Controlling the polymorphic phases within the thermal budget of atomic layer deposition (ALD) is essential for integrating high-k dielectrics into dynamic random-access memory (DRAM) capacitors. Rutile TiO2 offers a dielectric constant significantly higher than that of tetragonal ZrO2 and anatase TiO2. However, its application on industry-standard TiN electrodes is impeded by the lack of rutile-compatible lattice matching. A top-interface-driven stabilization strategy is demonstrated, where a structurally compatible RuO2 upper layer stabilizes rutile TiO2 at 400°C regardless of the crystallinity of the underlying ZrO2/TiN stack. Thickness-dependent phase maps reveal an interfacial-energy-driven anatase-to-rutile transition for thin amorphous TiO2 layers, enabling rutile formation even on amorphous ZrO2. The resulting TiO2/ZrO2/TiN capacitors exhibit a dielectric constant of approximately 80 and a reduced equivalent oxide thickness, comparable to that of ZrO2-based stacks. A methanol-assisted reduction-etching process allows selective removal of RuO2 by O3 with minimal TiN oxidation. This top-interface engineering concept offers a substrate-agnostic approach to rutile TiO2 that is compatible with DRAM process windows and can be extended to other polymorphic oxides.

Hydrogen peroxide (H2O2) is a green oxidant with an energy density comparable to that of compressed hydrogen, making it a promising candidate for chemical energy storage. Converting renewable energy into H2O2 via the photoelectrochemical water oxidation reaction offers a sustainable pathway, yet the competing oxygen evolution reaction limits the solar-to-chemical conversion (SCC) efficiency. Here, we develop a BiVO4 based photoanode combined with a conformal SnO2 passivation layer. A built-in electric field is established at the SnO2/BiVO4 heterojunction, which facilitates charge separation and promoting hole transport toward the SnO2 surface. The valence band edge of SnO2 is also thermodynamically favorable for H2O2 production. To further improve H2O2 production, a CaSnO3 cocatalyst is integrated on the photoanode, enabling enhanced reaction kinetics and selectivity toward 2e- water oxidation pathway. The resulting CaSnO3/SnO2/BiVO4 photoanode achieves an average Faradaic efficiency of 90% over wide potential range of 0.6-2.1 VRHE, with a H2O2 generation rate of 0.838 mu mol cm-2 min-1 and a photocurrent density of 5.44 mAcm-2 at 1.23 VRHE. Photoelectrochemical device composed of CaSnO3/SnO2/BiVO4 photoanode and perovskite/Si photovoltaic simultaneously produce H2O2 and H2 without applied bias, which achieving SCC efficiency of 1.12%, the highest record to date for bias-free H2O2 production at a single photoanode.

Hydrogen peroxide (H 2 O 2 ) is a green oxidant with an energy density comparable to that of compressed hydrogen, making it a promising candidate for chemical energy storage. Converting renewable energy into H 2 O 2 via the photoelectrochemical water oxidation reaction offers a sustainable pathway, yet the competing oxygen evolution reaction limits the solar‐to‐chemical conversion (SCC) efficiency. Here, we develop a BiVO 4 based photoanode combined with a conformal SnO 2 passivation layer. A built‐in electric field is established at the SnO 2 /BiVO 4 heterojunction, which facilitates charge separation and promoting hole transport toward the SnO 2 surface. The valence band edge of SnO 2 is also thermodynamically favorable for H 2 O 2 production. To further improve H 2 O 2 production, a CaSnO 3 cocatalyst is integrated on the photoanode, enabling enhanced reaction kinetics and selectivity toward 2e − water oxidation pathway. The resulting CaSnO 3 /SnO 2 /BiVO 4 photoanode achieves an average Faradaic efficiency of 90% over wide potential range of 0.6–2.1 V RHE , with a H 2 O 2 generation rate of 0.838 µmol cm −2 min −1 and a photocurrent density of 5.44 mA·cm −2 at 1.23 V RHE . Photoelectrochemical device composed of CaSnO 3 /SnO 2 /BiVO 4 photoanode and perovskite/Si photovoltaic simultaneously produce H 2 O 2 and H 2 without applied bias, which achieving SCC efficiency of 1.12%, the highest record to date for bias‐free H 2 O 2 production at a single photoanode.

