Project A6 - Microstructure and Structural Change of Magnetoelectric and Piezotronic Sensors

The current limitations of state-of-the-art magnetoelectric (ME) sensors in detecting ultra-low magnetic fields raise fundamental questions about the amorphous and crystalline structures of the sensor components, particularly concerning magnetostrictive layer structures. The specific nanostructure and its structural change must be correlated to growth conditions and heat treatments during sensor production, but also linked to the (long term) functionality of the operating sensor. Diverse material systems included in thin film sensor concepts are targeted in A6 to examine these structural and functional properties with advanced analytical methods of transmission electron microscopy (TEM) and synchrotron-based X-ray scattering combining synergistically multiscale information with excellent resolution and precision. The ultimate goal of our research is to develop in situ / in operando analytical methods that can provide feedback for improved sensor manufacturing processes. The methodological combination of synchrotron-based pair distribution analysis and novel electron diffraction methods will be further developed to determine the amorphous to (semi-)crystalline states of novel (exchange biased) magnetic (multi-)layer systems (based on, e.g., (Fe90Co10)78Si12B10, CoFeC, A1, A100), which are relevant for surface acoustic wave (SAW, A8, A9, A10), converse- (A7), ΔE- (A4) and low frequency hybrid ME-sensor concepts (A2). Project A6 aims to understand the impact of deposition conditions and annealing temperatures during sensor preparation and packaging as the essential processing parameters. In situ heating experiments in the TEM and within brilliant synchrotron X-ray sources will interrelate the short-to-long range ordering with magnetic properties of the sensors. In collaboration with A9, crystalline piezoelectric materials (e.g., AlScN) as components of novel SAW thin film sensors will be examined with respect to the crystallographic texture and strain distribution on multiscales. In this context, aberration-corrected Scanning TEM (STEM) provides information on epitaxial interface structures and local strain as also visualized in 3D via coherent X-ray diffraction imaging (CXDI). We will examine silicon and sapphire substrate-based SAW sensor structures during operation to investigate possible loss mechanisms, e.g., clamping of acoustic waves at structural defects. Novel methodological advances of in operando X-ray scattering will be exploited to design experiments for standing wave excitations and time-resolved pulsed-probe measurements coupled with in situ Scanning Electron Microscopy (SEM) observations. These results will further be used in conjunction with finite element simulations (A8, A9, A10) to link experiments with simulation.

Involved Researchers

Person		Role
	Dr. Bridget Murphy Physics Interface Physics	Project lead
	Prof. Dr. Lorenz Kienle Materials Science Synthesis and Real Structure	Project lead
	M. Sc. Otto Lippmann Physics Interface Physics	PhD student
	Dr.-Ing. Niklas Wolff Materials Science Synthesis and Real Structure	Postdoc researcher

Role within the Collaborative Research Centre

The unique combination of synchrotron-based techniques and atomically resolved electron microscopy enables us to analyze the magnetic multilayer materials from A1 and piezoelectric AlScN thin films for SAW sensors from A9, Z1 on all relevant length scales, ex situ, in situ and operando. A6 develops new and advanced examination methods in close collaboration with these projects. Moreover, A6 establishes the competence center for advanced nanoanalytical research within the CRC. and collaborates with projects A2, A4, A7, A8, A10 and B12.

The major goal of these experiments is to understand the role that structure and stress play in sensor performance from the atomic scale to grain size and microscopic sample size. By understanding these key parameters via XRD and TEM studies, we can work towards knowledge-based sensor design. In addition, we aim to develop micro and nanostructure analysis by achieving a united approach of these powerful structural determination methods.

Project A6 will participate in the focused research groups F1 - Magnetic Layers, F4 - Magneto­electric Sensors and F2 - Modelling.

Project-related Publications

K. Pingen, A. M. Hinz, P. Sandström, N. Wolff, L. Kienle, L. Scipioni, J. Greer, E. von Hauff, L. Hultman, J. Birch, C.-L. Hsiao: High Growth Rate Magnetron Sputter Epitaxy of GaN Using a Solid Ga Target, Vacuum , vol. 220, 112852, 2024.

N. Wolff, G. Schönweger, I. Streicher, Md R. Islam, N. Braun, P. Straňák, L. Kirste, M. Prescher, A. Lotnyk, H. Kohlstedt, S. Leone, L. Kienle, S. Fichtner: Demonstration and STEM Analysis of Ferroelectric Switching in MOCVD-Grown Single Crystalline Al0.85Sc0.15N, Adv. Phys. Res., 2300113, 2024.

K. Pingen, S. Neuhaus, N. Wolff, L. Kienle, A Žukauskaitė, E. von Hauff, A. M. Hinz: Influence of Si(111) Substrate Off-Cut on AlN Film Crystallinity Grown by Magnetron Sputter Epitaxy, Journal of Applied Physics, vol. 134, issue 2, 2023.

G. Schönweger, N. Wolff, Md R. Islam, M. Gremmel, A. Petraru, L.Kienle, H.Kohlstedt, S. Fichtner: In-Grain Ferroelectric Switching in Sub-5 nm Thin Al0.74Sc0.26N Films at 1 V, Advanced Science, 2302296, 2023.

V. Schell, E. Spetzler, N. Wolff, L.Bumke, L. Kienle, J. McCord, E. Quandt, D. Meyners: Exchange Biased Surface Acoustic Wave Magnetic Field Sensors, Scientific Reports, vol. 13, no. 8446, 2023.

R. Guido, P. D. Lomenzo, Md R. Islam, N. Wolff, M. Gremmel, G. Schönweger, H. Kohlstedt, L. Kienle, T. Mikolajick, S. Fichtner, U. Schroeder: Thermal Stability of the Ferroelectric Properties in 100 nm-Thick Al0.72Sc0.28N, ACS Appl. Mater. Interfaces, vol. 15, issue 5, p. 7030–7043, 2023.

Md R. Islam, G. Schönweger, N. Wolff, A. Petraru, H. Kohlstedt, S. Fichtner, L. Kienle: A Comparative Study of Pt/Al0.72Sc0.28N/Pt-Based Thin-Film Metal-Ferroelectric-Metal Capacitors on GaN and Si Substrates, ACS Appl. Mater. Interfaces 15, 35, 41606–41613, 2023.

G. Masciocchi, J. W. van der Jagt, M.-A. Syskaki, A. Lamperti, N. Wolff, A. Lotnyk, J. Langer, L. Kienle, G. Jakob, B. Borie, A. Kehlberger, D. Ravelosona, M. Kläui: Control of Magnetoelastic Coupling in Ni/Fe Multilayers using He+ ion Irradiation, Appl. Phys. Lett., vol. 121, issue 18 , 182401, 2022.

G. Schönweger, Md. R. Islam, N. Wolff, A. Petraru, L. Kienle, H.Kohlstedt, S.Fichtner: Ultrathin Al1−xScxN for Low-Voltage-Driven Ferroelectric-Based Devices, PSS rapid research letters, vol. 17, issue 1, 2200312, 2023.

N. Wolff, M. R. Islam, L. Kirste, S. Fichtner, F. Lofink, A. Žukauskaitė, L. Kienle: Al1−xScxN Thin Films at High Temperatures: Sc-Dependent Instability and Anomalous Thermal Expansion, Micromachines, no. 13, issue 8 , 01282, 2022.

M. T. Bodduluri , B.Gojdka , N.Wolff , L. Kienle , T. Lisec, F. Lofink: Article Investigation of Wafer-Level Fabricated Permanent Micromagnets for MEMS, Micromachines , no. 13, issue 5, pp. 742, 2022.

J. Su , S. Fichtner , M. Zubair Ghori , N. Wolff , M. R. Islam , A. Lotnyk , D. Kaden , F. Niekiel, L. Kienle, B. Wagner, F. Lofink: Growth of Highly c-Axis Oriented AlScN Films on Commercial Substrates, Micromachines , no. 13, issue 5, pp. 783, 2022.

G. Schönweger, A. Petraru, Md R. Islam, N. Wolff, B.t Haas, A. Hammud, C. Koch, L. Kienle, H. Kohlstedt, S. Fichtner: From Fully Strained to Relaxed: Epitaxial Ferroelectric Al1-xScxN for III-N Technology, Advanced Functional Materials, no. 32, issue 21 , pp. 2109632, 2022.

N. Wolff, T. Braniste, H.Krüger, S. Mangelsen, Md R.Islam, U. Schürmann, L. M. Saure, F. Schütt, S. Hansen, H.Terraschke, R.Adelung, I. Tiginyanu, L. Kienle: Synthesis and Nanostructure Investigation of Hybrid β-Ga2O3/ZnGa2O4 Nanocomposite Networks with Narrow-Band Green Luminescence and High Initial Electrochemical Capacity, Small, vol. 19, issue 18, 2207492, 2023.

L. Bumke, N. Wolff, C. Chluba, T. Dankwort, L. Kienle, E. Quandt: Coherent Precipitates as a Condition for Ultra-Low Fatigue in Cu-Rich Ti53.7Ni24.7Cu21.6 Shape Memory Alloys, Shape Memory and Superelasticity, volume 7, pp. 526–540, 2021.

P. Jordt, N. Wolff, S. B. Hrkac, S. Shree, D. Wang, R. J. Harder, C. Kübel, R. Adelung, O. G. Shpyrko, O. M. Magnussen, L. Kienle, B. M. Murphy: Visualizing Intrinsic 3D-Strain Distribution in Gold Coated ZnO Microstructures by Bragg Coherent X-Ray Diffraction Imaging and Transmission Electron Microscopy with Respect to Piezotronic Applications, Advanced Electronic Materials, vol. 7, issue 11, 2100546, 2021.

P. Pop-Ghe, N. Wolff, A. Rubab, L. Kienle, E. Quandt: Tailoring Growth Modes by Excess Alkali Addition in Magnetron Sputtered Potassium Sodium Niobate Thin Films, Materials Today Communications (2021), vol. 27, 102221, 2021.

P. Jordt, S. B. Hrkac, J. Gröttrup, A. Davydok, C. Krywka, N. Wolff, L. Kienle, R. Adelung, O. M. Magnussen, B. M. Murphy: Local Strain Distribution in ZnO Microstructures Visualized with Scanning Nano X-Ray Diffraction and Impact on Electrical Properties, Advanced Engineering Materials, vol. 23, issue 11, 110871, 2021.

M.R. Islam, N. Wolff, M. Yassine, G. Schönweger, B. Christian, H. Kohlstedt, O. Ambacher, F. Lofink, L. Kienle, S. Fichtner: On the Exceptional Temperature Stability of Ferroelectric Al1-xScxN Thin Films, Applied Physics Letters, vol. 118, issue 23, 232905, 2021.

N. Wolff, P. Jordt, J. Jetter, H. Vogt, A. Lotnyk, K. Seemann, S. Ulrich, E. Quandt, B. M. Murphy, L. Kienle: Nanostabilization of Tetragonal Distorted FeCo Variants in Ultra-Thin FeCo/TiN Multilayer Films, Materials Characterization, vol. 172, 110871, 2021.

N. Wolff, S. Fichtner, B. Haas, M.R. Islam, F. Niekiel, M. Kessel, O. Ambacher, C. Koch, B. Wagner, F. Lofink, L. Kienle: Atomic Scale Confirmation of Ferroelectric Polarization Inversion in Wurtzite-Type AlScN, Journal of Applied Physics, vol. 129, issue 3, 034103, 2021.

S. M. Curtis, N. Wolff, D. Dengiz, H. Lewitz, J. Jetter, L. Bumke, P. Hayes, E. Yarar, L. Thormählen, L. Kienle, D. Meyners, E. Quandt: Integration of AlN Piezoelectric Thin Films on Ultralow Fatigue TiNiCu Shape Memory Alloys, Journal of Materials Research 35, no. 10, pp. 1298–1306, 2020.

