MgO thin films have been prepared on Si substrates by a novel and simple sol-gel method using magnesium nitrate and collodion as starting material. Solutions consisting of magnesium nitrate in a mixture of collodion and ethanol were spin-coated onto silicon substrates. It was found that collodion was a necessary component to form stable sols and the crystallization and structures were clearly dependent on the amount of the collodion and the annealing temperature. The MgO thin films with good crystallization were obtained after annealing at 800°C. Meanwhile, the microstructure of the MgO films was examined by transmission electron microscopy and atomic force microscopy. 相似文献
A method is described to incorporate metals into fluorocarbon polymer films produced in a plasma environment by a simultaneous etching and polymerization process. The emphasis of this work is on a molybdenum-perfluoropropane system, and films produced in this manner were found to contain as much as 20% molybdenum by weight. Some aspects of their structure are discussed. 相似文献
Slow release of corrosion-inhibitive paint pigments is a great challenge to the paint industry, because of the urgent need to replace chromate-containing pigments. Unfortunately, most effective corrosion inhibitors are too soluble for use in paints. In this paper, we present a novel method to modify selected water-soluble organic inhibitor particles to achieve the purpose of slow release. A plasma polymerization technique was used to deposit an ultrathin polymer film on the surface of the inhibitor particles. Infrared spectroscopy (FTIR), time-of-flight secondary ion mass spectroscopy (TOFSIMS), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX), transmission electron microscopy (TEM), and contact angle data confirmed the successful deposition of the polymer thin film on the inhibitor particles. Using immersion tests and electrochemical techniques, we have demonstrated that the encapsulated water-soluble inhibitor can slowly release into the environment to protect a metal as needed. This technique is a feasible and promising method to promote the replacement of chromate pigments in paints. 相似文献
The growing mechanism and the structure of thin polystyrene film by the glow discharge-indirect method are discussed. A theoretical relationship between the growth rate of polymerized film and the discharge condition is deduced on the basis of Poll's model, taking the charge transport processes in the discharge space into consideration: 1) the ambipolar diffusion, 2) the recombination of charges forming the ion sheath, and 3) the effect of stray capacity. Substitution of possible values of physical parameters on the gaseous plasma into the theoretical relation give a reasonable growth rate which agrees well with the experimental results. From NMR, ESR, and dielectric experiments, it is suggested from the molecular and morphological structure of the film that small molecules and free radicals remain, but most of the film consists of a three-dimensional mesh structure. 相似文献
The deposition of GaN thin films in a nitrogen–hydrogen microwave plasma using Ga(CH3)3as a gallium precursor was investigated. The deposit was identified as stoichiometric GaN by XPS and XRD. The substrate was dielectrically heated in the microwave discharge and the substrate temperature was lower than that in usual thermal MOCVD. The NH radicals, which were the primary N-atoms precursors, and fragments of Ga(CH3)3were identified in the plasma by OES. The NH radical formation and the decomposition of Ga(CH3)3in the plasma may be one of the reasons for the lower deposition temperature of GaN. The position dependence of the substrate temperature showed similar tendency as the position dependence of the electron temperature. The plasma state contributes to the deposition of GaN thin films. The deposited GaN exhibited a wide optical band gap of 3.4eV. Material highly oriented along the c axis was detected in the deposit, and a PL spectrum which has the band head at about 450 mm was obtained.相似文献
CdS thin films were prepared by chemical-bath-deposited method and the effect of tempera-ture and time on the properties of CdS thin films was studied. Independent of the deposited temperature, the growth was mainly controlled by the ion-by-ion growth mechanism at the beginning of the film deposition, then the cluster-by-cluster mechanism came to be domi-nant. The growth rate increased faster with the increasing of temperature until the thickness reached the limitation, then thickness instead become thinner. The scanning electron micro-scope results revealed that the morphology of the CdS film changed from pinholes to rough,inhomogeneous surface with increasing deposition time and deposition temperature. The X-ray diffraction results showed the film structure was a mixture of two phases: hexagonal and cubic, and it was very important to controll deposition time to the film's crystal phase. All films in depth of approximate 100 nm existed above 65% transmittance, the absorption edge became 〝red-shift〞 with temperature rising. At 60 and 70 oC, with 20 min deposited-time, the energy band gap was more than 2.42 eV and decreased with time, while at 80 and 90 oC, the energy band gap was less than 2.42 eV and increased little when the time changed from 10 min to 15 min at 80 oC. 相似文献
