SiO2 Surface Research Articles

Construction of hollow mesoporous zirconia nanospheres with controllable particle size: Synthesis, characterization and adsorption performance

Organic dyes are difficult to remove effectively in water because of their stable physical and chemical properties. In this study, hollow mesoporous zirconia nanospheres with controllable particle sizes were successfully prepared by in-situ deposition of Zr(OH)4 on the surface of SiO2. The adsorption performance for malachite green (MG) and methylene blue (MB) were tasted. The adsorption removal rates for MG and MB could reach as high as 99 % and 98 %, respectively. The adsorption process could be explained by pseudo-second-order kinetic model and Langmuir isotherm model, and the maximum adsorption capacities for MG and MB were calculated by Langmuir model as 1354.24 and 24.63 mg/g, respectively. Thermodynamic study indicated that the adsorption process of MG and MB were spontaneous endothermic and spontaneous exothermic, respectively. The adsorption mechanism of hollow zirconia nanospheres for MG and MB mainly includes electrostatic interaction, hydrogen bonding and π-π interaction. The results of co-existence ions study demonstrated that the presence of Mg2+ and Ca2+ obviously reduced the removal rates of MB. Desorption-regeneration study showed that the adsorbents can be used for multiple cycles.

Scrutinizing pre- and post-device fabrication properties of atomic layer deposition WS2 thin films

In this work, we investigate the physical and electrical properties of WS2 thin films grown by a plasma-enhanced atomic layer deposition process, both before and after device fabrication. The WS2 films were deposited on thermally oxidized silicon substrates using the W(NMe2)2(NtBu)2 precursor and a H2S plasma at 450 °C. The WS2 films were approximately 8 nm thick, measured from high-resolution cross-sectional transmission electron imaging, and generally exhibited the desired horizontal basal-plane orientation of the WS2 layers to the SiO2 surface. Hall analysis revealed a p-type behavior with a carrier concentration of 1.31 × 1017 cm−3. Temperature-dependent electrical analysis of circular transfer length method test structures, with Ni/Au contacts, yielded the activation energy (Ea) of both the specific contact resistivity and the WS2 resistivity as 100 and 91 meV, respectively. The similarity of these two values indicates that the characteristics of both are dominated by the temperature dependence of the WS2 hole concentration. Change in the material, such as in sheet resistance, due to device fabrication is attributed to the chemicals and thermal treatments associated with resist spinning and baking, ambient and UV exposure, metal deposition, and metal lift off for contact pad formation.

Development of a pH-independent Post-CMP Cleaning Solution using Phosphoric Acid-based Surfactants for Removal of Ceria Nanoparticles

The global interest and demand for the advancement of semiconductor technology, including 3 nm generation semiconductors and gate-all-around semiconductors, continues to rise. This study presents an improvement plan aimed at enhancing performance and yield in the semiconductor manufacturing process, with particular emphasis on the post-CMP cleaning of SiO2 surface. The removal of residual ceria abrasives from SiO2 surfaces after the SiO2-chemical and mechanical planarization (SiO2-CMP) process is a sincere concern in the post-CMP cleaning process because the strong interaction between ceria nanoparticles and SiO2 makes their removal challenging. Herein, we propose a cleaning solution containing a phosphoric acid-based surfactant to address this issue. Three phosphoric-acid-based surfactants with varying numbers of phosphoric acid groups were evaluated, and etidronic acid (EA) with two phosphoric acid groups was found to be the most suitable surfactant. The EA demonstrated a reasonably negative zeta potential of the ceria nanoparticles, a key factor for efficient cleaning, despite variations in solution pH, pH adjuster cations, and surfactant and oxidizing agent (hydrogen peroxide) concentrations. Furthermore, the efficiency of the cleaning solution containing EA was evaluated, and the results confirmed the potential of EA as a promising surfactant for use in the post-CMP cleaning process.

Area-Selective Atomic Layer Deposition of ZnO on Si\SiO2 Modified with Tris(dimethylamino)methylsilane.

