Thin-film interface engineering of low-voltage tunable ferroelectric varactors with oxide electrodes

• Applicants: Professor Dr.-Ing. Rolf Jakoby; Dr. Philipp Komissinskiy
• Subject Area: Synthesis and Properties of Functional Materials
• Term: from 2012 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 206658696

• Final Report Year: 2025

Final Report Abstract

Development of tunable components in RF frontends provides great benefits in modern mobile communication and drives research in many fields. Among those, deploying novel materials enables multiple new designs of reconfigurable networks. Key reconfigurable microwave circuits in the analog radio frequency frontend such as tunable filters, phase shifters, adaptive impedance matching networks, frequency-agile and beam-steering antennas deploy tunable capacitors (varactors). As their capacitance is changed, the transmission properties of an impedance matching network or filter are affected. The results of the project work revived the concept of the all-oxide varactors due to making use of the extraordinary highly conducting oxide material SrMoO3 which in it’s single-crystal form has a higher electric conductivity than Pt. Our results indicate not only the feasibility of all-oxide varactors, but also that thin films of functional materials with contradicting thermodynamic growth conditions, namely, a highly conducting SrMoO3 and a functional tunable dielectric BST, can be combined in a single microelectronic device to exploit their unique functionalities. The interface between the two functional materials is engineered in such a way that non-equilibrium thermodynamic states can be maintained in the required range of growth and device application. High tunability of the all-oxide varactors with very low voltages less than 5 V and the observed suppression of acoustic resonances at the operation frequencies up to 10 GHz make them very promising candidates for applications in tunable filters and matching networks for mobile communications, where the transmission frequency can be altered, such that a single network can be used for receiving or transmitting multiple channels or services. The first demonstrated epitaxial all-oxide thin-film varactors grown on silicon substrates pave the way for the implementation of this emerging technology in industry.

Publications

• “Microelectronic electrode assembly useful as varactor and capacitor, comprises a first electrode arranged on a substrate and which comprises a thin layer of a first electrode material”, Granted Patent Numbers: US16/077,064, CN201780023108.4A, KR1020187026342A.
  A. Radetinac, A. Mani, P. Komissinskiy, L. Alff & M. Nikfalazar
  
• Effect of composition and strain on the electrical properties of LaNiO3 thin films. Applied Physics Letters, 103(14).
  Zhu, Mingwei; Komissinskiy, Philipp; Radetinac, Aldin; Vafaee, Mehran; Wang, Zhanjie & Alff, Lambert
  
• Highly conducting SrMoO3 thin films for microwave applications. Applied Physics Letters, 105(11).
  Radetinac, Aldin; Mani, Arzhang; Melnyk, Sergiy; Nikfalazar, Mohammad; Ziegler, Jürgen; Zheng, Yuliang; Jakoby, Rolf; Alff, Lambert & Komissinskiy, Philipp
  
• Modification of energy band alignment and electric properties of Pt/Ba0.6Sr0.4TiO3/Pt thin-film ferroelectric varactors by Ag impurities at interfaces. Journal of Applied Physics, 115(24).
  Hirsch, S.; Komissinskiy, P.; Flege, S.; Li, S.; Rachut, K.; Klein, A. & Alff, L.
  
• Joint effect of composition and strain on the anomalous transport properties of LaNiO3 films. Journal of Applied Physics, 117(15).
  Zhu, Mingwei; Komissinskiy, Philipp; Radetinac, Aldin; Wang, Zhanjie & Alff, Lambert
  
• Optical properties of single crystalline SrMoO3 thin films. Journal of Applied Physics, 119(5).
  Radetinac, Aldin; Zimmermann, Jörg; Hoyer, Karoline; Zhang, Hongbin; Komissinskiy, Philipp & Alff, Lambert
  
• Wet-chemical etching of SrMoO3 thin films. Materials Letters, 184, 173-176.
  Mani, Arzhang; Nikfalazar, Mohammad; Muench, Falk; Radetinac, Aldin; Zheng, Yuliang; Wiens, Alex; Melnyk, Sergiy; Maune, Holger; Alff, Lambert; Jakoby, Rolf & Komissinskiy, Philipp
  
• Growth and interface engineering in thin-film Ba0.6Sr0.4TiO₃/SrMoO₃heterostructures. Journal of Crystal Growth, 463, 134-138.
  Radetinac, Aldin; Ziegler, Jürgen; Vafaee, Mehran; Alff, Lambert & Komissinskiy, Philipp
  
• “Beam-Steering Passive Phased Array with Integrated Printed Ferroelectric Phase Shifters”, Ph.D. Thesis, TU Darmstadt 2017
  M. Nikfalazar
  