L. Siebert, N. Wolff, N. Ababii, M. Terasa, O. Luopan, A. Vahl, V. Duppel, H. Qiu, M. Tienken, M. Mirabelli, V. Sontea, F. Faupel, L. Kienle, R. Adelung: Facile Fabrication of Semiconducting Oxide Nanostructures by Direct Ink Writing of Readily Available Metal Microparticles and their application as Low Power Acetone Gas Sensors, Nano Energy, vol. 70, issue 2, 104420, 2020.

X. Tao, H. Jin, M. Mintken, N. Wolff, Y. Wang, R. Tao, Y. Li, H. Torun, J. Xie, J. Luo, J. Zhou, Q. Wu, S. Dong, J. Luo, L. Kienle, R. Adelung, Y. K. Mishra, Y. Q. Fu: Three-Dimensional Tetrapodal ZnO Microstructured Network Based Flexible Surface Acoustic Wave Device for Ultraviolet and Respiration Monitoring Applications, ACS Applied Nano Materials, vol. 3, issue 2, pp. 1468–1478, 2020.

N. Wolff, V. Ciobanu, M. Enachi, M. Kamp, T. Braniste, V. Duppel, S. Shree, S. Raevschi, M. Mendina-Sánchez, R. Adelung, G. Schmidt, L. Kienle, I. Tiginyanu: Advanced Hybrid GaN/ZnO Nanoarchitectured Microtubes for Fluorescent Micromotors Driven by UV Light, small, vol. 16, issue 2, 1905141, 2019.

S. Fichtner, N. Wolff, F. Lofink, L. Kienle, B. Wagner: AlScN: A III-V Semiconductor Based Ferroelectric, Journal of Applied Physics, vol. 125, issue 11, 114103, 2019.

N. Wolff, V. Hrkac, J. Ditto, V. Duppel, Y. Mishra, D. Johnson, R. Adelung, L. Kienle: Crystallography at the Nanoscale: Planar Defects in ZnO Nanospike, Journal of Applied Crystallography, vol. 52, pp. 1009-1015, 2019.

N. Wolff, P. Jordt, T. Braniste, V. Popa, E. Monaico, V. Ursaki, A. Petraru, R. Adelung, B. Murphy, L. Kienle, I. Tiginyanu: Modulation of Electrical Conductivity and Lattice Distortions in Bulk HVPE-Grown GaN, ECS Journal of Solid State Science and Technology, vol. 8, pp. 141–146, 2019.

E. Hadland, H. Jang, N. Wolff, R. Fischer, A. Lygo, G. Mitcheson, D. Li, L. Kienle, D. Cahill, D. Johnson: Ultralow Thermal Conductivity of Turbostratically Disordered MoSe2 Ultra-Thin Films and Implications for Heterostructures, Nanotechnology, vol. 30, no. 28, 285401, 2019.

O. Lupan, V. Postica, N. Wolff, J. Su, F. Labat, I. Ciofini, H. Cavers, R. Adelung, O. Polonskyi, F. Faupel, L. Kienle, B. Viana, T. Pauporté: Low-Temperature Solution Synthesis of Au-Modified ZnO Nanowires for Highly Efficient Hydrogen Nanosensors, ACS Applied Materials and Interfaces, vol. 11, issue 35, pp. 32115-32126, 2019.

V. Postica, I. Paulowicz, O. Lupan, F. Schütt, N. Wolff, A. Cojocaru, YK. Mishra, L. Kienle, R. Adelung: The Effect of Morphology and Functionalization on UV Detection Properties of ZnO Networked Tetrapods and Single Nanowires, Vacuum, vol. 166, pp. 393-398, 2019.