Delayed atomic layer deposition (ALD) of ZnO, i.e., area selective (AS)-ALD, was successfully achieved on silicon wafers (Si\SiO2) terminated with tris(dimethylamino)methylsilane (TDMAMS). This resist molecule was deposited in a home-built, near-atmospheric pressure, flow-through, gas-phase reactor. TDMAMS had previously been shown to react with Si\SiO2 in a single cycle/reaction and to drastically reduce the number of silanols that remain at the surface. ZnO was deposited in a commercial ALD system using dimethylzinc (DMZ) as the zinc precursor and H2O as the coreactant. Deposition of TDMAMS was confirmed by spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS), and wetting. ALD of ZnO, including its selectivity on TDMAMS-terminated Si\SiO2 (Si\SiO2\TDMAMS), was confirmed by in situ multi-wavelength ellipsometry, ex situ SE, XPS, and/or high-sensitivity/low-energy ion scattering (HS-LEIS). The thermal stability of the TDMAMS resist layer, which is an important parameter for AS-ALD, was investigated by heating Si\SiO2\TDMAMS in air and nitrogen at 330 °C. ALD of ZnO takes place more readily on Si\SiO2\TDMAMS heated in the air than in N2, suggesting greater damage to the surface heated in the air. To better understand the in situ ALD of ZnO on Si\SiO2\TDMAMS and modified (thermally stressed) forms of it, the ellipsometry results were plotted as the normalized growth per cycle. Even one short pulse of TDMAMS effectively passivates Si\SiO2. TDMAMS can be a useful, small-molecule inhibitor of ALD of ZnO on Si\SiO2 surfaces.

Low temperature Cu/SiO2 hybrid bonding via 〈1 1 1〉-oriented nanotwinned Cu with Ar plasma surface modification

Argon (Ar) plasma surface modification and highly (111)-oriented nanotwinned copper (nt-Cu) were combined to lower the bonding temperature of Cu/SiO2 hybrid joints. The contact angle of water on SiO2 could be reduced from 22.6° to 3.3° after the plasma treatment. Benefiting from the high surface diffusivity of nt-Cu and great hydrophilicity of the plasma-assisted SiO2, the bonding temperature could be reduced to 150 ℃. However, such a plasma treatment caused the serious oxidation of the activated Cu in the ambient. To balance the activation and oxidation of the Cu films, Ar plasma power was tuned. X-ray photoelectron spectroscopy (XPS) was used to analyze the SiO2 surfaces. We found an increase (13.6% to 28.3%) in Si-OH and decreases in Si-O and C-O intensities after the plasma activation. Such decreases in Si-O and C-O intensities could be attributed to the removal of organic compounds. Shear tests were also conducted to characterize the bonding strength of the joints. An excellent bonding strength > 35 MPa was achieved after the post annealing and plasma treatment.

Fluorination of SiOx as an effective strategy to enhance the cycling stability of lithium-ion batteries

Herein, fluorinate silicon monoxide (SiO-F) is prepared by heat treatment of SiO with ammonium bifluoride (NH4HF2) at low temperatures to improve the cycling stability of SiO. The fluorination of SiO is confirmed by X-ray photoelectron spectroscopy (XPS) and Fourier-Transform infrared spectroscopy (FT-IR). The SiO-F exhibits higher initial discharge capacity, rate capability, and cycling stability than untreated SiO (pristine SiO). The superior electrochemical performances of the SiO-F are attributed to the formation of a LiF-rich solid electrolyte interphase (SEI) layer formed by the reaction between Li-ion and F-groups on the surface of SiO during the charge and discharge cycle.

Hollow-polydopamine-nanocarrier-based near-infrared-light/pH-responsive drug delivery system for diffuse alveolar hemorrhage treatment.

