Role of cleaning methods on bond quality of Ti coated glass/imidex system

Thin film materials are widely used in the fabrication of semiconductor microelectronic devices. In thin film deposition, cleanliness of substrate surface have become critically important as over 50% of yield losses in integrated circuit fabrication are caused by microcontamination [1]. There are many wafer cleaning techniques. The most successful approach for silicon wafer cleaning technique is RCA clean [2]. But for glass substrate it is still not known which procedure of cleaning is the best. This paper provides an understanding of the right way of glass wafer cleaning method, with a focus towards identifying good bond strength. Two wafer cleaning techniques have been used for cleaning glass substrates in the context of laser micro-joining of dissimilar substrates. First cleaning procedure involves two steps, first cleaning in acetone solution and then in DI water solution. After each step dried with N₂. Second cleaning procedure involves four steps, first cleaning with 1% Alconox solution, second in DI water, third in acetone solution and finally in a methanol solution and dried with N₂ after each step. Deposition of Ti thin film on top of these two types of substrate using DC magnetron sputtering method also showed better adhesion of Ti film on glass for the second type of cleaning method. Scanning electron microscopy (SEM) analyses of the lap shear tested failed surfaces for these two kinds of samples revealed strong bond for samples prepared by second cleaning method compared to first cleaning method. Characterization of these two sets of samples using X-ray photoelectron spectroscopy (XPS) has shown excellent contamination removal for the second cleaning method. This modification is believed to be due to reduction of carbon contamination.     

Enhancement of carrier mobility in pentacene thin-film transistor on SiO2 by controlling the initial film growth modes

Pentacene thin-film transistors (TFTs) were fabricated on thermally grown SiO₂ gate insulator under the conditions of various pre-cleaning treatments. Initial nucleation and growth of the material films on treated substrates were observed by atomic force microscope. The performance of fabricated TFT devices with different surface cleaning approaches was found to be highly related to the initial film morphologies. In contrast to the three-dimensional island-like growth mode on SiO₂ under an organic cleaning process, a layer-by-layer initial growth occurred on the SiO₂ insulator cleaned with ammonia solution, which was believed to be the origination of the excellent electrical properties of the TFT device. Field effect mobility of the TFT device could achieve as high as 1.0 cm²/Vs on the bared SiO₂/Si substrate and the on/off ratio was over 10⁶.     

Laser plasma shockwave cleaning of SiO2 particles on gold film

A Nd:YAG laser (1064 nm) induces optical breakdown of the airborne above the gold-coated K9 glass surface and the created shockwave removes the SiO₂ particles contaminated on the gold films. The laser cleaning efficiency has been characterized by optical microscopy, dark field imaging, ultraviolet-visible-near infrared spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and the Image-pro software. The relationships between removal ratio and particle position and laser gap distance have been studied in the case of single pulse laser cleaning. The results show that the 1064 nm laser induced plasma shockwave can effectively remove the SiO₂ particles. The removal ratio can reach above 90%. The effects of particle position and laser gap distance on the cleaning efficiency are simulated for the single pulse laser cleaning. The simulated results are consistent with the experimental ones.     

Size-Dependent HCl Generation of PVC/SiO2 Micro- and Nanocomposites

In this study HCl generation of polyvinyl (chloride) (PVC)/SiO₂ composites during its combustion was investigated. SiO₂ with different particle sizes were used as HCl absorbers and their HCl uptake ability results were compared to that of CaCO₃. It was found that the amount of released HCl gas during PVC combustion decreased in the presence of SiO₂. The HCl uptake ability of SiO₂ improved with decreasing of its particle size. Although thermogravimetric analysis (TGA) results showed that SiO₂ particles decreased the first thermal degradation temperature (T _onset) of PVC by initiating dehydrochlorination of PVC at lower temperatures, SiO₂ particles had more effective HCl uptaking ability than that of CaCO₃. Scanning electron microscopy (SEM) micrographs showed that some aggregates whose size was less than 100 nm were formed when Si-25 nm was used as filler. When SiO₂ with micron size was added to PVC as filler, more uniform and better distribution of the SiO₂ on the surface was observed.     

