Soo-Hyun Kim

Self-assembled monolayers (SAMs) consist of long alkyl chains of large molecular size and low volatility, which require conventional solution-based processes that are incompatible with bottomless barrier structures, especially for sub-10 nm 3D semiconductor fabrication, leading to nonuniform inhibition and poor selectivity. Here, we introduce a bottomless barrier architecture strategy that selectively deposits barrier material on the SiO2 via-sidewall surfaces using area-selective atomic layer deposition (AS-ALD), while leaving the Cu bottom surface exposed. A phenylethyl mercaptan (PEM) small-molecule inhibitor (SMI) is employed as a Cu-selective passivating agent, exploiting strong Cu–S chemisorption and π–π stacking interactions to form a densely packed inhibition layer on Cu surfaces, thereby directing ZnO ALD exclusively onto the SiO2 sidewalls with superior selectivity compared to bulkier SAM-based approaches. ZnO is decided as the barrier material due to its low-temperature ALD capability (<150 °C), strong interfacial adhesion with Si-based dielectric, and effective suppression of Cu diffusion. The PEM inhibitor exhibited sufficient vapor pressure for a stable vapor-phase ALD-ZnO process that selectively adsorbs approximately 90% during a 50-cycle ZnO film with a thickness of about 9.1 nm. Notably, both H2 molecular and H2 plasma treatments are found to be efficient in removing PEM inhibitor from Cu surfaces before Ru deposition. ALD-Ru is subsequently deposited controllably as a low-resistivity (∼23 μΩ·cm) liner and seed layer with a thickness of ∼15 nm, further maintaining a low resistivity of ∼38.1 μΩ·cm even at a thickness of ∼6 nm, as well as nearly 100% step coverage in dual-trench structures with an aspect ratio of ∼6.3. The resulting Ru/ZnO bilayer on SiO2 sidewalls and the Ru layer on the Cu bottom surface could be incorporated into dual-damascene patterns prior to Cu filling for modern-day interconnects.

The effects of post-deposition annealing on the interfacial adhesion energy and film stress of Ru/ZnO thin films were systematically investigated using a double cantilever beam test and a multi-beam optical stress system, respectively. Interfacial adhesion energy increased from 2.03 ± 0.06 to 4.07 ± 0.16 J m ⁻² after annealing at 350 °C in Ar/H ₂ (4%), whereas it decreased when annealing at higher temperatures up to 500 °C. X-ray photoelectron spectroscopy revealed that Zn ₂ SiO ₄ bonds were formed at the ZnO/SiO ₂ interface, this formation was most prominent at 350 °C. Zn ₂ SiO ₄ bonds were considered to form through Zn diffusion from ZnO into SiO ₂ during annealing, increasing the interfacial adhesion energy. In terms of film stress, the initial compressive stress decreased from 1.05 to 0.60 GPa after post-deposition annealing at 350 °C, attributed to a decrease in impurities introduced during deposition and grain size increase accompanied by a volume reduction.

In the era of autonomous systems and multifunctional devices, sensors serve as vital sensory components in our Internet of Things and technologically advanced society. At the end of the synthetic 2D nanomaterials research, MXenes are not just chemicals but materials, depending on how they are synthesized for targeted applications, such as dual‐functional temperature and pressure‐sensitive wearable sensing. The current findings introduce the potential strategic role of nitrogen atoms to the Ti‐Carbonitride (Ti ₃ CNT _z ) structure in a controlled compositional stoichiometry of Ti ₃ C _1.8 N _0.2 T _z , Ti ₃ C _1.5 N _0.5 T _z , Ti ₃ CNT _z , Ti ₃ C ₂ T _x to deliver an ultrahigh sensitivity (300%–400% temperature & pressure sensitivity enhancement) and durability in real‐time human‐machine sensing interface applications. These recorded outstanding dual‐sensing performance outplays many other MXene stoichiometries, graphene‐related 2D nanomaterials, and their associated composites. Synchrotron radiation‐based X‐ray absorption fine structure and density functional theory analysis reveal that incorporating low N content (e.g., Ti ₃ C _1.8 N _0.2 T _z ) enhances temperature sensitivity by boosting electrical conductivity, and an upshift in the vibrational spectrum with increased lattice deformability significantly improves pressure sensitivity. We provide valuable insights for developing advanced sensing materials, emphasizing the need to investigate the fundamental mechanisms that control the interactions among layered 2D MXene materials and the sensing device functions that bridge human and machine interfaces.

