Explore the vast range of titles available.

In the present hyper-scaling era, memory technology is advancing owing to the demand for high-performance computing and storage devices. As a result, continuous work on conventional semiconductor-process-compatible ferroelectric memory devices such as ferroelectric field-effect transistors, ferroelectric random-access memory, and dynamic random-access memory (DRAM) cell capacitors is ongoing. To operate high-performance computing devices, high-density, high-speed, and reliable memory devices such as DRAMs are required. Consequently, considerable attention has been devoted to the enhanced high dielectric constant and reduced equivalent oxide thickness (EOT) of DRAM cell capacitors. The advancement of ferroelectric hafnia has enabled the development of various devices, such as ferroelectric memories, piezoelectric sensors, and energy harvesters. Therefore, in this review, we focus the morphotropic phase boundary (MPB) between ferroelectric orthorhombic and tetragonal phases, where we can achieve a high dielectric constant and thereby reduce the EOT. We also present the role of the MPB in perovskite and fluorite structures as well as the history of the MPB phase. We also address the different approaches for achieving the MPB phase in a hafnia material system. Subsequently, we review the critical issues in DRAM technology using hafnia materials. Finally, we present various applications of the hafnia material system near the MPB, such as memory, sensors, and energy harvesters.

Incorporating rare-earth elements into wurtzite nitride semiconductors, such as scandium-alloyed aluminum nitride (ScAlN), significantly enhances the piezoelectric response, which is vital for a broad range of acoustic, electronic, photonic, and quantum applications. To date, however, the measured piezoelectric response of nitride semiconductors is far below what theory has predicted. Herein, we demonstrate a simple, scalable, post-growth thermal annealing process that can dramatically boost the piezoelectric response of ScAlN. We achieve a 3.5-fold increase in the piezoelectric modulus, d 33 for ScAlN, from 12.3 pC/N in the as-grown state to 45.5 pC/N, which is eight times larger than that of AlN commercially used in 5 G cellphones. The observed enhancement is unambiguously confirmed by three separate measurement techniques. Detailed material characterization techniques reveal that optimized annealing conditions significantly improve the macroscopic structural quality, achieving a more homogeneous and ordered domain orientation, and reduces the lattice parameter ratio (c/a) in the wurtzite crystal structure. The dramatic enhancement of d 33 in ScAlN thin films promises extreme frequency scaling opportunities for bulk acoustic wave resonators for beyond-5 G applications. The authors present a process that boosts the piezoelectric properties of ScAlN thin films by 3.5 times, enhancing their performance for use in acoustic devices. The technique is scalable, cost effective, and could enable advanced sensors, clocks, and communication technologies.

ZnO thin films were prepared by RF reactive magnetron sputtering on phynox substrate at room temperature for four different thicknesses by varying deposition duration. The structural and morphological properties and composition of these films were characterized using XRD, SEM, and EDS, respectively. Suitability of these films for dynamic pressure sensing applications and the effect of film thickness on dynamic pressure sensing were evaluated experimentally using a shock tube equipment. Shock tube test results show the pure dynamic behavior of ZnO films with fast rise and discharge. Sensors with higher film thickness showed improved sensitivity which is on par with commercially available dynamic pressure sensors. This work demonstrates that the cost-effective sensors based on ZnO thin film are capable of sensing dynamic pressures for different pressure ranges.

This paper presents the synthesis of ZnO nanowire array on metallic alloy substrate, its packaging and experimental evaluation for dynamic pressure sensing applications. Vertically aligned dense nanowire array was synthesized using hydrothermal method. Crystal structure, morphology and chemical composition analysis were carried out using X-ray diffraction, field emission scanning electron microscopy and energy dispersive spectroscopy respectively. ZnO nanowires were grown to an average height of 2.2 µm with an average diameter of 200 nm. The as-synthesised nanowire array was packaged as a pressure sensor and was evaluated for its sensing properties. The sensor responded to shock pressure input with a sensitivity 1.65 ± 0.15 mV/bar, rise time 1.38 ms and discharge time 1.79 ms. ZnO nanowire array demonstrated highly promising features which are desirable for a dynamic pressure sensor.

