Field Of Microelectronics Research Articles

PHYSICO-MECHANICAL PROPERTIES OF METALLIC PARTS ELECTROCHEMICALLY PRINTED USING COPPER NITRATE ELECTROLYTE

The process of electrochemical 3D printing of copper parts using a concentrated copper nitrate electrolyte has been investigated. It was established that in a nitrate copper plating electrolyte with a copper nitrate concentration of 500 g/l, it is possible to obtain locally electrodeposited metal parts with a compact fine-crystalline structure and an average profile height of 150 μm. The working current densities of electrochemical printing in this case were 2.45…2.7 A/dm2. It has been shown that reducing the speed of movement of the working electrode (anode) leads to an improvement in the uniformity of metal deposition along the entire trajectory of movement and the reduction of the crystals size of the metal deposit. This is obviously a consequence of a change in the current mode of electrodeposition. It was established that on the surface with initial parameters of microroughness (Rz(1)=1.128 Ra(1)=0.2925) during electrochemical 3D printing, a metal structure with roughness parameters – Rz(1)=95.72 Ra(1)=16.32 has been formed. The formation of a compact but at the same time a highly rough metal structure makes the application of the electrochemical 3D printing method promising in the production technology of printed circuit boards and in the field of microelectronics as a whole. The micromechanical tests of samples of electrochemically printed copper deposits showed the following. The microhardness of the electrochemically printed copper deposit is approximately 30% higher, but the plasticity coefficient and Young’s modulus acquire values close to the corresponding parameters of hydrometallurgical copper. This indicates that the method of obtaining metal objects by electrochemical 3D printing does not contribute to a significant deterioration of the elasticity of the obtained material.

Fabricating 3D Si nanostructure via a novel Ga+ implantation enabled maskless dry etching process

Three-dimensional (3D) nanostructure is the key to the miniaturization of nonlinear photonic and electronic devices. Because of the great demand on the ultra-small nanostructures, the novel nanofabrication technologies with flexible 3D silicon (Si) fabrication capability are of great importance. Herein, by combining Ga+ FIB implantation and ICP dry etching processes, we proposed a novel Ga+ FIB implantation assisted maskless dry etching technology for direct fabrication of 3D Si nanostructures. We found that the implanted Ga+ induced amorphization layer in Si substrate acts as the ‘quasi-mask’ during the ICP dry etching process. The increase of Ga+ concentration in amorphization layer of Si substrate improves the etching resistance of the area. Moreover, enabled by high resolution and flexibility of FIB, the proposed technology is capable of directly fabricating various 3D Si nanostructures in a simple way, such as 3D nanoscale artificial bowtie arrays with sub-10 nm gaps, multi-scale 3D Si nanostructures with arbitrary patterns. More importantly, the proposed technology is compatible to current semiconductor manufacturing process. Benefiting by the advantages of simplicity and high efficiency, the proposed maskless dry etching process promises great application potential in the fields of nonlinear photonics and micro-electronics.

Inkjet assisted manufacturing of untethered magnetic devices: A comparison between three routes to pattern artificial water striders

AbstractUntethered devices controlled by an external magnetic field are becoming more and more widely used in a wealth of applicative fields: medicine, precise micromanipulation, and environment management. Their production strongly relies on the use of complex and time-consuming technologies typically borrowed from the microelectronic field. In an attempt to reduce costs and enhance manufacturing flexibility, additive manufacturing has been investigated as a relevant alternative for untethered microrobots production. Between the large number of additive manufacturing technologies, inkjet printing is relatively poorly investigated for the production of this kind of devices, and the present work aims at exploring its potential. The work establishes a comparison between different approaches for the inkjet manufacturing of magnetically guidable microdevices. In particular, it focuses on the manufacturing of fully inkjet-printed magnetic devices by proposing two methods of production. The first consists in the electroless metallization of non-magnetic devices printed with SU-8 resin, while the second is based on the inkjet printing of a dispersion of magnetic nanoparticles in SU-8 resin. As a result, inkjet-printed devices controllable by an external magnetic field can be obtained. Multi-step and one-step production methods are compared in terms of quality of the obtained elements, easiness of production, and mechanical properties. The morphology of the finished devices, their surface quality, and their magnetic actuability are analyzed and discussed.

