Atomic Layer Deposition Method Research Articles

Investigation on self-rectifying properties of Pt/HfO2/Ti with rivet-like structure based on ALD conformal technology

This work explores an architecture for nonvolatile resistive random-access memory (RRAM) systems. The study proposes a self-rectifying RRAM device utilizing a two-terminal 1R selector that harmonizes the gate control efficacy of transistors with the inherent simplicity of diode structures. A rivet-like HfO2-based RRAM array is meticulously constructed through atomic layer deposition (ALD), aiming to enhance device performance and retention stability. The conformal fabrication technique of ALD method is critical in achieving uniform coverage of isolation layers and precise electrode placement, which is instrumental in the fabrication of high-performance memory cells. Empirical analyses indicate significant improvements in rectification and ON/OFF ratios compared to existing RRAM models, bolstered by compatibility with established CMOS processes. It reveals that these advances are conducive to scalable, high-density memory integration, positioning the RRAM as a viable contender for future computational applications that require high efficiency and neuromorphic computing capabilities.

Lightweight titanium dioxide/carbon nanotube composites prepared by atomic layer deposition for broad-band microwave absorption

The microwave absorbing material with appropriate impedance matching and excellent attenuation ability can be applied to resist electromagnetic radiation. In this work, carbon nanotubes were modified by titanium dioxide via the atomic layer deposition method, to prepare lightweight composites with high microwave absorption performance. The impedance matching and attenuation ability of titanium dioxide/carbon nanotube (TiO2/CNT) composites could be precisely controlled by adjusting the number of titanium dioxide deposition cycles. The relationship between the microstructure and microwave absorption performance of the composite was analyzed in detail. When the number of TiO2 deposition cycles was 100, the composite displayed outstanding microwave absorption performance, due to appropriate impedance matching and strong attenuation ability. The maximum effective absorption bandwidth of the composite reached 5.19 GHz (1.6 mm), which almost covered the Ku band. The microwave attenuation mechanism of the composite has also been investigated. This work provided a new idea for fabricating lightweight microwave absorption materials.

Selectively Located Pt Clusters on Au/CeO2 for Highly Robust Water-Gas Shift Reaction via Atomic Layer Deposition

Au catalysts have shown outstanding low temperature catalytic activity toward water-gas shift (WGS) reaction, but they are struggling with the durability concerns. Herein, Pt clusters are selectively located on Au/CeO2 through atomic layer deposition method to activate the interfacial active sites poisoned by intermediate species. The selective method effectively avoids the coverage of Au surface sites by Pt atoms and maintains the low temperature catalytic activity of Au/CeO2 catalyst. Durability test indicates that the Pt-activated Au/CeO2 catalyst shows superior durability in WGS atmosphere (200 ºC), which only attenuates 7.9% (from 78.0% to 70.1%) after 150hours. The analysis of surface intermediates and density functional theory calculations reveal that the introduction of Pt ensures the regenerative capacity of Au/CeO2 active sites by facilitating the decomposition of intermediate species and the desorption of CO2.

Correlating the coating cycles, integrity and magnetic properties of Fe–Ni–Mo soft magnetic composites by a powder atomic layer deposition method

Coatings play a crucial role in minimizing eddy current loss in soft magnetic composites (SMCs). The powder atomic layer deposition (PALD) technique was utilized to coat Fe–Ni–Mo soft magnetic powder in this study. The Al2O3 coating fabricated via PALD enhanced corrosion resistance and reduced core loss in SMCs. Additional deposition cycles increased the resistivity of the Fe–Ni–Mo powder and the corrosion resistance of the Fe–Ni–Mo SMCs, indicating that the density and integrity of the amorphous Al2O3 coating were enhanced. Thinner coatings (20 cycles) exhibited anodic passivation in corrosion, which was attributed to insufficient density. Nevertheless, an excessively thick coating (100 cycles) resulted in a decrease in effective permeability and an increase in hysteresis loss. The fabricated Fe–Ni–Mo SMCs (50 cycles) demonstrated a core loss of 603.1 mW/cm3 at 100 kHz/100 mT, coupled with an effective permeability of 108.5 and a Q value of 97.8 at 100 kHz.

Colloidal Atomic Layer Deposition on Nanocrystals Using Ligand-Modified Precursors.