ABSTRACT The lack of high‐performance p‐type channel materials that can be processed at low temperatures has hindered the progress of monolithic 3D integration. Despite its high hole mobility, Te often exhibits discontinuous island‐like growth when deposited using atomic layer deposition (ALD) due to its weak surface interactions. This study introduces a new reductive transformation method that addresses this inherent issue by converting continuous ALD‐grown TeO 2 films into crystalline, impurity‐free Te layers. Notably, this approach allows for the formation of fully continuous Te films, even at thicknesses below approximately 5 nm. By utilizing a TeH 2 ‐assisted reduction pathway generated in situ, this self‐limiting process ensures complete removal of oxygen from both the bulk and interface regions while preserving exceptional conformality in structures with high aspect ratios. The resulting Te films exhibit excellent electrical properties, such as low contact resistance and stable switching in nonplanar transistor configurations. By decoupling the film continuity from surface wettability, this chemical transformation approach provides a breakthrough solution for integrating ultrathin p‐type chalcogenides into advanced back‐end‐of‐line architectures.

This study reports a strategy to enhance the thermoelectric performance of Bi2Te2.7Se0.3 (BTS) by introducing ultrathin In2O3 interfacial layers via atomic layer deposition (ALD). Conformal In2O3 coatings were preserved after spark plasma sintering, thereby suppressing grain growth. A small interfacial energy barrier (similar to 0.2 eV) was formed at the BTS/In2O3 interface, enabling carrier filtering that preferentially transmits high-energy electrons, thereby enhancing mobility. At the same time, the coatings suppressed Te volatilization during sintering, leading to reduced carrier concentration and increased Seebeck coefficient. Although electrical conductivity decreased, the power factor remained nearly unchanged, while total thermal conductivity was markedly reduced due to a lower electronic contribution. As a result, the 20-cycle In2O3-coated BTS achieved a maximum zT of 1.02 at 373 K, surpassing the pristine sample. These results highlight ALD-engineered interfacial barriers as an effective approach for carrier concentration control and thermoelectric performance optimization in bulk Bi2Te3-based materials.

Ru is a promising material for ultrathin interconnects and capacitor electrodes. However, achieving ultrathin, continuous metallic films with minimal surface roughness remains challenging in atomic layer deposition (ALD) due to nucleation limitations on dielectric surfaces. In this study, we demonstrate an ALD process for Ru films using a tricarbonyl(trimethylenemethane)ruthenium [Ru(TMM)(CO)3] precursor and O3. The O3-based process at 220 °C exhibits a high growth per cycle of 0.17 nm/cycle with a negligible incubation period on SiO2. In particular, electrical continuity is achieved even at sub-nanometer thicknesses, indicating a high nucleation density and effective suppression of island coalescence. This leads to ultra-smooth surface morphology even as the film scales toward practical thicknesses. Furthermore, we identify that phase evolution is critically governed by the O3 exposure conditions. High O3 flow rates suppress film growth associated with the formation of volatile species such as RuO4, whereas extended pulse durations at moderate fluxes promote progressive oxidation to RuO2. These findings demonstrate that phase evolution is governed not only by the total oxidant dose but also by the oxidant supply conditions, providing a strategy for controlling nucleation, surface morphology, and phase in Ru-based ALD.