Introducing phosphoric acid to fluorinated polyimide towards high performance laser induced graphene electrodes for high energy micro-supercapacitors

Micro-supercapacitors (MSCs) have wide application prospects in microelectronic fields such as wearable electronics due to merits of stable performance, high safety and easy integration. However, the relatively low energy density of MSCs limits their practical application. In this context, phosphorus and fluorine co-doped laser-induced graphene (FP-LIG) microelectrodes were fabricated from fluorinated polyimide containing phosphoric acid by laser direct writing (LDW) method. The introduced phosphoric acid slows down the decomposition of –CF3 during the LDW process, resulting in much more ordered and stable pores; meanwhile, phosphorus entered the graphene lattice to replace some carbon atoms, forming a C3PO structure, which not only stabilizes the interface between the electrode and the electrolyte and therefore achieves an enlarged working potential of 1.4 V, but also increases the wettability of the electrode. Using FP-3-LIG microelectrodes and PVA/H2SO4 as the gel electrolyte, the assembled FP-3-MSC demonstrates significantly enhanced energy density, delivering an energy density of 10.40 μWh cm−2 (@0.09 mA cm−2), 2.7 times that of F-MSC and 346.7 times that of MSC. FP-3-MSC has excellent cyclic stability, displaying an areal capacitance retention rate of above 90 % after 10,000 long cycles. In addition, FP-3-MSC demonstrates excellent flexibility, indicating promising potential in the field of flexible wearable electronics.

Surface Charge Regulation of Graphene by Fluorine and Chlorine Co-Doping for Constructing Ultra-Stable and Large Energy Density Micro-Supercapacitors.

Settling the structure stacking of graphene (G) nanosheets to maintain the high dispersity has been an intense issue to facilitate their practical application in the microelectronics-related devices. Herein, the co-doping of the highest electronegative fluorine (F) and large atomic radius chlorine (Cl) into G via a one-step electrochemical exfoliation protocol isengineered to actualize the ultralong cycling stability for flexible micro-supercapacitors (MSCs). Density functional theoretical calculations unveiled that the F into G can form the "ionic" C─F bond to increase the repulsive force between nanosheets, and the introduction of Cl can enlarge the layer spacing of G as well as increase active sites by accumulating the charge on pore defects. The co-doping of F and Cl generates the strong synergy to achieve high reversible capacitance and sturdy structure stability for G. The as-constructed aqueous gel-based MSC exhibited the superb cycling stability for 500,000 cycles with no capacitance loss and structure stacking. Furthermore, the ionic liquid gel-based MSC demonstrated a high energy density of 113.9mWhcm-3 under high voltage of up to 3.5V. The current work enlightens deep insights into the design and scalable preparation of high-performance co-doped G electrode candidate in the field of flexible microelectronics.

Optimization of GeSn nanostructures via tuning of femtosecond laser parameters

Semiconductor nanostructures are known to exhibit interesting electrical and optical properties, as well as functionalities that are significantly different from their bulk counterparts. These unique characteristics can be attributed to their quantum confinement effects, and large surface-to-volume ratios, along with the fact that their compositions can be tuned. This study proposes a new method for tuning the properties of GeSn nanostructures on a silicon substrate using femtosecond laser direct writing. A series of GeSn nanostructures with different compositions of Sn ranging from nanodots, nanoholes, nanostrips, nanogaps, and nano-cauliflowers were successfully prepared via tuning of femtosecond laser parameters. The morphology, composition of Sn, and crystalline properties of the formed nanostructures were also greatly influenced by the laser fluence and the effective pulse number. The femtosecond laser/GeSn interaction mechanism was thoroughly investigated based on the two-temperature Drude model. This work provides a novel strategy for tuning the bandgap and morphology of GeSn nanostructures, through which the properties of GeSn-based devices can be tailored according to the requirements of practical applications in the fields of microelectronics and photonics.

Preparation and Properties of Fluorinated Poly(aryl ether)s with Ultralow Water Absorption and Dielectric Constant by Cross-Linked Network Strategy.

