Section Experimental Characterization

Section Experimental Characterization

Mission

The section agglomerates a comprehensive spectrum of tools to characterize the materials grown at the institute and of scientific partners. This is done as scientific service by providing fast feedback for crystal growers to improve their materials and with the aim to perform basic research in the field of solid-state physics and crystal growth. Our tools comprise structural, optical, electrical and thermoanalytical techniques; they cover all length scales from the macroscopic to the atomic scale. Combining these experimental techniques, we aim at an interdisciplinary effort at tackling urgent questions in solid state physics and at providing reliable materials parameters.

Research activities

The section is engaged in studying basic materials properties. This comprises electrical, optical and structural properties. We focus on semiconductors and dielectrics. Materials under study are III-Nitrides, Oxides and classical III-V- and group IV semiconductors. Doping, atomic defects, epitaxial heterostructures, growth and relaxation phenomena as well as optical properties are the most important topics. The section has strong collaboration with groups working in solid state theory. Recently we have a strong activity are developing in-situ characterization techniques in transmission electron microscopy and x-ray diffraction.

In addition, the section operates the joint laboratory for electron microscopy (Joint Lab for Electron Microscopy Adlershof (JEMA)) and the test structure lab with the Humboldt-Universität zu Berlin.

Topics

Junior Group: Advanced synchrotron radiation techniques for multiscale analysis of crystals

Our goal is to use and develop synchrotron-based X-ray techniques to study the real structure of single crystals on all scales. Recent development of 4th generation synchrotron radiation sources and instrumentation offers new approaches to study crystalline materials from atomic via nano- towards macroscopic scale. Using X-rays is paramount for experiments on crystals in-situ (e.g. during growth, treatment or operation) and this way provides a deep insight into dynamics and transitions of crystal structures.

We study real structure of crystals and its impact on materials properties as a function of various environmental parameters. This spans from analysis of atomic displacements that define how crystals behave under influence of external fields, to imaging of lattice inhomogeneities that affect optical or electronic characteristics of semiconductor materials and contain information about local stoichiometry. Such imaging methods are ideal to correlate crystal structure and function within recent semiconductor devices.

Contact

Dr. Carsten Richter

Ph. +49 30 6392 2859

Email

Electron Microscopy

The electron microscopy group focuses on the relation between physical properties and structure of semiconductors and oxides and of epitaxial materials by cutting edge electron microscopy techniques. By discovery of novel phenomena, their fundamental understanding and by developing predictive models we aim at improving the materials perfection and open perspectives for their technological applications. To reach these goals we combine the whole spectrum of structural and analytical techniques and are engaged in methodological developments.

We study real structure of crystals and its impact on materials properties as a function of various environmental parameters. This spans from analysis of atomic displacements that define how crystals behave under influence of external fields, to imaging of lattice inhomogeneities that affect optical or electronic characteristics of semiconductor materials and contain information about local stoichiometry. Such imaging methods are ideal to correlate crystal structure and function within recent semiconductor devices.

Stefan Mohn, Natalia Stolyarchuk, Toni Markurt, Ronny Kirste, Marc P. Hoffmann, Ramón Collazo, Aimeric Courville Rosa Di Felice, Zlatko Sitar, Philippe Vennéguès, Martin Albrecht
Polarity control in group-III nitrides beyond pragmatism
Phys. Rev. Appl. 5, 054004 (2016)
DOI: 10.1103/PhysRevApplied.5.054004

Charlotte Wouters, Toni Markurt, Martin Albrecht, Enzo Rotunno, Vincenzo Grillo
Influence of  Bloch wave state excitations on quantitative HAADF STEM imaging
Physical Review B 100, 184106 (2019)
DOI: 10.1103/PhysRevB.100.184106

Robert Schewski, Konstantin Lion, Andreas Fiedler, Charlotte Wouters, Andreas Popp, Sergey V. Levchenko, Tobias Schulz, Martin Schmidbauer, Saud Bin Anooz, Raimund Grüneberg, Zbigniew Galazka, Günter Wagner, Klaus Irmscher, Matthias Scheffler, Claudia Draxl, Martin Albrecht
Step-flow growth in homoepitaxy of β-Ga2O3 (100)—The influence of the miscut direction and faceting
APL Mater. 7, 022515 (2019)
https://doi.org/10.1063/1.5054943

Contact

Dr. Martin Albrecht

Ph. +49 30 6392 3094

Email

X-Ray Diffraction

Using state-of-the-art X-ray techniques, we aim to achieve a fundamental understanding of the correlation of structural and physical properties in crystalline materials. These investigations will also contribute to improving material perfection and pointing out paths for possible technological applications. For this purpose, we have a number of highly specialized instruments at our disposal at IKZ, including sophisticated experiments at synchrotron radiation sources.

