HfO2-based ferroelectrics are highly expected to lead the new paradigm of nanoelectronic devices owing to their unexpected ability to enhance ferroelectricity in the ultimate thickness scaling limit (≤2 nm). However, an understanding of its physical origin remains uncertain because its direct microstructural and chemical characterization in such a thickness regime is extremely challenging. Herein, we solve the mystery for the continuous retention of high ferroelectricity in an ultrathin hafnium zirconium oxide (HZO) film (∼2 nm) by unveiling the evolution of microstructures and crystallographic orientations using a combination of state-of-the-art structural analysis techniques beyond analytical limits and theoretical approaches. We demonstrate that the enhancement of ferroelectricity in ultrathin HZO films originates from textured grains with a preferred orientation along an unusual out-of-plane direction of (112). In principle, (112)-oriented grains can exhibit 62% greater net polarization than the randomly oriented grains observed in thicker samples (>4 nm). Our first-principles calculations prove that the hydroxyl adsorption during the deposition process can significantly reduce the surface energy of (112)-oriented films, thereby stabilizing the high-index facet of (112). This work provides new insights into the ultimate scaling of HfO2-based ferroelectrics, which may facilitate the design of future extremely small-scale logic and memory devices.

The endurance characteristic of Zr-doped HfO2 (HZO)-based metal–ferroelectric–metal (MFM) capacitors fabricated under various deposition/annealing temperatures in the atomic layer deposition (ALD) process was investigated. The chamber temperature in the ALD process was set to 120 °C, 200 °C, or 250 °C, and the annealing temperature was set to 400 °C, 500 °C, 600 °C, or 700 °C. For the given annealing temperature of 700 °C, the remnant polarization (2Pr) was 17.21 µC/cm2, 26.37 µC/cm2, and 31.8 µC/cm2 at the chamber temperatures of 120 °C, 200 °C, and 250 °C, respectively. For the given/identical annealing temperature, the largest remnant polarization (Pr) was achieved when using the chamber temperature of 250 °C. At a higher annealing temperature, the grain size in the HZO layer becomes smaller, and thereby, it enables to boost up Pr. It was observed that the endurance characteristics for the capacitors fabricated under various annealing/chamber temperatures were quite different. The different endurance characteristics are due to the oxygen and oxygen vacancies in ferroelectric films, which affects the wakeup/fatigue behaviors. However, in common, all the capacitors showed no breakdown for an externally applied pulse (up to 108 cycles of the pulse).

For sequential stacking of an Al 2 O 3 passivation layer and a main HfO 2 gate dielectric layer on In 0.53 Ga 0.47 As, we used single-and dual-temperature atomic-layer deposition processes, and systematically compared their effects on the dielectric-related electrical properties. When the deposition of Al 2 O 3 passivation layer (approximately 0.7−0.8 nm) took place at relatively low temperatures of 100 °C, an increase in the subsequent deposition temperature for HfO 2 (from 100 to 300 °C) assisted in decreasing both capacitance-equivalent oxide thickness and the number of bulk-related traps. However, the valuable reduction in both near-interface defect density and leakage current through the low-temperature Al 2 O 3 passivation approach was monotonically lessened with an increase in the process temperature for the subsequent HfO 2 deposition, which suggests the need for a careful optimization of a thermal budget for the dualtemperature process. Keywords: HfO 2 , Al 2 O 3 , In 0.53 Ga 0.47 As, atomic-layer deposition, dual-temperature process

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The advances in modern intelligent electronic systems have a pressing need for smart electromagnetic interference (EMI) shielding capabilities in a frequency-selective manner to choose which electromagnetic waves in a certain range to be blocked. Herein, we present multilayered EMI shielding composites that can provide selective on-off characteristics for speci c frequency ranges across a broad spectrum. The composites are composed of outermost dielectric layers and conductive interlayers fabricated via solution-printing, wherein hexagonal boron nitride (BN) and silver-coated BN particles are embedded, respectively. The EMI shielding frequency range and on-off selectivity are controllable by varying the con guration of the composite structure in terms of the BN content and the number of composite layers, providing different interstitial spaces between the llers and interfacial dielectric properties. Furthermore, the optimal combination of these layers permits excellent combinatorial properties of EMI shielding (32-62 dB), thermal conductivity (7.61 W/m•K), and electrical insulation (4.03 kV/mm) in the through-plane direction. The developed composites and their synthetic pathways have enormous potential for tailored material design and exible system integration in next-generation EMI shielding technologies. HighlightsSilver/boron nitride/polyetherimide-based multilayered composites were developed using solution printing.Electromagnetic interference shielding frequency and on-off selectivity could be deliberately tuned by modifying the ller and composite layer design.Composites concurrently exhibited excellent EMI shielding effectiveness (32-62 dB), high thermal conductivity (7.61 W/m•K), and electrical insulation (4.03 kV/mm).