Atomic layer deposition (ALD) is a method to grow thin metal oxide layers on a variety of materials for applications spanning from electronics to catalysis. Extending ALD to colloidally stable nanocrystals promises to combine the benefits of thin metal oxide coatings with the solution processability of the nanocrystals. However, challenges persist in applying this method, which relate to finding precursors that promote the growth of the metal oxide while preserving colloidal stability throughout the process. Herein, we introduce a colloidal ALD method to coat nanocrystals with amorphous metal oxide shells using metal and oxygen precursors that act as colloidal stabilizing ligands. Our scheme involves metal-amide precursors modified with solubilizing groups and oleic acid as the oxygen source. The growth of the oxide is self-limiting and proceeds in a layer-by-layer fashion. Our protocol is generalizable and intrinsically scalable. Potential applications in display, light detection, and catalysis are envisioned.

ReS2-MoS2 heterojunction nanotube FET with superlattice structures for ultrasensitive detection of miRNA

Ultrasensitive detection of cancer biomarkers holds immense importance in facilitating the early diagnosis and treatment of cancer. Compared to conventional detection techniques, field-effect transistor (FET) biosensors have demonstrated substantial potential in achieving sensitive detection of cancer biomarkers. However, the ultrasensitive FET still remains great challenges due to the limited electron transport capacity and sensitivity of channel materials. Herein, we employed rhenium disulfide-molybdenum disulfide nanotube (ReS2-MoS2 NT) featuring superlattice structures as channel materials in FET biosensors for the highly sensitive detection of cancer biomarker miRNA-21. More concretely, ReS2-MoS2 NT featuring superlattice structures was synthesized using the anodic aluminum oxide (AAO) template sacrifice method and atomic layer deposition (ALD) method. The electrical properties of single ReS2-MoS2 NT FET were regulated by adjusting the total layers and number of heterojunction interfaces, and the optimal number of heterojunction interfaces of 7 was obtained. Finally, FET biosensors utilizing the network ReS2-MoS2 NT as the channel materials were fabricated and exhibited remarkable sensitivity in detecting miRNA-21 under an external light source. The linear range for detection spanned from 10 aM to 1 nM, with an exceptionally low detection limit of 2.1 aM. This study holds promise for replacing current channel materials and surpassing the detection threshold of cancer biomarkers in the future.

Emerging Non-Noble-Metal Atomic Layer Deposited Copper as Seeds for Electroless Copper Deposition.

Copper metal catalyst seeds have recently triggered much research interest for the development of low-cost and high-performance metallic catalysts with industrial applications. Herein, we present metallic Cu catalyst seeds deposited by an atomic layer deposition method on polymer substrates. The atomic layer deposited Cu (ALD-Cu) can ideally substitute noble metals Ag, Au, and Pd to catalyze Cu electroless deposition. The optimized deposition temperature and growth cycles of an ALD-Cu catalyzed seed layer have been obtained to achieve a flexible printed circuit (FPC) with a high performance electroless plating deposited Cu (ELD-Cu) film. The ELD-Cu films on the ALD-Cu catalyst seeds grown display a uniform and dense deposition with a low resistivity of 1.74 μΩ·cm, even in the through via and trench of substates. Furthermore, the ALD-Cu-catalyzed ELD-Cu circuits and LED devices fabricated on treated PI also demonstrate excellent conductive and mechanical features. The remarkable conductive and mechanical characteristics of the ALD-Cu seed catalyzed ELD-Cu process demonstrate its tremendous potential in high-density integrated FPC applications.

Modulation and optimisation of the properties of n-decanoic acid-tetradecanol phase change materials by nanocomposite carbon materials prepared by atomic layer deposition methods

Phase change materials limit practical applications due to their relatively weak thermal conductivity and leakage resistance. The present work focuses on the development of a novel composite PCM (CA-TD/ZnO/EG), which was prepared by adsorbing a binary mixture of n-decanoic acid-tetradecanol (CA-TD) based on the combination of expanded graphite (EG) and zinc oxide (ZnO) nanoparticles. A new support material, ZnO/EG, was assembled by depositing specially shaped ZnO onto the surface of an expanded graphite substrate using an atomic deposition method. In addition to maintaining the porous structure of EG and preventing the leakage of CA-TD, the ZnO/EG reduces the interfacial thermal resistance between the substrate and the PCM molecules, which leads to the maximisation of the thermal conductivity. The prepared CA-TD/ZnO/EG-10 composite has a phase transition temperature of 19.5 °C, a heat of 157.3 J/g, and a thermal conductivity of (6.131 W·m−1·K−1) improved by 351.7% compared to the CA-TD material. Its faster heat transfer rate is directly reflected in the infrared image, with a small enthalpy change of 1.2% during 200 cycles of heating-cooling, as well as some photothermal conversion capability. The results of this paper can provide prospects for the functional design, modification, and enhancement of composite PCM.

