Instrumentation
Ultrahigh-Vacuum Machines
© Michael Schmid/IAP
Vacuum Chamber: Room-Temperature-STM
This UHV machine is the workhorse of our group. The STM delivers excellent atomic resolution since 1991.
Besides the STM, the analysis chamber also features a hemispherical analyzer for XPS (x-ray photoelectron spectroscopy) and LEIS (low-energy ion scattering), a cylindrical mirror analyzer with coaxial electron source for AES (Auger electron spectroscopy) and LEED optics (low-energy electron diffraction). The preparation chamber is equipped with an ion source for sputtering, three electron-beam evaporators, a retractable gas doser with a microcapillary plate and a gas cracker for atomic oxygen or hydrogen. Sample heaters (electron bombardment of the sample plate, up to 1200 °C) are available in both chambers.
© Michael Schmid/IAP
Ultra-high vacuum system with the low-temperature STM
This machine is based on a commercial low-temperature (LT) STM and UHV system purchased in 1998. Its preparation chamber houses a manipulator with sample heating/cooling (≈100 … 1000 K), a separate annealing stage (up to ≈1300 K), an ion source for sputtering or LEIS (low-energy ion scattering), an electron source, a hemispherical analyzer for LEIS and AES and LEED optics. The chamber currently also houses an electron beam evaporator for thermal deposition, a quartz crystal microbalance (QCM), a capillary-plate gas doser and a residual gas analyzer (quadrupole mass spectrometer). The STM, which also allows Q-plus AFM operation, is in a separate UHV chamber, routinely reaching the 10-12 mbar range, and can be operated at room temperature or cooled by liquid nitrogen (77 K) or liquid helium (reaching a temperature of 5 K). We can also heat the sample for temperatures in between.
© Michele Riva/IAP
Molecular beam epitaxy system
The MBE (molecular beam epitaxy, opens an external URL in a new window) machine is an ultrahigh vacuum system based on a setup acquired from Specs (hence, also named Specs machine) with a preparation chamber optimized for growth of thin films. Besides a sample manipulator with electron beam heater, ion source for sputtering, evaporators, and a quartz crystal microbalance, the preparation chamber also houses an oxygen plasma source. The analysis chamber is equipped with XPS, LEED and a variable-temperature STM.
In 2014, the machine has been extended with a laser-MBE system, where oxides can be grown by pulsed laser deposition with in-situ control of the growth mode by RHEED (reflection high-energy electron diffraction). The samples can be transferred from the growth chamber to the analysis chamber through an ultrahigh-vacuum transfer line. Growing complex oxides layer by layer with well-defined structure and stoichiometry is a challenging task, but highly rewarding: For many materials, samples suitable for surface science can be obtained only this way.
As you can imagine when looking at the image, it is currently the largest UHV machine of our group…
© Jan Balajka/IAP
Ultra-high vacuum chamber of the Q-Plus low-temperature STM/AFM, suspended on bungee chords
The ultrahigh-vacuum low-temperature STM/AFM uses the so-called qPlus sensor for nc-AFM (non-contact atomic force microscopy). It consists of a tiny quartz tuning fork with an even tinier tip glued to the end of one of its prongs.
The machine is situated on the 5th floor in a noisy city environment, thus it needs an excellent vibration isolation system: We have suspended the one-metric-ton machine from the ceiling on 40 bungee cords! This design also features accurate leveling and has been patented, opens an external URL in a new window. For more information, see the Youtube video, opens an external URL in a new window.
We have also added an improved preamplifier (design by Giessibl's group, opens an external URL in a new window). Now the machine delivers excellent results.
© Michael Schmid/IAP
Vacuum Chamber: Omega
This machine, also called Omega for short, is based on an Omicron Compaqlab UHV system. It consists of a main chamber (preparation and analysis, p<10-10 mbar) and load lock chamber for quick sample loading. The sample can be brought into contact with liquid water under ultra-pure conditions in an additional tiny side chamber.
