Scientific Facilities

The Stuttgart Center for Electron Microscopy (StEM), led by Peter A. van Aken, adds exceptional strength to the analytical capabilities of the Max Planck Institute for Solid State Research (MPI-FKF). StEM possesses outstanding expertise in the field of transmission electron microscopy (TEM), scanning electron microscopy (SEM), focused ion-beam (FIB) applications, and methodology development. The StEM predominantly serves all institutional departments to provide researchers with ultrahigh-resolution electron-microscopy instrumentation at the forefront of technology. Thus, challenging characterization problems in materials can be solved at unprecedented spatial and energy resolution, and a research venue can be created, where researchers from various disciplines are able to interact and develop collaborations.

The overarching goal of StEM's research in supporting the institute's scientific mission is to provide accurate, precise and quantitative atomic-scale structure and composition data to inform the synthesis, structure and properties rational materials design cycle. This is accomplished through a combination of high precision, high throughput and big data acquisition from state-of-the-art electron microscopy reinforced by continuous computational modelling, data processing, and theory and methodology development. The StEM is constantly exploring and expanding new capabilities made possible by recent technological developments such as monochromators, aberration correctors, energy filters, and fast pixelated direct electron detectors to provide general development and application strategies for enhanced investigation capabilities of topical issues in materials physics and chemistry.

StEM currently has six TEMs, including two state-of-the-art aberration-corrected JEOL ARM200Fs and the unique Zeiss SESAM for high-resolution analytical and imaging work. The group also operates a SEM and a FIB/SEM as well as advanced sample preparation labs with facilities to expertly prepare a very wide variety of materials. Just recently, a large instrument proposal for the acquisition of a new atomic-resolution multi-dimensional TEM has been granted by the Max Planck Society.

StEM's research and services focus on the characterization of interfaces, functional complex oxide heterostructures, strained semiconductors, nanostructured thin films, nanoparticles and nanomaterials, as well as molecules on 2D materials, including their structural, magnetic, electronic, and optical properties at the atomic scale. StEM’s research mission is the advancement of the in-depth knowledge of atomic and electronic structure, and of the microscopic understanding of materials with respect to their functionality and structure–property relationships.

The Computer Service groups runs the institute's central mail, print, software, backup and web servers, as well as file servers for the various departments and Max Planck Research Groups, all running the Linux operating system. Backup remains based on IBM Spectrum Protect (formerly Tivoli Storage Manager); currently the total backup data volume approaches 540 TB, 140 TB of which are archived data, the central Storage Area Network has been extended to 800 TB. The estimated total number of desktops and data acquisition PCs remains around 750. Of these about 75%  run Windows, 20% run Linux, the number of Macs is rising slowly.

With the setup of the new theory department headed by Ali Alavi in 2014, the number of High Performance Computing (HPC) nodes exploded to 536 and the number of computing cores to 13164  cores with 88 TB accumulated memory. Despite this sharp rise in computing power the HPC associated electricity consumption rose only by a factor of two to 100 kW. In reaction to this the server rooms 6B13 (infrastructure), 2E2 (High Performance Computing and Networking) were trimmed for energy and cooling efficiency using water cooled racks and backdoors. These installations use the 1.3 MW inhouse process cooling water plant.  The archieved temperature spread of 17/23°C permits free (radiative) cooling throughout eight months of the year.

For the Alavi group a distributed 1.5 PB filesystem accessible from the Stuttgart Campus as well as from the MP/CDF computing and data center in Garching was implemented over a dedicated 10 GbE fiber connection. 100 computing nodes of the Alavi department are hosted at the MP/CDF due to cooling constraints in the local server room.

The Xen-virtualisation platform for central services was updated and relies now on a CEPH based distributed storage backend. The services can move freely between three locations  in the main building and the new High Precision Lab in order to ensure High Availability of the services.