Microwave absorbing performance of reduced graphene oxide @ alumina fabricated by atomic layer deposition method

In this work, a series of alumina coating reduced graphene oxide (RGO@Al2O3) composites with core-shell structure was synthesized by the atomic layer deposition (ALD) method. The alumina (Al2O3) thickness of the RGO@Al2O3 could be controlled by changing the number of ALD cycles. The microstructure, high-temperature resistance, and microwave absorbing properties of the composites were investigated in detail. The composite could provide excellent high-temperature resistance and microwave absorbing properties. The composite started decomposition at 620 °C. The maximum reflection loss value of the composite obtained by applying 200 Al2O3 deposition cycles is −14.2 dB at 15.7 GHz, and its effective absorption bandwidth reaches 5.0 GHz (13.0–18.0 GHz). The results show that the RGO@Al2O3 composite has the potential application in high-temperature microwave absorbing fields, due to excellent high-temperature resistance, reflection loss, and effective absorption bandwidth.

High enhancement, low cost, large area surface enhanced Raman scattering substrates all by atomic layer deposition on porous filter paper

We successfully developed an atomic layer deposition (ALD) method for making Ag noble nanoparticles on cheap, commercial filter paper consisting of three-dimensional porous glass fibers and investigated the evolution of Ag nanostructures with some key process parameters. By tuning Ag particle sizes and controlling the cycle numbers of ALD deposited Ag films, we were able to obtain high-density isolated Ag nanoparticles with average sizes in 3–9 nm without the formation of agglomerates and continuous Ag films. We proved the presence of strong localized surface plasmon resonance peaks near a target wavelength of 632 nm. We further proved the presence of surface enhanced Raman scattering (SERS) signals on the Ag coated filter paper substrates using pyridine as the test analyte. Our results demonstrate that ALD is a very promising technique for a rational design of SERS substrates and, thus, has great potential for the fabrication of large-area, low-cost SERS substrates for future commercial applications, as compared to other existing techniques.

Al2O3-Coated Bonding Wire with Electrical Insulation & Promoted Adhesion

Conventional bond wires composed of Au, Ag, & Cu don’t meet market demands for strong adhesion, electrical insulation, and corrosion passivation due to their conductive metallic surfaces. We propose a solution through the applications of a ceramic (Al2O3) coating at nanometer scales on these metal wires, thereby improving their adhesion to encapsulation, electrical insulation, and resistance to corrosion. We used ALD (Atomic Layer Deposition) methods to coat Au and Ag metal wires with diameters ranging from 18um to 48um (0.7mil~1.9mil) with Al2O3. Our paper details the innovative processes we used to incubate the idea of Al2O3 coating on conventional bond wires, focusing on wire bondability and dependability. Our findings demonstrate enhanced electrical insulation between crossing wires and increased reliability related to the wires’ adhesion to encapsulation.

Atomic layer deposited Fe-sulfide layers with pyrrhotite structure controlled by the deposition temperature

Atomic layer deposition was used to grow epitaxial iron sulfide layers on α-Al2O3 substrates. According to the transmission electron microscopic measurements, these Fe-sulfide films had 1C pyrrhotite structure (Fe1-xS). In the case of pyrrhotite materials, both the magnetic and electric properties depend significantly on their iron content and on the ordering of iron vacancies. By tuning the parameters of the atomic layer deposition method, the structure of epitaxial pyrrhotite films could be controlled, thus the electronic properties of the Fe1-xS films could be influenced: At deposition temperatures below 350 °C, the structure contained many faults, and the layers were n type semiconductors, while at higher temperatures, the resulting films were p-type with excellent crystalline structures with disordered vacancies. A post deposition annealing could further improve the crystallinity and induce p-type conductivity.

