Adhesion promoters for polythiophene

Polythiophene layers have been grafted onto silicon, iron, platinum and titanium for applications as organic semi‐conducting films on solid surfaces. In general, the adhesion between the polymer films and substrates is insufficient for technical and microelectronic applications. The use of adhesion promoters between substrate and polymer and enables the formation of a strongly bonded composite. The polymers were synthesized by chemical or electrochemical surface polymerization.     

锂离子电池锡薄膜负极制备及电化学性能研究

应用真空蒸发法在泡沫铜基底上制备锡薄膜负极.XRD、SEM分析表征薄膜的物相结构及其微观形貌,并测试了材料的电化学性能.结果表明,泡沫铜基底的三维结构增强了活性物质与基底的结合力.在同一基底温度下,锡颗粒随蒸发时间延长逐渐增大,电池电化学性能降低;而在同一时间内,升高基底温度,颗粒无明显变化,电池循环寿命有了很大提高.样品A″电池(基底温度:200℃,蒸发时间:0.5 h)经100次充放电循环后比容量仍达407.3 mAh·g-1.     

Biofunctionalization of a "clickable" organic layer photochemically grafted on titanium substrates

We have developed a general method combining photochemical grafting and copper-catalyzed click chemistry for biofunctionalization of titanium substrates. The UV-activated grafting of an α,ω-alkenyne onto TiO(2)/Ti substrates provided a "clickable" thin film platform. The selective attachment of the vinyl end of the molecule to the surface was achieved by masking the alkynyl end with a trimethylgermanyl (TMG) protecting group. Subsequently, various oligo(ethylene glycol) (OEG) derivatives terminated with an azido group were attached to the TMG-alkynyl modified titanium surface via a one-pot deprotection/click reaction. The films were characterized by X-ray photoelectron spectroscopy (XPS), contact angle goniometry, ellipsometry, and atomic force microscopy (AFM). We showed that the titanium surface presenting click-immobilized OEG substantially suppressed the nonspecific attachment of protein and cells as compared to the unmodified titanium substrate. Furthermore, glycine-arginine-glycine-aspartate (GRGD), a cell adhesion peptide, was coimmobilized with OEG on the platform. We demonstrated that the resultant GRGD-presenting thin film on Ti substrates can promote the specific adhesion and spreading of AsPC-1 cells.     

Fabrication and characterization of porous Si-Al films anode with different macroporous substrates for lithium-ion batteries

Porous Si-Al films were fabricated by magnetron sputtering (co-sputtering) using three different copper substrates as current collectors, respectively. The morphology, compositions, structure, and crystallinity of the porous Si-Al films anodes were examined by using SEM, EDX, TEM, XRD, and Raman spectroscopy. The electrochemical properties of the porous Si-Al films anodes were evaluated by galvanostatic cycling. The Si-Al film deposited on copper foam showed higher insertion/extraction capacity, capacity retention, and longer cycle life in comparison to the Si-Al films deposited on expanded copper mesh and even copper mesh grid, which could be attributed to its unique three-dimensional macroporous structure. The three-dimensional macroporous structure could offer larger materials/electrolyte contact area, a much better adhesion, lower electrical resistance (i.e., well conductive), and stress-alleviated environment to partly accommodate volume expansion that leads to exfoliation during cycling.     

Cyclic voltammetry and galvanostatic cycling characteristics of LiNiVO4 thin films during lithium insertion and re/de-insertion

In this communication, we investigated the effects of LiNiVO₄ thin film electrodes composition, thickness, electrolytes, cycling temperature, crystallization of films, and substrates on the kinetics during lithium insertion/de-insertion behaviour, which were studied in detail by cyclic voltammetry. The stoichiometric and non-stoichiometric thin films were formed by using rf-sputtering by varying the partial pressure of oxygen, and the host films were characterized by a variety of methods like Nuclear techniques and surface science analytical methods. The galvanostatic studies give the lithium insertion amounts and the best electrochemical performance of 1300 mAh/g capacity has been obtained from the stoichiometric film deposited on a stainless steel substrate during the first discharge cycle. The lithium diffusion coefficients of the film during the first discharge–charge cycle were measured by using galvanostatic intermediate titration method. Overall, the voltammetric behaviours of LiNiVO₄ thin film electrodes are highly sensitive to the composition, thickness, cycling temperature, scan rate, substrates and crystal structure, and the above observed behaviours are discussed.     

