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An in-depth discussion of pore formation is presented in this paper by first reinterpreting in situ observations reported in the literature as well as assumptions commonly made to model pore formation in aluminum castings. The physics of pore formation is reviewed through theoretical fracture pressure calculations based on classical nucleation theory for homogeneous and heterogeneous nucleation, with and without dissolved gas, i.e., hydrogen. Based on the fracture pressure for aluminum, critical pore size and the corresponding probability of vacancies clustering to form that size have been calculated using thermodynamic data reported in the literature. Calculations show that it is impossible for a pore to nucleate either homogeneously or heterogeneously in aluminum, even with dissolved hydrogen. The formation of pores in aluminum castings can only be explained by inflation of entrained surface oxide films (bifilms) under reduced pressure and/or with dissolved gas, which involves only growth, avoiding any nucleation problem. This mechanism is consistent with the reinterpretations of in situ observations as well as the assumptions made in the literature to model pore formation.

Base metal electrode (BME) multilayer ceramic capacitors (MLCCs) continue to advance with higher volumetric capacitance, higher voltage, and higher-temperature operational ranges with greater numbers of capacitors being manufactured and integrated into the electronic infrastructure of society. Many of these applications range from aerospace, transport, computation, medical, satellite, military, and the internet of things means the interdependence of these devices require higher reliability at a collective and individual component level. Thus, determining the lifetime reliability of MLCCs is critical to provide more reliable components, and no weak links to the electrified infrastructure. For some of the more costly systems that support military and satellite systems, the reliability testing is very extensive. The burn-in test is a screening procedure used to remove components with higher probability of infant mortality failures. In this process, components are exposed to high temperatures and voltages relative to their design. The thermal stimulated depolarization current results revealed that burn-in test caused the intragranular and transgranular migration of oxygen vacancies, which will not be relaxed after the burn-in test. Time to failure data obtained through in situ highly accelerated lifetime tests demonstrated that not only burn-in tests were ineffective at detecting infant mortality failures, but they also had a negative impact on reliability of BME MLCCs by creating a weak population. The electromigration of oxygen vacancies during burn-in tests shorten the lifetime of MLCC population by reducing the protection effects of double Schottky barriers at the grain boundaries and electrode interfaces.

Aluminum melts sustain damage to its quality when surface oxides are entrained into bulk liquid. To quantify the extent of entrainment damage, four castings were produced in reduced pressure test (RPT) apparatus; one machined out of the continuously cast ingot, and the other three by pouring the metal from a height of 25, 37.5, and 150 mm. Analyses of RPT samples via micro-computer tomography (μ-CT) scanning demonstrated that the number and volume fraction of pores in aluminum casting increased with increasing velocity of the liquid. However, average and maximum pore sizes first increased with velocity, then decreased, indicating that additional kinetic energy of the metal breaks entrained bifilms. The investigation of the cross sections of RPT specimens via scanning electron microscopy and X-ray maps showed that oxygen was present inside, around, and between the pores, providing further evidence that bifilms act as initiation sites for pores. Moreover, there were unopened bifilms near pores, suggesting that entrainment damage is more extensive than what can be ascertained by the pore size measurements.

Development of next generation devices for high power, high frequency emitters, high efficiency electrical power conversion, and short wavelength (UV) emitters requires further development of the group III-N material system. Of particular challenge is the incorporation of indium (In) into the ternary or quaternary system (AlGaInN) due to its low decomposition temperature. In-containing films require reduced growth temperatures as compared to gallium or aluminum-containing films. To address this challenge, a new tool is proposed which can operate at elevated pressures up to 100 atm to increase the associated decomposition temperature. The proposed High-Pressure Spatial Chemical Vapor Deposition (HPS-CVD) reactor will permit high-quality growth of the complete solid solution of GaN-InN and AlN-InN at temperatures of at least 1000 oC, which opens the door for comprehensive bandgap engineering of device. CVD growth at elevated pressures faces multiple fluid dynamical, thermal, and mechanical challenges. To address these, computational fluid dynamics (CFD) techniques were carried out to analyze the fluid/thermal phenomena in this new CVD reactor design. The impact of rector design, chamber height, system pressure, inlet flow rate, and rotational speed were investigated and discussed. Flow instabilities arising from the heated and rotating susceptor have been minimized. Growth rates are anticipated to be enhanced by approximately a factor of 10 compared to an existing super-atmospheric horizontal MOCVD reactor design.

This paper presents high-temperature ferroelectric characterization of 40~nm Al\\(_1-x-y\\)B\\(_x\\)Sc\\(_y\\)N (AlBScN) thin film capacitors grown by co-sputtering Al\\(_0.89\\)B\\(_0.11\\) and Sc targets onto Pt(111)/Ti(002)/Si(100) substrates. Structural analysis confirmed a c-axis-oriented wurtzite structure with a low surface roughness of 1.37~nm. Ferroelectric switching, characterized by positive-up-negative-down (PUND) measurements up to 600~\\(^\\)C, exhibited a linear decrease in coercive fields from 6.2~MV/cm at room temperature to 4.2~MV/cm at 600~\\(^\\)C, while remanent polarization remained stable with temperature. Direct current I-V measurements highlight a significant suppression of leakage currents, over two orders of magnitude lower compared to AlScN capacitors fabricated under similar conditions. These results position AlBScN thin films as strong candidates for ferroelectric applications in extreme environments.

