ experiment, wurtzite InAs nanowires containing only very few stacking faults were investigated. Using the STM tip as nanoprobe, the electrical conductivity of individual upstanding nanowires is measured. The stacking faults distribution within the same nanowires is investigated by CBDI, allowing to study the impact of stacking faults on the electrical conductivity on the individual nanowire level.
In situ electrical measurements are performed in combination with X-ray diffraction by mounting a specifically designed STM onto the goniometer of a nanofocus beamline. Here, we will present the concept of these experiments, aiming at the in situ characterization of Joule heating, piezoelectric response, or local strain induced by the nanoprobe, together with some initial results obtained on individual GaN nanowires.
[1] J. Wallentin, “InP Nanowire Array Solar Cells Achieving 13.8% Efficiency by Exceeding the Ray Optics Limit”, Science 339, 1057, 2013;
[2] E. Lind et al., ”III-V Heterostructure Nanowire Tunnel FETs”, IEEE J. El. Dev. Soc. 3, 96, 2015
[3] V. Favre-Nicolin et al., “Analysis of strain and stacking faults in single nanowires using Bragg coherent diffraction imaging,” New J. Phys., 12, 035013, 2010.
[4] R.Timm et al., ”Current-Voltage Characterization of Individual As-Grown Nanowires Using a Scanning Tunneling Microscope”, Nano Lett. 13, 5182, 2013.

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