Article
Physics, Applied
Md Redwanul Islam, Niklas Wolff, Mohamed Yassine, Georg Schoenweger, Bjorn Christian, Hermann Kohlstedt, Oliver Ambacher, Fabian Lofink, Lorenz Kienle, Simon Fichtner
Summary: This study found that the ferroelectric-to-paraelectric transition temperature of Al1-xScxN thin film can exceed 1100 degrees C, surpassing the transition temperature of virtually any other thin film ferroelectric. Through high-temperature X-ray diffraction and permittivity measurements, it was discovered that the wurtzite-type structure of Al0.73Sc0.27N remains stable during the entire 1100 degrees C annealing cycle.
APPLIED PHYSICS LETTERS
(2021)
Article
Nanoscience & Nanotechnology
Valerie Yoshioka, Jian Lu, Zichen Tang, Jicheng Jin, Roy H. Olsson, Bo Zhen
Summary: Silicon photonics has enabled large-scale production of integrated optical devices for various applications, but faces challenges when used in nonlinear devices. Scandium-doped aluminum nitride thin films exhibit enhanced optical second-order susceptibility, offering potential advantages for developing CMOS-compatible devices with strong nonlinearity.
Article
Materials Science, Multidisciplinary
C. Yuan, M. Park, Y. Zheng, J. Shi, R. Dargis, S. Graham, A. Ansari
Summary: This study investigates phonon scattering processes and thermal conductivity in Al1-xScxN alloys grown by molecular beam epitaxy. The results show a decreasing trend in thermal conductivity with increasing scandium content, with an increase in thermal conductivity with temperature below 200 K and a plateau at higher temperatures. Application of an analytical model helps estimate the effects of scattering mechanisms on thermal conductivity behavior.
MATERIALS TODAY PHYSICS
(2021)
Article
Chemistry, Analytical
Niklas Wolff, Md Redwanul Islam, Lutz Kirste, Simon Fichtner, Fabian Lofink, Agne Zukauskaite, Lorenz Kienle
Summary: Research on wurtzite-type aluminum scandium nitride (Al1-xScxN) thin films revealed an anomalous thermal expansion at high temperatures, attributed to the coupling contributions of intrinsic and extrinsic factors. This finding is significant for the manufacturing and operation of Al1-xScxN-based devices.
Article
Chemistry, Analytical
Zichen Tang, Giovanni Esteves, Jeffrey Zheng, Roy H. Olsson
Summary: Due to their favorable electromechanical properties, Aluminum Nitride (AlN) and Aluminum Scandium Nitride (Al1-xScxN) thin films have been widely used in radio frequency (RF) acoustic devices. However, the resistance to etching at high scandium alloying has hindered the realization of devices that can fully utilize the highest electromechanical coupling coefficients. In this study, the etch rates of AlN and Al1-xScxN with different scandium concentrations were investigated. The findings provide valuable insights for structure/composition analysis and potential applications.
Article
Physics, Applied
Haochen Wang, Nicholas Adamski, Sai Mu, Chris G. van de Walle
Summary: This study provides a detailed analysis of the spontaneous and piezoelectric polarization behaviors of aluminum nitride alloy with Sc addition. It is found that the virtual crystal approximation produces accurate results for polarization but falls short in describing the phase stability of the alloy. Additionally, the internal-strain contribution dominantly enhances the piezoelectric properties induced by Sc, with the value of u increasing with scandium concentration, bringing the alloy closer to a layered hexagonal structure locally.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Physics, Applied
Keisuke Yazawa, Andriy Zakutayev, Geoff L. Brennecka
Summary: This study presents a thermodynamic analysis of nitride ferroelectric materials using the classic Landau-Devonshire approach. The results show that the energy barrier's strain sensitivity in wurtzite ferroelectrics is higher compared to classic perovskite ferroelectrics.
APPLIED PHYSICS LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Georg Schoenweger, Adrian Petraru, Md Redwanul Islam, Niklas Wolff, Benedikt Haas, Adnan Hammud, Christoph Koch, Lorenz Kienle, Hermann Kohlstedt, Simon Fichtner
Summary: This paper presents the first in-depth structural and electrical characterization of all-epitaxial, all-wurtzite-type ferroelectric III-N semiconductor heterostructures. The results show that Al1-xScxN films have multiple strain states and exhibit splitting of the ferroelectric displacement current into separate peaks. It is also observed that films grown on the metal-polar GaN template feature an initial multidomain state.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Physics, Applied
John Hayden, Joseph Shepard, Jon-Paul Maria
Summary: Ferroelectric Al0.93B0.07N thin films were prepared on (100) Si substrates with the necessary c-axis out-of-plane orientation achieved through initial plasma treatment and subsequent layer growth. The resulting films exhibited strong polarization hysteresis, making them useful for integration with mainstream semiconductors.