Poly(aryl ether) materials are used in a wide range of applications in the communications and microelectronics fields for their outstanding mechanical and dielectric properties. In order to further improve the comprehensive performance, this work reports a series of cross-linkable poly(aryl ether)s (UCL-PAEn) containing trifluoroisopropyl and perfluorobiphenyl structures using 2,2-bis(4-hydroxyphenyl)hexafluoropropane, 2,2'-diallyl bisphenol A, and perfluorobiphenyl as starting materials. Their chemical structures and the effect of changes in the allyl content on the properties are thoroughly investigated. Owing to the introduction of fluorine atoms and cross-linked networks, the cross-linked poly(aryl ether) films present low dielectric constants (Dk = 1.93-2.24 at 1 MHz), low water absorption (0.14% -0.25%), and hydrophobic film surfaces (94.3-99.4°). Additionally, because of the presence of cross-linked networks, the CL-PAEn films exhibit superior thermal stability, with the 5% weight loss temperatures all above 445 °C and the maximum thermal decomposition rate temperatures all above 550 °C. The cross-linked films also demonstrate excellent mechanical properties, with tensile strength in the range of 57.1 -146.7 MPa and tensile modulus in the range of 1.8 GPa-4.5 GPa.

Exploring the Development of Photoresists in Lacquer under the Background of Global Carbon Neutrality: A Mini Review

With the establishment of a global carbon-neutral target, green and sustainable design concepts, materials, and processes have become the key to scientific and technological innovation, which highlights the development and utilization of environmentally-friendly materials and renewable energy sources. At present, almost all the raw materials in commercial photoresist are from oil resources. In order to implement the policy of “green chemistry”, there is an urgent need to take the place of petroleum with renewable, biodegradable, and green biomass resources in photoresist production. As a kind of green and natural high polymer material from China, lacquer has excellent physical and chemical properties and has great application potential in the field of electronics. In this paper, the potential connections between photoresist and lacquer, especially in the green development of photoresist, are sorted out. The introduction of lacquer and its derivatives may help to improve the environmentally-friendly production of photoresist and its performance. Therefore, in the context of global carbon neutrality, the study of photoresists in the “lacquer” is of great significance in promoting the application of eco-friendly materials in the field of microelectronics.

Novel deuterated cyclopentadienyl zirconium/hafnium precursors for atomic layer deposition of high-performance ZrO2/HfO2 thin films

The need to improve the electrical properties of ZrO2 and HfO2 thin films deposited by atomic layer deposition (ALD), which is widely used in the field of microelectronics, is growing. Attempts to improve precursor stability unavoidably lead to reduced reactivity and diminished utility. Therefore, we synthesized and developed two new ALD precursors by introducing deuterium, which simultaneously exhibit enhanced thermal stability and enhanced reactivity as a result of the introduction of deuterium. For the substitution of deuterium for hydrogen in the precursors responsible for the enhanced thermal stability, we experimentally and theoretically demonstrated that thermal stability and reactivity can be simultaneously enhanced by reducing the bonding dissociation energy of ligands that have not undergone deuterium substitution. This observation led to the development of ZrO2 and HfO2 ALD processes that result in no impurities within the thin films and minimal substrate damage even at a very high deposition temperature of 400 °C. In particular, the improvement in crystallinity through ultra-high-temperature ALD deposition resulted in excellent electrical properties in a metal–insulator–metal capacitor in which the film was incorporated; the capacitor demonstrated a dielectric constant of 37.9 and leakage current of 3.52 × 10−9 A cm−2, without the need for a subsequent annealing process.

Influence of synergistic effect on the structure and dielectric property of La2(TiZrSnHfGe)2O7 high entropy oxides

In this study, La2(TiZrSnHfGe)2O7 high entropy oxides were firstly prepared by solid state reaction method. The effects of different sintering temperatures on the structure, morphology and dielectric properties were studied. When the pre-calcination temperature is 1300 °C, the powder exhibits a single pyrochlore phase instead of defective fluorite phase. The existence of high entropy affects the changes in the crystal structure of A2B2O7 type oxides, resulting in lattice distortion. The dielectric results showed that the ceramics have certain frequency dispersion, and the dielectric properties are affected by temperature and frequency. Due to the high entropy effect, the La2(TiZrSnHfGe)2O7 ceramic exhibits good dielectric stability at both high and low frequencies. The formation of defect dipole clusters in the system results in the increase of dielectric constant. It is feasible to change the dielectric properties of ceramics by designing high entropy oxides, which showed the potential value in microelectronics field.

Energy-Dispersive X-Ray Microanalysis – as a Method for Study the Aluminium-Polysilicon Interface after Exposure with Long-Term and Rapid Thermal Annealing

Energy dispersive X-ray microanalysis is one of the main methods for determining the elemental composition of matter. Possessing high locality and a relatively shallow penetration depth of the electron beam (< 1 μm), this method has found wide application in the field of microelectronics, as the main method for analyzing the elemental composition of matter. The method allows to study the surface of a substance both pointwise and over an area with the construction of element distribution maps. In the paper we investigated the influence of long-term and rapid heat treatments on the formation of the aluminum-polysilicon interface in order to study the formation of ohmic contacts in the element base of integrated circuits. The aluminumpolysilicon interface was studied using energy-dispersive X-ray microanalysis. It has been established that during long-term thermal annealing (450 °C, 20 min) polysilicon is completely dissolved in aluminum followed by its segregation in the form of separate agglomerates in the aluminum film, which can lead to a complete failure of the integrated circuit. During rapid thermal annealing (450 °C, 7 s) such a phenomenon was not detected. Thus it is advisable to use rapid thermal annealing as an alternative to traditional long-term thermal annealing in microelectronics. This makes it possible to significantly reduce the dissolution of polysilicon in aluminum, avoid the destruction of ohmic contacts and increase the percentage of yield of workable 0products in the process of integrated circuits' manufacturing.

Diamond/cubic boron nitride (111) heterojunction interface: Rational regulation of high two-dimonsional electron gas

Wide-bandgap diamond exhibits excellent physical and chemical properties, making it an ideal substrate material for developing high-temperature and high-power semiconductor devices and broadening its application prospects in the field of microelectronics and optoelectronic devices. However, because of the Fermi pinning effect, it is difficult to achieve n-type diamond with excellent transport properties. Cubic boron nitride (cBN) has similar structural properties and a smaller lattice mismatch with diamond. Thus, making the two-dimensional electron gas of the diamond/cBN heterojunction provides a new idea to solve the problem of diamond n-incorporation difficulty and small bandgap regulation range. The diamond/cBN heterojunction is applied to study the law of influence factors on the heterojunction band structure, band alignment, and polarization strength. Further, a regulation mechanism for two-dimensional electron gas density is established at heterojunction interfaces, which can help solve the core difficulties of diamond n-type doping, small bandgap regulation range, and high impedance, providing a theoretical basis for realizing diamond power devices with high power density and low power consumption.

Reaction synergy of bimetallic catalysts on ZSM-5 support in tailoring plastic pyrolysis for hydrogen and value-added product production

Hydrogen, viz. a green energy carrier, is poised to considerably contribute to the empowerment of a sustainable society. By valorizing plastics, catalytic pyrolysis was envisaged as a promising route to produce green hydrogen and value-added product here. Firstly, the screening of optimal catalyst support (from activated carbon and four zeolites: M-zeolite, B-zeolite, Y-zeolite, ZSM-5) was executed by studying catalytic polypropylene (PP) pyrolysis over supported Ni catalysts. In view of the highest H2 yield (19.2 mmol/gPP) of Ni/ZSM-5, ZSM-5 was put forth as the optimal catalyst support. Then, the identification of optimal active metal (from Ni, Fe, Co, FeNi, FeCo, and NiCo) was performed by running the catalytic PP pyrolysis over ZSM-5 supported catalysts. For catalytic PP pyrolysis, NiCo/ZSM-5 was the optimal catalyst with the highest H2 yield (28.7 mmol/gPP), while the resulting pyrolysis oil demonstrated potential for use as jet fuel. From catalytic pyrolysis of various plastics over NiCo/ZSM-5, polystyrene gave the highest H2 composition (83.2 vol%) of pyrolysis gas and high composition (52.8 area%) of benzocyclobutene (useful chemicals for semiconductor and microelectronics fields) in pyrolysis oil. Lastly, the catalytic mechanism was discussed based on the results, revealing NiCo's remarkable enhancement in H2 yield to 28.7 mmol/g, which surpassed the individual yields of Ni (19.2 mmol/g) and Co (10.2 mmol/g), thereby underscoring the synergistic effect of NiCo. This study supports the recycling of plastics waste into hydrogen energy and valuable products, contributing to environmental pollution mitigation.

Near‐Infrared Thermometer Based on Stark Energy Levels of Yb3+ in Garnet

A Yb3+‐doped Gd3Al2Ga3O12 garnet (GAGG) Boltzmann thermometer is prepared and studied in this work. Due to the Boltzmann distribution of the population of Stark sublevels of Yb3+, the photoluminescence peaks of Yb3+ in the wavelength range of 950–1000 and 1000–1050 nm exhibit opposite temperature dependencies, which makes the luminescence intensity ratio (LIR) of two Yb3+ peaks work as a luminescence thermometer with a relative sensitivity of 1.6% K−1 at 200 K. It is worth nothing that this LIR value still follows the Arrhenius model at temperatures as low as 200 K. In these results, it is suggested that Yb3+‐doped GAGG thermometer can achieve high sensitivity for accurate temperature measurements. In addition, the accurate position of various Stark sublevels of Yb3+ in GAGG is obtained for the first time. In this work, it is confirmed that the Yb3+‐doped GAGG thermometer exhibits potential applications in the fields of microelectronics and biology.

Crystal Structure and Spectroscopic Characterization of a New Hybrid Compound, (C12H17N2)2[CdBr4], for Energy Storage Applications.

Organic-inorganic hybrid materials have recently found a vast variety of applications in the fields of energy storage and microelectronics due to their outstanding electric and dielectric characteristics, including high dielectric constant, low conductivity, and low dielectric loss. However, despite the promising properties of these materials, there remains a need to explore novel compounds with improved performance for practical applications. In this research paper, the focus is on addressing this scientific challenge by synthesizing and characterizing the new-centrosymmetric (C12H17N2)2[CdBr4] crystal. This compound offers potential advancements in energy storage technologies and microelectronics due to its unique structural and electronic properties. The chemical mentioned above crystallizes in the monoclinic system, and its protonated amine (C12H17N2)+ and isolated anion [CdBr4]2- are bound by C-H···π and N-H···Br hydrogen bonds to form its zero-dimensional structure. Through optical absorption analysis, the semiconductor nature of the material is verified, showcasing a band gap of around 2.9 eV. Furthermore, an in-depth examination of Nyquist plots reveals the material's electrical characteristics' sensitivity to frequency and temperature variations. By applying Jonscher's power law to analyze ac conductivity plots, it is observed that the variation in the exponent "s" accurately characterizes the conduction mechanism, aligning with CBH models. The compound exhibits low dielectric loss values and a high permittivity value (ε ∼ 105), making it a promising candidate for energy storage applications. By managing the scientific challenge of improving material performance for energy storage and microelectronics, this research contributes to advancing the field and opens avenues for further exploration and application of organic-inorganic hybrid materials.

Recent advancements in carbon-based materials for resistive switching applications

In the dynamic field of microelectronics, there is a notable trend towards leveraging carbon materials, favored for their ease of synthesis, biocompatibility, and abundance. This trend is particularly evident in the development of memristor devices, which benefit from the unique electronic properties of carbon, leading to enhanced device performance. The appeal of carbon materials lies in their ability to offer distinctive resistive switching (RS) mechanisms, sparking significant interest among researchers. This article aims to provide an insightful overview of the advancements in carbon-based memristive devices, focusing on the resistive switching mechanisms enabled by carbon materials. It delves into the various classes of carbon-based memristor devices, ranging from zero-dimensional (0D) to three-dimensional (3D) structures, each with its unique advantages and applications. Additionally, the discussion extends to innovative next-generation memristive devices, including those designed for health monitoring and skin-adhesive, self-powered applications. Moreover, the article touches upon the synthesis techniques and functionalization strategies that are crucial for optimizing the performance of carbon-based memristors. It also outlines the future opportunities in this rapidly advancing field, highlighting the potential for further research and development towards energy-efficient, compact, and bio-integrated memristive systems.

Simple Isopropanol-Assisted Direct Soft Imprint Lithography for Residue-Free Microstructure Patterning.

A direct soft imprint lithography was proposed to realize the direct fabrication of residue-free, well-shaped functional patterns through a single step. This imprint method requires only a simply prepared isopropanol-treated polydimethylsiloxane (PDMS) stamp without any additional resists. Residue-free Ag patterns were successfully fabricated on different substrates by directly imprinting the Ag ink with the isopropanol-treated PDMS stamp. Furthermore, the coffee-ring effect of the imprinting Ag patterns can be eliminated by optimizing the imprinting time, isopropanol-treating time, and imprinting temperatures. Studies show that the residual Ag ink in the contact region can be absorbed by the isopropanol-treated PDMS stamp due to the "like dissolves like" principle. Finally, this method was employed to fabricate the Ag electrodes for the thin-film transistors, attaining a mobility of ∼8 cm2 V-1 s-1, which is comparable to those with vacuum-processed electrodes. This process provides a simple, low-cost, residue-free, coffee-ring-free, and fast patterning method in the field of microelectronics.

