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Abstract:
We combine novel atomic scale surface microscopy, advanced light sources, and tailored low dimensional structures and devices. This allow development and use of a new generation of imaging techniques with orders of magnitude better resolution in both time and space for studying complex nanostructures and devices even during operation. Our methods are applicable to nanostructures of many different materials combinations and dimensionalities, here we cover two main examples:
Despite the many semiconductor nanowire technologies under current development, be it solar cells, light emitting diodes or high speed/low power electronics, the atomic scale structure of nanowire surfaces and their impact on device function is poorly understood. We have developed novel Scanning Tunneling Microscopy (STM) concepts to directly image surfaces both inside, outside and topside of III-V semiconductor nanowires down to the single atom level [1], revealing geometric/electronic structure [2] as well as electrical/mechanical/chemical properties [3]. We now extended this to direct imaging of nanowire devices in operation[4]. Our most recent special device designs allows for full surface preparation of functioning devices to >700K, and imaging of individual atoms and defects during application of high voltage device biases.
The local enhancement of few-cycle laser pulses by nanostructures opens up for spatiotemporal control of optical interactions on a nanometer and few-femtosecond scale. However, spatially characterization of this dynamics poses a major challenge due to the extreme length and time scales involved. We combine the femtosecond and attosecond time resolution of novel advanced lasers with the nanoscale spatial resolution of PhotoEmission Electron Microscopy (PEEM). The combination of advanced lasers and PEEM allows for very sensitive measurements of plasmonics fields, surface chemistry and pump-probe experiments on ultrafast time scales - all in the same picture. We directly observe attosecond differences within the first few optical cycles in near-field enhancement in noble metal and semiconductor nanostructures [5]. We demonstrate nanoscale imaging using <100 attosecond laser pulses with central energies between 30-100ev in combination with peem (attopeem) [6].
[1] ACS Nano 6 (2012) 9679 ; Nano Lett., 8 (2008) 3978 ; Nature Mater. 3 (2004) 519
[2] ACS Nano, 8 (2014) 12346 ; Nano Lett., 13 (2013) 4492;
[3] Nature Comm. 5 (2014) 3221 ; Nano Lett., 13 (2013) 5182; Nano Lett. 10 (2010) 3893
[4] Nano Lett. 15 (2015) 3684 ; Nano Res., 7 (2014) 877 ; Nano Lett. 15 (2015) 4865
[5] Nano Lett. 15 (2015) 6601 ; Optics express 23(2015)31460
[6] Chapter 10 in “Attosecond Nanophysics: From Basic Science to Applications”, Wiley‐VCH Verlag GmbH & Co (2015)
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