Introduction: Diffuse alveolar hemorrhage (DAH) is a serious complication caused by systemic lupus erythematosus (SLE). Tissue damage and changes in immune response are all associated with excessive free radical production. Therefore, removing excess reactive oxygen species are considered a feasible scheme for diffuse alveolar hemorrhage treatment. Cyclophosphamide is often used as the main therapeutic drug in clinics. However, CTX carries a high risk of dose-increasing toxicity, treatment intolerance, and high recurrence rate. The combination of therapeutic drugs and functional nanocarriers may provide an effective solution. PDA is rich in phenolic groups, which can remove the reactive oxygen species generated in inflammatory reactions, and can serve as excellent free radical scavengers. Methods: We developed a hollow polydopamine (HPDA) nanocarrier loaded with CTX by ionization to prepare the novel nanoplatform, CTX@HPDA, for DAH treatment. The monodisperse silica nanoparticles were acquired by reference to the typical Stober method. PDA was coated on the surface of SiO2 by oxidation self-polymerization method to obtain SiO2@PDA NPs. Then, HPDA NPs were obtained by HF etching. Then HPDA was loaded with CTX by ionization to prepare CTX@HPDA. Then we tested the photothermal effect, animal model therapeutics effect, and biosafety of CTX@HPDA. Results: Material tests showed that the CTX@ HPDA nanoplatform had a uniform diameter and could release CTX in acidic environments. The vitro experiments demonstrated that CTX@HPDA has good photothermal conversion ability and photothermal stability. Animal experiments demonstrated that the CTX@HPDA nanoplatform had good biocompatibility. The nanoplatform can dissociate in acidic SLE environment and trigger CTX release through photothermal conversion. Combining HPDA, which scavenges oxygen free radicals, and CTX, which has immunosuppressive effect, can treat pulmonary hemorrhage in SLE. Micro-CT can be used to continuously analyze DAH severity and lung changes in mice after treatment. The pulmonary exudation in the various treatment groups improved to varying degrees. Discussion: In this study, we report a photothermal/PH-triggered nanocarrier (CTX@HPDA) for the precise treatment of SLE-DAH. CTX@HPDA is a simple and efficient nanocarrier system for DAH therapy. This work provides valuable insights into SLE treatment.

Unveiling the SO2 Resistance Mechanism of a Nanostructured SiO2(x)@Mn Catalyst for Low-Temperature NH3-SCR of NO.

Low N2 selectivity and SO2 resistance of Mn-based catalysts for removal of NOx at low temperatures by NH3-SCR (selective catalytic reduction) technology are the two main intractable problems. Herein, a novel core-shell-structured SiO2@Mn catalyst with greatly improved N2 selectivity and SO2 resistance was synthesized by using manganese carbonate tailings as raw materials. The specific surface area of the SiO2@Mn catalyst increased from 30.7 to 428.2 m2/g, resulting in a significant enhancement in NH3 adsorption capacity due to the interaction between Mn and Si. Moreover, the N2O formation mechanism, the anti-SO2 poisoning mechanism, and the SCR reaction mechanism were proposed. N2O originated from the reaction of NH3 with O2 and the SCR reaction, as well as from the reaction of NH3 with the chemical oxygen of the catalyst. Regarding improving the SO2 resistance, DFT calculations showed that SO2 was observed to preferentially adsorb onto the surface of SiO2, thus preventing the erosion of active sites. Adding amorphous SiO2 can transform the reaction mechanism from Langmuir-Hinshelwood (L-H) to Eley-Rideal (E-R) by adjusting the formation of nitrate species to produce gaseous NO2. This strategy is expected to assist in designing an effective Mn-based catalyst for low-temperature NH3-SCR of NO.

Enhancement of Catalytic Activity on Crude Palm Oil Hydrocracking over SiO2/Zr Assisted with Potassium Hydrogen Phthalate.

