微波功率对(100)晶面取向金刚石薄膜制备的影响

以H2和CH4的混合气体为气源,使用实验室自制10 kW新型装置,采用微波等离子体化学气相沉积法(MPCVD)在Si(100)基体上沉积金刚石薄膜,然后采用扫描电镜(SEM)、Raman光谱以及XRD光谱,以得到表面形貌、样品质量和晶面取向等信息,由此获得微波功率对金刚石薄膜取向的影响。结果表明,微波功率对金刚石膜的质量、表面形貌和晶面取向都有明显地影响,随着微波功率升高,金刚石薄膜的形貌变得规则,薄膜中Isp3/Isp2由1.52提高到6.58,其沉积晶面的I(100)/I(111)由0.38提高到3.93。当微波功率为4 900 W时,所得沉积样品晶面以(100)为主,形貌规则,纯度很高。     

From nanowires to cubes of CdO: Ethanol gas response

The cadmium oxide (CdO) thin films have been synthesized by chemical bath deposition (CBD) method from an aqueous cadmium acetate solution for different time periods. The effect of film thickness on structural, morphological and wettability properties have been investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and contact angle measurements. The chemically deposited CdO thin films were polycrystalline with face centered cubic crystal structure. The average crystallite size was found to be in the range of 28-31 nm. An interesting morphological transition from nanowires to microcubes was observed with change in deposition time from 25 to 100 h at room temperature. The deposited CdO films exhibit excellent sensing properties against ethanol at 673 K. The 0.8239 μm thick films comprising nanowires deposited for 75 h showed the better ethanol gas performance as compared to other films.     

MgB2超导薄膜的化学气相沉积

探索了采用化学气相沉积法，在LaAlO3单晶基片上原位制备了MgB2超导薄膜。X射线衍射(XRD)分析表明薄膜的相纯度不理想，扫描电子显微镜(SEM)观察表明薄膜的表面比较粗糙，用标准四引线法测得薄膜的起始转变温度（Tconset)为30K，零电阻温度(Tc0)为18K。     

Fabrication of a hydrogen sensor using palladium-coated silver dendrites formed electrochemically

Here, we report a cost-effective method for making palladium-coated silver (Ag) dendrites for hydrogen sensing. Ag dendrites, 50–150 nm in diameter, are made through electrochemical migration in a micro-electrochemical cell. They are then coated with a 200-nm-thick palladium (Pd) thin film. The hydrogen sensor made of palladium-coated Ag dendrites showed better hydrogen sensing characteristics than ones made of a pure Pd film. This is due to the large surface area of the Ag dendrites. Heat-treatment made the hydrogen sensing curve more stable, which is attributable to an alloying effect between Pd and Ag.     

Synthesis and characterization of electroless deposited Co-W-P thin films as diffusion barrier layer

Selective barriers against copper diffusion deposited by electroless reaction are interesting in term of electromigration. In this article, the barrier layer of cobalt-tungsten-phosphorus (Co-W-P) alloy was electroless deposited onto copper substrates for ultra large scale integration (ULSI) applications. The Co-W-P thin film was formed directly on copper, without a palladium catalyst, from citrate plating baths with sodium hypophosphite as reducing agents. The influence of tungsten addition on the barrier properties has been studied and the optimum conditions to obtain films with the highest oxidation protection have been determined. Co-W-P layer properties such as chemical composition, surface morphology, and phase structure and corrosion behavior have been investigated. The deposited CoWP layer showed higher oxidation and corrosion resistance and soft magnetic behavior.     

TiO2 nanocrystal films for sensing applications based on surface plasmon resonance

Spherical and rod shaped organic-capped TiO₂ nanocrystals (NCs), prepared by a hydrolytic route, were deposited as thin films and characterized by means of atomic force microscopy (AFM), X-ray diffraction (XRD) and surface plasmon resonance (SPR). SPR was assessed as transduction technique in order to test the sensing ability of the prepared films for detection of alcohol vapours as a function of NC shape and thermal treatment. The performances of the TiO₂ nanocrystals were found to be dependent on the titania nanocrystal morphology and thermal treatment conditions, pointing to the beneficial effect of a rod-like shape as compared to a spherical one, and to a possible role of the titania surface organic coating in enhancing the sensor response.     

A layer-wise topographic study of a polymeric light-emitting diode: indium-tin oxide/poly (2,3-diphenyl-p-phenylene vinylene) / Ag

Scanning tunneling microscopy was used to characterize surface topographies relevant to polymeric light-emitting diodes (LEDs) whose active medium is a thin film of poly(2,3-diphenyl-p-phenylene vinylene) (DP-PPV). We performed a sequence of topographic studies on an indium-tin oxide (ITO) substrate, a DP-PPV film deposited on the ITO substrate, and a Ag layer of thickness of about 100 Å as evaporated on the DP-PPV film. ITO showed a granular structure, DP-PPV exhibited a fibrous-like bundled structure, and the Ag layer formed clusters whose surface roughness was comparable to the layer thickness. The different surface topographies were quantified by using the scaling of the height-height correlation functions.     