A series of {(9,9‐dioctylfluorene)0.7?x‐(dibenzothiophene‐S,S‐dioxide)0.3‐[4,7‐bis(2‐thienyl)‐2,1,3‐benzothiadiazole]x} (PFS30‐TBTx), where x represents the minor percentage of the red emitter 4,7‐bis(2‐thienyl)‐2,1,3‐benzothiadiazole (TBT) randomly incorporated into the copolymer backbone, is investigated in order to follow the energy transfer from PFS30 to TBT moieties. The emission of the donor poly[(9,9‐dioctylfluorene)0.7‐(dibenzothiophene‐S,S‐dioxide)0.3 identified by PFS30 and peaking at 450 nm, is clearly quenched by the presence of the red TBT chromophore emitting at 612 nm, with an isoemissive point observed when the spectra are collected as a function of temperature. A plot of the ratio between the TBT and PFS30 emissions as a function of the reciprocal of temperature gives a clear linear trend between 290 and 200 K, with an activation energy of 20 meV and showing a turn over to a non‐activated regime below 200 K. Picosecond time‐resolved fluorescence decays collected at the PFS30 and TBT emission wavelengths, show a decay of the PFS30 emission and a fast build‐in, followed by a decay, of the TBT emission, confirming that the population of the TBT excited state occurs during the PFS30 lifetime(~600 ps). The population of the TBT excited state occurs on a time regime around 150 ps at 290 K, showing an energy barrier of 20 meV that turns over to a non‐activated regime below 200 K in clear agreement with the steady‐state data. The origin of the activation barrier is attributed to the presence of physical and energetic disorder, affected by fast thermal fluctuations that dynamically change the energy landscape and control the exciton migration through the polymer density of states.相似文献
Pb(Zr0.53Ti0.47)O3 (PZT) films of 10 to 50 m in thickness were prepared by a new sol-gel process using an interfacial polymerization technique. The interfacial polymerization process is that an alkoxide precursor solution is poured on the surface of water in a container to form a gel film at the interface between the two immiscible liquids. The precursor solution was prepared by adding PZT alkoxide solution, PZT powders coated with Pb5Ge3O11 (PG), and a surfactant into hexane solvent. After the polymerization at the interface, the gel films were gently placed on a silicon substrate by draining the water in the container. The gel films containing PZT powders were sintered at 950°C for 10 min to obtain crystallized PZT films. The remanent polarization of a PZT thick film was 33.1 C/cm2. The piezoelectric d33 constant measured with a Mach-Zehnder interferometer was 225 pm/V and was independent of frequency from 0.2 to 3 kHz. 相似文献
The self‐organization of pre‐assembled aggregates is an efficient stepwise strategy for fabricating nanostructures with a second level of hierarchy. Herein, we report that anisotropic spindle‐like micelles, self‐assembled from polypeptide graft copolymers with rigid backbones, can serve as ideal pre‐assembled subunits for constructing one‐dimensional materials with hierarchical structures. By adding organic solvents and dialyzing against water, reactive points can be generated at the ends of the spindle‐like micelles, which subsequently drive the anisotropic micelles to grow as rods in a chain and eventually self‐assemble into hierarchical nanowires in a stepwise manner. The second self‐assembly step is a hierarchical process that resembles step polymerization. Hierarchical structures can be precisely synthesized by this new type of polymerization. These nanostructures can be tailored by the activity of the reactive points, which depends on the nature of the solvent and the molecular architecture. 相似文献
A series of polymer chemosensors containing naphthalimide signal moiety and imide recognition moiety for the selective detection of fluoride ions (F−) were synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization. The polymer chemosensors display obvious absorption and fluorescence variations upon the addition of F−, which can be observed by both naked eyes and optical responses. The polymers showed higher fluorescence enhancement than its monomer, and the polymers with higher molecular weight have higher sensitivity than those with lower molecular weight. Other halide anions are found to hardly induce any variation of either the absorption or fluorescence spectra.