• “Chipless Wireless High-Temperature Sensing in Time-Variant Environments”, Ph.D. Thesis, TU Darmstadt 2017
  B. Kubina
  
• “Epitaxial ferroelectric all-oxide varactors for application in reconfigurable RF front ends”, Ph.D. Thesis, TU Darmstadt 2017
  A. Mani
  
• “Hochleitfähiges SrMoO3: Vom Schichtwachstum zur Anwendungseignung”, Ph.D. Thesis, TU Darmstadt 2017
  A. Radetinac
  
• “Tunable Ferroelectric Matching Networks implemented into High Power RF Amplifiers for High Dynamic and Wideband Efficiency”, 2017, Cuvillier Verlag, ISBN-10: 3-7369-8511-8
  A. Wiens
  
• All-Oxide Thin Film Varactor: From Test Structure to SMD Component. 2019 49th European Microwave Conference (EuMC), 184-187. IEEE.
  Walk, D.; Kienemund, D.; Salg, P.; Zeinar, L.; Radetinac, A.; Komissinskiy, P.; Alff, L.; Jakoby, R. & Maune, H.
  
• Atomically interface engineered micrometer-thick SrMoO3 oxide electrodes for thin-film BaxSr1-xTiO3 ferroelectric varactors tunable at low voltages. APL Materials, 7(5).
  Salg, P.; Walk, D.; Zeinar, L.; Radetinac, A.; Molina-Luna, L.; Zintler, A.; Jakoby, R.; Maune, H.; Komissinskiy, P. & Alff, L.
  
• Characterization and Deembedding of Negative Series Inductance in On-Wafer Measurements of Thin-Film All-Oxide Varactors. IEEE Microwave and Wireless Components Letters, 29(3), 213-215.
  Walk, Dominik; Kienemund, Daniel; Zeinar, Lukas; Salg, Patrick; Radetinac, Aldin; Komissinskiy, Philipp; Alff, Lambert; Jakoby, Rolf & Maune, Holger
  
• Highly Accurate Analytic Modeling of Dispersive Field Distributions in MIM Capacitances With Electrodes Thinner Than Skin Depth. IEEE Transactions on Microwave Theory and Techniques, 67(12), 4665-4673.
  Walk, Dominik; Maune, Holger; Kienemund, Daniel; Salg, Patrick; Zeinar, Lukas; Radetinac, Aldin; Molina-Luna, Leopoldo; Komissinskiy, Philipp; Alff, Lambert & Jakoby, Rolf
  
• Matching conflicting oxidation conditions and strain accommodation in perovskite epitaxial thin-film ferroelectric varactors. Journal of Applied Physics, 128(21).
  Zeinar, Lukas; Salg, Patrick; Walk, Dominik; Petzold, Stefan; Arzumanov, Alexey; Jakoby, Rolf; Maune, Holger; Alff, Lambert & Komissinskiy, Philipp
  
• Optical Properties of Highly Conductive SrMoO3 Oxide Thin Films in the THz Band and Beyond. Journal of Infrared, Millimeter, and Terahertz Waves, 41(10), 1170-1180.
  Regensburger, Stefan; Mohammadi, Mahdad; Khawaja, Arslan A.; Radetinac, Aldin; Komissinskiy, Philipp; Alff, Lambert & Preu, Sascha
  
• Oxygen diffusion barriers for epitaxial thin-film heterostructures with highly conducting SrMoO3 electrodes. Journal of Applied Physics, 127(6).
  Salg, Patrick; Zeinar, Lukas; Radetinac, Aldin; Walk, Dominik; Maune, Holger; Jakoby, Rolf; Alff, Lambert & Komissinskiy, Philipp
  
• Spectroscopy of highly conductive SMO thin film in the THz range. 2020 45th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 1-2. IEEE.
  Regensburger, Stefan; Radetinac, Aldin; Komissinskiy, Philipp; Alff, Lambert & Preu, Sascha
  
• Suppression of Acoustic Resonances in All-Oxide Varactors. 2020 IEEE/MTT-S International Microwave Symposium (IMS), 139-142. IEEE.
  Walk, Dominik; Kienemund, Daniel; Agrawal, Prannoy; Salg, Patrick; Zeinar, Lukas; Komissinskiy, Philipp; Alff, Lambert; Jakoby, Rolf & Maune, Holger
  
• All-Oxide Varactor Electromechanical Properties Extracted by Highly Accurate Modeling Over a Broad Frequency and Electric Bias Range. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 68(8), 2804-2814.
  Walk, Dominik; Agrawal, Prannoy; Zeinar, Lukas; Salg, Patrick; Arzumanov, Alexey; Komissinskiy, Philipp; Alff, Lambert; Jakoby, Rolf; Rupitsch, Stefan J. & Maune, Holger
  