Using nanoparticles as direct-injection printing ink to fabricate conductive silver features on a transparent flexible PET substrate at room temperature

Conductive metallic features that are flexible could have application in integrated circuits, ranging from large-area electronics to low-end applications. This paper shows the creation of conductive silver thin film and wire on the transparent flexible polyethylene terephthalate (PET) substrate by a room-temperature chemical reduction process. One-step synthesis and spectroscopic characterizations of size-controlled silver nanoparticles are also described. Transmission electron microscopy, Fourier transform infrared spectroscopy, thermal gravimetric-mass analysis, X-ray photoelectron spectroscopy and synchrotron radiation X-ray diffraction were used to characterize the dodecanoate-protected silver nanoparticles. Silver metal film and wire were produced by soaking the dodecanoate-protected silver nanoparticle film and wire, which were prepared, respectively, by spin-coating and by directly drawing with a commercial Epson T50 inkjet printer onto the flexible PET substrate using Ag nanoparticles suspended in cyclohexane (10 wt.%) as the ink, in an aqueous solution containing 80% N₂H₄. The resistivities of the Ag films are actually lower compared with the Ag thin films prepared by other conventional chemical routes, such as using silver salts as metallo-organic precursors. It is suggested that the use of nanoparticles as a precursor may be an explanation for the lower resistivity.     

Optical strain detectors based on gold/elastomer nanoparticulated films

The application of two different optical effects is demonstrated for the detection of strain applied to elastomeric films. On one hand, dense coatings made of silica-coated gold nanoparticles (Au@SiO₂ NPs), which are built up onto poly(dimethylsiloxane) (PDMS) elastomeric films, using the layer-by-layer (LbL) method, provide intense surface plasmon resonance (SPR) absorption. On the other hand, polystyrene spheres can be deposited as ordered monolayers to create patterned PDMS films with well-defined light diffraction. Both effects were used to monitor the structural damage of such PDMS films upon stretching, remaining both physical phenomena (absorption from the gold film and diffraction from the ordered structure) active for optical sensing applications in the early detection of structural damage in critical infrastructures.     

In-situ high temperature stress analysis of Ti(C,N) coatings on functionally graded cemented carbides by energy dispersive synchrotron X-ray diffraction

We report on in-situ high temperature X-ray thermal stress analysis of chemically graded Ti(C,N) coatings deposited on functionally graded cemented carbide substrates by chemical vapor deposition. The in-situ analyses were performed by energy dispersive X-ray diffraction using synchrotron radiation. The samples were subjected to one individual thermal cycle from room temperature to 800 °C and cooled down to room temperature again. The stresses were determined using the sin²ψ method in the Ψ geometry combined with scattering vector measurements in order to unravel the compositional influences on the lattice strain distributions. It was found that the Ti(C,N) thin film presents a cycling residual stress behavior (tensile–compressive–tensile) connected to the temperature cycle. If top-blasting is applied on the thin film layer after the coating process, compressive stresses are generated. These compressive stresses induced by top-blasting are partially released after the high temperature thermal cycle. The functionalization of the cemented carbide substrate influences the level of stresses developed in the coating. The stress behavior as a function of temperature is discussed with the support of finite element modeling by introducing a bi-linear plasticity model to calculate strain relationships which is in agreement with the synchrotron measurements.     

Influence of organic gate dielectrics on the performance of pentacene thin film transistors

The electronic transport of polycrystalline pentacene thin film transistors is investigated. The thermally evaporated pentacene films prepared on organic dielectrics like benzocyclobutane exhibit mobilities comparable with inorganic dielectrics like thermal oxide and plasma enhanced chemical vapor deposited silicon nitride. To gain insights in the electronic transport behavior of the organic thin film transistors (TFTs) the I/V characteristics were simulated by a one-dimensional density-of-states transistor model. The experimental data can be described by using a broad distribution of acceptor-like states deep in the bandgap and a narrow distribution of donor-like states close to the valance band. The influence of the different dielectrics on the defect distribution and the electronic transport will be discussed.     

Tarnish protection of silver by octadecanethiol self-assembled monolayers prepared in aqueous micellar solution

Silver will tarnish when it is exposed to the sulfur polluted atmosphere. Self-assembled monolayers are an efficient, invisible and protective film against tarnishing. SAMs prepared by the adsorption of octadecanethiol onto silver in aqueous micellar solution are explored. The silver was first degreased by acetone in an ultra-sonicate bath, followed by activation in 10% sulphuric acid solution, then, immersed in aqueous micellar solution with 0.15 mol/L octadecanethiol and 40 g/L Cetane trimethyl ammonium bromide (CTAB), