Article
Chemistry, Multidisciplinary
Shanquan Chen, Jhong-Yi Chang, Qinghua Zhang, Qiuyue Li, Ting Lin, Fanqi Meng, Haoliang Huang, Yangyang Si, Shengwei Zeng, Xinmao Yin, My Ngoc Duong, Yalin Lu, Lang Chen, Er-Jia Guo, Hanghui Chen, Chun-Fu Chang, Chang-Yang Kuo, Zuhuang Chen
Summary: The spin state of Co ions in epitaxial LaCoO3 thin films under tensile strain has been determined to have mixed high-spin and low-spin states, while it is practically a low-spin state under compressive strain. The identification of this spin state ratio explains the origin of ferromagnetism in LaCoO3 films. This study highlights the importance of spin state degrees of freedom and thin-film strain engineering in creating new physical properties that do not exist in bulk materials.
Article
Materials Science, Multidisciplinary
Ramasis Goswami, Syed B. Qadri
Summary: In this study, we investigated the effect of interfacial strain on the microstructure, interfaces and phase-formation behavior in epitaxially grown Fe films. Our results showed that films with higher thicknesses exhibited an equilibrium alpha-Fe phase, while thinner films transformed the metastable delta-Fe phase to an equilibrium alpha-Fe phase through annealing.
Article
Engineering, Electrical & Electronic
Zexuan Zhang, Yongjin Cho, Mingli Gong, Shao-Ting Ho, Jashan Singhal, Jimy Encomendero, Xiang Li, Hyunjea Lee, Huili Grace Xing, Debdeep Jena
Summary: Using plasma-assisted molecular beam epitaxy (MBE), significantly improved ferrimagnetic Mn4N layers are successfully grown on GaN, with unique epitaxial registry and comparable magnetotransport properties.
IEEE TRANSACTIONS ON MAGNETICS
(2022)
Article
Chemistry, Physical
Yujun Zhang, Jiahui Chen, Keisuke Ikeda, Kohei Yamagami, Yue Wang, Yongseong Choi, Akira Yasui, Jing Ma, Yuanhua Lin, Cewen Nan, Hiroki Wadati
Summary: In this study, the magnetism and electronic structure changes across the AFM-FM transition of Ni-doped FeRh epitaxial thin films were investigated using XMCD and HAXPES techniques. The results showed that the remnant FM phase at low temperature possesses a smaller Rh moment than the normal FM phase, while an increase of Rh 4d density of state at the Fermi level and a possible well-screened Ni 2p state were found in the FM phase. In addition, the FM fluctuation of the inter-site Fe-Fe exchange coupling within the AFM phase was observed.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Chemistry, Multidisciplinary
Igor Yanilkin, Amir Gumarov, Igor Golovchanskiy, Bulat Gabbasov, Roman Yusupov, Lenar Tagirov
Summary: Experimental and theoretical studies were conducted on standing spin waves in epitaxial films of the ferromagnetic Pd1-xFex alloy with different distributions of the magnetic properties. The influence of the magnetic profile on the spin wave resonances was demonstrated, and the potential application of engineering standing spin waves in graded ferromagnetic films was discussed.
Article
Chemistry, Physical
Sebastian M. J. Beer, Arbresha Muriqi, Patrick Lindner, Manuela Winter, Detlef Rogalla, Michael Nolan, Andreas Ney, Jorg Debus, Anjana Devi
Summary: Europium sulfide (EuS) thin films grown via chemical vapor deposition (CVD) exhibit high quality, stoichiometry, and tunability, with the advantage of avoiding the use of toxic hydrogen sulfide.
