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QUESTforENERGY

Make our Planet great again 

 


The project is part of the campaign MAKE THE PLANET GREAT AGAIN, supported by DAAD and BMBF



The goal of the research project Quantifying Ultrafast non-Equilibrium dynamicS in semiconducTor quantum nanomaterials for nExt geNEration eneRGY Materials - QUESTforENERGY - is the time-resolved observation and control of the carrier and lattice dynamics in two-dimensional semiconductor materials driven out of equilibrium at femtosecond time scales. This interdisciplinary program interfaces between Material Science, Physical Chemistry, Optics and fundamental Physics. Studying the ultrafast photoresponse and directly observing the excitation followed by thermalization of the systems allows to predict fundamental limitations for devices, observing new quantum phases with potentially even enhanced properties and providing input for advanced modelling of these materials. Understanding and controlling the optoelectronic properties in these nanomaterials will pave the way for novel multijunction solar cells and highly efficient and highly integrated optoelectronic devices that will perform significantly beyond current silicon-based technology.

The QUESTforENERGY project is funded by the Federal Ministry of Education and Research (BMBF) under the "Make our Planet Great Again - German Research Initiative", grant number 57427209, implemented by the German Academic Exchange Service (DAAD).

Method: Extreme Ultraviolet Core-level Spectroscopy

pump-probe scheme

(a) Typical pump-probe scheme, here in germanium as example. A VIS-NIR pulse photoexcites the semiconductor, initiating valence to conduction band transitions. A time-delayed broadband XUV pulse probes the transient state of the material by promoting a core-level electron to unoccupied states. (b) Broadband attosecond pulse spectra are shown that can be produced across a wide spectral range, giving core-level access to dynamics in various materials. The energy separations allow probing different atomic species separately in semiconductor compounds. (c) Time-resolved XUV absorption spectroscopy allows measuring carrier populations, electronic effects such as Coulomb screening, lattice expansions (phonons) as well as many-body effects (e.g. carrier-carrier scattering), that each result in distinct spectroscopic signatures around the chosen absorption edge (exemplary differential XUV absorbances in germanium are indicated).

 

Instrumentation (New experiment starting 12/2018)

Instrumentation

Core element is a 30 fs, 7mJ Ti:Sa femtosecond laser system operating at 1 kHz. About 2 mJ of pulse energy will be compressed to the few-cycle level (4 fs) in a hollow core fiber. About 90% of the compressed pulse will be used to generate broadband XUV probe pulses (20 eV ... 150 eV) and 10% will be used to photoexcite the sample. The remaining 5 mJ will be converted into the near-infrared using an optical parametric amplifier followed by a difference frequency unit. This will generate tunable femtosecond pulses with low photon energies (250 meV to 950 meV).


Group members:


Zuerch-1
Dr. Michael Zürch
(Junior group leader)
Rudrakant-Sollapur-1
Rudrukant Sollapur
(PhD student)
Rajesh-1
Rajesh Thotakura
(Internposition)
 Spielmann-1
Prof. Christian Spielmann
(Host-Director Abbe Center of Photonics)

Opportunities:

We are constantly looking for highly motivated and skilled team members. Starting January 2019, there will be positions available for post-doc and PhD candidates. There are also opportunities to complete internships, bachelor and master thesis within the project. If you are interested, please send your letter of motivation and CV to:


Publications:

[1]  S. K. Cushing, A. Lee, L. M. Carneiro, H.-T. Chang, M. Zürch, S. R. Leone. Differentiating Photoexcited Carrier and Phonon Dynamics in the ∆, L, and Γ Valleys of Si(100) with Transient Extreme Ultraviolet Spectroscopy, submitted (2018).

[2]  S. K. Cushing, M. Zürch, P. M. Kraus, L. M. Carneiro, A. Lee, H.-T. Chang, C. J. Kaplan, S. R. Leone. Hot phonon and carrier relaxation in Si(100) determined by transient extreme ultraviolet spectroscopy, Structural Dynamics 5, 054302 (2018).

[3]  C. J. Kaplan, P. M. Kraus, A. D. Ross, M. Zürch, S. K. Cushing, M. F. Jager, H.-T. Chang, E. M. Gullikson, D. M. Neumark, S. R. Leone. Femtosecond Tracking of Carrier Relaxation in Germanium with Extreme Ultraviolet Transient Reflectivity, Physical Review B 97, 205202 (2018).

[4] P. M. Kraus, M. Zürch, S. K. Cushing, D. M. Neumark, S. R. Leone. The Ultrafast X-ray Spectrocopic Revolution in Chemical Dynamics, Nature Reviews Chemistry 2, 82-94 (2018).

[5] M. Zürch, H.-T. Chang, P. M. Kraus, S. K. Cushing, L. J. Borja, A. Gandman, J. S. Prell, D. Prendergast, C. D. Premmaraju, D. M. Neumark, and S. R. Leone. Carrier Thermalization and Trapping in Silicon-Germanium Alloy Probed by Attosecond XUV Transient Absorption Spectroscopy, Structural Dynamics 4 (4), 044029 (2017).

[6] M. Zürch, H.-T. Chang, L. J. Borja, P. M. Kraus, S. Cushing, A. Gandman, C. J. Kaplan, M. H. Oh, J. S. Prell, D. Prendergast, C. D. Premmaraju, D. M. Neumark, and S. R. Leone. Direct and Simultaneous Observation of Ultrafast Electron and Hole Dynamics in Germanium, Nature Communications 8:15734, 1-11 (2017).



Funding:

Planet  daad-logo

  MfBF

 

Contact:

Dr. Michael Zürch

 

Insitute of Optics and Quantum Electronics

Friedrich Schiller University Jena

Max Wien Platz 1

07743 Jena

Germany

 

Email:

Phone: +49 3641 947-213

Room: 321A