Immobilization of quaternary ammonium salts on grafting particle polystyrene/SiO2 and preliminary study of application performance

Polystyrene (PSt) was grafted on the surface of silica gel particles in the manner of “grafting from” in a solution polymerization system, and grafting particles PSt/SiO₂ was obtained. The chloromethylation reaction of the grafted polystyrene was performed using a novel chloromethylation reagent, 1,4-bis(chloromethyoxy)butane which is un-carcinogenic, and grafting particles CMPS/SiO₂ was gained. Subsequently, grafted CMPS was quaternized (denoted as QPS) using tertiary amine, and finally functional composite-type particles QPS/SiO₂, on which quaternary ammonium groups were immobilized, were prepared. The catalysis activity of the particle QPS/SiO₂ as a triphase catalyst in phase-transfer catalysis systems and its antibacterial activity as a water-insoluble antibacterial material were studied preliminarily. The experimental results show that the particle QPS/SiO₂ exhibits higher catalysis activity as a triphase catalyst for the reaction between benzyl chloride in organic phase and sodium acetate in aqueous phase to form benzyl acetate, and under a mild condition of 60 °C for 7 h of reaction time a conversion of 66% for benzyl chloride can be obtained. The particle QPS/SiO₂ has high antibacterial activity as a water-insoluble antibacterial material against Escherichia coli (E. coli).     

Laser cleaning of particle and grease contaminations on the surface of optics

In the high power laser facility, surface contaminations on the optics will worsen the laser beam quality and damage the optics. Particle and grease contaminations are two of the usual contaminations on the surface of optics. In this work, the 1064-nm laser induced plasma shockwave cleaning is utilized to remove SiO₂ particle contaminations on the K9 glass surface. The results indicate the removal ratio can reach above 95%. The effects of parameters (particle position, laser gap distance and laser energy) on the cleaning efficiency have been studied in the case of single pulse laser cleaning. In addition, CO₂ laser (10.6 μm) is utilized to remove the dimethylsilicone oil contaminations on the gold-coated K9 glass surface. The results show that CO₂ laser can effectively remove the dimethylsilicone oil by properly controlling the laser parameters. The cleaned area increases with the increased laser power or irradiation time when the other parameters are constant.     

Effect of Polyethylene Functionalization on Mechanical Properties and Morphology of PE/SiO2 Composites

In this study composites of high density polyethylene (HDPE) with various SiO₂ content were prepared by melt compounding using maleic anhydride grafted polyethylene (PE-g-MAH) as a compatibilizer. The composites containing 2, 4 and 6% by weight of SiO₂ particles were melt-blended in a co-rotating twin screw extruder. In all composites, polyethylene-graft-maleic anhydride copolymer (PE-g-MAH, with 0.85% maleic anhydride content) was added as a compatibilizer in the amount of 2% by weight. Morphology of inorganic silica filler precipitated from emulsion media was investigated. Mechanical properties and composite microstructure were determined by tensile tests and scanning electron microscopy technique (SEM). Tensile strength, yield stress, Young's modulus and elongation at break of PE/SiO₂ composites were mainly discussed against the properties of PE/PE-g-MAH/SiO₂ composites. The most pronounced increase in mechanical parameters was observed in Young's modulus for composites with polyethylene grafted with maleic anhydride. The increase in the E-modulus of PE/PE-g-MAH/SiO₂composites was associated with the compatibility and improvement of interfacial adhesion between the polyethylene matrix and the nanoparticles, leading to an increased degree of particle dispersion. This finding was verified on the basis of SEM micrographs for composites of PE/PE-g-MAH/4% by weight of SiO₂. The micrographs clearly documented that addition of only 2 wt% of the compatibilizer changed the composite morphology by reducing filler aggregates size as well as their number. Increased adhesion between the PE matrix and SiO₂ particles was interpreted to be a result of interactions taking place between the polar groups of maleic anhydride and silanol groups on the silica surface. These interactions are responsible for reduction of the size of silica aggregates, leading to improved mechanical properties.     