In this study, the catalytic activity of bifunctional SiO2/Zr catalysts prepared by template and chelate methods using potassium hydrogen phthalate (KHF) for crude palm oil (CPO) hydrocracking to biofuels was investigated. The parent catalyst was successfully prepared by the sol-gel method, followed by the impregnation of zirconium using ZrOCl2·8H2O as a precursor. The morphological, structural, and textural properties of the catalysts were examined using several techniques, including electron microscopy energy-dispersive X-ray with mapping, transmission electron microscopy, X-ray diffraction, particle size analyzer (PSA), N2 adsorption-desorption, Fourier transform infrared-pyridine, and total and surface acidity analysis using the gravimetric method. The results showed that the physicochemical properties of SiO2/Zr were affected by different preparation methods. The template method assisted by KHF (SiO2/Zr-KHF2 and SiO2-KHF catalysts) provides a porous structure and high catalyst acidity. The catalyst prepared by the chelate method assisted by KHF (SiO2/Zr-KHF1) exhibited excellent Zr dispersion toward the SiO2 surface. The modification remarkably enhanced the catalytic activity of the parent catalyst in the order SiO2/Zr-KHF2 > SiO2/Zr-KHF1 > SiO2/Zr > SiO2-KHF > SiO2, with sufficient CPO conversion. The modified catalysts also suppressed coke formation and resulted in a high liquid yield. The catalyst features of SiO2/Zr-KHF1 promoted high-selectivity biofuel toward biogasoline, whereas SiO2/Zr-KHF2 led to an increase in the selectivity toward biojet. Reusability studies showed that the prepared catalysts were adequately stable over three consecutive runs for CPO conversion. Overall, SiO2/Zr prepared by the template method assisted by KHF was chosen as the most prominent catalyst for CPO hydrocracking.

Gradient removal of Si and P impurities from phosphogypsum and preparation of anhydrous calcium sulfate

Phosphogypsum (PG) is a solid waste generated during the production of wet -process phosphoric acid. The silicon and phosphorus impurities in PG greatly affect its resource utilization. In this study, these impurities were removed at atmospheric pressure using a two-step gradient method that simultaneously converted the calcium sulfate dihydrate (CaSO4·2H2O) phase to anhydrous calcium sulfate (CaSO4). Firstly, the SiO2 impurities were extracted and removed by adding a silane coupling agent (KH590) and tributyl phosphate (TPB). Then, the desilicated PG was subjected to phase transformation in a dilute mixed solution of H2SO4-NaCl, during which the co-crystalline phosphorus encapsulated in the gypsum lattice was fully dissolved. Bulk CaSO4 with complete crystalline morphology was obtained after this gradient impurity removal and crystal transformation treatment, and the SiO2 content, P content, and whiteness under optimal treatment conditions were 0.11%, 0.04%, and 92.5%, respectively. Mechanistic study revealed that the key to efficient SiO2 removal is hydrophobic modification of the SiO2 surface by KH590, which improves the extraction rate of SiO2 by TPB. Also, the phase transformation from PG to anhydrous CaSO4 plays a dominant role in the deep removal of P. The phase transformation rate and crystal morphology of PG were further enhanced by adding edetate disodium (EDTA-2Na) as a coordination agent. Moreover, dissolution of phosphorus was promoted in the phase transformation process of dissolution-recrystallization. This work provides practical bases for the disposal and resource recycling of industrial by-product gypsum.

Adsorption and Surface Diffusion of Atomic Ru on TiN and SiO2: A First-Principles Study

Ruthenium (Ru) has been suggested as one of the promising materials for nanoscale interconnects to substitute copper (Cu) that is currently used in the semiconductor industry. Through density functional theory (DFT) calculations, we present the rationales for varying deposition behavior of Ru on different types of substrates. For the SiO2 and TiN substrates, with and without adsorbed hydrogen, our calculation results reveal the adsorption sites and their adsorption energy, the surface diffusion paths and their activation energy, and the surface diffusion coefficients. We confirm that the adsorption of Ru is more stable on TiN than on SiO2 substrates, and that the surface diffusion of Ru adatom is faster on TiN than on SiO2 surface.