Ageing and fatigue of lead titanate and lead zirconate titanate thin ferroelectric films

The phenomena of ageing and fatigue have been experimentally investigated in lead titanate and lead zirconate titanate thin ferroelectric films for samples on different substrates and with different materials of the measuring electrodes. A certain broadening of the dielectric permittivity peak is observed for the films on the silicon substrate after a year keeping without external actions. The lead titanate films on corundum substrates did not demonstrate visible changes in structural and dielectric parameters in the course of this time. In the course of repeated cycling the reduction of switching polarization in the lead titanate and lead zirconate titanate films on silicon substrates takes place at considerably greater number of cycles as compared to the same films on corundum substrates under the identical conditions. The above changes of dielectric and switching characteristics can be relevant to the changes in the domain structure of the materials under investigation in the process of their ageing and repeated switching. The reason for the acceleration of the ageing processes in the films on corundum substrates could be either an increase in the absolute magnitude of the switching field or an increase of the internal bias field, that facilitate the migration of oxygen vacancies in the films with the perovskite structure to the electrode–ferroelectric surface with the consequent fixation of domain walls.     

Process study of thermal plasma chemical vapor deposition of diamond,part I: Substrate material,temperature, and methane concentration

Effects of process parameters on diamond film synthesis in DC thermal plasma jet reactors are discussed including substrate material, methane concentration and substrate temperature. Diamond has been deposited on silicon, molybdenum, tungsten, tantalum, copper, nickel, titanium, and stainless steel. The adhesion of diamond film to the substrate is greatly affected by the type of substrate used. It has been found that the methane concentration strongly affects the grain size of the diamond films. Increased methane concentrations result in smaller grain sizes due to the increased number of secondary nucleations on the existing facets of diamond crystals. Substrate temperature has a strong effect on the morphology of diamond films. With increasing substrate temperature, the predominant orientation of the crystal growth planes changes from the (111) to the (100) planes. Studies of the variation of the film quality across the substrate due to the nonuniformity of thermal plasma jets indicate that microcrystalline graphite formation starts at the corners and edges of diamond crystals when the conditions become unfavorable for diamond deposition.     

Photocontrol of cell adhesion on amino-bearing surfaces by reversible conjugation of poly(ethylene glycol) via a photocleavable linker

Dynamic control of cell adhesion on substrates is a useful technology in tissue engineering and basic biology. This paper describes a method for the control of cell adhesion on amino-bearing surfaces by reversible conjugation of an anti-fouling polymer, poly(ethylene glycol) (PEG), via a newly developed photocleavable linker, 1-(5-methoxy-2-nitro-4-prop-2-ynyloxyphenyl)ethyl N-succinimidyl carbonate (1). This molecule has alkyne and succinimidyl carbonate at each end, which are connected by photocleavable 2-nitrobenzyl ester. Under this molecular design, the molecule crosslinked azides and amines, whose linkage cleaved upon application of near-UV light. By using aminosilanised glass and silicon as model substrates, we studied their reversible surface modification with PEG-azide (M(w) = 5000) based on contact angle measurements, ellipsometry, and AFM morphological observations. Protein adsorption and cell adhesion dramatically changed by PEGylation and the following irradiation, which can be used for cellular patterning. Also, the capability of the substrate to change cell adhesiveness by photoirradiation during cell cultivation was demonstrated by inducing cell migration. We believe this method will be useful for dynamic patterning of cells on protein-based scaffolds.     