Immobilization of metalloporphyrins on P(4VP-co-St)/SiO2 by the quaternarization reaction

Poly(4vinylpyridine-co-styrene) (P(4VP-co-St)) was grafted on silica gel particles in the manner of “grafting from”, and the grafting particle P(4VP-co-St)/SiO₂ was gained. The chloromethylation reaction for the tetraphenylporphyrin (TPP) was performed using a chloromethylation reagent, 1,4-bis(chloromethyoxy)butane which was uncarcinogenic, and the tetra-chloromethylphenyl-porphyrin (TMCPP) was prepared. Then, the quaternization reaction between the benzyl chloride groups on TMCPP and pyridine groups of the grafted P(4VP-co-St) macromolecules occurred and the bonding of TMCPP on the particles P(4VP-co-St)/SiO₂ was realized, resulting in the functional composite-type particles TMCPP-P(4VP-co-St)/SiO₂. Subsequently, the metallation of the bonded particles TMCPP-P(4VP-co-St)/SiO₂ was carried out via the coordination reaction between TMCPP-P(4VP-co-St)/SiO₂ and metal salt, resulting in the supported metalloporphyrin (MP) catalysts MP-P(4VP-co-St)/SiO₂. The supported catalysts were characterized by UV-Vis spectra. The effects of various factors on the bonding process of TMCPP on P(4VP-co-St)/SiO₂ were studied in detail. In addition, the catalytic activity of the supported catalysts MP-P(4VP-co-St)/SiO₂ have been studied in oxidation process of ethyl benzene with molecular oxygen to acetophenone without the use of sacrificial co-reductant. The experimental results showed that the tetra-chloromethylphenyl-porphyrin (TMCPP) could be successfully bonded onto the P(4VP-co-St)/SiO₂ surfaces by means of the quaternization reaction between TMCPP and the pyridine groups on grafted P(4VP-co-St) macromolecules. The supported catalysts MP-P(4VP-co-St)/SiO₂ exhibited the fine catalytic activity. Moreover, the supported cobalt porphyrin was more active than the supported iron and manganese porphyrins.     

Photoluminescence of colloidal YVO4:Eu/SiO2 core/shell nanocrystals

YVO₄:Eu, and YVO₄:Eu/SiO₂ nanocrystals (NCs) were prepared by hydrothermal method with citrate as capping ligands. Their morphologies, structures, components, and photoluminescence properties were investigated and presented in this paper. A remarkable fluorescence enhancement up to 2.17 times was observed in colloidal YVO₄:Eu/SiO₂ NCs, compared to that of colloidal YVO₄:Eu NCs. This is mainly attributed to the formation of the outer protecting layers of biocompatible SiO₂ shells; which shield the Eu³⁺ ions effectively from water and thus reduces the deleterious effects of water on the luminescence. Meanwhile, on the basis of laser selective excitation, two kinds of luminescent centers were confirmed in the NCs, namely, inner Eu³⁺ ions and surface Eu³⁺ ions. The surface modifications for YVO₄:Eu NCs effectively reduced the surface defects and accordingly enhanced the luminescence. The core/shell NCs exhibited long fluorescence lifetime and high photostability under ultraviolet radiation.     

HLDPE/organic functionalized SiO2 nanocomposites with improved thermal stability and mechanical properties

High-pressure low-density polyethylene (HLDPE)/organic functionalized SiO₂ nanocomposites were synthesized using melt-blending technique in a sigma internal mixer. The properties of the nanocomposites were studied using two different organic functional modifiers: diglycidyl ether of bisphenol-A (DGEBA) and triacetoxyvinylsilane. Reinforcing, thermal stability and toughening effects of organic functionalized nanosilica on the polymer matrix were found at loading of 2.5% nanosilica functionalized with 2.8% of DGEBA and silane coupling agent respectively. Organic functionalization on the nanosilica particle surface led to different microstructures when compared with that of the pure polymer. Organic functionalization on the nanosilica particle surface produced good interfacial adhesion and homogeneous dispersion in the polymer matrix, while the use of nanosilica resulted in aggregated silica particles in the polymer matrix. There was no significant improvement in thermal stability and mechanical properties when only nanosilica was added to the pure polymer. On the contrary, the addition of pretreated nanosilica with organic functional modifiers led to an increase of thermal stability from 313–363°C, elastic modulus and toughness from 0.12–0.18 GPa and 3.23–9.81 MJ/m³ respectively.     