The incorporation of rare-earth elements in wurtzite nitride semiconductors, e.g., scandium alloyed aluminum nitride (ScAlN), promises dramatically enhanced piezoelectric responses, critical to a broad range of acoustic, electronic, photonic, and quantum devices and applications. Experimentally, however, the measured piezoelectric responses of nitride semiconductors are far below what theory has predicted. Here, we show that the use of a simple, scalable, post-growth thermal annealing process can dramatically boost the piezoelectric response of ScAlN thin films. We achieve a remarkable 3.5-fold increase in the piezoelectric modulus, d33 for 30% Sc content ScAlN, from 12.3 pC/N in the as-grown state to 45.5 pC/N, which is eight times larger than that of AlN. The enhancement in piezoelectricity has been unambiguously confirmed by three separate measurement techniques. Such a dramatic enhancement of d33 has been shown to impact the effective electromechanical coupling coefficient kt2 : increasing it from 13.8% to 76.2%, which matches the highest reported values in millimeter thick lithium niobate films but is achieved in a 100 nm ScAlN with a 10,000 fold reduction in thickness, thus promising extreme frequency scaling opportunities for bulk acoustic wave resonators for beyond 5G applications. By utilizing a range of material characterization techniques, we have elucidated the underlying mechanisms for the dramatically enhanced piezoelectric responses, including improved structural quality at the macroscopic scale, more homogeneous and ordered distribution of domain structures at the mesoscopic scale, and the reduction of lattice parameter ratio (c/a) for the wurtzite crystal structure at the atomic scale. Overall, the findings present a simple yet highly effective pathway that can be extended to other material families to further enhance their piezo responses.

Aluminum scandium nitride (AlScN) has emerged as a highly promising material for high-temperature applications due to its robust piezoelectric, ferroelectric, and dielectric properties. This study investigates the behavior of Al0.7Sc0.3N thin films in extreme thermal environments, demonstrating functional stability up to 1000C, making it suitable for use in aerospace, hypersonics, deep-well, and nuclear reactor systems. Tantalum silicide (TaSi2)/Al0.7Sc0.3N/TaSi2 capacitors were fabricated and characterized across a wide temperature range, revealing robust ferroelectric and dielectric properties, along with significant enhancement in piezoelectric performance. At 1000C, the ferroelectric hysteresis loops showed a substantial reduction in coercive field from 4.3 MV/cm to 1.2 MV/cm, while the longitudinal piezoelectric coefficient increased nearly tenfold, reaching 75.1 pm/V at 800C. Structural analysis via scanning and transmission electron microscopy confirmed the integrity of the TaSi2/Al0.7Sc0.3N interfaces, even after exposure to extreme temperatures. Furthermore, the electromechanical coupling coefficient was calculated to increase by over 500%, from 12.9% at room temperature to 82% at 700C. These findings establish AlScN as a versatile material for high-temperature ferroelectric, piezoelectric, and dielectric applications, offering unprecedented thermal stability and functional enhancement.

Aluminum scandium nitride (AlScN) has emerged as a highly promising material for high-temperature applications due to its robust piezoelectric, ferroelectric, and dielectric properties. This study investigates the behavior of Al0.7Sc0.3N thin films in extreme thermal environments, demonstrating functional stability up to 1000C, making it suitable for use in aerospace, hypersonics, deep-well, and nuclear reactor systems. Tantalum silicide (TaSi2)/Al0.7Sc0.3N/TaSi2 capacitors were fabricated and characterized across a wide temperature range, revealing robust ferroelectric and dielectric properties, along with significant enhancement in piezoelectric performance. At 1000C, the ferroelectric hysteresis loops showed a substantial reduction in coercive field from 4.3 MV/cm to 1.2 MV/cm, while the longitudinal piezoelectric coefficient increased nearly tenfold, reaching 75.1 pm/V at 800C. Structural analysis via scanning and transmission electron microscopy confirmed the integrity of the TaSi2/Al0.7Sc0.3N interfaces, even after exposure to extreme temperatures. Furthermore, the electromechanical coupling coefficient was calculated to increase by over 500%, from 12.9% at room temperature to 82% at 700C. These findings establish AlScN as a versatile material for high-temperature ferroelectric, piezoelectric, and dielectric applications, offering unprecedented thermal stability and functional enhancement.