CHEMISTRY OF MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Yoonho Ahn, Jong Yeog Son
Summary: We investigate the ferromagnetic properties of conducting filament nanodots formed on epitaxial BiFeO3 thin film and provide new insights for the design of multistate memory cells with resistive switching and magnetic spin ordering.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2022)
Article
Physics, Applied
Andrew W. Forbes, Niraj Bhattarai, Christopher Gassen, Raghad S. H. Saqat, Ian L. Pegg, John Philip
Summary: Thin films of ferromagnet Fe2Ge were successfully grown via molecular beam epitaxy, and their magnetic and electrical properties were measured experimentally. The material showed strong spin polarization, as indicated by the observed high-temperature maximum in the longitudinal resistivity and the suppression of electron-magnon scattering at low temperatures. Measurements of the Hall resistivity revealed contributions from both the ordinary and anomalous Hall effects, providing information about the charge carrier concentration and mobility. Additionally, small negative magnetoresistance was observed in both longitudinal and transverse geometries. Fe2Ge holds promise as a spintronic material due to its compatibility with semiconductors.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Chemistry, Multidisciplinary
Yu-Hong Lai, Jun-Ding Zheng, Si-Cheng Lu, Yin-Kuo Wang, Chun-Gang Duan, Pu Yu, Yun-Zhe Zheng, Rong Huang, Li Chang, Ming-Wen Chu, Ju-Hung Hsu, Ying-Hao Chu
Summary: In condensed matter physics, oxide materials exhibit diverse and intriguing physical properties, making the development of functional oxides an important field of study. This research focuses on stabilizing PbSnO3 thin films with different orientations using a heteroepitaxial approach supported by theoretical calculations. Through X-ray diffraction and transmission electron microscopy, the structural information of the thin films is revealed. The electrical characterizations confirm the anticipated antiferroelectric behavior, including double hysteresis and butterfly loops. The study also investigates the phase transition and determines the transition temperatures based on temperature-dependent structural and electrical characterizations. Furthermore, scanning transmission electron microscopy provides atomic resolution images, revealing the microscopic antiferroelectric order. This work represents a significant breakthrough in synthesizing epitaxial PbSnO3 thin films and comprehensively understanding their anisotropic antiferroelectric behavior.
Article
Physics, Applied
Xu Wen Zhao, Sheung Mei Ng, Lok Wing Wong, Hon Fai Wong, Yu Kuai Liu, Wang Fai Cheng, Chee Leung Mak, Jiong Zhao, Chi Wah Leung
Summary: In this study, the magnetic ground state of LaMnO3 (LMO) thin film was investigated. It was found that the modulation of magnetic properties in LMO thin films can be attributed to the creation/annihilation of oxygen vacancy. The study highlights the importance of functional defects in perovskite oxides and sheds light on the potential of electric-field modulation of magnetism in spintronic devices.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Applied
Siyue Zhang, Yu Miyazaki, Tomoyuki Yokouchi, Yuki Shiomi
Summary: We experimentally demonstrated the phase change control of Hall effects in ferromagnetic MnBi thin films at room temperature. Two distinct ferromagnetic phases were obtained using different cooling methods, and the Hall resistivity showed different characteristics between the two phases. By optimizing the ratio, the sign of the Hall resistivity can be repeatedly switched.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Applied
Dong Gao, Zheng Peng, Ningbin Zhang, Yunfei Xie, Yucong Yang, Weihao Yang, Shuang Xia, Wei Yan, Longjiang Deng, Tao Liu, Jun Qin, Xiaoyan Zhong, Lei Bi
Summary: This study reports the structure, magneto-optical, and transport properties of epitaxial Mn3Sn thin films fabricated by pulsed laser deposition (PLD). The anomalous Hall effect and longitudinal magneto-optical Kerr effect of the epitaxial films were found comparable to Mn3Sn single crystals. The work paves the way for future device applications of high-quality Mn3Sn epitaxial thin films.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Applied
H. Li, H. Yamahara, H. Tabata, M. Seki
Summary: Epitaxial Fe2-xTi1+xO5 solid solution thin films were fabricated on SrTiO3 substrates with promising thermoelectric properties and significant ferromagnetic behavior, depending on the different ratios of Fe2+, Fe3+, and Ti4+ ions. The Fe1.5Ti1.5O5 film exhibited electrical conduction obeying the Arrhenius law at 200-300 K and transitioned to three-dimensional variable range hopping at 120-180 K. These results potentially provide a foundation for future spintronics applications.
APPLIED PHYSICS LETTERS
(2021)
Review
Engineering, Environmental
Jie Tu, Jiaqi Ding, Guoqiang Xi, Hangren Li, Qianqian Yang, Jianjun Tian, Linxing Zhang
Summary: In this study, stable multifunctional multiferroic Bi0.5Sm0.5FeO3 (BSFO) double-perovskite epitaxial thin films were successfully synthesized by regulating the deposition temperature. The BSFO thin films exhibited robust ferroelectric polarization and excellent photoresponse, and its switchable ferroelectric photovoltaic feature demonstrated the potential for ferroelectric storage.
CHEMICAL ENGINEERING JOURNAL
(2023)
Article
Nanoscience & Nanotechnology
G. De Luca, J. Spring, U. Bashir, M. Campanini, R. Totani, C. Dominguez, A. Zakharova, M. Dobeli, T. Greber, M. D. Rossell, C. Piamonteze, M. Gibert
Summary: The study shows that LNMO thin films maintain insulating behavior and a stable Curie temperature, regardless of the epitaxial strain conditions. This suggests that this material could be used in multi-layer device architectures that require a high-temperature ferromagnetic insulating state.