The conductivity effect of the top coating on optical properties of thin Cu(Ag)-layered structures

This study examines the optical properties of thin Cu (Ag)-layered structures covered with protective layers based on graphene, titanium (TiO2), or aluminium (Al2O3) oxides. The objective is to investigate the impact of these coatings on the optical behaviors of underlying metallic layers, specifically in the spectral range of excitation of surface plasmon resonances. Combining the methods of spectroreflectometry and spectro-ellipsometry was used to analyze the optical characteristics of the hybrid metal-oxide-graphene films. The study shows that graphene, due to its exceptional electrical conductivity and unique optoelectronic properties, significantly modifies the optical behavior of investigated structures. It includes notable changes in refractive and absorption indices, and optical conductivity indicating potential for enhancing light-matter interactions in plasmonic-graphene layered structures with the aim to apply as biosensor. It is important that addition of TiO2 and Al2O3 layers has also strong effects on the optical properties, which are relevant to their respective applications in the fields of optoelectronics and microelectronics. Employing the effective medium approximation and the Tauc–Lorentz model promotes deeper understanding the interplay between interband and intraband electronic transitions at the nanoscale level. It was revealed that the layer thickness of constituted materials and their individual dielectric functions together with addition of a graphene monolayer commit the significance for altering the optical properties of hybrid layered structures. The obtained results are important for the fields of plasmonics and nanotechnology, providing insights for designing sensors and devices with improved optical characteristics.

Effect of Sn nanoparticles on the optical properties of PEDOT:PSS thin films

Introduction: In this study, we focus on enhancing the optical properties of PEDOT:PSS thin films by incorporating pure Sn nanoparticles (NPs) synthesized using the ultrasonic ablation technique. The objective is to investigate the impact of Sn concentration on the optical characteristics of the films, with a specific emphasis on applications in organic solar cells.Methods: We systematically varied the concentrations of Sn in PEDOT:PSS thin films and characterized their optical properties. The index of refraction (n) and extinction coefficient (k) were precisely determined by analyzing the transmission and reflection spectra of the films. Additionally, Sellmeier’s dispersal model was employed to elucidate the obtained results of n, and dispersive factors were calculated and interpreted.Results: The incorporation of Sn nanoparticles led to improvements in the energy bandgap (Eg) values of PEDOT:PSS films. Notably, as the concentration of Sn increased, the n values decreased, indicating enhanced suitability for organic solar cell applications. The study also unveiled a decrease in the dielectric constant of PEDOT:PSS/Sn films with increasing Sn content, resulting in improved transmittance velocity and enhanced efficacy of microelectronic devices. This, in turn, promotes the development of large-frequency and large-velocity stretchy circuit boards.Discussion: The comprehensive assessment of optical and dielectric parameters, including complex dielectric constant, complex optical conductance, and nonlinear optical constants, provides valuable insights into the potential applications of PEDOT:PSS/Sn films. The larger nonlinear optical constants observed in the present films suggest their suitability for diverse applications such as all-optical switching, limiting, phase modulation, and frequency conversion. Overall, our findings highlight the promising potential of Sn-incorporated PEDOT:PSS thin films in advancing the field of optoelectronics and microelectronics.

Precursor design and cascade mechanism of RuO2·xH2O atomic layer deposition

As the unique nanofabrication technique, atomic layer deposition (ALD) can be used to deposit high-quality, uniform, and conformal nanoparticle coatings. Ru and its oxides (RuOx) are important materials in the fields of microelectronics and catalysis. In this work, the reaction of Ru precursors with different ligands on the hydroxylated surfaces were explored. The elimination of the pyrrolyl (Py) ligand is easier than that of the cyclopentadienyl (Py) ligand on the hydroxylated surface. The reaction involved in RuO2·xH2O ALD using RuPy2 and H2O as precursors was further investigated. During the RuPy2 reaction, the pyrrolyl ligand is eliminated by the substitution reaction with a surface hydroxyl group. However, the desorption of the pyrrole molecule is difficult due to the strong adsorption between the pyrrole molecule and Ru surface. During the H2O reaction, the H2O molecules further help the elimination of pyrrolyl ligands from the surface and the dissociative desorption of pyrrole molecules This unique reaction mechanism involved in the ALD of RuO2 with the assistance of H2O can be termed new cascade mechanism. These findings provide theoretical guidance for precursor design and ALD growth of metal oxides.