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AG Festkörperphysik

In der Arbeitsgruppe Festkörperphysik werden ultradünne 2D-Materialien mit Methoden der Oberflächenforschung präpariert und charakterisiert. Ausgehend vom prototypischen Graphen (Physiknobelpreis 2010), das aus einer monoatomaren Schicht Kohlenstoff besteht, sind in den letzten Jahren zahlreiche weitere Mitglieder dieser Materialklasse entdeckt worden. Theoretisch  sind sogar einige hundert verschiedene Materialien möglich, von denen allerdings nur sehr wenige bereits synthetisiert werden konnten.

Unsere wichtigste Untersuchungsmethode ist die Rastertunnelmikroskopie (STM), mit der atomare Auflösung erreicht werden kann. Wir präparieren fortgeschrittene 2D-Materialien wie Komposite aus Graphen und hexagonalem Bornitrit oder ultradünne Halbleiter wie MoS2 unter  genau kontrollierten Bedingungen, und modifizieren diese Schichten gezielt, um z. B. eine Dotierung zu bewirken oder die Wechselwirkung mit potenziell störenden Gasen aus der Umgebung zu untersuchen. In den letzten Jahren konnten wir so unter anderem zeigen, dass man Elektronen in Quantenpunkten aus Graphen einsperren kann, in welcher Form Graphen durch den Beschuss mit energetischen Ionen beschädigt wird, und wie es schaffen, zwischen 2D-Materialien und ihre Unterlage zu kriechen (Interkalation).

Neueste Nachrichten / Latest News (for quick updates follow us on Twitter : @2DM_Siegen)

 06.05.2024 Our paper "Tin Halide Perovskite Epitaxial Films on Gold Surfaces: Atomic Structure and Stability" has been published in Advanced Functional Materials. In this work we study CsSnBr3 on Au(111) and Au(100) by STM, LEED, XPS and DFT. Our results reveal the atomic structure of the films and show Sn is stabilized in the desired Sn2+ oxidation state. Upon exposure to air rapid degradation occurs leading to the oxidation state of Sn4+. Authors are: M. Abbasli, J. Hieulle, J. Schrage, D. Wilks, A. Samad, U. Schwingenschlögl, A. Redinger, C. Busse, and R. Ohmann.

Tin halide perovskite CsSnBr3

25.1.2024 We submitted a manuscript entitled "Tailoring the intrinsic interactions in MoS2 by self-intercalation" to Nano Letters. In this work we describe how the electronic structure of an ultrathin semiconductor can be tuned by strain and screening. Authors are B. Pielić, M. Mužević, D. Novko, J. Cai, A. Bremerich, R. Ohmann, M. Kralj, I. Šrut Rakić, and C. Busse.


22.1.2024 Our paper "Transition from fractal-dendritic to compact islands for the 2D-ferroelectric SnSe on graphene/Ir(111)" has been accepted by Nanotechnology. Here, we study the growth of ultra-thin ferroelectrics with special focus on the relaxation of the edges. Authors are P. Aleksa, M. Ghorbani-Asl, S. Iqbal, M. A. Martuza, A. Bremerich, D. Wilks, J. Cai, T. Chagas, R. Ohmann, A. Krasheninnikov, and C. Busse.


11.12.2023 We submitted our manuscript "Defect-free two-dimensional core-shell heterostructures: MoS2-TaS2/Au(111)" to 2D Materials. We found that sequential growth can produce an MoS2 quantum dot seamlessly encapsulated in a TaS2 shell. Authors are K. Mehlich, D. Sahm, T. Chagas, D. Weber, C. Grover, D. Dombrowski, and Carsten Busse.


26.10.2023 Christoph Schuster handed in his Bachelor's Thesis "Commission of an ultra-high-vacuum system for characterization of surfaces and two-dimensional materials". Congratulations!

19.10.2023 We published a paper entitled "What governs the atomic structure of the interface between 2D transition metal dichalcogenides in lateral heterostructures?" in 2D Materials. Authors are F. H. Davies, K. Mehlich, C. Busse and A. V. Krasheninnikov.

19.9.2023 Marina Hammer joined the group for her Master's Thesis in Materials Science and Engineering.

1.7.2023 Borna Pielić startet his project 2D-InTune (Tuning the electronic structure of two-dimensional semiconductor junctions) for which he recieved a Marie-Curie-Fellowship (MSCA PF) from the European Commission.

12.6.2023 Christoph Schuster started a research project on the freshly discovered 2D material hexagonal GeSe which will eventually be part of his Bachelor's Thesis.