Mouse bone marrow‐derived mesenchymal stem cell response to nanostructured titanium substrates produced by high‐pressure torsion

Mesenchymal stem cells (MSCs) with the ability to differentiate into various mesoderm‐like cells are known to migrate to various organs to repair injured tissues. They can attach to the implant surface, differentiate into bone‐forming cells, and ultimately osseointegrate with the prosthesis. This study investigates bone marrow‐derived mesenchymal stem cellular response to the grain structure of titanium substrates produced by high‐pressure torsion and annealing processes. Cell attachment, proliferation, viability, and morphology are evaluated on the surface of differently processed nanostructured and coarse‐grained samples. The bacterial adhesion and calcium phosphate crystal formation and growth are also assessed on the surface of the substrates. The nanostructured titanium shows significantly higher cell adhesion, proliferation, spreading, and viability compared with the untreated and coarse‐grained titanium substrates. The adhesion of bacteria is lower and surface bioactivity is higher on the surface of the nanostructured titanium substrate. The results demonstrate the superior MSC compatibility, antibacterial efficacy, and surface bioactivity of the nanostructured titanium substrates, which could lead to early implant fixation and improved osseointegration. Copyright © 2012 John Wiley & Sons, Ltd.     

New type of the nanostructured composite Si/C electrodes

The silicon-carbon composite films, with the silicon and carbon relative content from 39.5: 60.5 to 87: 13 and thickness 100–480 nm, are prepared by magnetron sputtering with layer-by-layer deposition of the components. The film structure is studied by using X-ray diffraction analysis and atomic-force microscopy. All studied films were found to be roentgen-amorphous. Despite the films were deposited in a layer-by-layer mode, they have granular structure, with the granules sized 10–80 nm. The lithium incorporation from LiClO₄ solution in propylene carbonate-dimethoxyethane mixture is studied. All studied films reversibly incorporate lithium; thus, they can serve as the basis for negative electrodes of lithium-ion batteries. The initial capacity of the composite-film electrodes is 1.5 to 2.8 A h/g. As the films are submerged to cycling, the capacity decreases, mainly due to the films’ insufficiently strong adhesion to the substrate, which results in the film defoliation. The most cycling-resistant are the thinnest films containing no less than 30% carbon. The capacity of the best samples is as high as 1 A h/g after 200 cycles.     

Structural properties of lithium thio-germanate thin film electrolytes grown by radio frequency sputtering

In this study, lithium thio-germanate thin film electrolytes have been successfully prepared by radio frequency (RF) magnetron sputtering deposition in Ar gas atmospheres. The targets for RF sputtering were prepared by milling and pressing appropriate amounts of the melt-quenched starting materials in the nLi(2)S + GeS(2) (n = 1, 2, and 3) binary system. Approximately 1 μm thin films were grown on Ni coated Si (Ni/Si) substrates and pressed CsI pellets using 50 W power and 25 mtorr (～3.3 Pa) Ar gas pressures to prepare samples for Raman and Infrared (IR) spectroscopy, respectively. To improve the adhesion between the silicon substrate and the thin film electrolyte, a sputtered Ni layer (～120 nm) was used. The surface morphologies and thickness of the thin films were determined by field emission scanning electron microscopy (FE-SEM). The structural properties of the starting materials, target materials, and the grown thin films were examined by X-ray diffraction (XRD), Raman, and IR spectroscopy.     

Using a low‐energy proton beam to cross‐link polymer films for the protection of inorganic substrates

Oxidation and corrosion effects on virgin copper and silicon substrates under ambient conditions largely restrict their electronic and microelectronic applications in industrial fields. In this paper, we first aimed to fabricate cross‐linked organic thin films on a copper substrate by bombardment with a low‐energy proton beam, thus enhancing the films' anti‐oxidization ability under ambient conditions, as confirmed using X‐ray photoelectron spectroscopy and atomic force microscopy. The anti‐oxidization ability of the cross‐linked polymer films on silicon substrate was also considered. Copyright © 2016 John Wiley & Sons, Ltd.     

