The department aims to prepare and provide single crystal materials with tailored properties and high yield for use as substrates or components in novel and energy-efficient electronic, optoelectronic, optical/laser, and piezo-/ferroelectric applications. For anticipated industrial application we are fulfilling purity and structural quality constraints while working on reproducibility and yield. We also use our competence to provide unique crystals as a service for materials research.
Research activities
Our materials portfolio ranges from elementary (Si, Ge) and compound semiconductors (GaAs, InP) to the novel oxide semiconductors (e.g. β-Ga2O3), oxide substrates for films with novel functionalities (e.g. strained ferroelectrics), and bulk optical, laser (including fluorides), and piezoelectric crystals. We specialize in high temperature melt growth techniques such as Czochralski, Floating Zone, Bridgman/VGF and EFG. Tailored materials, growth conditions, and numerical modeling are employed to optimize the growth process.
The section specializes in the bulk growth of oxide and fluoride single crystals. Such crystals are used as substrates for ferroelectric and oxide electronic applications as well as optical, piezoelectric, or laser components. We also prepare reference and benchmark samples to enable studies on the properties of materials with highest structural perfection and purity. Through collaborations and service to companies and research institutions we provide the materials basis for many research projects inside and outside IKZ.
Research activities
In our section, we develop single crystal substrates of oxide semiconductors such as β-Ga2O3. We prepare oxide crystals with perovskite structure as lattice-matched substrates e.g. for strained ferroelectric layers or thin films comprising new functionalities. We research tailored oxide and fluoride crystals for optical applications and lasers. And we provide thermochemical analysis and develop tailored growth techniques to enable crystal growth of novel compounds.
Research topics in my group ("section")
Junior Research Group "Fluoride Crystals for Photonic Applications"
Fluoride single crystals are key components for a variety of photonics applications such as laser materials, high power optical isolators, as well as nonlinear frequency converters and optical windows with superior properties in the deep-UV region. Fluoride compounds can overcome the current limitation in handling power of optical isolators. They are also very promising for solid state laser cooling (optical refrigeration), a technique enabling to cool down solid materials to cryogenic temperature by laser excitation.
We manufacture transparent conducting or semiconducting oxide single crystals. The topic is primarily known from our pioneering work on 2" β-Ga2O3 single crystals (Czochralski method), and other binary oxides (In2O3, SnO2). In recent years, we have developed gallium based spinels (MgGa2O4, ZnGa2O4, CoGa2O4), barium stannate (BaSnO3) and lanthanum indate (LaInO3). As substrates and thin films, these crystals enable new device structures in power electronics, optoelectronics, for sensors and ferrimagnetic thin layers, and as scintillator material.
Our primary focus is to develop new bulk crystals with tailored lattice parameters, mainly with perovskite, pyrochlore or magnetoplumbite structure. As substrates, such crystals serve as the literal foundation for the preparation of epitaxially grown oxide thin films with interesting ferroelectric, superconducting, ferromagnetic, piezoelectric, multiferroic, or electron transport properties. Some of the bulk crystals are attractive for optical applications as well. Most of the compounds are exclusively grown at IKZ for our academic and industrial research partners.
Individual single crystals are demanded as benchmark and reference materials in different fields of science, e.g. geology, materials science, solid-state chemistry and physics. They are used by research institutions, companies and technology ventures for detailed investigation, to demonstrate their application potential or to assess conditions for a commercial production. If the required material falls within our range of capabilities and is not commercially available, we can prepare and provide it.
We use thermochemical analysis to determine how a particular material can be best grown as a single crystal with desired properties. Incongurent melting, material decomposition, or metal oxidation state instability are common problems that can be mitigated by establishing proper phase diagrams. We optimise source material compositions for the respective growth methods and suggest the optimal growth atmosphere. With our expertise we also support the other IKZ activities regarding their process technologies.
Aluminium nitride (AlN) crystals are grown by physical vapor phase transport (PVT) in crucibles of TaC or W and must have low dislocation densities and relevant diameters (1") regardless of the intended application. Prerequisites for the growth of AlN crystals of high crystalline quality are the availability of low-defect seeds, the avoidance of impurity precipitation during heating up and an optimal T-field design (e.g. high T).
I supervised the "Aluminium Nitride" group at IKZ until 2019, when the group moved to the department "Application Science". Since then, activity lead is Dr. Thomas Straubinger.
The Center for Laser Materials (ZLM) is dedicated to research on crystalline materials for optical applications. To this end we use our state-of-the art laser and spectroscopy laboratories as well as the interdisciplinary research infrastructure at the IKZ. In close collaboration with the research group ‘oxides & fluorides’ in the department ‘volume crystals’ the ZLM acts as a one-stop shop for optical crystals for laser applications, optical isolators and nonlinear frequency conversion.
The Center for Laser Materials at IKZ is led by PD Dr. Christian Kränkel.
The joint mission of the "IKZ-Cornell Joint Lab for Unleashing Hidden Properties to Empower Oxide Electronics" with Prof. Darrell G. Schlom is the coordinated research on the development of large-area single-crystal oxide substrates enabling the discovery of materials with unprecedented properties for the next generation of oxide electronic devices.
The IKZ-Cornell Joint Lab contact is Dr. Christo Guguschev.
IKZ is a key partner within the Leibniz ScienceCampus "Growth and Fundamentals of Oxides for Electronic Applications" (GraFOx). The Science Campus is devoted to study in particular the basic materials research for future oxide electronic applications. Focus topics are "Gallium oxide", "Strontium titanate" and "Oxides with high electron mobility" (BaSnO3 u.a.). The IKZ engages in bulk crystal growth, epitaxy, and materials characterization.
The DFG research unit "Periodic low-dimensional defect structures in polar oxides " is focused on systematic investigations of polar oxide lithium niobate-lithium tantalate (LiNb1-xTaxO3, LNT) solid solutions. Due to the miscibility over the entire compositional range as well as the tunable ferroelectric domain structure, they represent a model system for uncovering and application of novel phenomena in material science and physics. The exceptional thermal stability of the system, as well as the inherent point defects, domain structure, and their interaction open up a novel and broad range of emerging applications not only in high-temperature sensor and actuator technologies, but also in integrated acoustics and photonics. The IKZ project part is focussed on the growth of Li(Nb,Ta)O3 single crystals from the melt.
The IKZ project part is led by Dr. Steffen Ganschow geleitet.
The Leibniz-Institut für Kristallzüchtung (IKZ) Berlin is one of the leading institutes in the field of growth and preparation of crystalline solids. These materials provide the basis for e.g. photovoltaics, micro-, opto-, and power electronics, in sensors, optics, and laser technology. The research topics span from fundamental research and development to growth technologies applicable in industry.
The colleagues at IKZ - scientists, technicians, young researchers and administrative staff - constitute the institute's success. Our strength is based on their long-term expertise and knowledge. Teaching and training of new team members is the key for future success. The IKZ is dedicated to care for work-life balance and equal opportunities employment and is audited with certificate.
