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Pingen K, Wolff N, Mohammadian Z, Sandström P, Beuer S, von Hauff E, Kienle L, Hultman L, Birch J, Hsiao CL, Hinz AM. III-Nitride Magnetron Sputter Epitaxy on Si: Controlling Morphology, Crystal Quality, and Polarity Using Al Seed Layers. ACS APPLIED MATERIALS & INTERFACES 2024; 16:34294-34302. [PMID: 38886009 PMCID: PMC11231972 DOI: 10.1021/acsami.4c03112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2024] [Revised: 05/06/2024] [Accepted: 05/10/2024] [Indexed: 06/20/2024]
Abstract
Group III-nitride semiconductors have been subject of intensive research, resulting in the maturing of the material system and adoption of III-nitrides in modern optoelectronics and power electronic devices. Defined film polarity is an important aspect of III-nitride epitaxy as the polarity affects the design of electronic devices. Magnetron sputtering is a novel approach for cost-effective epitaxy of III-nitrides nearing the technological maturity needed for device production; therefore, control of film polarity is an important technological milestone. In this study, we show the impact of Al seeding on the AlN/Si interface and resulting changes in crystal quality, film morphology, and polarity of GaN/AlN stacks grown by magnetron sputter epitaxy. X-ray diffraction measurements demonstrate the improvement of the crystal quality of the AlN and subsequently the GaN film by the Al seeding. Nanoscale structural and chemical investigations using scanning transmission electron microscopy reveal the inversion of the AlN film polarity. It is proposed that N-polar growth induced by Al seeding is related to the formation of a polycrystalline oxygen-rich AlN interlayer partially capped by an atomically thin Si-rich layer at the AlN/Si interface. Complementary aqueous KOH etch studies of GaN/AlN stacks demonstrate that purely metal-polar and N-polar layers can be grown on a macroscopic scale by controlling the amount of Al seeding.
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Affiliation(s)
- Katrin Pingen
- Fraunhofer
Institute for Organic Electronics, Electron Beam and Plasma Technology, Winterbergstrasse 28, D-01277 Dresden, Germany
- Institute
of Solid State Electronics, Technische Universität
Dresden, Mommsenstrasse
15, D-01069 Dresden, Germany
| | - Niklas Wolff
- Synthesis
and Real Structure, Department of Material Science, Kiel University, Kaiserstrasse
2, D-24143 Kiel, Germany
- Kiel
Nano, Surface and Interface Science, Kiel
University, Christian-Albrechts-Platz
4, D-24118 Kiel, Germany
| | - Zahra Mohammadian
- Department
of Physics, Chemistry and Biology, Linköpings
Universitet, SE-581 83 Linköping, Sweden
| | - Per Sandström
- Department
of Physics, Chemistry and Biology, Linköpings
Universitet, SE-581 83 Linköping, Sweden
| | - Susanne Beuer
- Fraunhofer
Institute for Integrated Systems and Device Technology, Schottkystrasse 10, D-91058 Erlangen, Germany
| | - Elizabeth von Hauff
- Fraunhofer
Institute for Organic Electronics, Electron Beam and Plasma Technology, Winterbergstrasse 28, D-01277 Dresden, Germany
- Institute
of Solid State Electronics, Technische Universität
Dresden, Mommsenstrasse
15, D-01069 Dresden, Germany
| | - Lorenz Kienle
- Synthesis
and Real Structure, Department of Material Science, Kiel University, Kaiserstrasse
2, D-24143 Kiel, Germany
- Kiel
Nano, Surface and Interface Science, Kiel
University, Christian-Albrechts-Platz
4, D-24118 Kiel, Germany
| | - Lars Hultman
- Department
of Physics, Chemistry and Biology, Linköpings
Universitet, SE-581 83 Linköping, Sweden
| | - Jens Birch
- Department
of Physics, Chemistry and Biology, Linköpings
Universitet, SE-581 83 Linköping, Sweden
| | - Ching-Lien Hsiao
- Department
of Physics, Chemistry and Biology, Linköpings
Universitet, SE-581 83 Linköping, Sweden
| | - Alexander M. Hinz
- Fraunhofer
Institute for Organic Electronics, Electron Beam and Plasma Technology, Winterbergstrasse 28, D-01277 Dresden, Germany
- Institute
of Solid State Electronics, Technische Universität
Dresden, Mommsenstrasse
15, D-01069 Dresden, Germany
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Phakatkar AH, Shokuhfar T, Shahbazian-Yassar R. Nanoscale chemical and structural investigation of solid solution polyelemental transition metal oxide nanoparticles. iScience 2023; 26:106032. [PMID: 36818279 PMCID: PMC9929587 DOI: 10.1016/j.isci.2023.106032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Revised: 12/25/2022] [Accepted: 01/17/2023] [Indexed: 01/25/2023] Open
Abstract
Although it has been shown that configurational entropy can improve the structural stability in transition metal oxides (TMOs), little is known about the oxidation state of transition metals under random mixing of alloys. Such information is essential in understanding the chemical reactivity and properties of TMOs stabilized by configurational entropy. Herein, utilizing electron energy loss spectroscopy (EELS) technique in an aberration-corrected scanning transmission electron microscope (STEM), we systematically studied the oxidation state of binary (Mn, Fe)3O4, ternary (Mn, Fe, Ni)3O4, and quinary (Mn, Fe, Ni, Cu, Zn)3O4 solid solution polyelemental transition metal oxides (SSP-TMOs) nanoparticles. Our findings show that the random mixing of multiple elements in the form of solid solution phase not only promotes the entropy stabilization but also results in stable oxidation state in transition metals spanning from binary to quinary transition metal oxide nanoparticles.
