In this Letter, we report a back-end-of-line (BEOL), complementary metal–oxide–semiconductor (CMOS)-compatible Al_0.64Sc_0.36N-based ferroelectric diode that shows polarization-dependent hysteresis in its leakage currents. Our device comprises a metal/insulator/ferroelectric/metal structure (Pt/native oxide/Al_0.64Sc_0.36N/Pt) that is compatible with BEOL temperatures (≤ 350 °C) grown on top of a 4-in. silicon wafer. The device shows self-selective behavior as a diode with > 10⁵ rectification ratio (for 5 V). It can suppress sneak currents without the need for additional access transistors or selectors. Furthermore, given the polarization-dependent leakage, the diode current–voltage sweeps are analogous to that of a memristor with an on/off ratio of ∼ 50 000 between low and high resistance states. Our devices also exhibit stable programed resistance states during DC cycling and a retention time longer than 1000 s at 300 K. These results demonstrate that this system has significant potential as a future high-performance post-CMOS compatible nonvolatile memory technology.

Ferroelectric switching was studied in 20 nm thick Al0.68Sc0.32N and Al0.64Sc0.36N films (with ∼4 nm surface oxides) on platinized silicon wafers by multiple electrical characterization methods. Positive up negative down (PUND) measurements were conducted using 100 μs monopolar triangular waveform excitation. At room temperature, Al0.68Sc0.32N exhibited an apparent remanent polarization, Pr = 140 μC/cm2 and a coercive field, Ec = 6.5 MV/cm, while film leakage prevented quantitative measurement of the Al0.64Sc0.36N ferroelectric properties. Remanent polarizations of 75 μC/cm2 for Al0.68Sc0.32N and 25μC/cm2 for Al0.64Sc0.36N were measured at 120 K. Partial ferroelectric switching was confirmed at room temperature for both materials via the measured transverse piezoelectric coefficients (e31,f) of -1.3 C/m2 (down-switching) and -0.3 C/m2 (up-switching) for Al0.68Sc0.32N, and -0.9 C/m2 (down-switching) and -0.7 C/m2 (up-switching) for Al0.64Sc0.36N.

This paper describes a cold sintering process for Pb(Zr,Ti)O₃ ceramics and the associated processing-property relations. Pb(Zr,Ti)O₃ has a very small, incongruent solubility that is a challenge during cold sintering. To circumvent this, a Pb(NO₃)₂ solution was used as the transient liquid phase. A bimodal lead zirconate titanate powder was densified to a relative density of 89% by cold sintering at 300 °C and 500 MPa. After the cold sintering step, the permittivity was 200, and the dielectric loss was 2.0%. A second heat-treatment involving a 3 h anneal at 900 °C increased the relative density to 99%; the resulting relative dielectric permittivity was 1300 at room temperature and 100 kHz. The samples showed well-defined ferroelectric hysteresis loops, having a remanent polarization of 28 μC/cm². On poling, the piezoelectric coefficient d₃₃ was ∼200 pC/N. With a 700 °C 3 h post-annealing, samples show a lower room temperature relative permittivity (950 at 100 kHz), but a 24 h hold time at 700 °C produces ceramics where there is an improved relative dielectric constant (1050 at 100 kHz).

In this study, we report the effects of a multilayer architecture on the electrical breakdown strengths and ferroelectric characteristics of 45 nm thick aluminum scandium nitride (AlScN) films. Multilayered films (three-layer, five-layer, and seven-layer) are deposited via sequential deposition of Al_0.72Sc_0.28N and Al_0.64Sc_0.36N while maintaining constant volume ratios in all three samples. The effect of the increased number of interfaces is compared to 45 nm single layer Al_0.72Sc_0.28N and single layer Al_0.64Sc_0.36N films. The Weibull analysis shows an increase in the characteristic breakdown field from 5.99 and 5.86 MV/cm for single layer Al_0.72Sc_0.28N and Al_0.64Sc_0.36N to as high as 7.20 MV/cm in the seven-layered sample. The breakdown field to coercive field (E_BD/E_c) ratios also increase from 1.37 and 1.26 in single layer Al_0.72Sc_0.28N and Al_0.64Sc_0.36N to up to 1.44 in the seven-layered sample with no significant change in remanent polarization. The enhancement of the characteristic breakdown field can be understood as the propagation of the electrical tree being deflected by multilayer interfaces and/or being slowed by the relative compressive stress in the alternating layers.

The past few years have witnessed a growing demand for self-powered wearables that can enable vigilant health monitoring, with 24/7 operation. Energy harvesting from human-body motion is attractive for wearables; however, conventional unidirectional single-cantilever-beam piezoelectric energy harvesters (PEHs) [1]-[4] suffer from several body-motion harvesting challenges: such as multi-axial motion, irregular frequencies, and unpredictable amplitudes with frequent low-power levels [5]. To address these challenges, an eccentric rotor-based inertial PEH has been developed, which utilizes multiple magnetically plucked flexible thin-film (60 μm) PZT-nickel-PZT beams to significantly increase the harvested energy within a small volume [5]; compared to bulk-PZT beams that are more feasible in direct-force-driven PEHs. The wrist-worn multi-beam PEH, shown in Fig. 27.4.1, converts multi-axial body motion into AC voltages with different phases and decaying amplitudes (up to several volts) within the frequency range of 90-160Hz for each beam.