9.6.2023 We took our new low-temperature scanning  probe microscope (Infinity from Scienta Omicron) into operation.

23.5.2023 Andrew Koerner from Lehigh University started a RISE-DAAD summer internship with us. He will recieve training in surface science methods and the physics of 2D-materials.

5.5.2023 Alessia Bardazzi from Università di Bologna joined our group for a 3-month internship. She will investigate novel 2-dimensional phases of tantalum and sulfur.

13.3.2023 Our paper "Nucleation stage for the oriented growth of tantalum sulfide monolayers on Au(111)" was published in J. Phys. Chem. C. In this work we describe small TaS3-units that are the nuclei for the further growth of tantalum sulfide monolayers and govern the orientation of the resulting films. Authors are T. Chagas, K. Mehlich, A. Samad, C. Grover, D. Dombrowski, J. Cai, U. Schwingenschlögl and C. Busse


1.3.2023 We carried out our second group retreat at Burg Bilstein.Bilstein2023

24.2.2023 Catherine Grover handed in her thesis as the final step in obtaining the Master degree in Physics. Well done!

31.1.2023 Veronika Blecker finished her research phase with the submission of her Master's thesis. Congratulations!

24.1.2023 Our paper "Phase engineering in tantalum sulfide monolayers on Au(111)" appeared in 2D Materials. In this work, we describe two different phases of two-dimensonal tantalum sulfide and how they can be converted into each other. Authors are D. Dombrowski, A. Samad, K. Mehlich, T. Chagas, U Schwingenschlögl and C. Busse


2.1.2023 Borna Pielic joined the group as a Postdoc. He will investigate heterostructures of two-dimensional seminconductors. Welcome!

11.7.2022 Jenny Schrage handed in her Bachelor thesis on testing and commissioning our new vaccum suitcase. Well done!

1.7.2022 Dina Wilks startd her PhD-project on two-dimensional ferroelectrics. Good luck!

28.3.2022 Our paper  "Metal-insulator transition in monolayer MoS2 via contactless chemical doping" was published in 2D Materials. Here, we describe how we can dope an ultrathin semiconductor by placing donors or acceptors close by. Authors are C. van Efferen, C. Murray, J. Fischer, C. Busse, H.-P. Komsa, T. Michely and W. Jolie.

01.03.2022 Alice Bremerich started her doctoral studies on the preparation and characterization of two-dimensional TMDC materials. All the best!

14.02.2022 Jenny Schrage started her Bachelor studies on the setup of the new low-temperature scanning probe microscope. Welcome!

31.1.2022 Thaís bagged a prestiguous fellowship from the Alexander von Humboldt Foundation. Congratulations! See also the press release.Thais_AvH

26.1.2022 Our paper "Spatial variation of geometry, binding, and electronic properties in the moiré superstructure of MoS2 on Au(111)" was published in 2D Materials. Authors are C.  C. Silva, D. Dombrowski, Nicolae Atodiresei, W. Jolie, F. Farwick zum Hagen, J. Cai, P. T. P. Ryan, P. Thakur, V. Casiuc, S. Blügel, D. A. Duncan, T. Michely, T.-L. Lee, and C. Busse.


10.01.2022 Veronika Blecker started her Master studies on the preparation and characterization of 2D ferroelectric materials. Welcome! 

22.12.2022 Alice has handed in her Master Thesis "Heterojunctions of epitaxially grown transition metal dichalcogenides" as the culmination of the work towards her MSc Physics degree. Congrats!

27.11.2021 Dany successfullly passed her PhD-defense. Congratulations, Dr. Dombrowski!

9.11.2021 Our paper "Structure of 2H-TaS2 on Au(111)" was published by Physical Review B. It  contains a detailed characterisation of the geometry of the system derived by X-ray standing waves (XSW), corroborated by density functional theory calculations (DFT). Authors are C. Silva, D. Dombrowski, A. Samad, J. Cai, W. Jolie, J. Hall, P. T. P. Ryan, P. Thakur, D. A. Duncan, T.-L. Lee, U. Schwingenschlögl, and C. Busse.



4.11.2021 We have obtained a research grant from the German Science Foundation (DFG) to investigate two-dimensional ferroelectris. Ferroelectric materials are a recent addition to the two-dimensional world with fascinating fundamental properties as well as a high potential for applications. In analogy to ferromagnets, ferroelectrics show a permanent electrical polarization that can be switched by an external electric field.