Mechanistic Origin of Selective Methane to Methanol Oxidation on Vanadium-Doped Mesoporous Amorphous Silica Photocatalyst

Selective direct oxidation of methane to methanol is an important reaction for efficient utilization of natural gas. Photocatalytic routes for methane oxidation processes have advantages over traditional thermal catalysis as they can be more easily deployed at small-scale and remote off-grid sites, potentially reducing the rate of methane release and flaring. Hu and co-workers identified single-site vanadium-doped mesoporous amorphous silica photocatalysis which demonstrated methane conversion with high methanol selectivity ( J. Photochem. Photobiol., A 2013, 264, 48−55, DOI: 10.1016/j.jphotochem.2013.05.005). Photocatalysts using amorphous SiO2 frameworks are significantly less studied than other heterogeneous photocatalysts. As a result, computational studies are important for elucidating mechanisms in order to gain fundamental understanding as to how amorphous SiO2-based photocatalysts can be used for partial oxidation of methane. This work uses density functional theory to establish the reaction barriers associated with the photocatalytic methane to methanol reaction combined with microkinetic modeling. The work is able to elucidate the role of terminal versus bridging oxygens at the photocatalytic center in enhancing photocatalytic efficiency. In addition, avoiding non-Mars–van Krevelen reaction pathways, in which the oxygen vacancy is filled before methanol is formed, is found to be important, owing to overstabilization of reaction intermediates leading to subsequent high energy reaction barriers. Finally, the amorphous SiO2 surface is found to modify reaction barriers by stabilizing intermediates through dispersion and preventing the photocatalytic center from forming the optimum coordination geometry.

Quantum dots TiO2 loaded amorphous SiO2 composite photocatalysts: Significant performance enhancement and the effect of SiO2 surface hydroxyl groups

Using amorphous SiO2 (A-SiO2) and tetrabutyl titanate (TBOT) as raw material, a composite photocatalyst with surface loaded quantum dot size TiO2 (A-SiO2/TiO2, AST) was prepared. The degradation of tetracycline hydrochloride as well as mechanism of performance improvement by A-SiO2 were investigated. The TiO2 on the composite was anatase with a content of 9.96 wt% and a size of 7–8 nm (quantum dot level). TiO2 was uniformly distributed and was closely bonded at the interface by chemical bonds. The degradation rate of AST was 95% after 60 min UV exposure, which was comparable to pure nano-TiO2. The particle size of TiO2 in AST was reduced from 20–50 nm to 7–8 nm comparing with pure nano-TiO2 and changed from a highly agglomerated to a well-dispersed state due to abundant hydroxyl groups on A-SiO2 surface. TiO2 bandgap width increased from 3.25 eV to 3.39 eV. These led to the exposing of active sites on TiO2 and significantly increased photogenerated carrier separation efficiency. This study provides a feasible and simple method to improve TiO2 nanoparticles’ photocatalytic activity, reduce the usage and achieve recycling to cut the application cost by surface coated.

Reduction of surface leakage current of InAs/GaSb long-wavelength superlattice detectors using SiO2 and anodic sulfide composite passivation

We investigate two passivation methods for long-wavelength infrared type-II InAs/GaSb superlattice (T2SL) photodiodes with the PπBN structure containing an InAs/AlSb hole barrier layer. In order to eliminate the surface defects of T2SL better to further reduce the surface dark current, anodic vulcanization and SiO2 composite passivation method is adopted to optimize the original SiO2 passivation method. At 77 K, the I–V curve of the devices under the two passivation methods are obtained. Compared with passivation-only SiO2, the dark current density of the anode sulfide and SiO2 composite passivation detector is reduced by one order of magnitude, and the surface resistivity is effectively improved by an order of magnitude. Additionally, the composite passivation method not only improves the uniformity of the device, but also prevents the peeling of the S layer to improve the quality of passivation. This work offers a stable and high-quality passivation method, and it could be popularized passivation in the field of optics, electronics, optoelectronics, and switching devices.