Article
Physics, Applied
Akira Nagaoka, Kensuke Nishioka, Kenji Yoshino, Ryoji Katsube, Yoshitaro Nose, Taizo Masuda, Michael A. Scarpulla
APPLIED PHYSICS LETTERS
(2020)
Article
Energy & Fuels
Mashad Uddin Saleh, Chris Deline, Evan Benoit, Samuel Kingston, Ayobami S. Edun, Naveen Kumar Tumkur Jayakumar, Joel B. Harley, Cynthia Furse, Michael Scarpulla
IEEE JOURNAL OF PHOTOVOLTAICS
(2020)
Article
Engineering, Electrical & Electronic
Ayobami S. Edun, Naveen Kumar Tumkur Jayakumar, Samuel R. Kingston, Cynthia M. Furse, Michael A. Scarpulla, Joel B. Harley
Summary: Spread spectrum time domain reflectometry (SSTDR) has traditionally been used for detecting hard faults in transmission lines, with little research on impedance issues of circuit elements in the middle of the line. This study considers transmission lines with different impedances on each wire and provides accurate analytical expressions for reflection coefficients.
IEEE SENSORS JOURNAL
(2021)
Article
Physics, Applied
Rujun Sun, Yu Kee Ooi, Praneeth Ranga, Arkka Bhattacharyya, Sriram Krishnamoorthy, Michael A. Scarpulla
Summary: In this study, photoluminescence spectroscopy was used to monitor changes in emission bands of n-type Ga2O3 films under different annealing temperatures in an oxygen environment. The results show an increase in non-radiative defects with higher temperatures and a decrease in UV intensity. Different activation energies were observed for defect generation at different depths, indicating the importance of understanding the formation and propagation of defects in materials.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2021)
Article
Energy & Fuels
Mashad Uddin Saleh, Chris Deline, Evan J. Benoit, Samuel R. Kingston, Joel B. Harley, Cynthia M. Furse, Michael A. Scarpulla
Summary: Current technologies can detect issues with PV modules, but lack the ability to accurately locate them. SSTDR technology shows promise in achieving this goal, especially in identifying damage within PV strings.
IEEE JOURNAL OF PHOTOVOLTAICS
(2021)
Article
Engineering, Electrical & Electronic
Ayobami S. Edun, Cody LaFlamme, Samuel R. Kingston, Harsha Vardhan Tetali, Evan J. Benoit, Michael Scarpulla, Cynthia M. Furse, Joel B. Harley
Summary: This article discusses the use of supervised and unsupervised dictionary learning approaches for detecting and locating disconnections in a PV array. The unsupervised approach focuses on detecting and localizing faults, while the supervised approach is used for classifying data to identify fault types.
IEEE SENSORS JOURNAL
(2021)
Article
Nanoscience & Nanotechnology
F. Mirkhosravi, A. Rashidi, J. Gallagher, M. Monavarian, A. Aragon, K. Ahn, Y. K. Ooi, A. Lintereur, E. K. Mace, M. A. Scarpulla, D. Feezell
Summary: The impact of high-dose gamma-ray irradiation on Ga-polar and N-polar GaN-based p-n diodes grown by metalorganic chemical vapor deposition was investigated. Changes in electrical characteristics after irradiation were found to be temporary, potentially due to the metastable occupancy of traps. Different types of initial defects and surface electronic states were identified on Ga-polar and N-polar samples, providing insight into the different electrical behavior observed after gamma-ray interactions.
Article
Engineering, Electrical & Electronic
Evan Benoit, Jack Mismash, Samuel R. Kingston, Ayobami S. Edun, Hunter Ellis, Cody LaFlamme, Michael A. Scarpulla, Joel B. Harley, Cynthia M. Furse
Summary: SSTDR is a non-intrusive method for electrical fault detection and localization that enables continuous monitoring of live electrical systems. This paper establishes a method of determining the window of uncertainty and minimum-detectable change in impedance for SSTDR measurements, demonstrated using a photovoltaic (PV) system. The study evaluates how variability in SSTDR measurements, caused by normal maintenance actions in the PV system, translates to a minimum-detectable change in impedance and its relation to common faults in PV systems.
IEEE SENSORS JOURNAL
(2021)
Article
Physics, Applied
K. Ahn, Y. K. Ooi, F. Mirkhosravi, J. Gallagher, A. Lintereur, D. Feezell, E. K. Mace, M. A. Scarpulla
Summary: The study reveals that GaN p(+)n diodes grown on freestanding substrates exhibit higher radiation resistance compared to those grown on sapphire substrates. The p-type contact interface and adjacent p(++) Mg-doped layer are found to be sensitive to irradiation. Additionally, the pre-irradiation Schottky behavior of the p-type contact can predict significant changes in the diodes' IV characteristics upon gamma-ray irradiation.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Energy & Fuels
Ayobami S. Edun, Samuel Kingston, Cody LaFlamme, Evan Benoit, Michael A. Scarpulla, Cynthia M. Furse, Joel B. Harley
Summary: This article explores the possibility of using spread spectrum time domain reflectometry (SSTDR) for detecting disconnections in a large-scale photovoltaic (PV) array, finding that the technology is effective under specific system parameters.
IEEE JOURNAL OF PHOTOVOLTAICS
(2021)
Article
Engineering, Electrical & Electronic
Ayobami S. Edun, Cody LaFlamme, Samuel R. Kingston, Cynthia M. Furse, Michael A. Scarpulla, Joel B. Harley
Summary: This article uses variational autoencoder (VAE) and spread spectrum time domain reflectometry (SSTDR) to detect and locate anomalous data in photovoltaic (PV) arrays. By learning the distribution of non-faulty input signals and using predicted baselines, it handles imbalanced data effectively. The results demonstrate high accuracy and detection rates in disconnect detection.
IEEE SENSORS JOURNAL
(2022)
Article
Energy & Fuels
Cody LaFlamme, Evan Benoit, Ayobami Edun, Cynthia M. Furse, Paul K. Kuhn, Michael A. Scarpulla, Joel B. Harley
Summary: This article investigates the effects of environmental factors on SSTDR measurements in photovoltaics, finding that illuminance, temperature, and humidity significantly impact reflections from panels. The research suggests using multiple baselines to prevent environmental variations from obscuring faults, and motivates future work in baseline prediction.
IEEE JOURNAL OF PHOTOVOLTAICS
(2022)
Article
Physics, Applied
F. Mirkhosravi, A. Rashidi, A. T. Elshafiey, J. Gallagher, Z. Abedi, K. Ahn, A. Lintereur, E. K. Mace, M. A. Scarpulla, D. Feezell
Summary: Studies on the radiation tolerance and electrical behavior of GaN-based devices are crucial for the development of next-generation high-power and high-voltage electronics that are likely to be exposed to severe environments. This research investigates the electrical characteristics of Ga-polar and N-polar GaN Schottky diodes before and after neutron irradiation. The results indicate that the reverse leakage current decreases significantly and the differential resistance increases in the forward bias after neutron irradiation. The study also reveals that the electrical responses of Ga-polar and N-polar diodes to fast and thermal neutron irradiations differ.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Energy & Fuels
Phillip J. Dale, Michael A. Scarpulla
Summary: Cumulative publications serve as a proxy for total R&D efforts in photovoltaic technologies, showing that silicon, CIGSe, CdTe, and halide perovskite technologies have followed the same learning curve of 20-24% efficiency within 10,000 publications and a consistent 5% efficiency increase per factor of 10 in publications. This analysis provides insights into PV technology trajectories but does not account for learning spillover, cross-pollination, and hidden commercial efforts. Trajectories below the learning curve require more effort per performance, and efficiency plateaus at high publication numbers may indicate fundamental barriers. Technologies with higher marginal slopes are identified as examples to watch.
SOLAR ENERGY MATERIALS AND SOLAR CELLS
(2023)
Article
Energy & Fuels
Michael A. Scarpulla, Brian McCandless, Adam B. Phillips, Yanfa Yan, Michael J. Heben, Colin Wolden, Gang Xiong, Wyatt K. Metzger, Dan Mao, Dmitry Krasikov, Igor Sankin, Sachit Grover, Amit Munshi, Walajabad Sampath, James R. Sites, Alexandra Bothwell, David Albin, Matthew O. Reese, Alessandro Romeo, Marco Nardone, Robert Klie, J. Michael Walls, Thomas Fiducia, Ali Abbas, Sarah M. Hayes
Summary: Cadmium telluride (CdTe)-based cells have become the leading commercialized thin film photovoltaic technology with high efficiency and stability. Achievements in this field were enabled by manufacturing innovations, window layer optimization, and alloyed CdSexTe1-x (CST) absorbers. Further efficiency gains depend on increasing open circuit voltage (Voc) and fill factor (FF) through innovations in materials, fabrication methods, and device stacks. The progress in this remarkable photovoltaic technology is reviewed along with opportunities for future development.
SOLAR ENERGY MATERIALS AND SOLAR CELLS
(2023)