• Molecular dynamics simulation of crystal structure and heat capacity in perovskite-type molybdates SrMoO3 and BaMoO3. Computational Materials Science, 197, 110609.
  Wang, Shuai; Mohammadi, Mahdad; Dirba, Imants; Hofmann, Kathrin; Albert, Barbara; Alff, Lambert; Komissinskiy, Philipp & Molina-Luna, Leopoldo
  
• Optical Plasmon Excitation in Transparent Conducting SrNbO3 and SrVO3 Thin Films. Advanced Optical Materials, 9(17).
  Mirjolet, Mathieu; Kataja, Mikko; Hakala, Tommi K.; Komissinskiy, Philipp; Alff, Lambert; Herranz, Gervasi & Fontcuberta, Josep
  
• “All-Oxide Thin-Film Varactors: RF Characterization - Modeling - Integration”, Ph.D. Thesis, TU Darmstadt 2021
  D. Walk
  
• “Invited: Advanced RF Modeling of Varactors with Thin Oxide Electrodes”. In: Electronic Materials and Applications. The American Ceramic Society, Jan. 2021.
  D. Walk, P. Salg, P. Komissinskiy, L. Alff, R. Jakoby & H. Maune
  
• Tailoring Optical Properties in Transparent Highly Conducting Perovskites by Cationic Substitution. Advanced Materials, 35(7).
  Mohammadi, Mahdad; Xie, Ruiwen; Hadaeghi, Niloofar; Radetinac, Aldin; Arzumanov, Alexey; Komissinskiy, Philipp; Zhang, Hongbin & Alff, Lambert
  
• “Elektrodenmaterial”, Patent Application Number: DE 10 2020 123 450 A1, 2022.03.10,
  A. Radetinac, M. Mohammadi Farshkhooni, P. Komissinskiy & L. Alff
  
• High performance all-oxide thin film tunable capacitors on Si substrates for agile microwave applications. Oxide-based Materials and Devices XIV, 70. SPIE.
  Ruan, Yating; Matic, Stipo; Salg, Patrick; Walk, Dominik; Lukas, Zeinar; Komissinskiy, Philipp; Jakoby, Rolf & Alff, Lambert
  
• Operando two-terminal devices inside a transmission electron microscope. Communications Engineering, 2(1).
  Recalde-Benitez, Oscar; Jiang, Tianshu; Winkler, Robert; Ruan, Yating; Zintler, Alexander; Adabifiroozjaei, Esmaeil; Arzumanov, Alexey; Hubbard, William A.; van Omme, Tijn; Pivak, Yevheniy; Perez-Garza, Hector H.; Regan, B. C.; Alff, Lambert; Komissinskiy, Philipp & Molina-Luna, Leopoldo
  
• “Optische Eigenschaften in hochleitfähigen Perowskiten“, Ph.D. Thesis, TU Darmstadt 2023
  M. Mohammadi Farshkhooni
  
• All-oxide thin-film varactors with SrMoO₃-bottom electrodes and Mn/Ni-doped BST for sub-6 GHz applications. Ceramics International, 50(21), 40756-40773.
  Matic, Stipo; Ruan, Yating; Sáez, Alejandro Jiménez; Liang, Zhili; Bondino, Federica; Napal, Ilargi; Magnano, Elena; Alff, Lambert; Komissinskiy, Philipp & Jakoby, Rolf
  
• Giant Critical Thickness in Highly Conducting Epitaxial SrMoO3 Electrodes Investigated by Lift‐Off Membranes. Advanced Functional Materials, 34(21).
  Ruan, Yating; Schreyer, Philipp; Jiang, Tianshu; Liang, Fei; Arzumanov, Alexey; Dürrschnabel, Michael; Molina‐Luna, Leopoldo; Komissinskiy, Philipp & Alff, Lambert
  
• Weld-free mounting of lamellae for electrical biasing operando TEM. Ultramicroscopy, 260, 113939.
  Recalde-Benitez, Oscar; Pivak, Yevheniy; Jiang, Tianshu; Winkler, Robert; Zintler, Alexander; Adabifiroozjaei, Esmaeil; Komissinskiy, Philipp; Alff, Lambert; Hubbard, William A.; Perez-Garza, H. Hugo & Molina-Luna, Leopoldo
  
• “Electromagnetic Modelling of Barium Strontium Titanate and Magnesium Borate Bulk Composite Varactors”, Ph.D. Thesis, TU Darmstadt 2024
  P. Agrawal