Improved photoluminescence and afterglow in CaTiO3:Pr with addition of nanosized SiO2

Enhancement of the ¹D₂-³H₄ red emission in CaTiO₃:Pr³⁺ with addition of nanosized SiO₂ fabricated by a solid state reaction method is reported. The dynamical processes for the improvement of red emission were systematically investigated using photoluminescence (PL) and PL excitation spectra, and diffused reflectance spectra as well as time decay patterns of PL and persistent afterglow. Higher efficiency of energy transfer from CaTiO₃ host to the activator Pr³⁺ due to the improvement of crystallinity by SiO₂ addition was discussed in comparison with that of the SiO₂ free sample. The enhancement of persistent afterglow after the cessation of excitation in SiO₂ added CaTiO₃:Pr³⁺ was also analyzed by theoretically fitted results.     

Synthesis and characterization of Mn-doped Zn2SiO4/SiO2 phosphor particles in core-shell structure

Manganese-doped zinc silicate (Zn₂SiO₄:Mn) is a kind of phosphor material that has a photo-luminescent (PL) and cathode-luminescent (CL) properties with intensive green light emission at 520 nm. The particles consisting of SiO₂@Zn₂SiO₄:Mn (SiO₂ core-Zn₂SiO₄:Mn shell) were synthesized via colloidal process and forced precipitation. After drying, the Zn/Mn precipitates were coated on the surface of SiO₂ particles. The Zn/Mn precipitates reacted with SiO₂ and transformed to Zn₂SiO₄:Mn by suitable calcination. The microstructure, crystalline phase, and luminescent characteristics of the products were studied. Besides, a CL device consisting of the core-shell powder was characterized.     

The hybrid photocatalyst of TiO2–SiO2 thin film prepared from rice husk silica

The TiO₂–SiO₂ thin film was prepared by self-assembly method by mixing SiO₂ precursor with titanium precursor solution and aged to obtain a co-precipitation of silica and titanium crystals. Dip coating method was applied for thin film preparation on glass slide. The X-ray diffraction (XRD) of the self-assembly thin film had no characteristic property of SiO₂ and even anatase TiO₂ but indicated new crystal structure which was determined from the Fourier Transform Infrared Spectrophotometer (FTIR) as a hybridized Ti–O–Si bonding. The surface area and surface volume of the self-assembly sample were increased when SiO₂ was incorporated into the film. The self-assembly TiO₂–SiO₂ thin film exhibited the enhanced photocatalytic decolorization of methylene blue (MB) dye. The advantages of SiO₂ are; (1) to increase the adsorbability of the film and (2) to provide the hydroxyl radical to promote the photocatalytic reaction. The self-assembly thin film with the optimum molar ratio (SiO₂:TiO₂) as 20:80 gave the best performance for photocatalytic decolorization of MB dye with the overall efficiency of 81%.     

Preparation and characterization of novel Pd/SiO2 and Ca-Pd/SiO2 egg-shell catalysts with porous hollow silica