27.10.2021 Carsten Busse was elected as chairman of the Department of Physics.

18.10.2021 Our manuscript "Electronic structure of quasi-freestanding WS2/MoS2 heterostructures" has been published in by ACS Applied Materials & Interfaces. In this work, we study the band alignement at heterojunctions between two-dimensional semiconductors using STS. Authors are Borna Pielic, Dino Novko, Iva S’rut Rakic, Jiaqi Cai, Marin Petrovic, Robin Ohmann, Natasa Vujicic, Mario Basletic, Carsten Busse, and Marko Kralj.


5.10.2021 Catherine Grover started the research phase of her Master studies in our research group. She will work on ultrathin semiconductors. Welcome!

 2.10.2021 High-school students in 9th grade can now lear something about atomic structure using STM-images taken by our NaioSTM as an example.


30.9.2021 Daniel Kurz submitted his Master thesis "Präparation und Rastertunnelmikroskopie von Vanadiumsulfiden unter Ultrahochvakuumbedingungen". Good job!

22.9.2021 We returned from our first group retreat in Freusburg.

27.8.2021 Physical Review B accepted our paper "Sub-Poissonian distribution of Cs and K ions in the valleys of hBN/Ru(0001)" by Jiaqi Cai, Robin Ohmann, and Carsten Busse. Here, we demonstrate that alkali metal atoms adsorbed on hexagonal boron nitride show a more even distribution as expected by simple statistics, caused by the mutual Coulomb repulsion.


1.8.2021 Dr.Thaís Chagas Peixoto Silva (re-)joined the group as a postoc to investigate phase engineering in two-dimensional transition metal dichalcogenides. Welcome!23.7.2021 Our paper "Two Phases of Monolayer Tantalum Sulfide on Au(111)" is published in ACS Nano. In this work, we describe a novel sulfur poor phase of tantalum sulfide on Au(111). Authors are Daniela Dombrowski, Abdus Samad, Clifford Murray, Marin Petrovic, Pascal Ewen, Thomas Michely, Marco Kralj, Udo Schwingenschlögl and Carsten Busse. 


19.5.2021 Jiaqi Cai successfully defended his thesis as the last step in his PhD. Congratulations, Dr. Cai!

3.5.2021 Sammer Iqbal handed in his thesis  “Preparation of 2-D Group-IV Monochalcogenides” as the last step of his Master degree in Nanoscience and Nanotechnology. Well done!


15.2.2021 Muhammad Ali Martuza joined the group. He works on the preparation of 2D-materials for advanced characterization methods.

 9.11.2020 Alice Bremerich started the research phase of her Master studies with a project on ultrathin MoS2-WS2-junctions 

6.10.2020 Daniel Kurz joined the group to work on lateral TMDC heterostructures.

5.10.2020 Sammer Iqbal started his master thesis on the preparation of 2D group-IV monochalcogenides.

5.3.2020 Our paper "Sulfur structures on bare and graphene-covered Ir(111)" has been published in Journal of Physical Chemistry C.  Here, we describe a novel and very dense structure of a sulfur layer intercalated between graphene and its substrate. Authors are B. Pielic, J. Hall, V. Despoja, I. Srut Rakic, M. Petrovic, A. Sohani, C. Busse, T. Michely and M. Kralj. 

14.1.2020 Caio Silva successfully defended his thesis as the final step in obtaining the Dr. rer. nat. Congratulations!

15.11.2019 Madad Abbasli joined the group to work on his PhD-thesis "Epitaxially Grown Tin Perovskites".

17.10.2019 Veronika Blecker presented the main findings of her Bachelor's thesis "Pyrit als Schwefelquelle in der physikalischen Gasphasendeposition". Good job!

15.10.2019 Kai Mehlich started his PhD-thesis on ultrathin transition metal dichalcogenides.

1.10.2019 Dina Wilks joined the group as a masters student.

21.9.2019 Kai Mehlich presented his main findings in a talk "In plane heterostructures in transition metal dichalcogenides" as the final step of his M. Sc. in Physics. Congratulations!

9.9.2019 Alice Bremerich handed in her Bachelor's thesis "Inbetriebnahme eines Auger Spektrometers". Well done!

8.5.2019 Our paper "Lifting Epitaxial Graphene by Intercalation of Alkali Metals" was published in J. Phys. Chem. C. We have precisely determined the structure of intercalated graphene and find that already a small amount of Lithium is sufficient to fully delaminate graphene from Ir(111). Authors are C. C. Silva, J. Cai, W. Jolie, D. Dombrowski, F. H. Farwick zum Hagen, A. J. Martínez-Galera, C. Schlueter, T.-L. Lee and C. Busse.

29.4.2019 Veronika Blecker joined our group. She will establish evaporation of sulfur from FeS2 for the growth of ultrathin films.

 April 2019 Our new VT-STM from Scienta Omicron arrived and got installed.