Substrate-induced modulation of the Raman scattering signals from self-assembled organic nanometric films

Raman scattering signals recorded by microscopy from organic self-assembled monolayers (thin nanometric films of calibrated thickness) on silica substrates were found to be much stronger than those obtained from identical films assembled on bulk silicon substrates. This effect, observed in the backscattering geometry, is shown to result from interferences between the direct and reflected beams (including both the excitation and scattered radiation) in front of a smooth reflecting surface. Strong dependence of the effect on the distance between the sampled monolayer and the bulk silicon substrate allows enhancement of the Raman signals of organic monolayer films on silicon by factors up to approximately 70 by using appropriate silica spacers. The dependence of the Raman signal intensity on film thickness was also studied for thicker nanometric films comprising a series of self-assembled organosilane multilayers on bulk silicon and fused silica substrates, and the predicted deviation from linearity in the case of the silicon substrate is experimentally confirmed.     

Investigations on the influence of the substrate on the crystal structure of sputtered LiCoO2

The influence of the uppermost substrate layer on the structural properties of sputtered lithium cobalt oxide (LiCoO₂) is discussed in this work. For this purpose, bare, oxidized, and platinum-coated silicon wafers, as well as stainless steel and titanium sheets, were used as substrates. The resulting crystal structure of LiCoO₂ deposited on these substrates was analyzed and discussed. The LiCoO₂ thin films were deposited by RF magnetron sputtering with different film thicknesses. A subsequent annealing step at 700 °C was performed to induce the crystallinity of LiCoO₂. The crystal orientation was determined by X-ray diffraction. The obtained results show a strong dependency of LiCoO₂'s crystal structure on the surface the film is deposited on. However, the strong influence of the film thickness reported in previous publications could not be observed. If LiCoO₂ is deposited on the substrates with a metallic surface, a strong (003) preferential orientation is obtained for a wide range of film thicknesses. In contrast, sputtering of LiCoO₂ on bare and on oxidized silicon wafers results in a (101) dominated crystal structure for the different film thicknesses. These experiments show the importance of the characterization of LiCoO₂'s crystal structure in the intended battery setup.     

光响应性超疏水偶氮苯自组装多层膜的制备及性质研究

近年来,偶氮苯类化合物的光学顺反异构现象已引起人们的广泛关注[1~7].在紫外光照射下,偶氮苯由反式结构转变为顺式结构,引起分子的偶极矩发生变化,导致分子的吸收光谱、尺寸及表面能等均发生变化[7].偶氮苯表面能的改变可引起其表面浸润性发生变化.据文献[1~4]报道,偶氮苯膜在紫外光照射前后接触角最大改变了11°.浸润性是固体表面的一个重要特性,主要受固体表面的化学组成和微观几何结构(粗糙度)影响[8~11].通常,与水的接触角大于150°的表面称为超疏水表面;而与水的接触角小于5°的表面称为超亲水表面.本文以2-(4-偶氮苯基苯氧基)丙烯酸…     

Effect of the substrate nature on the formation of thin titanium dioxide films by molecular layering

Results of structural studies of titanium dioxide films synthesized on glass, silicon, and mica substrates by molecular layering are presented. An analysis of data furnished by electron and X-ray diffraction analyses and atomic-force microscopy of the samples in different growth stages revealed the effect of the substrate nature on the structure of the titanium oxide coatings synthesized.     

Sacrificial adhesion promotion layers for copper metallization of device structures

The adhesion of copper films to adjacent device layers including TiN, Ta, and TaN diffusion barriers is a crucial reliability issue for integrated circuits. We report that ultrathin layers of poly(acrylic acid) (PAA) prepared on barrier surfaces or on the native oxide of Si wafers dramatically increase the interfacial adhesion of Cu films deposited by the H2 assisted reduction of bis(2,2,7-trimethyloctane-3,5-dionato)copper in supercritical carbon dioxide. Similar improvements were achieved on Si wafers using a simple vapor phase exposure of the substrate to acrylic acid prior to metallization. The deposited films and the substrate/Cu interfaces were analyzed by X-ray photoelectron spectroscopy (XPS), electron microscopy, atomic force microscopy, and variable-angle spectroscopic ellipsometry. No trace of the adhesion layer was detected at the interface, indicating it was sacrificial at the deposition conditions used. Moreover, the presence and subsequent decomposition of the PAA layer during deposition substantially reduced or eliminated metal oxides at the substrate interface. For depositions on PAA-treated Si wafers, copper was present primarily as Cu0 at the interface and Si was present only as Si0. On PAA-treated Ta substrates, XPS analysis indicated Ta was present primarily as Ta0 at the metallized interface whereas Ta2O5 dominated the interface of samples prepared without the adhesion layers. The technique can be extended to patterned substrates using adsorption of acrylic acid or thermal/UV polymerization of acrylic acid.     