Metastable phases characterized by their higher-energy states offer promising functionalities for electronic, catalytic, and energy applications. However, their synthesis is often hindered by high formation energy barriers and thermodynamic constraints. Atomic layer deposition (ALD) has attracted significant interest for a wide range of applications, including semiconductors, advanced electronics, and energy-related applications, owing to its exceptional features, including low-temperature processing, precise atomic-scale control, and excellent conformality. Despite these advantages, the inherently low thermal budget of ALD poses significant challenges for the synthesis of metastable phases. This review presents a comprehensive overview of the recent advances in the engineering of metastability via ALD. This review categorizes the manifestations of metastability in ALD into two main directions: polymorphic transformations and valence state control. For polymorphs, strategies, such as temperature modulation, substrate-induced lattice matching, grain-size refinement, doping, and solid-solution formation, enable selective phase stabilization. Approaches for valence control include temperature modulation, the design and selection of the precursor/reactant, and post-deposition treatments. By linking reaction mechanisms with material phases, this review offers insights into the stabilization of metastable phases and practical design principles for achieving them. These insights will pave the way for new functional materials that surpass conventional thermodynamic limitations and advance next-generation devices and technologies.

Realizing tunable charge carrier polarity is essential for programmable complementary logic circuits. While two-dimensional (2D) semiconductors have demonstrated polarity controllability through Schottky barrier modulation or contact engineering, their high interfacial sensitivity limits scalability and integration. Here, we present a robust polarity-conversion strategy for tin oxide (SnO) semiconductors based on electrolyte-gated transistors (EGTs). In situ electrochemical doping enables the conversion of p-type SnO to n-type SnO2 via Sn2+ to Sn4+ oxidation. Both p- and n-type EGTs exhibit outstanding electrical characteristics, including low-voltage operation, high ON/OFF current ratios, sharp switching behavior, and reliable long-term stability. Furthermore, we demonstrate the monolithic integration of complementary logic gates, including inverter, NAND, and NOR gates, through spatially selective electrochemical doping of a single SnO layer. Overall, this work provides a scalable and versatile pathway toward oxide-based programmable complementary circuits.

The lack of high-performance p-type channel materials that can be processed at low temperatures has hindered the progress of monolithic 3D integration. Despite its high hole mobility, Te often exhibits discontinuous island-like growth when deposited using atomic layer deposition (ALD) due to its weak surface interactions. This study introduces a new reductive transformation method that addresses this inherent issue by converting continuous ALD-grown TeO2 films into crystalline, impurity-free Te layers. Notably, this approach allows for the formation of fully continuous Te films, even at thicknesses below approximately 5 nm. By utilizing a TeH2-assisted reduction pathway generated in situ, this self-limiting process ensures complete removal of oxygen from both the bulk and interface regions while preserving exceptional conformality in structures with high aspect ratios. The resulting Te films exhibit excellent electrical properties, such as low contact resistance and stable switching in nonplanar transistor configurations. By decoupling the film continuity from surface wettability, this chemical transformation approach provides a breakthrough solution for integrating ultrathin p-type chalcogenides into advanced back-end-of-line architectures.

Two-dimensional (2D) layered Zintl compounds have emerged as promising candidates for thermoelectric applications due to their favorable electronic structures, efficient charge transport pathways, and loosely bound cations. In this study, we engineered 2D-layered structures in polycrystalline ZnSb through alkali metal (A = Li, Na, K) alloying, inducing a bonding transition from sp(3) to sp(2) hybridization that promotes the formation of layered structures. Structural analysis confirmed the formation of layered phases, with increasing texturing fractions from Li to K. Electrical transport measurements revealed that LiZnSb exhibited high electrical conductivity (similar to 6561 S cm(-1)) due to a high carrier concentration, while NaZnSb showed moderate conductivity (similar to 213 S cm(-1)) with a carrier concentration close to the theoretical value (7.38 x10(18) cm(-3)). In contrast, KZnSb demonstrated extremely low conductivity, hindering reliable carrier concentration analysis. As a result, NaZnSb achieved a maximum ZT of 0.079 at 375 K, which is significantly higher than that of LiZnSb. The single parabolic band (SPB) model suggests that NaZnSb may be further optimized through extrinsic doping at the Zn site, whereas LiZnSb remains limited by intrinsic cation deficiencies. These results demonstrate that alkali metalinduced bonding transitions offer a viable strategy for engineering 2D structures in Zintl compounds to enhance thermoelectric performance.