Novel egg-shell structured monometallic Pd/SiO₂ and bimetallic Ca-Pd/SiO₂ catalysts were prepared by an impregnation method using porous hollow silica (PHS) as the support and PdCl₂ and Ca(NO₃)₂·4H₂O as the precursors. It was found from transmission electron microscope (TEM), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) that Pd was loaded on PHS with a particle size of 5-12 nm in Pd/SiO₂ samples and the Pd particle size in Ca-Pd/SiO₂ was smaller than that in Pd/SiO₂ since Ca could prevent Pd particles from aggregating. X-ray photoelectron spectroscopy (XPS) analyses exhibited that Pd 3d_5/2 binding energies of Pd/SiO₂ and Ca-Pd/SiO₂ were 0.2 and 0.9 eV lower than that of bulk Pd, respectively, as a result of the shift of the electron cloud from Pd to oxygen in Pd/SiO₂ and to both oxygen and Ca in Ca-Pd/SiO₂. The activity of Ca-Pd/SiO₂ egg-shell catalyst for CO hydrogenation and the selectivity to methanol, with a value of 36.50 mmol_CO mol⁻¹_Pd s⁻¹ and 100%, respectively, were much higher than those of the catalysts prepared with traditional silica gel as the support, owing to the porous core-shell structure of the PHS support.     

A novel method for immobilization of Co tetraphenylporphyrins on P(4VP-co-St)/SiO2: Efficient catalysts for aerobic oxidation of ethylbenzenes

In this paper, poly(4vinylpyridine-co-styrene) (P(4VP-co-St)) was grafted on silica gel particles in the manner of “grafting from”, and the grafting particle P(4VP-co-St)/SiO₂ was gained. The grafting particle P(4VP-co-St)/SiO₂ is a novel kind of supports for immobilizing metalloporphyrin catalysts. Then, the immobilization of cobalt tetraphenylporphyrin (CoTPP) on the supports P(4VP-co-St)/SiO₂ was carried out via the axial coordination reaction between CoTPP and the pyridine groups of the grafted P(4VP-co-St), resulting in the heterogenised catalysts CoTPP-P(4VP-co-St)/SiO₂. The synthesized catalysts were characterized by FTIR and the axial coordination process between CoTPP and the grafted P(4VP-co-St) was confirmed by UV-vis. The effects of various factors on the immobilization reaction of CoTPP were studied in detail. Finally, the catalytic performance of CoTPP-P(4VP-co-St)/SiO₂ in the catalytic oxidation process of ethyl benzene was investigated. The experimental results show that the axial coordination reaction is a very easy and novel method for favorably immobilizing CoTPP onto the P(4VP-co-St)/SiO₂ surfaces. During the immobilization process of CoTPP on P(4VP-co-St)/SiO₂, the most bonding amount of CoTPP (0.19 g/g) is obtained under the lower temperature (5 °C) and the higher concentration of CoTPP(6.0 mg/ml) lasting 4 h. Moreover, the supported catalyst CoTPP-P(4VP-co-St)/SiO₂ can effectively activate the dioxygen, and obviously catalyze the transform of ethylbenzene into acetophenone. So it exhibits the fine catalytic activity.     

Deposition and characterization of binary Al2O3/SiO2 coating layers on the surfaces of rutile TiO2 and the pigmentary properties

Binary Al₂O₃/SiO₂-coated rutile TiO₂ composites were prepared by a liquid-phase deposition method starting from Na₂SiO₃·9H₂O and NaAlO₂. The chemical structure and morphology of binary Al₂O₃/SiO₂ coating layers were investigated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, TG-DSC, Zeta potential, powder X-ray diffraction, and transmission electron microscopy techniques. Binary Al₂O₃/SiO₂ coating layers both in amorphous phase were formed at TiO₂ surfaces. The silica coating layers were anchored at TiO₂ surfaces via Si-O-Ti bonds and the alumina coating layers were probably anchored at the SiO₂-coated TiO₂ surfaces via Al-O-Si bonds. The formation of continuous and dense binary Al₂O₃/SiO₂ coating layers depended on the pH value of reaction solution and the alumina loading. The binary Al₂O₃/SiO₂-coated TiO₂ composites had a high dispersibility in water. The whiteness and brightness of the binary Al₂O₃/SiO₂-coated TiO₂ composites were higher than those of the naked rutile TiO₂ and the SiO₂-coated TiO₂ samples. The relative light scattering index was found to depend on the composition of coating layers.     

