Ultrahochvakuum Ramanspektrometer

• Subject Area: Condensed Matter Physics
• Term: Funded in 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 276693341

• Final Report Year: 2019

Final Report Abstract

The ultra-high vacuum (UHV) Raman spectrometer is a home-built experimental tool that is designed to perform Raman measurements in UHV conditions at liquid Helium temperatures. The main motivation for such a setup is the desire to study the Raman spectrum and the luminescence of air-sensitive quantum materials. Raman spectroscopy is a valuable characterization technique that measures the frequency of Raman active phonons. Photoluminescence is a related technique that allows one to measure the optical band gap of a material. The in-situ preparation and the functionalization of materials requires UHV conditions and additional structural characterization by low energy electron diffraction. The key experiments that we have performed in the first three years after the start of operation are the following. 1) Investigation of the Raman spectrum of heavily alkali metal doped 2D materials, in particular graphene and MoS2. Here, UHV Raman is a key method because of the high air sensitivity of alkali metals. The Raman spectrum of alkali metal doped graphene allowed us to determine the electron-phonon coupling. In MoS2 we have also looked to the photoluminescence and studied how charged alkali metal impurities affect the valley polarization, i.e. the degree of circular polarization in the emitted light. 2) In-situ investigation of the effects of hydrogenation on the luminescent properties of graphene nanoribbons. UHV Raman investigation of boron doped graphene nanoribbons. The boron sites are notoriously known to be air-sensitive and therefore need to be investigated in UHV. 3) Combined Raman and transport experiments on doped graphene and graphene nanoribbons. We have modified the sample holders of the UHV Raman spectrometer so that we can measure transport in-situ as well. The combination of high sensitivity in electronic transport measurements with the selectivity of Raman spectroscopy is a new, powerful approach to study functional materials. To date (5.2019), my group has published 10 journal papers where UHV Raman is a key experimental method.

Publications

• Making Graphene Nanoribbons Photoluminescent. Nano Letters, 17(7), 4029-4037.
  Senkovskiy, B. V.; Pfeiffer, M.; Alavi, S. K.; Bliesener, A.; Zhu, J.; Michel, S.; Fedorov, A. V.; German, R.; Hertel, D.; Haberer, D.; Petaccia, L.; Fischer, F. R.; Meerholz, K.; van Loosdrecht, P. H. M.; Lindfors, K. & Grüneis, A.
  
• Semiconductor‐to‐Metal Transition and Quasiparticle Renormalization in Doped Graphene Nanoribbons. Advanced Electronic Materials, 3(4).
  Senkovskiy, Boris V.; Fedorov, Alexander V.; Haberer, Danny; Farjam, Mani; Simonov, Konstantin A.; Preobrajenski, Alexei B.; Mårtensson, Niels; Atodiresei, Nicolae; Caciuc, Vasile; Blügel, Stefan; Rosch, Achim; Verbitskiy, Nikolay I.; Hell, Martin; Evtushinsky, Daniil V.; German, Raphael; Marangoni, Tomas; van Loosdrecht, Paul H. M.; Fischer, Felix R. & Grüneis, Alexander
  
• Spectroscopic characterization of N = 9 armchair graphene nanoribbons. physica status solidi (RRL) – Rapid Research Letters, 11(8).
  Senkovskiy, B. V.; Haberer, D.; Usachov, D. Yu.; Fedorov, A. V.; Ehlen, N.; Hell, M.; Petaccia, L.; Di Santo, G.; Durr, R. A.; Fischer, F. R. & Grüneis, A.
  
• Boron-Doped Graphene Nanoribbons: Electronic Structure and Raman Fingerprint. ACS Nano, 12(8), 7571-7582.
  Senkovskiy, Boris V.; Usachov, Dmitry Yu.; Fedorov, Alexander V.; Marangoni, Tomas; Haberer, Danny; Tresca, Cesare; Profeta, Gianni; Caciuc, Vasile; Tsukamoto, Shigeru; Atodiresei, Nicolae; Ehlen, Niels; Chen, Chaoyu; Avila, José; Asensio, Maria C.; Varykhalov, Andrei Yu.; Nefedov, Alexei; Wöll, Christof; Kim, Timur K.; Hoesch, Moritz ... & Grüneis, Alexander
  
• Combined Ultra High Vacuum Raman and Electronic Transport Characterization of Large‐Area Graphene on SiO2. physica status solidi (b), 255(12).
  Hell, Martin G.; Falke, Yannic; Bliesener, Andrea; Ehlen, Niels; Senkovskiy, Boris V.; Szkopek, Thomas & Grüneis, Alexander
  
• Effect of lithium doping on the optical properties of monolayer MoS2. Applied Physics Letters, 112(12).
  Saigal, Nihit; Wielert, Isabelle; Čapeta, Davor; Vujičić, Nataša; Senkovskiy, Boris V.; Hell, Martin; Kralj, Marko & Grüneis, Alexander
  
• Narrow photoluminescence and Raman peaks of epitaxial MoS 2 on graphene/Ir(1 1 1). 2D Materials, 6(1), 011006.
  Ehlen, Niels; Hall, Joshua; Senkovskiy, Boris V.; Hell, Martin; Li, Jun; Herman, Alexander; Smirnov, Dmitry; Fedorov, Alexander; Yu Voroshnin, Vladimir; Di Santo, Giovanni; Petaccia, Luca; Michely, Thomas & Grüneis, Alexander
  
• Resonance Raman Spectrum of Doped Epitaxial Graphene at the Lifshitz Transition. Nano Letters, 18(9), 6045-6056.
  Hell, Martin G.; Ehlen, Niels; Senkovskiy, Boris V.; Hasdeo, Eddwi H.; Fedorov, Alexander; Dombrowski, Daniela; Busse, Carsten; Michely, Thomas; di Santo, Giovanni; Petaccia, Luca; Saito, Riichiro & Grüneis, Alexander
  
• Synthesis and spectroscopic characterization of alkali–metal intercalated ZrSe2. Dalton Transactions, 47(9), 2986-2991.
  Nikonov, Konstantin; Ehlen, Niels; Senkovskiy, Boris; Saigal, Nihit; Fedorov, Alexander; Nefedov, Alexei; Wöll, Christof; Di Santo, Giovanni; Petaccia, Luca & Grüneis, Alexander
  
• Ultrahigh Vacuum Optical Spectroscopy of Chemically Functionalized Graphene Nanoribbons. Encyclopedia of Interfacial Chemistry, 367-374. Elsevier.
  Grüneis, A.; Senkovskiy, B.V.; Fedorov, A.V.; Hell, M. & Michel, S.
  
• Combined spectroscopic and electronic t0ransport characterization of doped graphene
  Hell, Martin