01.04.2019 We welcome Alice Bremerich as a new group member. In her Bachelorthesis, she will use Auger electron spectroscopy (AES) to characterize surfaces especially 2D materials.

28.3.2019 Our paper "Tomonaga-Luttinger liquid in a box: Electrons confined within MoS2 mirror-twin boundaries" was published in Physical Review X. Here, we observe spin-charge separation in one-dimensional wires. Authors are W. Jolie, C. Murray, P. S. Weiß, J. Hall, F. Portner, N. Atodiresei, A. V. Krasheninnikov, C. Busse, H.-P. Komsa, A. Rosch und T. Michely.

26.3.2019 Our paper "Comprehensive tunneling spectroscopy of quasi-freestanding MoS2 on graphene on Ir(111)" was published in Phys. Rev. B. Here, we use a combination of different modes of scanning tunneling spectroscopy (STS) to reveal the band gap of MoS2 as well as additional critical point energies in the band structure. Authors are C. Murray, W. Jolie, J. A. Fischer, J. Hall, C. van Efferen, N. Ehlen, A. Grüneis, C. Busse, and T. Michely.

15.3.2019 We welcome Paulus Aleksa as a new group member. In his PhD-thesis, he will investigate two-dimensional ferroelectric materials.12.3.2019 Our paper "Charge density wave phase of VSe2"  was published in Phys. Rev. B. In this work we use scanning tunneling spectroscopy (STS) to investigate the change in the electronic structure of VSe2 induced by correlated electrons. Authors are W. Jolie, T. Knispel, N. Ehlen, K. Nikonov, C. Busse, A. Grüneis and T. Michely.

8.1.2019 Our scanning tunneling microscope "TuMA 3" arrived from Münster.

28.11.2018 Our paper "Modifying the geometric and electronic structure of hexagonal boron nitride on Ir(111) by Cs adsorption and intercalation" was published in Phys. Rev. B.  Here, we show how the geometric and electronic properties of the ultrathin insulator hBN can me tuned by interacion with the electron donor Cs. Authors are J. Cai, W. Jolie, C. Silva, M. Petrovic, C. Schlueter, T. Michely, M. Kralj, T.-L. Lee, and C. Busse.

6.11.2018 New Member: Thaís Chagas joins the group.

30.10.2018 Joshua Fuhrmann successfully completed his Bachelor thesis: Aufbau eines Rastertunnelmikroskops unter Umgebungsbedingungen

9.10.2018 Dina Wilks successfully completed her Bachelor thesis: Elektrochemischer Transfer von Graphen und hexagonalem Bornitrid

29.8.2018 Our paper "Resonance Raman Spectrum of Doped Epitaxial Graphene at the Lifshitz Transition" was published in Nano Letters. Authors are M. G. Hell, N. Ehlen, B. V. Senkovskiy, E. H. Hasdeo, A. Fedorov, D. Dombrowski, C. Busse, T. Michely, G. di Santo, L. Petaccia, R. Saito, and  A. Grüneis. Here, we employ ultra-high vacuum (UHV) Raman spectroscopy in tandem with angle-resolved photoemission (ARPES) to investigate the doping-dependent Raman spectrum of epitaxial graphene on Ir(111).

20.7.2018 Our paper "Valleys and hills of graphene on Ru(0001)" was published in J. Phys. Chem. C. In this work, we precisely determine the shape of a single layer of graphene using X-ray Standing Waves and find a good match to results from Density Functional Theory. Authors are C. Silva, M. Iannuzzi, D. Duncan,P. Ryan, K. Clarke, J. Küchle, J. Cai, W. Jolie, C. Schlueter, T.-L. Lee, and C: Busse

04.06.2018  New Members: Joshua Fuhrmann and Dina Wilks join the group.

01.05.2018  New Member: Dr. Robin Ohmann joins the group. 16.04.2018  New Member: Dennis Rybakowski joins the group.

08.03.2018  Our paper "Suppression of quasiparticle scattering signals in bilayer graphene due to layer polarization and destructive interference" was published in Phys. Rev. Lett. In this work, we demonstrate that electrons in bilayer graphene can be localized in one of the two layers only.


 19.01.2018 Our paper "Molecular beam epitaxy of quasi-freestanding transition metal disulphide monolayers on van der Waals substrates: a growth sstudy" was published in 2D Materials. In this work, we describe a new approach to grow transition metal dichalcogenides on top of graphene and hexagonal boron nitride.

 01.11.2017   The formation of our new group was featured in Siegener Zeitung (SZ) and  Westfalenpost (WP) (see also  the university's news).

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