A. Piorra, V. Hrkac, N. Wolff, C. Zamponi, V. Duppel, J. Hadermann, L. Kienle, E. Quandt: (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 Thin Films Prepared by PLD: Relaxor Properties and Complex Microstructure, Journal of Applied Physics, vol. 125, issue 24, 244103, 2019.

I. Paulowicz, V. Postica, O. Lupan, N. Wolff, S. Shree, A. Cojocaru, M. Deng, Y. K. Mishra, I. Tiginyanu, L. Kienle, R. Adelung: Zinc Oxide Nanotetrapods with Four Different Arm Morphologies for Versatile Nanosensors, Sensors and Actuators B: Chemical, vol. 262, pp. 425-435, 2018.

O. Lupan, N. Wolff, V. Postica, T. Braniste, I. Paulowicz, V. Hrkac, Y. K. Mishra, I. Tiginyanu, L. Kienle, R. Adelung: Properties of a Single SnO2:Zn2SnO4 - Functionalized Nanowire Based Nanosensor, Ceramics International, vol. 44, issue 5, pp. 4859-4867, 2018.

M. Hoppe, O. Lupan, V. Postica, N. Wolff, V. Duppel, L. Kienle, I. Tiginyanu, R. Adelung: ZnAl2O4-Functionalized Zinc Oxide Microstructures for Highly Selective Hydrogen Gas Sensing Applications, Physica Status Solidi A, vol. 215, issue 7, 2018.

U. Schürmann, C. Chluba, N. Wolff, D. Smazna, R. Lima de Miranda, P. Junker, R. Adelung, E. Quandt, L. Kienle: Functional NiTi Grids for in situ Straining in the TEM, Ultramicroscopy, vol. 182, pp. 10-16, 2017.

S. B. Hrkac, C. T. Koops, M. Abes, C. Krywka, M. Müller, M. Burghammer, M. Sztucki, T. Dane, S. Kaps, Y. K. Mishra, R. Adelung, J. Schmalz, M. Gerken, E. Lage, C. Kirchhof, E. Quandt, O. M. Magnussen, B. M. Murphy: Tunable Strain in Magnetoelectric ZnO Microrod Composite Interfaces, ACS Appl. Mater. Interfaces, 9 (30), pp. 25571–25577 , 2017.

D. Smazna, N. Wolff, S. Shree, F. Schütt, Y.K. Mishra, L. Kienle, R. Adelung: Enhancing the Conductivity of ZnO Micro- and Nanowire Networks with Gallium Oxide, IEEE 7th International Conference Nanomaterials: Application and Properties (NAP), Odessa, pp. 01FNC07-1-01FNC07-5, 2021.

S. Fichtner, N. Wolff, G. Krishnamurthy, A. Petraru, S. Bohse, F. Lofink, S. Chemnitz, H. Kohlstedt, L. Kienle, B. Wagner: Identifying and Overcoming the Interface Originating C-Axis Instability in Highly Sc Enhanced AlN for Piezoelectric Micro-Electromechanical Systems, Journal of Applied Physics, vol. 122, issue 3, 035301, 2017.

S. Kaps, S. Bhowmick, J. Gröttrup, V. Hrkac, D. Stauffer, H. Guo, O. L. Warren, J. Adam, L. Kienle, A. M. Minor, R. Adelung, Y. K. Mishra: Piezoresistive Response of Quasi-One-Dimensional ZnO Nanowires Using an in Situ Electromechanical Device, Acs Omega, 2(6), pp. 2985-2993, 2017.

E. Yarar, V. Hrkac, C. Zamponi, A. Piorra, L. Kienle, E. Quandt: Low Temperature Aluminum Nitride Thin Films for Sensory Applications, AIP Advances, 6 , 075115, 2016.

M. Abes, C. T. Koops, S. B. Hrkac, J. McCord, N. O. Urs, N. Wolff, L. Kienle, W. J. Ren, L. Bouchenoire, B. M. Murphy, O. M. Magnussen: Domain Structure and Reorientation in CoFe2O4, Physical Review B 93 , 195427, 2016.