APPLIED PHYSICS LETTERS
(2023)
Article
Chemistry, Physical
Wenzheng Jiang, Lei Zhu, Lingli Chen, Yumeng Yang, Xi Yu, Xiaolong Li, Zhiqiang Mu, Wenjie Yu
Summary: In this study, an in situ method based on synchrotron X-ray diffraction (XRD) system was proposed to characterize the longitudinal piezoelectric constant d(33) of Al1-xScxN film. The measurement results showed the piezoelectric effect of Al1-xScxN films by lattice spacing variation upon applied external voltage. The in situ synchrotron XRD measurement was proven to be an effective method for precise piezoelectric coefficient d(33) characterization.
Article
Materials Science, Multidisciplinary
Georg Schoenweger, Md Redwanul Islam, Niklas Wolff, Adrian Petraru, Lorenz Kienle, Hermann Kohlstedt, Simon Fichtner
Summary: This letter reports on room temperature switchable ultra-thin (10 nm) ferroelectric Al0.72Sc0.28N films, which are important for potential applications in neuromorphic computing and memory devices. All-epitaxial Al0.72Sc0.28N/Pt heterostructures are grown by magnetron sputtering, and the Al0.72Sc0.28N film surface is protected by in situ Pt capping to avoid oxidation. The films exhibit good epitaxy and show only moderate scaling effects in terms of relative permittivity and coercive field dependence, suggesting that the critical thickness for ferroelectricity has not yet been reached.
PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS
(2023)
Article
Chemistry, Physical
Yishui Ding, Xiangyu Hou, Tengyu Jin, Yanan Wang, Xu Lian, Yuan Liu, Yihe Wang, Sisheng Duan, Xiangrui Geng, Meng Wang, Jingyu Mao, Yuanyuan Zhang, Peirong Tang, Minghua Li, Huamao Lin, Yao Zhu, Siewlang Teo, Qiang Zhu, Ming Lin, Wei Chen
Summary: In this study, the growth mechanism and interfacial chemistry of ultrathin platinum and molybdenum films on high-crystalline Al1-xScxN surface were investigated. The chemical and electronic structure evolution of the interface during the deposition process were examined using in-situ X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. The structural properties of the interface were characterized by cross-sectional transmission electron microscopy, X-ray diffraction spectroscopy, and atomic force microscopy. The study reveals the formation of ionic Pt2+-N bonds at the Pt/Al1-xScxN interface, while molybdenum does not bond with the substrate. Furthermore, electron transfer induces upward band-bending effects on the Al1-xScxN surface upon both platinum and molybdenum interactions. The research on the chemical and structural properties of ultrathin metal electrodes and Al1-xScxN interfaces provides guidance for designing high-performance micro-electromechanical devices.
APPLIED SURFACE SCIENCE
(2023)
Article
Multidisciplinary Sciences
Martin F. Sarott, Marta D. Rossell, Manfred Fiebig, Morgan Trassin
Summary: This study demonstrates the ability to continuously modulate the remanent polarization at the nanoscale in PbZr0.52Ti0.48O3 films by driving the system towards the instability at the morphotropic phase boundary, achieving multilevel switching.
NATURE COMMUNICATIONS
(2022)
Article
Physics, Multidisciplinary
Hang Zang, Zhiming Shi, Mingrui Liu, Yuping Jia, Ke Jiang, Jianwei Ben, Yang Chen, Shunpeng Lv, Xiaojuan Sun, Dabing Li
Summary: In this study, the atomic structure of Al1-xScxN and its effect on its piezoelectric and ferroelectric properties were investigated using first-principles calculations. It was found that Al1-xScxN with a phase separation feature was more stable than the corresponding wurtzite structure. The piezoelectric response of Al1-xScxN depended strongly on the atomic arrangements, with different structures exhibiting positive and negative piezoelectric coefficients.
SCIENCE CHINA-PHYSICS MECHANICS & ASTRONOMY
(2023)
Article
Physics, Applied
Junji Kataoka, Sung-Lin Tsai, Takuya Hoshii, Hitoshi Wakabayashi, Kazuo Tsutsui, Kuniyuki Kakushima
Summary: Research on 50 nm thick ferroelectric Al0.78Sc0.22N films with TiN electrodes revealed that the leakage current gradually shifted during initial switching, stabilizing at a specific value. This change was interpreted as the formation of a tunneling barrier due to nitrogen vacancies at the metal interface.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2021)
Article
Physics, Applied
Tianning Liu, Pannawit Tipsawat, Wanlin Zhu, Thomas N. Jackson, Mani Sivaramakrishnan, Peter Mardilovich, Thorsten Schmitz-Kempen, Susan Trolier-McKinstry
Summary: When using double-beam laser interferometry to measure the piezoelectric coefficient of a film on a substrate, it is important to consider the limitations when the film experiences excessive bending deformation. This work demonstrates the challenges faced when measuring fully released PZT films and highlights the errors that can occur.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Materials Science, Multidisciplinary
Gavin Hennessey, Travis Peters, Pannawit Tipsawat, Marti Checa, Liam Collins, Susan Trolier-McKinstry
Summary: This paper investigates the effect of microstructural features on domain wall motion pinning in PZT films on polycrystalline substrates. The study reveals that the behavior varies with the misorientation angle and proximity to grain boundaries. Random grain boundaries exhibit deeper minima and larger widths of influence compared to coincident site lattice boundaries. Triple points with more random boundaries exhibit non-Rayleigh behavior, suggesting deep potential minima or regions unfavorable for domain wall motion.