Surface properties of silicon oxide films deposited using low-pressure dielectric barrier discharge

The deposition of SiO_X films from low-pressure dielectric barrier discharge plasmas has been investigated using tetraethoxysilane (TEOS)/O₂ as the feed gas. Films were analyzed using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), AFM-based nanoindentation/nanowear techniques, and conductive AFM. Film deposition rates and hydrocarbon incorporation in the SiO_X film decrease with addition of O₂. High-quality SiO_X films with extremely low surface roughness are deposited at high oxidant concertrations. Addition of oxidant to the feed gas leads to a change in the SiO_X film structure from precursor-like to a dense SiO_X structure. The SiO_X films deposited with TEOS/O₂ plasmas were found to have soft surface layers, 0.5-1.5 nm thick, which contribute to an improvement of their field emission properties. The effect of gas phase compositions on the surface properties of the conductive surface layer was discussed.     

焙烧温度对SiO2负载的Co3O4纳米粒子表面氧缺陷浓度和CO氧化催化性能的影响

以传统的浸渍法,在不同焙烧温度下制备了用于CO氧化反应的Co₃O₄/SiO₂催化剂．通过激光拉曼光谱(Raman)、X射线光电子能谱(XPS)、X射线衍射(XRD)、程序升温还原(TPR)和X射线吸收精细结构谱(XAFS)表征了该系列催化剂的结构．在所有的催化剂中,XRD和Raman光谱都只检测到了Co₃O₄晶相的存在．与Co₃O₄体相相比,XPS结果表明在200 oC焙烧的(Co₃O₄(200)/SiO₂)催化剂中Co₃O₄表面上存在着过量的Co²⁺．与XPS的结果一致,TPR结果表明Co₃O₄(200)/SiO₂催化剂中Co₃O₄表面上存在氧缺陷, 并且XAFS结果也表明Co₃O₄(200)/SiO₂催化剂中Co₃O₄具有更多的Co²⁺．提高焙烧温度使得过量的Co²⁺进一步氧化为Co³⁺,同时降低了表面氧缺陷浓度,从而得到计量比的Co₃O₄4/SiO₂催化剂．在所有的负载催化剂中Co₃O₄(200)/SiO₂催化剂表现出了最好的CO氧化催化性能,表明过量Co²⁺和表面氧缺陷的存在能够促进Co₃O₄催化CO氧化反应的活性.     

Synthesis and Optical Properties of SiO2-Coated CeO2 Nanoparticles

Silica (SiO₂)-coated ceria (CeO₂) nanoparticles were prepared using water-in-oil microemulsion. Polyoxyethylene (15) cetylether and cyclohexane were used as a surfactant and organic solvent. SiO₂-coated CeO₂ nanoparticles were obtained by hydrolysis of metal alkoxide (tetraethylorthosilicate, TEOS) in the solution containing CeO₂ precursor nanoparticles. The effects of CeO₂ sources (Ce metal salt) and CeO₂ particle-forming agents on the morphology of SiO₂–CeO₂ particles were investigated. Observation via transmission electron microscopy revealed that the type of particle-forming agent affected the nanoparticles' morphology and that CeO₂ nanoparticles were spherically coated with SiO₂ when using oxalic acid ((COOH)₂) as a particle-forming agent of CeO₂. Furthermore, the transmittance of the particles was high in the visible region (above 400 nm) and decreased in the ultraviolet region.     

Novel catalysts: Indium implanted SiO2 thin films

Interactions of Indium (In) and silicon (Si) atoms are known to catalyze certain organic chemical reactions with high efficiency. In an attempt of creating a material that manifests the interactions, In implanted SiO₂ thin films were prepared by ion beam injection and their catalytic abilities for organic chemical reactions were examined. It has been found that, with an injection energy of approximately 0.5 keV, a thin In film is formed on a SiO₂ substrate surface and the In implanted SiO₂ thin film can catalyze an organic chemical reaction. It has been also shown that there is an optimal ion dose for the highest catalytic ability in the film preparation process. Thin-film-type catalyzing materials such as the one proposed here may open a new way to enhance surface chemical reaction rates.