Minjae Kim

Energy‐efficient computing is a critical challenge for artificial intelligence and edge applications. Although self‐powered memory systems that integrate sensing, energy harvesting, and storage are promising, they often suffer from high leakage currents, poor reproducibility, and material incompatibility. Here, we present a dual‐functional N‐doped ZnO (NZO) platform that electrically couples an interface‐type memristor with a piezoelectric nanogenerator (PENG), enabling self‐powered memory programming. Uniform N‐doping via low‐temperature atomic layer deposition passivates oxygen‐related defects, suppresses leakage currents, and stabilizes resistive switching. A thin TiO _2‐x interfacial layer acts as an oxygen reservoir and enables precise barrier engineering for reversible, low‐power multilevel operation. At the same time, the reduced carrier concentration in NZO enhances PENG performance through suppression of electrostatic screening effects. Density functional theory (DFT+U) calculations further predict N‐induced changes in elastic stiffness and compliance, suggesting a possible secondary contribution to the electromechanical response through modified strain accommodation. As a result, the rectified PENG output directly programs the memristor without an external bias. The coupled system exhibits stable multilevel storage, robust endurance, and synaptic plasticity. By co‐designing energy harvesting, sensing, and memory on a unified oxide platform, this work establishes a practical pathway toward energy‐autonomous neuromorphic computing and intelligent tactile memory systems.

Enhancing the energy‐storage performance of dielectric capacitors requires the simultaneous increase of saturated polarization, suppression of remanent polarization, and improvement of dielectric breakdown strength (DBS). Although nanocomposite and multiphase strategies exploiting interfacial effects have been widely investigated to achieve high energy density, it remains thermodynamically challenging to fabricate composite architectures in which multiple ferroelectric phases coexist as discrete nanoscale crystals, making it difficult to sustain true multiphase heterointerfaces. We address these challenges by fabricating a multiphase nano‐clustered (MN) structure composed of three ferroelectrics‐BaTiO ₃ (BT), PbZrO ₃ (PZ), and PbTiO ₃ (PT)‐using a room‐temperature aerosol deposition (AD) process without post‐thermal treatment. This route effectively suppresses interphase reactions and preserves the intrinsic crystal structure of each constituent, thereby enabling the formation of three‐dimensional nanoscale interfaces that cannot be achieved through conventional sintering. Owing to the large work‐function differences among BT, PZ, and PT, interfacial charge trapping is induced, which suppresses space‐charge transport and inhibits breakdown‐path propagation. The MN BT–PZ–PT film exhibits a DBS of 5.8 MV cm ⁻¹ (∼260% enhancement) and a recoverable energy density of 68.6 J cm ⁻³ (∼300% increase) compared with a single‐phase BPZT film. Despite room‐temperature fabrication, the composite demonstrates excellent energy‐storage performance, thermal stability, and fatigue endurance, enhanced DBS.

Ferrite materials offer promising advantages for non-volatile memory and energy-efficient neuromorphic computing, owing to their multifunctional properties and potential for advanced data storage and processing.

Reliable detection of SO ₂ at low operating temperatures remains a significant challenge for metal oxide gas sensors, particularly in harsh refinery environments where selectivity and stability are critical. In this study, ZnFe ₂ O ₄ thin films with compact and porous morphologies are deposited via spray pyrolysis to investigate their suitability for SO ₂ sensing in refinery environments. The rigorous structural analysis reveals a strong correlation between crystalline features and sensing performance. In particular, an increased degree of spinel inversion enhances the sensor response by facilitating charge transport and surface reactivity. The porous films exhibit superior sensing behavior compared to compact films, owing to their higher surface area and increased availability of active adsorption sites. The optimized ZP375 sensor demonstrates a linear response towards SO ₂ concentration up to 200 ppm, with a low detection limit of 0.41 ppm. The sensor exhibits optimal performance at an operating temperature of 150°C and demonstrates excellent selectivity towards SO ₂ in the presence of other common interfering gases typically encountered in refinery environments. The sensor further exhibits long‐term stability extended up to 30 days. The results highlight the potential of spray‐deposited ZnFe ₂ O ₄ thin films as robust and energy‐efficient sensing materials for SO ₂ monitoring in industrial emissions from petrochemical refineries.