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Jesper Wallentin

Position:    Assistant Professor

E-mail:    jesper.wallentin@sljus.lu.se
Phone:   
Cell phone:    +46 70 559 3949
Room:    K542
Address:    Professorsgatan 1
22100 Lund
      Sweden

University:    Lund University
Division:    Synchrotron Radiation Research
Research Area(s):    Materials Science
Nanoelectronics- & photonics
Interests:    X-ray analysis of nanostructures

 
jesper.wallentin

Teaching:

I teach physics at the Faculty of Science:
* FYSA01 General physics. Responsible for the Quantum physics part of the course.
* FYSN11 Physics experiments in Research and Society

If you are interested in a MSc project, don't hesitate to contact me.


Research:

Currently hiring postdoc in Nanoscale X-ray physics: lu.mynetworkglobal.com/en/what:job/jobID:238826/

My research studies single nanostructure devices using coherent X-ray imaging and X-ray diffraction. In particular, I'm developing techniques for investigations that combine hard X-ray imaging and X-ray diffraction with electrical measurements [3,5]. Hard X-rays can penetrate through thick samples, allowing measurements of devices in operando. The X-rays can both be used as a pump, to study for instance X-ray induced electrical conductance [5], or as a probe of the structure in nanodevices [3]. Nanowires have demonstrated much stronger response to hard X-rays than expected from bulk data [5]. We have shown that the shape of bent nanowires can be reconstructed in 3D with nanometre precision [2,3].

The image below shows a 3D reconstruction of a nanowire changing shape under the influence of a strong electric field [3].
NW_model_projections_xvid_gif_001.gif

The experiments require intense nanofocused X-ray beams that are only available at synchrotrons such as Petra-III and ESRF, and now also at MAX IV.

The image below shows a recent ptychographic reconstruction from the Nanomax beamline at the new MAX IV synchrotron, depicting a standing GaInP nanowire (courtesy Vilgaile Dagyte and Magnus Borgström).
particle_2_ptycho_object_cropped.jpg

We have simulated the heating from pulsed X-rays using the finite-element software Comsol [1]:
Repeated_pulses_angle_video_gif.gif


For an updated lists of publications, please see ResearcherID or Google Scholar. A selected list of recent work:
  1. L. Chayanun, G. Otnes, A. Troian, S. Hammarberg, D. Salomon, M. T. Borgström, and J. Wallentin, "Nanoscale mapping of carrier collection in single nanowire solar cells using X-ray beam induced current" J. Synchrotron Radiat. In press (2018)
  2. A. Troian, G. Otnes, X. Zeng, L. Chayanun, V. Dagyte, S. Hammarberg, D. Salomon, R. Timm, A. Mikkelsen, M. T. Borgström, and J. Wallentin, "Nanobeam X-ray fluorescence dopant mapping reveals dynamics of in situ Zn-doping in nanowires" Nano Lett. 18 (10), 6461 (2018) dx.doi.org/10.1021/acs.nanolett.8b02957
  3. L. Chayanun, V. Dagyte, A. Troian, D. Salomon, M. T. Borgström, and J. Wallentin, "Spectrally resolved X-ray beam induced current in a single InGaP nanowire" Nanotechnology 29, 454001 (2018) doi.org/10.1088/1361-6528/aadc76
  4. H Wallander, J Wallentin: Simulated sample heating from a nanofocused X-ray beam J. Synchrotron Radiat. 24 (5) (2017) doi.org/10.1107/S1600577517008712
  5. J Wallentin, D Jacobsson, M Osterhoff, MT Borgström, T Salditt: Bending and twisted lattice tilt in strained core-shell nanowires revealed by nanofocused X-ray diffraction Nano Lett. 17 (7) (2017) (dx.doi.org/10.1021/acs.nanolett.7b00918)
  6. J. Wallentin, M. Osterhoff, and T. Salditt, "In operando X-ray diffraction reveals electrically induced strain and bending in single nanowire device" Adv. Mater. 28 (9), 1788 (2016) http://dx.doi.org/10.1002/adma.201504188
  7. J. Wallentin, M. Osterhoff, R. N. Wilke, K.-M. Persson, L.-E. Wernersson, M. Sprung, and T. Salditt, "Hard X-ray detection using a single 100 nm-diameter nanowire" Nano Lett. 14 (12), 7071 (2014) http://dx.doi.org/10.1021/nl5040545

Jesper Wallentin's pages

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