Article
Physics, Applied
Travis Peters, Wanlin Zhu, Marti Checa, Liam Collins, Susan Trolier-McKinstry
Summary: In undoped lead zirconate titanate films, domain walls move in clusters with a correlation length of 0.5-2 μm. Nb doping increases the concentration or mobility of domain walls without changing the cluster area, while Mn doping reduces the contribution of mobile domain walls without changing the cluster area. In both Nb and Mn doped films, the cluster area increases and the cluster density drops as the film thickness increases from 250 to 1250 nm, as observed from the analysis of irreversible to reversible ratios of the Rayleigh coefficients.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Wanlin Zhu, Fan He, John Hayden, Jung In Yang, Pannawit Tipsawat, Jon-Paul Maria, Susan Trolier-McKinstry
Summary: This paper presents the retention behavior of Al0.93B0.07N thin films, which belong to the novel family of wurtzite ferroelectrics. The experimental results show that bipolar cycling of the film stacks induces wake-up and a region of constant switchable polarization. The films exhibit excellent retention of the stored polarization state. The opposite state measurements show slightly inferior data retention, but even after 3.6 x 10(6) s (1000 h) at 200 degrees C, the OS signal margin still exceeds 200 mu C/cm(2). The predicted OS retention is 82% after 10 years of baking at 200 degrees C.
APPLIED PHYSICS LETTERS
(2023)
Article
Multidisciplinary Sciences
V. Sebastian Calderon, John Hayden, Steven M. Baksa, William Tzou, Susan Trolier-McKinstry, Ismaila Dabo, Jon -Paul Maria, Elizabeth C. Dickey
Summary: Ferroelectric wurtzites have the potential to revolutionize modern microelectronics. This study observed and quantified real-time polarization switching of ferroelectric wurtzite at the atomic scale. A polarization reversal model was proposed, providing an important first step for property engineering efforts.
Article
Chemistry, Physical
Betul Akkopru-Akgun, Susan Trolier-McKinstry
Summary: Lead zirconate titanate (PZT) films with high Nb concentrations (6-13 mol%) were fabricated by chemical solution deposition method. The stoichiometry of the films can be self-compensated up to 8 mol% Nb, and single phase films can be obtained with 10 mol% PbO excess in the precursor solution. However, higher Nb concentrations resulted in multi-phase films unless the excess PbO level was reduced. The dielectric and piezoelectric properties of the films were significantly degraded with increased Nb concentrations, but can be improved by reducing the PbO level to 6 mol%.
Article
Materials Science, Multidisciplinary
Yongke Yan, Liwei D. Geng, Li-Qian Cheng, Xiaotian Li, Haoyang Leng, Ke Wang, Bed Poudel, Amin Nozariasbmarz, Mohan Sanghadasa, Susan Trolier-McKinstry, Qi-Ming Zhang, Yu U. Wang, Shashank Priya
Summary: The physical properties of complex perovskite ferroelectrics depend on the degree of order/disorder and the scale of the ordered domains. In this study, the electrocaloric properties of three representative complex perovskite ferroelectrics were evaluated. The high EC performance of Pb(Sc1/2Ta1/2)O-3 (PST) was found to be related to the ordering of B-site cations (Sc3+ and Ta5+) and a long coherence length.
Article
Physics, Applied
Jon F. Ihlefeld, Travis Peters, Samantha T. Jaszewski, Takanori Mimura, Benjamin L. Aronson, Susan Trolier-McKinstry
Summary: The influence of biaxial stress on the maximum and remanent polarizations of 10 nm thick hafnium zirconium oxide thin films has been studied. It was found that reducing the intrinsic strain through the application of a compressive uniaxial stress resulted in a decrease in the remanent and maximum polarizations. The observed variation in polarization with strain is consistent with strain impacting ferroelastic switching.
APPLIED PHYSICS LETTERS
(2023)
Article
Materials Science, Ceramics
Abdullah Jabr, Haley N. Jones, Andrea P. Arguelles, Susan Trolier-McKinstry, Clive Randall, Raul Bermejo
Summary: The cold sintering process (CSP) densifies ceramics at temperatures below 300 degrees C using a transient phase and applied pressure. Flaws compromising the mechanical strength of cold sintered materials were detected using ultrasonic evaluation, and load transfer misalignments and fast heating rates were identified as major sources of defects. By using precisely aligned punches and slow heating rates, multiple disc-shaped samples achieved homogeneous densification, high relative density (>97%), and improved strength (-120 MPa), demonstrating the feasibility of industrial implementation for CSP scaling up.
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
(2023)