X-ray absorption of nitrogen-doped amorphous carbon films for determining sp2/sp3 bonding concentrations

A method of analyzing X-ray absorption spectra of nitrogen-doped amorphous carbon (a-C) samples was developed to determine their sp² bonding concentrations. The films under consideration are simultaneously deposited onto polytetrafluoroethylene (PTFE) polymer or silicon wafer substrates by hot wire plasma sputtering of graphite. sp² bonding concentrations of a-C films deposited on PTFE increase from 74% to 93% with growing nitrogen doping. Silicon substrate films yield the same general trend, but show that the near surface electronic structure of a-C films depends on the substrate.     

pH-driven assembly of various supported lipid platforms: a comparative study on silicon oxide and titanium oxide

Supported lipid platforms are versatile cell membrane mimics whose structural properties can be tailored to suit the application of interest. By identifying parameters that control the self-assembly of these platforms, there is potential to develop advanced biomimetic systems that overcome the surface specificity of lipid vesicle interactions under physiological conditions. In this work, we investigated the adsorption kinetics of vesicles onto silicon and titanium oxides as a function of pH. On each substrate, a planar bilayer and a layer of intact vesicles could be self-assembled in a pH-dependent manner, demonstrating the role of surface charge density in the self-assembly process. Under acidic pH conditions where both zwitterionic lipid vesicles and the oxide films possess near-neutral electric surface charges, vesicle rupture could occur, demonstrating that the process is driven by nonelectrostatic interactions. However, we observed that the initial rupturing process is insufficient for propagating bilayer formation. The role of electrostatic interactions for propagating bilayer formation differs for the two substrates; electrostatic attraction between vesicles and the substrate is necessary for complete bilayer formation on titanium oxide but is not necessary on silicon oxide. Conversely, in the high pH regime, repulsive electrostatic interactions can result in the irreversible adsorption of intact vesicles on silicon oxide and even a reversibly adsorbed vesicle layer on titanium oxide. Together, the results show that pH is an effective tool to modulate vesicle-substrate interactions in order to create various self-assembled lipid platforms on hydrophilic substrates.     

The structure and charge-storage capacitance of carbonized films based on silicon-polymer nanocomposites

New film materials for electrodes of lithium batteries were synthesized and studied. Thin-film silicon-polymer composites were prepared by vacuum cocondensation of silicon and the monomer onto a substrate cooled with liquid nitrogen; the polymerization and formation of the nanostructured composite were performed at room temperature. The films were carbonized by vacuum annealing. The film composition and microstructure were studied by AFM, SEM, Raman spectroscopy, and X-ray spectral microanalysis. It was shown that the polymer matrix became almost fully carbonized because of pyrolysis. The silicon concentration in the films varied from 2 to 5 at %. The concentration of silicon nanoparticles on carbonized film surfaces was ∼10⁶ cm⁻². Electrochemical experiments with lithium insertion into the composite films were performed in standard three-electrode cells under galvanostatic conditions. The specific capacitance of the films was measured. It was shown that the samples were capable of long-term cycling; the capacitance decreased by only 6% during the first 200 cycles; after 250 cycles, the capacitance still exceeded 80% of its initial value. The mechanism of lithium insertion into the films was discussed. It was concluded that long-term stability during cycling was caused by the presence of silicon both as nanoparticles and in the atomically dispersed form.