Besides the determination of crystal orientation and crystal phases, we are primarily concerned with the elucidation of the real structure in bulk crystals and epitaxial layer systems. For ferroelectric thin films, we aim at a fundamental understanding of phase and domain formation, whereby phase transformations are identified and characterized by complex in situ experiments.  For the verification of real structure models, corresponding simulations are developed.

Martin Schmidbauer, Albert Kwasniewski, Jutta Schwarzkopf
High-Precision Absolute Lattice Parameter Determination of SrTiO3, DyScO3 and NdGaO3 Single Crystals
Acta Cryst. B 68, 8-14 (2012)
DOI: 10.1107/S0108768111046738

Martin Schmidbauer, Dorothee Braun, Toni Markurt, Michael Hanke, Jutta Schwarzkopf
Strain Engineering of Monoclinic Domains in K0.9Na0.1NbO3 Epitaxial Layers: A Pathway to Enhanced Piezoelectric Properties
Nanotechnology 28, 24LT02 (2017)
DOI: 10.1088/1361-6528/aa715a

Laura Bogula, Leonard von Helden, Carsten Richter, Michael Hanke, Jutta Schwarzkopf, Martin Schmidbauer
Ferroelectric Phase Transitions in Multi-Domain K0.9Na0.1NbO3 Strained Thin Films
Nano Futures 4, 035005 (2020)
DOI: 10.1088/2399-1984/ab9f18

Contact

Dr. Martin Schmidbauer

Ph. +49 30 6392 3097

Email

Transport and Electrical Properties

Control over the electrical conductivity of semiconductor crystals is essential prerequisite to realize the semiconductor devices needed in modern electronics. To assess the electrical properties of the semiconductors grown at IKZ we use current transport and capacitive measurements to determine, e.g., the concentration and mobility of free charge carriers, the concentration of dopants and that of compensating impurities or defects in close relation to growth and doping conditions.

Conductivity and Hall effect measurements (20-1100 K), deep level transient spectroscopy (20-800 K) and photo-thermal ionization spectroscopy as well as appropriate contact preparation techniques are continuously adapted and extended to meet the different requirements the various semiconductor crystals impose, e.g., additional photoexcitation for wide-bandgap semiconductors. Our present focus is on semiconducting oxides with potential for power electronics and resistive switching.

Andreas Fiedler, Robert Schewski, Michele Baldini, Zbigniew Galazka, Günter Wagner, Martin Albrecht, Klaus Irmscher
Influence of incoherent twin boundaries on the electrical properties of β-Ga2O3 layers homoepitaxially grown by metal-organic vapor phase epitaxy
J. Appl. Phys. 122, 165701 (2017)
DOI: 10.1063/1.4993748

Klaus Irmscher, Zbigniew Galazka, Mike Pietsch, Reinhard Uecker, Roberto Fornari
Electrical properties of β-Ga2O3 single crystals grown by the Czochralski method
J. Appl. Phys. 110, 063720 (2011)
DOI: 10.1063/1.3642962

Contact

Dr. Klaus Irmscher

Ph. +49 30 6392 3090

Email

Optical Spectroscopy

Optical spectroscopy is an indispensable tool in studying and understanding electronic and vibrational properties of solids. We analyze spectra of absorbed, emitted or scattered light to determine intrinsic parameters of novel crystals grown at our institute such as bandgaps and phonon modes. Additional features appearing in the spectra of imperfect crystals contain information about the defects’ nature which we use to identify the defects and to explore their growth-related formation.

Optical transmission/reflection spectrometers covering the wavelength range from 120 nm (VUV) to 100 µm (THz) and a micro-Raman spectrometer with six excitation wavelengths (325 to 785 nm) are available for the investigation of our bulk crystals and epitaxial layers at temperatures between 4 and 1600 K. Focus is presently on intrinsic and extrinsic properties of novel semiconducting oxides. Own methodological developments include imaging techniques, noteworthy laser scattering tomography.

Ivan Gamov, Eberhard Richter, Markus Weyers, Günther Gärtner, Klaus Irmscher
Carbon doping of GaN: Proof of the formation of electrically active tri-carbon defects
J. Appl. Phys. 127, 205701 (2020)
DOI: 10.1063/5.0010844

Klaus Irmscher, Martin Naumann, Mike Pietsch, Zbigniew Galazka, Reinhard Uecker, Tobias Schulz, Robert Schewski, Martin Albrecht, Roberto Fornari
On the nature and temperature dependence of the fundamental band gap of In2O3
Phys. Status Solidi Appl. Mater. Sci. 211, 54–58 (2014)
DOI: 10.1002/pssa.201330184

Contact

Dr. Klaus Irmscher

Ph. +49 30 6392 3090

Email