A new Firewall and VPN remote access strategy was implemented together with significant changes in the institute‘s Identity Management (IdM). The groups focus here was to rely on open industry standards whereever possible to avoid customer lock-in. When needed, proprietary systems like Microsoft Active Directory were provisioned with external help from open sources like Open-LDAP in order to permit software and patch roll-out in Windows environments.  These measures focus on the protection of the institute data and infrastructure while enable scientists to access them from other locations. The international collaboration and the inherent nonlocality of science make these tasks highly complex.

An Intrusion Detection System (IDS) was implemented to facilitate the detection of the growing number and intensity of cyber attacks.

The X-Ray Diffraction group provides scattering and diffraction measurement and analysis of powders using laboratory, synchrotron, and neutron sources, under ambient and non-ambient conditions. Research is focused on the determination of crystal structures, microstructural properties (strain, domain size, stacking faults), and phase composition of condensed matter, along with methodological development within this area. Scientific cooperation is offered in all fields of routine and non-routine analysis. Special expertise in ab initio solution and refinement of crystal structures from powder diffraction data is provided. Long-term research projects deal with structure–property relationships of functional materials (e. g. thermochromic-, photochromic-, electronic-, magnetic-, and construction materials). The structures of corrosion phases found on heritage objects are determined to guide conservation methods. Disordered and nanostructured materials are characterized using total scattering and pair distribution function methodologies, e. g. for assessment of processing effects on the structure and stability of semicrystalline and amorphous polymers and active pharmaceutical ingredients. Reaction and transformation mechanisms are studied using in situ monitoring including solution-based and mechanochemical syntheses and gas loading of metal-organic frameworks (MOFs). Lectures and workshops on crystallography are offered and textbooks are written in regular intervals

The central Information Service for the institutes of the Chemical Physical Technical (CPT) Section of the Max Planck Society offers database searches, which are too complex or demanding for end users, and provide access to information sources not included in the range of end user databases commonly accessible. Most important are the various field-specific literature and patent databases as well as the citation databases accessible via Web of Science and Scopus. Establishing impact data for research evaluation has become a major field of activity of the information service. The determination of meaningful indicators and the proper interpretation of citation impact data require some experience and sound background information. Research and publication activities in the newly emerging fields of bibliometrics and altmetrics address the need for such experience when using and interpreting citation data.

The Crystal Growth group focuses on applying, modifying and developing techniques to grow large and high-quality single crystals from melt, solution or vapor. The techniques used comprise the traveling solvent floating zone method, flux or top-seeded solution growth, vapor transport, Bridgman, Czochralski and hydrothermal growth. There is continual interest in further study of superconductivity in the cuprate compounds, such as, REBa₂Cu₃O_7-d (RE = Rare earth), YBa₂Cu₄O_8, Bi₂Sr₂Ca_n-1Cu_nO_2+4n+d. (n = 1,2,3) and Bi₂Sr_2-xLa_xCuO₆. A typical example is the CDW induced by an in-plane field, setting in above the dome in single-layered Bi₂Sr_2-xLa_xCuO₆. A modified flux method was applied to grow iron-based single crystals. The Co-doped KFeCoAs₂ is recognized as isoelectronic to the parent compound of BaFe₂As₂. New results of structural magnetic fluctuations were obtained by doping Mn local moments in BaFe₂As₂. A modified Bridgman method was used to grow high-quality topological superconductor crystals of Cu_xBi₂Se₃ (x ≈ 0.8, 1.0, 1.2 and 1.5). A pronounced peak effect was observed by magnetization and electrical transport measurements in a Cu_0.10Bi₂Se₃ single crystal. Organic-inorganic hybrid perovskite CH₃NH₃PbX₃ single crystals for solid–state solar cell devices were grown using a hydrohalic acid solution method. Recent research highlights include the hydrothermal growth of (Li_1−xFe_x)OHFeSe (11111) compounds. Also, we have set up new types of high-pressure cells and have just started the single crystal growth under high pressure in collaboration with department Takagi. Additionally, we have started to search for new interesting materials in solid-state physics and chemistry in parallel, by using single crystal growth.