Effect of La Spatial Uniformity on Ferroelectric Properties of HfO2 Films Deposited by Atomic Layer Deposition Method

In this study, the effect of supercycle scheme for La‐doping in HfO2 films by atomic layer deposition (ALD) on their ferroelectric properties is investigated along with the variation of La distribution in HfO2 films. La is doped into HfO2 films by two ALD supercycle methods: metal‐oxidant‐dopant‐oxide (MODO) and metal‐dopant‐oxidant (MDO). Secondary ion mass spectrometry analys is shows that the MDO supercycle method results in a uniform distribution of La in the depth direction, while the MODO supercycle method results in depth‐dependent segregation of La in the HfO2 film. For similar La concentrations, HfO2 films doped with La by the MDO supercycle show a higher percentage of orthorhombic phase with higher oxygen vacancy concentrations than films by the MODO supercycle. For 3% La, the HfO2 film by MDO shows a remanent polarization (2Pr) of ≈31 μC cm−2 at ± 4 MV cm−1, which is twice as large as the remanent polarization of 15 μC cm−2 for the HfO2 film by MODO. In addition, the La‐doped HfO2 film by MDO with a larger fraction of orthorhombic phase shows a smaller wake‐up effect than the La‐doped HfO2 film by MODO.

Tuning interfaces between Cu and oxide via atomic layer deposition method for CO2 hydrogenation to methanol

The specific Cu/10c-ZnO/CeO2 catalyst was designed using the atomic layer deposition method and the Cu+–Zn0–Ce4+ structure is the active site for methanol synthesis from CO2 hydrogenation.

Preparation of high-performance large-area perovskite solar cells by atomic layer deposition of metal oxide buffer layer

Perovskite solar cells have been widely recognized as the most promising new-type photovoltaic device due to its power conversion efficiency rapidly increasing from 3.8% to over 26% in merely fifteen years. However, the high performances are achieved mainly on small area cells with an active area lower than 0.1 cm<sup>2</sup>. When enlarging the active area of perovskite solar cells, the efficiency falls dramatically. So, how to reduce the gap between performances of small area cells and large area cells gradually becomes a critical point in the path towards the commercialization of perovskite photovoltaic technology. Herein, a strategy of pre-growing thin layer of TiO<sub>2</sub> on a rough FTO substrate by atomic layer deposition method before spin-coating SnO<sub>2</sub> nanoparticles is proposed. Due to the inherent conformal film growth mode of atomic layer deposition, the FTO substrate can be completely covered by TiO<sub>2</sub>, thus preventing the direct contact between local protrusions of FTO and perovskite layer and impeding the current leakage phenomenon, which can be verified by the measurements from X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy, and further proved by the dark current measurement. By using this method, the repeatability and consistency of the small area cell fabrication technology on the same substrate are improved obviously. The improved electron transport process revealed by photoluminescence results and incident light management process revealed by external quantum efficiency results also brings about better solar cell performances. More importantly, highly efficient 0.5 cm<sup>2</sup> large area perovskite solar cells are fabricated through optimization of TiO<sub>2</sub> thickness. When growing 200 cycles TiO<sub>2</sub> (~9 nm in thickness) by using atomic layer deposition technology, the champion large area perovskite solar cell possesses a power conversion efficiency as high as 24.8% (certified 24.65%). The device performances also show excellent repeatability between different fabrication batches. The perovskite solar cell with TiO<sub>2</sub> buffer layer grown by the atomic layer deposition method can still retain over 95% of its initial efficiency after having been stored in a nitrogen atmosphere for 1500 h. The technique proposed in this paper can be helpful in manufacturing perovskite solar cell modules in the realistic photovoltaic market and can be extended to the large area fabrication of other perovskite optoelectronic devices such as light emitting diode, laser and detector.

High-Performance of InGaZnO TFTs With an Ultrathin 5-nm Al₂O₃ Gate Dielectric Enabled by a Novel Atomic Layer Deposition Method

High-Performance of InGaZnO TFTs With an Ultrathin 5-nm Al₂O₃ Gate Dielectric Enabled by a Novel Atomic Layer Deposition Method

Atomic/molecular layer deposition strategies for enhanced CO2 capture, utilisation and storage materials.

Elevated levels of carbon dioxide (CO2) in the atmosphere and the diminishing reserves of fossil fuels have raised profound concerns regarding the resulting consequences of global climate change and the future supply of energy. Hence, the reduction and transformation of CO2 not only mitigates environmental pollution but also generates value-added chemicals, providing a dual remedy to address both energy and environmental challenges. Despite notable advancements, the low conversion efficiency of CO2 remains a major obstacle, largely attributed to its inert chemical nature. It is imperative to engineer catalysts/materials that exhibit high conversion efficiency, selectivity, and stability for CO2 transformation. With unparalleled precision at the atomic level, atomic layer deposition (ALD) and molecular layer deposition (MLD) methods utilize various strategies, including ultrathin modification, overcoating, interlayer coating, area-selective deposition, template-assisted deposition, and sacrificial-layer-assisted deposition, to synthesize numerous novel metal-based materials with diverse structures. These materials, functioning as active materials, passive materials or modifiers, have contributed to the enhancement of catalytic activity, selectivity, and stability, effectively addressing the challenges linked to CO2 transformation. Herein, this review focuses on ALD and MLD's role in fabricating materials for electro-, photo-, photoelectro-, and thermal catalytic CO2 reduction, CO2 capture and separation, and electrochemical CO2 sensing. Significant emphasis is dedicated to the ALD and MLD designed materials, their crucial role in enhancing performance, and exploring the relationship between their structures and catalytic activities for CO2 transformation. Finally, this comprehensive review presents the summary, challenges and prospects for ALD and MLD-designed materials for CO2 transformation.