Structural dynamics of an enzyme plays a crucial role in enzymatic activity and substrate specificity, yet rational engineering of the dynamics for improved enzymatic properties remains a challenge. Here, we present a new biochemical strategy of intermediate state stabilization that modulates the multistep dynamic mechanisms of enzyme reactions to improve substrate specificity. We employ this strategy to enhance CRISPR-Cas9 nuclease specificity. By incorporating positively charged residues into the noncatalytic REC2 domain of Cas9, we stabilize the REC2-DNA interaction that forms exclusively in a catalytically inactive intermediate conformation of the Cas9 complex. This enables off-target trapping in the inactive conformation and thus reduces off-target cleavage in human cells. Furthermore, we combine the REC2 modification with mutations in previous rational variants, leading to the development of a combinational variant named Correct-Cas9, which connotes "combined with rationally engineered REC-Two" Cas9. Assessed by high-throughput analysis at thousands of target sequences, Correct-Cas9 exhibits increased target specificity compared to its parental variants, demonstrating a synergy between our strategy and previous rational approaches. Our method of intermediate state stabilization, either alone or combined with conventional approaches, could be applied to various nucleic acid-processing enzymes that undergo conformational changes upon target binding, to enhance their target specificity effectively.

An appropriate synthesis technique for growing high-quality indium-free ZnSnOx (ZTO) films should be developed to achieve high-performance thin-film transistors (TFTs) utilizing ZTO films. This study investigated the growth characteristics and electrical properties of ZTO thin films grown via plasma-enhanced atomic layer deposition (PEALD) using bis(1-dimethylamino-2-methyl-2-propoxide)Sn, diethylzinc, and O2 plasma to optimize the composition and enhance the device performance. Deviations were observed in the growth per cycle when using PEALD for ZTO, compared with binary oxides. In the PEALD of the ZTO films, the introduction of the SnO2 sub-cycle enhanced the mass gain in the ZnO sub-cycle, whereas the mass gain in the SnO2 sub-cycle decreased with the addition of the ZnO sub-cycle. This was attributed to changes in the density of the functional groups on the reaction surface. Precise control over the composition was achieved, enabling the identification of the optimal Zn58Sn42Ox composition. Post-deposition annealing significantly improved the TFT performance, with devices showing enhanced mobility, positive shifts in the threshold voltage, and reduced subthreshold swing values. These improvements stemmed from reductions in oxygen vacancies and sub-gap defect states. These findings highlight the potential of PEALD-grown ZTO films for use in high-performance, cost-effective TFTs, facilitating their integration into modern semiconductor electronics.

The accumulation of polyethylene terephthalate (PET) waste poses a serious environmental challenge due to its durability and resistance to degradation. Enzymatic PET hydrolysis offers a sustainable solution, but efficient high-throughput screening tools for PET-degrading enzymes remain limited. Here, we report a genetically encoded biosensor (GEB) for terephthalic acid (TPA)─the primary monomer released during PET degradation─that enables rapid and sensitive detection of enzymatic activity. We engineered a TphR-based biosensor in Escherichia coli, combining an optimized transcriptional system with diverse TPA uptake transporters to enhance intracellular TPA accumulation. This dual strategy improved the signal intensity and broadened the detection range. The best-performing configuration, integrating a high-affinity transporter with fine-tuned genetic components, achieved a detection limit of 1  μM TPA─a 1,000-fold sensitivity improvement over the initial design. We validated the system using PETases, including Ideonella sakaiensis-derived FAST-PETase, and benchmarked it against HPLC assays. The biosensor reliably distinguished PETase variants based on hydrolytic activity, demonstrating its utility for directed evolution, metagenomic screening, and enzyme engineering. This work establishes a rapid, scalable, and ultrasensitive biosensor platform for monitoring PET hydrolysis. The engineered GEB offers a robust, low-cost alternative to conventional analytics, accelerating the discovery and optimization of PET-degrading enzymes for plastic upcycling and circular bioeconomy applications.