Calcium substituted lead titanate thin films have been prepared by a sol-gel method, deposited by spin-coating, and thermally
treated so as to obtain a perovskite structure. Two types of thermal treatments were given, differing in the heating rate,
which in conventional treatments was of some 10°C/min, and in rapid treatments >500°C/min. With rapid heating, materials are
obtained in which greater polarizations are commuted and bias fields are smaller. This, together with the fact that additional
(undesired) phases are not observed by X-ray diffractometry when rapid treatments are used, shows that these are to be preferred
over conventional treatments. 相似文献
Surface modification of poly(tetrafuoroethylene) (PTFE) film by plasma polymerzation and deposition of glycidyl methacrylate (GMA), in the presence and absence of Ar or O2 plasma pre-activation, was carried out to enhance the adhesion with polyimides (PI) film in the presence of an epoxy adhesive. For deposition carried out at low RF power, a high epoxide concentration was preserved in the plasma-polymerized GMA (pp-GMA) layer on PTFE (pp-GMA-PTFE). However, high adhesion strength of the PI/pp-GMA-PTFE laminate was obtained only in the presence of O2 plasma pre-activation of the PTFE substrates prior to plasma polymerization and deposition of GMA. In the absence of any plasma pre-activation or in the presence of Ar plasma pre-activation, the deposited pp-GMA layer on the PTFE surface could be readily removed by solvent extraction. The adhesion enhancement of the PI/pp-GMA-PTFE laminates in the presence of O2 plasma pre-activation was attributed to the preservation of the epoxide functional groups in the pp-GMA layer, the curing of the GMA chains into the matrix of the epoxy adhesive, and the covalent bonding of the pp-GMA layer on the PTFE surface. 相似文献
Silicon carbonitride films were synthesized by plasma enhanced chemical vapor deposition using silyl derivatives of asymmetric dimethylhydrazine, (CH3)2HSiNHN(CH3)2 and (CH3)2Si[NHN(CH3)2]2, as molecular precursors. The film material consists of an amorphous matrix with nanocrystalline inclusions. Indexing of synchrotron radiation Xray diffraction patterns suggests that the structure of the nanocrystals is tetragonal with lattice parameters a = 9.6 and c = 6.4. Xray photoelectron spectra indicate that Si—N and C—N sp3 hybrid bonds are predominant. The absence of G or Dmodes in Raman spectra, which are otherwise typical of structures possessing sp2 bonding, provides further support for the tetragonal structure of the nanocrystals. 相似文献
The homogeneous transition metal oxide Fe2O3 thin films are synthesized in a modified sol-gel process by spin coating. The third order nonlinear optical susceptibility of the film is about 2 × 10–9 esu at 488 nm wavelength by the z-scan method with a 180 femtosecond pulse laser beam. The film is expected to be useful for the application of nonlinear optical devices. 相似文献
In this paper, we attempt to formally establish the chemistry of a vapor-gel process for the low temperature deposition of thin films. A number of applications of such a process will be discussed mostly on a theoretical basis, with the exception of one or two particular aspects that we have experimentally demonstrated so far. The essential components of the deposition apparatus will be described in detail along with some discussions on their operation conditions. Finally, we conclude this paper by systematically comparing the vapor-gel method to other well-known thin film fabrication techniques including the sol-gel method. 相似文献