The properties of dielectric and piezoelectric oxides are determined by their processing history, crystal structure, chemical composition, microstructure, dopants (or defect) distribution, and defect kinetics. These materials are essential in a diverse range of applications including aerospace, medical, military, transportation, power engineering, and communication, where they are used as ceramic discs, thick and thin films, multilayer devices, etc. Significant advances in understanding the materials, processing, properties, and reliability of these materials have led to their widespread use in consumer electronics, military, and aerospace applications. This review delves into electrical degradation in dielectrics and piezoelectrics, focusing on defect chemistry and key characterization techniques. It also provides a detailed discussion of various spectroscopic, microscopic, and electronic characterization techniques essential for analyzing defects and degradation mechanisms.

Ferroelectric aluminum scandium nitride (Al1-xScxN, AlScN) offers CMOS-compatible integration but suffers from high coercive fields and leakage currents that hinder thickness scaling. Further reduction in thickness is essential for low-voltage embedded nonvolatile memory applications. Boron incorporation into AlScN (AlBScN) suppresses leakage current in films down to 40 nm, yet its ferroelectric characteristics in ultrathin films remains unexplored. This letter demonstrates robust ferroelectric switching in 10 nm sputtered AlBScN capacitors with a low coercive field and approximately two orders of magnitude lower leakage than AlScN. Notably, ferroelectric switching was observed at 2.2 MV/cm in capacitance-voltage measurements, and symmetric polarization reversal occurred near 4.6 MV/cm in positive-up-negative-down (PUND) measurements using 2 s pulses. Moreover, Weibull analysis revealed a breakdown-to-coercive-field ratio (EBD/Ec) of ~2.2. These findings demonstrated AlBScN as a promising candidate for CMOS back-end-of-line (BEOL) compatible ferroelectric applications with improved energy consumption and reduced leakage current.

In this work, we demonstrate a high-performance surface acoustic wave (SAW) delay line based on a Scandium alloyed aluminum nitride (AlScN)-on-sapphire platform operating at 5.9 GHz with an exceptionally high acoustic propagation Q-factor. An 800 nm AlScN thin film with 40% scandium alloying concentration was deposited on a thick sapphire substrate to achieve strong acoustic energy confinement and large electromechanical coupling effect, thereby minimizing the insertion loss (IL) and propagation loss (PL) of the acoustic delay line (ADL). The proposed ADL was designed to operate in the Sezawa mode using a Single-Phase Unidirectional Transducer (SPUDT) electrode configuration for better unidirectionality. The fabricated ADLs with different delay lengths, after conjugate matching, exhibited delay times spanning 13 to 214 ns and IL ranging from 7.6 to 18.3 dB. The extracted PL reached as low as 9.2 dB/mm at 5.9 GHz, with a group velocity (v_g) of around 5,779 m/s. Based on these results, the proposed ADLs exhibit a high acoustic propagation Q-factor of 3,044. These findings highlight the potential of AlScN-on-sapphire platforms for high operational frequency, low-loss SAW ADL devices in advanced RF applications.

Ferroelectric aluminum scandium nitride (Al1-xScxN, AlScN) offers CMOS-compatible integration but suffers from high coercive fields and leakage currents that hinder thickness scaling. Further reduction in thickness is essential for low-voltage embedded nonvolatile memory applications. Boron incorporation into AlScN (AlBScN) suppresses leakage current in films down to 40 nm, yet its ferroelectric characteristics in ultrathin films remains unexplored. This letter demonstrates robust ferroelectric switching in 10 nm sputtered AlBScN capacitors with a low coercive field and approximately two orders of magnitude lower leakage than AlScN. Notably, ferroelectric switching was observed at 2.2 MV/cm in capacitance-voltage measurements, and symmetric polarization reversal occurred near 4.6 MV/cm in positive-up-negative-down (PUND) measurements using 2 s pulses. Moreover, Weibull analysis revealed a breakdown-to-coercive-field ratio (EBD/Ec) of ~2.2. These findings demonstrated AlBScN as a promising candidate for CMOS back-end-of-line (BEOL) compatible ferroelectric applications with improved energy consumption and reduced leakage current.

The properties of dielectric and piezoelectric oxides are determined by their processing history, crystal structure, chemical composition, microstructure, dopants (or defect) distribution, and defect kinetics. These materials are essential in a diverse range of applications including aerospace, medical, military, transportation, power engineering, and communication, where they are used as ceramic discs, thick and thin films, multilayer devices, etc. Significant advances in understanding the materials, processing, properties, and reliability of these materials have led to their widespread use in consumer electronics, military, and aerospace applications. This review delves into electrical degradation in dielectrics and piezoelectrics, focusing on defect chemistry and key characterization techniques. It also provides a detailed discussion of various spectroscopic, microscopic, and electronic characterization techniques essential for analyzing defects and degradation mechanisms.