(Invited) Fabrication Technique of Ferroelectric HfxZr1−XO2 Thin Films Using ALD-ZrO2 Nucleation Layers

Ferroelectric HfxZr1−xO2 (HZO) thin films have attracted considerable attention towards high-density and low-power ferroelectric memory devices of ferroelectric random access memory (FeRAM) and ferroelectric field-effect transistors (FeFETs) [1]. To obtain ferroelectric orthorhombic (O) phase of HZO films, several techniques have been investigated, such as the TiN stressor layer technique [2] and controlled annealing conditions [3]. On the other hand, we pay attention to the ZrO2 nucleation layer technique because ZrO2 films deposited by atomic layer deposition (ALD) method formed a nanocrystalline structure and consisted dominantly of O, tetragonal (T), and cubic (C) phases, whose lattice constants are considerably close to that of ferroelectric O phase for HfO2 [4]. In this paper, we report the crystallinity and ferroelectricity of HZO films fabricated using the ZrO2 nucleation layer technique for metal-ferroelectric-metal (MFM) and metal-ferroelectric-semiconductor (MFS) capacitors.First, four types of MFM capacitors of TiN/HZO/TiN (MFM w/o), TiN/HZO/bottom-ZrO2/TiN (MFM B-ZrO2), TiN/top-ZrO2/HZO/TiN (MFM T-ZrO2), and TiN/top-ZrO2/HZO/bottom-ZrO2/TiN (MFM D-ZrO2) were systematically investigated for the FeRAM applications [5]. The thicknesses of the ALD-grown HZO and ZrO2 films were 10 and 2 nm, respectively. The post-deposition annealing was performed at 600°C. The remanent polarization (2P r = P r + − P r −) of the MFM capacitors increased in the following order: MFM w/o (12 µC/cm2) < MFM B-ZrO2 (15 µC/cm2) < MFM T-ZrO2 (23 µC/cm2) < MFM D-ZrO2 (29 µC/cm2), while all capacitors showed almost the same coercive electric field (E c) value of around 1.2 MV/cm. Therefore, maximum 2P rvalue of the MFM capacitor was obtained using the top- and bottom-ZrO2 nucleation layers. For the MFM capacitors with ZrO2 nucleation layers, epitaxial-like grain growth of the HZO film occurred on the nanocrystalline top- and bottom-ZrO2 layers. Moreover, the relative ratio of O/T/C phases in the ferroelectric film, which was estimated using the peak area ratio of O(111)/T(101)/C(111)/{M(−111)+ O(111)/T(101)/C(111)+M(111)}, increased in the following order: MFM w/o < MFM B-ZrO2 < MFM T-ZrO2 < MFM D-ZrO2. Therefore, the top- and bottom-ZrO2 layers play an important role as nucleation layers for the crystallization of the HZO film, resulting in a larger relative ratio of O/T/C phases in the ferroelectric film compared to w/o. Moreover, these results indicate that the top-ZrO2 layer was more effective to form the ferroelectric phase compared to the bottom-ZrO2 layer.Next, two types of MFS capacitors of TiN/HZO/Si (MFS w/o) and TiN/top-ZrO2/HZO/Si (MFS T-ZrO2) were fabricated by low-temperature processes at 300°C of ALD and post-metallization annealing (PMA) for the FeFET applications [6]. The thicknesses of both HZO and ZrO2 films were 10 nm. Both MFS w/o and MFS T-ZrO2 were found to form an extremely thin SiO2 interfacial layer with a thickness of one or two monolayers between the HZO film and Si substrate due to a low temperature fabrication process of 300°C. The HZO film of the MFS T-ZrO2 formed O/T/C phases even with a low thermal budget of 300°C, while that of the MFS w/o had an amorphous structure. This result is attributed to the beneficial role of the nanocrystalline top-ZrO2 nucleation layer for the crystallization of an amorphous HZO film during the PMA process. Therefore, a higher 2P r value of 15 µC/cm2 was obtained for the MFS T-ZrO2 than that (2.2 µC/cm2) for the MFS w/o. Moreover, the endurance properties of the MFS T-ZrO2 were free from the wake-up effect and exhibited less degradation of switching polarization (P sw). This could be attributed to the insertion of a ZrO2 film at the TiN/HZO interface, which promoted the preferential formation of the ferroelectric orthorhombic phase and prevent the formation of oxygen vacancies at the ZrO2/HZO interface. Thus, we concluded that superior ferroelectricity with wake-up free properties and higher fatigue resistance of HZO-based MFS capacitors were achieved by using the ZrO2 nucleation layer technique.These results suggest that the fabrication technique of ferroelectric HZO films using nanocrystalline ALD-ZrO2 nucleation layers is one of the promising processes for the next-generation non-volatile memory device applications.This work was supported by JSPS KAKENHI (Nos. JP21J01667, JP20H02189, and JP18J22998) and MEXT Leading Initiative for Excellent Young Researchers (No. JPMXS0320220213).[1] T. Mikolajick et al., J. Appl. Phys. 129, 100901 (2021).[2] S. J. Kim, et al., Appl. Phys. Lett. 111, 242901 (2017).[3] S. Migita et al., Jpn. J. Appl. Phys. 58, SBBA07 (2019).[4] T. Onaya et. al., Appl. Phys. Express. 10, 081501 (2017).[5] T. Onaya et al., APL Mater. 7, 061107 (2019).[6] T. Onaya et al., APL Mater. 10, 051110 (2022).