Improving thermoelectric material performance is essential for energy harvesting and solid-state cooling applications. This study demonstrated a novel structure of Bi2Te3-based thermoelectric materials with ZnO nanowire-bundled grain boundaries, realized via atomic layer deposition (ALD) and subsequent spark plasma sintering (SPS). The ZnO nanowires formed at the interfaces due to the rearrangement of the ALD-grown ZnO ultrathin layer over Bi0.4Sb1.6Te3 powder, driven by localized heating during the SPS process and the anisotropic nature of ZnO. The nanowire-bundled interfaces enhanced phonon scattering, thereby reducing lattice thermal conductivity while maintaining excellent electrical transport. This structural innovation achieved a high figure-of-merit, zTmax = 1.69 ± 0.09 at 373 K and an average zT of 1.55 over the range of 300-473 K. A thermoelectric module fabricated with 127 p-n pairs achieved a record-high conversion efficiency of 6.57% at a temperature difference of 163 K. These findings highlight the potential of nanowire-bundled interfaces to enhance the thermoelectric material performance and pave the way for scalable next-generation energy conversion technologies.

This study presents considerable improvements in the electrical characteristics of atomic-layer-deposited 3-nm-thick In2O3 thin-film transistors (TFTs), which were achieved by introducing a 2-nm-thick amorphous Al2O3 interfacial layer to passivate the surface of a polycrystalline HfO2 gate dielectric. The resulting devices exhibited exceptional electrical characteristics, including an ultrahigh field-effect mobility (μFE) of approximately 147.5 ± 16.6 cm2/V s, subthreshold swing of 103.7 ± 9.1 mV/dec, and threshold voltage (VTH) of 0.5 ± 0.1 V. These enhancement-mode devices represent increases of more than threefold in μFE compared to devices without an amorphous passivation layer. This is despite all the fabrication processes being identical, except for the introduction of the Al2O3 interfacial layer. This improvement can be primarily attributed to the reduced electron scattering through suppressed remote Coulomb interactions. Furthermore, the In2O3 TFTs exhibited enhanced operational stability, showing minimal VTH shifts of 0.15 and −0.01 V under positive and negative bias-stress conditions, respectively. The findings of this study emphasize the critical role of the surface passivation of polycrystalline HfO2 dielectrics in improving the electrical performance of ultrathin In2O3 TFTs.

In this study, we examine the atomic layer deposition (ALD) growth behavior of crystalline MoS2 films on various substrates, including SiO2, mica, and Al2O3, at deposition temperatures of >= 650 degrees C. The results show that the substrate surface energy and temperature significantly influence the MoS2 growth dynamics, affecting the layer nucleation, surface morphology, and growth rate. High temperatures generally favor a stepwise growth pattern with a step size of one monolayer; however, the substrate surface energy distinctly affects the grain size and crystallinity. MoS2 growth on mica, which has the lowest surface energy, results in larger, highly crystalline triangular grains and enables multilayer growth, whereas Al2O3, which has the highest surface energy, produces smaller, less crystalline grains. Temperature elevation further enhances the lateral grain expansion and crystallinity, especially on Al2O3 substrates with higher surface energies. By tailoring the substrate surface and deposition temperature, the key pathways for optimizing MoS2 ALD growth are highlighted with the aim of enhancing the film uniformity and quality for nanoelectronic applications. This study provides critical insights into the ALD parameters that govern the growth of crystalline MoS2 with implications for advancing scalable, high-performance 2D materials.