A First-Principles Investigation of the Driving Forces Defining the Selectivity of TiO2 Atomic Layer Deposition

Area-selective deposition (ASD) is a technique to deposit material only on a defined area of a prepatterned surface, while no deposition occurs on adjacent surface areas. It is the subject of intense investigations by the scientific and engineering communities as it offers the prospect to simplify and improve patterning processes for fabrication of nanoelectronic devices as well as to reduce the manufacturing costs. Numerous efforts have been dedicated to identify process conditions for highly selective ASD processes. Still, the search for optimal conditions is often an empirical process due to the limited understanding of the mechanisms that take place at the atomic scale. Understanding the links between precursor reactivity, surface treatments, and the reactor operating conditions could greatly contribute to the development of highly selective ASD processes. In this paper, we therefore combine first-principles calculations with statistical thermodynamics to understand the role of the precursors in area-selective TiO2 atomic layer deposition (ALD). First, we investigate the selectivity loss mechanisms for TiCl4/H2O ALD on SiO2 nongrowth surfaces with different surface terminations (e.g., OH groups and trimethylsilyl groups). We link the resulting thermodynamic driving forces to experimental reports. Subsequently, we extend the investigation to a total of 26 commercially available titanium precursors and to three different oxygen sources and rank their potential for TiO2 ASD for the SiO2 surfaces with different surface terminations (OH groups and trimethylsilyl groups). We find that the combination of TiCl4 with H2O offers the best performance in terms of selectivity. The theoretical approach proposed here is expected to greatly assist and accelerate the design of precursors for different ASD approaches.

Dielectric-on-Dielectric Achieved on SiO2 in Preference to W by Water-free Chemical Vapor Depositions with Aniline Passivation.

Selective and smooth dielectric-on-dielectric was achieved by water-free single-precursor chemical vapor deposition (CVD) processes with the help of aniline passivation. Aniline selective passivation was demonstrated on W surfaces in preference to SiO2 at 250, 300, and 330 °C. After aniline passivation, selective HfO2, Al2O3, and TiO2 were deposited only on the HF-cleaned SiO2 surface by water-free single-precursor CVD using hafnium tert-butoxide Hf(OtBu)4, aluminum-tri-sec-butoxide (ATSB), and titanium isopropoxide Ti(OiPr)4 as the precursor reactants, respectively. Hf(OtBu)4 and Ti(OiPr)4 single-precursor CVD was carried out at 300 °C, while the ATSB CVD process was conducted at 330 °C. HfO2 and Al2O3 nanoselectivity tests were performed on W/SiO2 patterned samples. Transmission electron microscopy images of the W/SiO2 patterned samples after deposition demonstrated nanoselectivity and low surface roughness of HfO2 and Al2O3 deposition on the SiO2 regions only.

PROMISING NANOBIOTECHNOLOGY FOR POULTRY FARMING BASED ON SILVER NANOPARTICLES EMBEDDED IN POLYMER-INORGANIC HYBRID CARRIERS

A promising composite material is proposed to reduce the endogenous and exogenous contamination of chicken eggs with pathogenic microflora during their formation and storage. It is based on hybrid biocompatible and biodegradable silica/polyacrylamide nanocarriers containing small silver nanoparticles (dav=2.4±1.0 nm) that are orally administered to laying hens with drinking water. The features of the formation of nanosilver in hybrid carriers by borohydride reduction of a silver salt at its various concentrations in an aqueous solution have been studied. An interesting effect of the sharp appearance of the second surface plasmon resonance band in the UV-Vis spectra of a silver salt/hybrid mixture at a high salt concentration was found. This was explained by sharp structural changes in the hybrid carriers caused by the simultaneous growth of many AgNPs in them. It was assumed that the intensive growth of many AgNPs in one hybrid particle was accompanied by detachment of the grafted PAAm chains from the SiO2 surface due to the breaking of hydrogen bonds. The change in the state of the composite material under the influence of the pH of the solution, the concentration of nanoparticles, the presence of NaCl (as in a “physiological solution”), and visible light was studied by UV-Vis spectroscopy, potentiometric titration, and TEM. Nanosilver in carriers showed high stability with respect to most of these factors. The influence of the composite material on the clinical state of laying hens and important parameters of their eggs and blood was studied when it was administered orally with drinking water three times every 10 days at doses of 0.2 and 0.4 mg per chicken per day. A striking effect of selective endogenous accumulation of silver in eggshells has been revealed. This confirmed the penetration of the nanosilver composite into the circulatory system of chickens by passing through the digestive tract, absorption through the intestinal epithelium and further transport into the tissues of the chickens, including the oviducts, where protein and eggshell are formed. Such penetration did not cause a toxic effect on the body of laying hens.

Highly dispersed nanocomposites based on polymer/inorganic hybrids and nickel nanoparticles: the role of the matrix structure in the process of in situ formation

A series of polymer/inorganic hybrids based on silica sol and polyacrylamide (SiO2-g-PAAm) with different number and length of PAAm chains was obtained by radical graft polymerization of acrylamide from the surface of SiO2. The main molecular and structural parameters of the hybrids, such as the chemical composition, average radius and charge of SiO2 particles, the number of grafts per one particle and their molecular weight, the average diameter and hydrodynamic volume of hybrid particles, and the thickness of the PAA layer, were determined. For this, elemental analysis, DTGA, static light scattering, viscometry, potentiometric titration, and TEM were used. The functional properties of hybrids as hydrophilic matrices in the in situ synthesis of nickel nanoparticles by borohydride reduction of metal ions from the Ni(NO3)2·6H20 salt in an aqueous medium have been studied. Using the method of UV-Vis spectroscopy and the developed original approach, the kinetics and efficiency of the formation of NiNPs in hybrid solutions were characterized, depending on the structure and concentration of the hybrid matrices and the concentration of the metal salt. An increase in the rate of accumulation and yield of NiNPs in solutions of all hybrids was found with an increase in salt concentration in the range of 0,010-0,078 kg·m-3, as well as a predominant decrease in the reaction rate with an increase in the concentration of hybrid matrices from 0,5 to 2,0 kg·m-3. It was shown that the structure of the hybrid matrices, determined by the number and length of PAAm chains, as well as the permeability of the grafted polymer layer, was one of the key factors affecting the formation rate and yield of NiNPs. It provided greater or lesser accessibility of the active groups of the "corona" and the inorganic "core" for metal ions and reducing agent molecules. Morphological studies of purified reduction products were carried out by TEM. Based on them, the main structural elements of highly dispersed NiNPs/SiO2-g-PAAm nanocomposites were established – swollen hairy particles of hybrids with small amorphous NiNPs (1,7±0,8 nm) included in the polymer "corona".

Pyridine-Catalyzed Atomic Layer Deposition of SiO2 from Hexachlorodisilane and Water: An In Situ Mechanistic Study

Pyridine-catalyzed atomic layer deposition (ALD) of SiO2 from hexachlorodisilane and water was studied by in situ analyses using Fourier-transform infrared spectrometry and a quartz crystal microbalance. Although it has been observed that ALD SiO2 can grow even when only one half-reaction is catalyzed, typical self-limiting growth of SiO2 by catalytic ALD has been achieved when both half-reactions are catalyzed by pyridine. The in situ analyses revealed that the unexpected growth of SiO2, when only one half-reaction was catalyzed, was caused by the presence of residual pyridine that had not yet desorbed from the previous half-reaction. The retardation of catalyst desorption was more prominent on the OH-terminated SiO2 surface than on the Cl-terminated surface, which is related to the significantly higher desorption energy of pyridine species on the hydroxyl surface calculated using density functional theory.

Atomic Layer Deposition of La2O3 Film with Precursor La(thd)3-DMEA

In this paper, a new precursor La(thd)3-DMEA (thd = 2,2,6,6-tetramethyl-3,5-heptanedione, DMEA = N,N′-dimethylethylenediamine) was synthesized and characterized with 1H-NMR and X-ray single crystal diffraction. The thermal properties of La(thd)3-DMEA were checked by thermogravimetric analysis (TGA), which confirmed that the volatility and suitability of La(thd)3-DMEA are suitable for atomic layer deposition (ALD). We studied the atomic layer deposition of La2O3 films on a SiO2 surface with La(thd)3-DMEA and O3 as precursors. Self-limiting deposition behaviors were found for the prepared films. The purity and surface morphology of the as-grown La2O3 films, which possessed a constant growth rate of ~0.4 Å/cycle at 250–280 °C, were confirmed by XPS, SEM, and AFM. The results show that La(thd)3-DMEA is a suitable precursor for the atomic layer deposition of La2O3 film.