Major instruments

Our laboratories are equipped with the following facilities:

1. Millikelvin STM (8T / 8T / 30 mK) (Rev. Sci. Inst. 92, 063701 (2021))
   Ultra-high vacuum STM that uses adiabatic demagnetization of electron magnetic moments for controlling its operating temperature ranging between 30 mK and 1 K with an accuracy of up to 7 μK rms. At the same time, high magnetic fields of up to 8 T can be applied perpendicular to the sample surface.
   
2. Unisoku 1300 STM/ AFM (9/2/2T / 0.3 K / Microwave cabling)
   With this combined STM/AFM we study spin systems on surfaces. The analyzed systems range from individual atomic and molecular spins, over complexly coupled spin structures and self-organized spin lattices, to the magnetic properties of 2D heterostructures. Its combination of vector field, low temperature, and extremely-high time resolution enables experiments in the field of coherent quantum control and dynamical measurements in correlated electron systems.
   
3. CreaTec STM/AFM (5K)
   This ultra-high vacuum low-temperature STM/NC-AFM from CreaTec Fischer GmbH is primarily used to explore molecular manipulation and fabrication with the SPM tip as an actuator. The instrument operates at 5K and has the option to use qPlus-type NC-AFM sensors. In our lab it is extended by custom-build control hardware for molecular manipulation and scanning quantum dot microscopy.
   
4. Sigma STM/AFM (5T / 1K)
   This STM/AFM is used to study van der Waals heterostructures at low temperatures and in magnetic fields, facilitated by its good optical access to the tunneling junction. It further has high frequency lines to the tip/sample, enabling pump/probe and ESR experiments.
   
5. Four-tip STM (STM) with an optical microscope (Rev. Sci. Inst. 83, 033707 (2012))
   This instrument is used for charge transport at nanostructures of quantum materials.
   
6. Four-tip STM combined with SEM (5K) (Rev. Sci. Inst. 89, 101101 (2018))
   This instrument combines low temperature transport measurements with the local perspective.
   
7. Combined multi-tip AFM/STM/SEM with needle sensor (Rev. Sci. Inst.86, 123703 (2015))
   This instrument is used to study the charge transport in conducting nanostructures on insulating substrates.
   
8. SPA-LEED / XPS / ARUPS
   The combination of high resolution (SPA-)LEED and standard electron spectroscopy techniques in one UHV machine allows us to achieve information on geometric and electronic structure from the very same sample preparation. With a transfer width better than 1000 Å (corresponding to a k-space resolution better 0.006 Å-1), the Omicron SPA-LEED instrument is able to provide not only structural information on the atomic scale, as conventional LEED instruments, but can also be used to study facets and step trains, surface roughness, island sizes and distributions, and other features on the mesoscopic length scale. The ARPES unit is equipped with a monochromatized high-power He lamp (Scienta VUV5k), a soft x-ray source (Prevac RS 40B1) and an electron analyzer (Scienta R3000, < 3 meV maximum resolution).
   
9. AC-LEEM / SPE-PEEM
   Our aberration-corrected spectroscopic Elmitec LEEM/PEEM III microscope is used to investigate both organic adsorbates as well as 2D single- and multilayer structures on various substrates. In particular, we are interested in kinetic processes such as layer growth and phase transitions, which are studied in situ and in real time. A spatial resolution better than 2 nm can be reached in LEEM mode, owing to the aberration corrector. Beside LEEM with different contrast mechanisms and µ-LEED, we can also record PEEM, ARUPS and POT data when using UV light instead of electrons for illumination of the sample. Energy filtering in the spectroscopic mode provides an energy resolution of approx. 150 meV.
   
10. 2D fabrication lab
    This lab hosts a glovebox, which includes an exfoliation work place, optical microscope and transfer stage, to fabricate van der Waals heterostructures for study with STM. Additional equipment include an ambient condition AFM for heterostructure analysis and cleaning and spin coater for preparation of transfer polymers.
    
11. Toroidal electron analyser
    The toroidal electron analyser is located at the Metrology Light Source beam line of the Physikalisch-Technische Bundesanstalt (PTB), Germany’s national metrology institute. A unique combination of a wide (±90°) acceptance of the analyser (constructed by Prof. John Riley, La Trobe University) and the metrological source of a monochromatic light (4-400 nm) with a calibrated photon flux allows a quantitative k-space-resolved study of the valence bands of low-dimensional structures.
    
12. Zeiss Sigma 500 SEM
13. Photoemission and electron energy loss spectroscopy (Rev. Sci. Inst. 88, 033903 (2017))
    The analysis chamber is equipped with a R4000 electron analyzer from Scienta, a monochromatized source of x-ray light for XPS (MX650 from Scienta), a monochromatized source of UV light for ARUPS (VUV5k from Scienta), and a home-build monochromatized source of electrons for HREELS. Additionally, we have a MCP-LEED from OCI. The sample is held by a He-cooled 6-axis iGonio manipulator from AVC.

Research at these facilities is complemented by our synchrotron work in which we mainly apply the methods of X-ray Standing Waves (XSW), Photo-Electron Spectroscopy (PES) and Photoemission Orbital Tomography (POT) to surface problems.

Abbreviations