The role of TiO2, ZnO, and ZnTiO3 as supports for rhodium has been investigated for the CO2 hydrogenation. Rh/TiO2 demonstrated a high selectivity for CH4, which is typical for Rh catalysts; however, Rh/ZnO and Rh/ZnTiO3 shifted the product selectivity to CO almost exclusively. The difference in behavior is attributed to the modulation of strong metal-support interactions (SMSIs) by the supports. Detailed characterization revealed the formation of a distinct metallic Zn overlayer covering the RhZnx alloyed nanoparticle in Rh/ZnO, altering the electronic states of Rh, and a RhTix overlayer in Rh/ZnTiO3, suppressing the CO adsorption on Rh in bridged and tilted geometry and polarizing the CO bond. These structural features significantly modify the CO adsorption strength and mode, together with the intermediate hydrogenation behavior, influencing product formation. The study highlights the potential of tailoring SMSI states by modifying the support composition and interfacial coupling with metal nanoparticles, enabling improved CO-selective hydrogenation. These findings offer deeper insights into engineering metal-support interactions, with broad implications for advancing industrial processes involving CO, including Fischer-Tropsch synthesis, the water-gas shift reaction, and methanol synthesis.

Stabilizing metastable TiO2 phases in thin films remains a significant challenge. This paper demonstrates a strain-driven approach for selectively stabilizing the metastable phases of orthorhombic TiO2-II and rutile using (111)-oriented face-centered cubic (FCC) metal substrates via low-temperature atomic layer deposition. Epitaxial FCC metal substrates, including Ir and Pt, exhibit a strong preferential (111) orientation and promote the formation of TiO2-II with a preferential (200) orientation through favorable lattice matching. In contrast, TiO2 grown on (111)-textured polycrystalline FCC metals crystallizes into rutile with a preferential (110) orientation despite identical growth conditions, which is attributed to strain relaxation arising from the random in-plane orientations of FCC metals. Compared to the stable anatase phase, TiO2-II films exhibit higher density (4.45-4.51 g cm-3), higher refractive indices, and higher dielectric constants (≈75-77). These findings reveal that in-plane strain and lattice matching can be strategically utilized to engineer metastable TiO2 phases, offering a new approach for the phase-selective growth of functional oxide films at low temperatures.

Achieving uniform dopant distribution and fine compositional tuning in atomic layer deposition (ALD) processes remains a significant challenge, particularly for ultrathin films, due to their cyclic nature. This study systematically investigates the inherent limitations of compositional uniformity and the minimum thickness achievable in depositing doped films using ALD. Furthermore, a strategy is implemented to resolve the compositional nonuniformity in the ALD-grown doped films by employing inhibitors. Utilizing Sn-doped In2O3 films as the model system, this approach examines the influences of carboxylic acids, including acetic acid, isobutyric acid, and 2-ethylbutyric acid, as inhibitors, resulting in a significant reduction of the growth per cycle of a SnOx doping layer to 1/10 to 1/20 of the levels observed without inhibitors. The degree of inhibition correlates with the size of the carboxylic acid, allowing precise control over dopant composition and enabling uniform doping in films as thin as 2 nm. Also, atomistic simulations reveal that steric hindrance plays as the major inhibition mechanism among the carboxylic acids, providing mechanistic insights into the design criteria for optimal inhibitors. The results suggest that inhibitor-assisted ALD processes offer a viable pathway to improve dopant control and alleviate thickness limitations, enhancing the performance of advanced materials.

We present a novel approach for synthesizing continuous, single-phase SnS thin films through the kinetically confined sulfurization of SnO. The process utilizes a chemically inert Al2O3 confinement layer to enable kinetically controlled sulfurization, effectively suppressing surface migration while allowing H2S diffusion. This confinement addresses the discontinuity issues frequently encountered in conventional deposition and sulfurization techniques. The method achieves uniform film coverage at a minimal thickness of 4 nm. Structural and compositional analyses confirm the formation of stoichiometric SnS with high phase purity and a preferred orientation of van der Waals (040) planes parallel to the substrate. Mechanistic studies reveal that sulfurization predominantly initiates at the surface and proceeds inward, with rapid grain boundary diffusion resulting in localized acceleration of the transformation. The Al2O3 layer can be selectively removed without compromising the integrity of the SnS film. This strategy provides a scalable route for the fabrication of high-quality SnS and holds potential for application to other metal chalcogenide systems.