(Invited) Nucleation, Growth and Location Regulation of Heterogeneous Catalysts Synthesized by Atomic Layer Deposition

For supported catalysts, the particle surface or metal-support interface and its vicinity are the main areas providing active sites. In this regard, surface and interface engineering of heterogeneous catalysts is effective and critical for optimizing their catalytic performances. During the formation of active components, the structural uniformity, stability and location of nucleation sites determine the structural and scale uniformity, stability and environmental consistency of active sites, and ultimately determine their catalytic performance. Therefore, the regulation of nucleation, growth and location of active components is the key to precisely regulate the surface and interface structure and properties of supported catalysts. However, traditional preparation methods (such as impregnation method and precipitation method) have limitations in precise regulation of particle size, location and microstructure of catalysts due to the surface heterogeneity of supports and the high surface energy of nanoparticles, which makes it difficult to reliably reveal the structure-activity relationship of the catalyst. Therefore, the development of advanced fabrication methods is of vital significance to realize the nucleation, growth and location regulation of heterogeneous catalysts at atomic level precision. Atomic layer deposition (ALD) is a powerful scientific tool for catalytic research due to its self-limiting, atom-by-atom growth features. However, there is still a lack of rational knowledge of the nucleation and growth mechanism of catalytic particles prepared by ALD, the microscopic mechanism of interface structure modification, and the catalytic reaction mechanism. This is the topic of this lecture, in which we discuss the latest progress made in our group in precisely regulating the microstructure, size and location of ALD-deposited active components by several effective methods including nucleation site engineering, deposition kinetics engineering and template-assisted ALD method, as well as elucidating the nucleation and growth mechanism of ALD-deposited active components by in-situ and operando XAFS characterization based on our designed and built ALD-XAFS device. Through the above works, the nucleation and growth mechanisms of the deposited species and modification species, the microscopic mechanism of interface structure modification, and the influence of the size effect, the interface effect, and the distance effect on the catalytic performance were clarified. The structure-activity relationship was understood at the atomic/molecular level. These works will provide new ideas and scientific basis for the catalyst design and the performance regulation.

Surface Functionalization of TiO2 Nanotubes Modified with a Thin Film of BiFeO3

The atomic layer deposition method allows for the production of a thin film with a high aspect ratio on the uneven surface of titanium dioxide nanotubes TiO2(Nt). A modified BiFeO3/TiO2(Nt)/Ti (BFOT) structure with controllable electrical characteristics was obtained. BFOT possesses both ferroelectric and semiconductor properties with nonlinear conductivity dependent on the magnitude and duration of the voltage supply. Analysis of the temperature dependence of charge variation showed leakage currents in the BFOT structure due to the capture and release of charge carriers from defect levels. Surface modification of nanotubes with the multiferroic BiFeO3 allows for the creation of semiconductors with adaptive functional properties.