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Affiliation(s)
- Abhijit H. Phakatkar
- Department of Biomedical Engineering, University of Illinois at Chicago, Chicago, IL, USA
| | - Tolou Shokuhfar
- Department of Biomedical Engineering, University of Illinois at Chicago, Chicago, IL, USA,Corresponding author
| | - Reza Shahbazian-Yassar
- Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, IL, USA,Corresponding author
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Tyukalova E, Vimal Vas J, Ignatans R, Mueller AD, Medwal R, Imamura M, Asada H, Fukuma Y, Rawat RS, Tileli V, Duchamp M. Challenges and Applications to Operando and In Situ TEM Imaging and Spectroscopic Capabilities in a Cryogenic Temperature Range. Acc Chem Res 2021; 54:3125-3135. [PMID: 34339603 DOI: 10.1021/acs.accounts.1c00078] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
ConspectusIn this Account, we describe the challenges and promising applications of transmission electron microscopy (TEM) imaging and spectroscopy at cryogenic temperatures. Our work focuses on two areas of application: the delay of electron-beam-induced degradation and following low-temperature phenomena in a continuous and variable temperature range. For the former, we present a study of LiMn1.5Ni0.5O4 lithium ion battery cathode material that undergoes electron beam-induced degradation when studied at room temperature by TEM. Cryogenic imaging reveals the true structure of LiMn1.5Ni0.5O4 nanoparticles in their discharged state. Improved stability under electron beam irradiation was confirmed by following the evolution of the O K-edge fine structure by electron energy-loss spectroscopy. Our results demonstrate that the effect of radiation damage on discharged LiMn1.5Ni0.5O4 was previously underestimated and that atomic-resolution imaging at cryogenic temperature has a potential to be generalized to most of the Li-based materials and beyond. For the latter, we present two studies in the imaging of low-temperature phenomena on the local scale, namely, the evolution of ferroelectric and ferromagnetic domains walls, in BaTiO3 and Y3Fe5O12 systems, respectively, in a continuous and variable temperature range. Continuous imaging of the phase transition in BaTiO3, a prototypical ferroelectric system, from the low-temperature orthorhombic phase continuously up to the centrosymmetric high-temperature phase is shown to be possible inside a TEM. Similarly, the propagation of domain walls in Y3Fe5O12, a magnetic insulator, is studied from ∼120 to ∼400 K and combined with the application of a magnetic field and electrical current pulses to mimic the operando conditions as in domain wall memory and logic devices for information technology. Such studies are promising for studying the pinning of the ferroelectric and magnetic domains versus temperature, spin-polarized current, and externally applied magnetic field to better manipulate the domain walls. The capability of combining operando TEM stimuli such as current, voltage, and/or magnetic field with in situ TEM imaging in a continuous cryogenic temperature range will allow the uncovering of fundamental phenomena on the nanometer scale. These studies were made possible using a MEMS-based TEM holder that allowed an electron-transparent sample to be transferred and electrically contacted on a MEMS chip. The six-contact double-tilt holder allows the alignment of the specimen into its zone axis while simultaneously using four electrical contacts to regulate the temperature and two contacts to apply the electrical stimuli, i.e., operando TEM imaging. This Account leads to the demonstration of (i) the high-resolution imaging and spectroscopy of nanoparticles oriented in the desired [110] zone-axis direction at cryogenic temperatures to mitigate the electron beam degradation, (ii) imaging of low-temperature transitions with accurate and continuous control of the temperature that allowed single-frame observation of the presence of both the orthorhombic and tetragonal phases in the BaTiO3 system, and (iii) magnetic domain wall propagation as a function of temperature, magnetic field, and current pulses (100 ns with a 100 kHz repetition rate) in the Y3Fe5O12 system.
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Affiliation(s)
| | | | - Reinis Ignatans
- Institute of Materials, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | | | | | - Masaaki Imamura
- Department of Electrical Engineering, Fukuoka Institute of Technology, Fukuoka 811-0295, Japan
| | - Hironori Asada
- Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Ube 755-8611, Japan
| | - Yasuhiro Fukuma
- Department of Physics and Information Technology, Kyushu Institute of Technology, Iizuka 820-8502, Japan
- Research Center for Neuromorphic AI Hardwares, Kyushu Institute of Technology, Kitakyushu 808-0196, Japan
| | | | - Vasiliki Tileli
- Institute of Materials, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
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