The Thin Film Technology group provides expertise in synthesis, thermal treatment and characterization of complex oxide epitaxial thin films and heterostructures with high precision to all members of MPI-FKF. By using the pulsed laser deposition (PLD) and ozone assisted molecular beam epitaxy (MBE) and reactive sputtering we synthesize different complex oxides including cuprates, manganates, nickelates, cobaltates, vanadates, ruthenates, iridates and many other. Our research interests are grouped into three categories: (i) the development of state-of-the-art instruments for novel oxide thin film deposition and defect control to ensure a material base suitable for the forefront research within MPI-FKF, (ii) physics and chemistry at oxide interfaces, (iii) the electronic devices based on novel oxides. The main customers are the researchers from the departments Keimer, Maier, Mannhart and Takagi. The Thin Film Technology Facility group has executed the projects in close collaboration not only with research departments also with the StEM group that has ability for an atomic scale imaging of oxide heterostructures. In addition, we support other projects with materials deposition such as metals (Au, Pt, Ti, Cr etc.) and insulators (SiO_x, TiO_2, Al₂O₃), dry chemical etching, patterned contact fabrication, ultrasonic bonding and physical properties measurements such as thermoelectricity, resistivity, mutual inductance, XRD and AFM.

The Interface Analysis groupinvestigates the atomic and electronic structure of solid-solid and gas-solid interfaces. Using electron spectroscopy techniques, diffraction, scanning probe microscopy and secondary ion mass spectrometry (SIMS), atomic geometry, electronic band structure, chemical composition and bond coordination are determined. Thin films and buried interfaces are accessible by sputtering and cleaving techniques. Experimental methods include time-of-flight SIMS to quantify the chemical composition at the surface, within the film and at interfaces. Chemical and electronic properties are investigated using electron spectroscopy. Photoemission electron microscopy (PEEM), in the so-called k-space microscopy mode completes the electronic structure investigations with high energy, spatial and momentum resolution. The atomic structure is analyzed by low-energy electron diffraction (LEED). The group’s research is directed towards ultrathin films of novel materials such as graphene and other 2D-materials. Material growth, heterojunctions, molecular adsorbates and metallization are investigated on an atomic level. In particular, graphene layers grown on silicon carbide (SiC) are investigated. Quasi-free standing, homogeneous, large area epitaxial graphene films are grown on SiC. Their electronic structure is tailored on an atomic level by doping and intercalation. The graphene valence bands are analyzed using angle-resolved photoelectron spectroscopy (ARPES) and k-space microscopy. For additional scientific investigations the group utilizes beamtimes at various synchrotron facilities.

In 2011, the cleanroom facility of the von Klitzing department became part of the newly established Scientific Facility Nanostructuring Lab (NSL). Under class-10 cleanroom conditions with stable room humidity and temperature, samples are processed by students or in service by the NSL team using photolithography, dry and wet etching, and material deposition under vacuum. For the fabrication of structures down to 10 nm – on small but also large area, two electron beam lithography systems using acceleration voltages up to 100 kV are available. A focused ion beam system allows to cut and to sculpture samples under vision of a scanning electron microscope. Two state-of-the-art scanning electron microscopes, including analytic tools like EBIC, EDX, EBDS and – from 06/2020 – scanning probe microscopy inside the SEM chamber, allow the characterization to nanometer scale.

The infrastructure is intended to be used in parallel by many students on their own, is dedicated to deal with different materials avoiding cross-contamination, and especially to handle small sample sizes (typical 5 mm by 5 mm), but also wafers up to 4 inches. At present, the NSL has more than 100 customers – from the Institute, the MPI of Intelligent Systems, and the University of Stuttgart.

Besides introducing students into the usage of the equipment and offering processing service, the NSL team continuously develops sample processing recipes and the infrastructure further. Here we especially focus on excluding the exposure of samples to oxygen, water and humidity in and between processing and characterization steps.

A small group of PhD and Master students develops and operates a unique scanning probe microscope at 40 mK with a linear array of single-electron transistors and Hall sensors as probes. Recently, we have measured the Hall potential profile and therefore the current distribution in several fractional quantum Hall regimes.