The UHV chamber contains:
- A room-temperature scanning tunneling microscope (Omicron STM-1)
- Hemispherical energy analyzer Specs Phoibos 150 for LEIS and XPS
- LEED optics Omicron SpectaLEED
- Differentially pumped ion gun Specs IQE 12/38
- Dual anode (Mg|Al) X-ray source
- Quadrupole mass spectrometer (SRS RGA 100/12)
- Sample manipulator, radiative heating up to 1200K
- E-beam evaporator (Focus EFM3)
- Quartz crystal microbalance
© Michael Schmid/IAP
Ultrahigh-vacuum system for temperature-programmed desorption and spectroscopy
Ultrahigh-vacuum system for temperature-programmed desorption and spectroscopy
The machine for reactivity studies was optimized for temperature programmed desorption (TPD). A molecular beam can be used to dose gasses on a well-defined area (≈ 3.5 mm diameter) of the sample; this avoids background signals from ill-defined surfaces and the sample holder. The machine also contains a large hemispherical analyzer for various spectroscopy techniques (XPS with monochromatized source, UPS, LEIS). Recently, the machine has been equipped with an infrared spectrometer (Bruker Vertex 80v) for vibrational spectroscopy.
© Michael Schmid/IAP
Vacuum Chamber: LEED and MOKE
Having its roots in the early 1980ies, this ultrahigh-vacuum (UHV) machine has seen many generations of students doing work in widely varying fields, e.g. photoemission in the early days, low-energy ion scattering (LEIS), quantitative low-energy electron diffraction (LEED) and magneto-optic Kerr effect (MOKE) measurements of surface magnetism; the latter available in the recent years. The system has seen a major renewal in 2009, with a new chamber, ion source, residual gas analyzer and much more.
The mu-metal UHV chamber houses a sample manipulator with heating and cooling (100 … 1000 K; down to 50 K with liquid-helium cooling), two ion sources, a cylindrical mirror analyzer with concentric electron source for AES, as well as LEED optics and several deposition sources. The MOKE setup uses atmospheric-side coils with yokes reaching into the vacuum chamber, reaching a maximum field of ≈ 0.1 T in the 3-cm gap. Kerr rotation and ellipticity of the HeNe laser beam reflected on the sample are measured with a modulation technique, using a photoelastic modulator.
Instrumentation Development
© Michele Riva & Michael Schmid
Symbolic image for the ViPErLEED project
The ViPErLEED package (Vienna Package for Erlangen LEED) provides an all-in-one solution for surface crystallography with quantitative LEED (low-energy electron diffraction):
- Hardware (electronics) and software for data acquisition
- Spot Tracker and I(V) Editor for data analysis, arXiv:18413
- Simulation and structure optimization, arXiv:18821
For more information, see the detailed description at viperleed.org, opens an external URL in a new window (and the source code at github, opens an external URL in a new window). The first two papers on ViPErLEED will appear in Phys. Rev. Research very soon! (In the meanwhile use the arXiv links above.)
© Jan Balajka/IAP
Ultra-pure water drop in a vacuum chamber
The surface physics group has devised a setup for bringing surfaces into contact with liquid water, without exposing the sample to atmosphere or protective gas. We consider this water drop the purest water in the world, since it is created by distillation of ultrapure water and never exposed to any gas (except its own water vapor),
- J. Balajka, J. Pavelec, M. Komora, M. Schmid, and U. Diebold
Apparatus for Dosing Liquid Water in Ultrahigh Vacuum
Rev. Sci. Instrum. 89, 083906 (2018). - J. Balajka, M. A. Hines, W. J. I. DeBenedetti, M. Komora, J. Pavelec, M. Schmid, and U. Diebold
High-affinity adsorption leads to molecularly ordered interfaces on TiO2 in air and solution
Science 361, 786 (2018). (Full text is publically available via a link at our Download page)
We are currently working on a modification of this setup for measuring the surface tension of water with unprecedented accuracy.