The development of high-performance switching cerium dioxide (CeO₂) thin films is critical for advancing neuromorphic computing technologies, where atomic layer deposition (ALD) offers unparalleled control over the conformality, stoichiometry, and microstructure of oxide thin films. Here, we report the CeO₂ deposition using a newly developed heteroleptic amidinate framework liquid precursor, bis­(n-propylcyclopentadienyl)­(N,N′- diisopropylpropionamidinato)­Ce­(III)­[(n-PrCp)₂(iPr₂-pamd)­Ce­(III)], via thermal ALD (Th-ALD) and plasma-enhanced ALD (PE-ALD) processes with O₂ and O₂ plasma coreactants, respectively. Both methods were optimized at 200 °C, achieving growth per cycle values of 1.7 Å/cycle (Th-ALD) and 1.2 Å/cycle (PE-ALD), which revealed striking contrasts in film properties. PE-ALD produced highly crystalline cubic CeO₂ with larger grains (∼7 nm), higher density (∼7.1 g/cm³), and greater surface roughness (∼1.1 nm), while Th-ALD yielded nanocrystalline, smoother, and less dense films. X-ray photoelectron spectroscopy confirmed near-stoichiometric Ce₁O_2.1 composition without detectable impurities for PE-ALD, whereas Th-ALD films were oxygen-deficient (Ce₁O_0.8) and carbon-contaminated. Optical analysis revealed a refractive index of 2.5 and a well-defined bandgap (3.2 eV) for PE-ALD films, compared to 1.8 for Th-ALD. Despite reduced step coverage (∼56%) on high-aspect-ratio features compared to Th-ALD (excellent conformality, ∼100%), only PE-ALD-CeO₂ enabled analog resistive switching in Pt/CeO₂/Pt devices, demonstrating synaptic behavior essential for neuromorphic computing. Notably, the PE-ALD-CeO₂ device achieved a high dynamic range (a resistance ratio of 7.6 × 10²), underscoring the importance of oxygen-vacancy-mediated analog synaptic weight updates via plasma-activated ALD for reliable artificial synapse functionality. These findings reveal how precursor chemistry and plasma processes govern film quality and synaptic behavior, offering a scalable route to oxide-based artificial synaptic devices.

High-performance electrode materials are vital for developing next-generation supercapacitors with enhanced energy storage capability. Mixed metal oxyhydroxides can exhibit better performance due to their high pseudo-capacitance and tunable redox activity. Thus, introducing another metal led to an enhancement of their electrochemical performance through synergistic effects and the creation of new redox-active sites. Here, Mn was incorporated into ZnFeOOH (FZ) to develop a ternary oxyhydroxide, which demonstrates the effect of Mn (FZMn-0 to FZMn-20) on the structural and electrochemical properties. Among them, FZMn-15 exhibited the most favorable characteristics, achieving a high specific capacitance of 1531 F g⁻¹ at 1 A g⁻¹ in a three-electrode system, while the corresponding asymmetric FZMn-15‖AC device delivered 92 F g⁻¹. Furthermore, charge storage analysis indicated a diffusion-dominated process with additional capacitive contributions, highlighting the combined effect of Mn incorporation on electrochemical activity. These findings demonstrate that Mn-modified ZnFeOOH electrodes can serve as efficient and reliable materials for advanced supercapacitor applications.

An- ABC-type Ru ALD process with NH ₃ addition at 310 °C enhanced Ru thin films: ∼100% step coverage, 1.2 nm roughness, 12.3 g cm ⁻³ density, 13.4 µΩ cm resistivity and 0.3 at% impurities enabling high-quality Ru interconnects.

Inherently selective Ru ALD is achieved without inhibitors on metallic substrates via substrate-dependent adsorption and oxygen-driven adatom removal mechanisms.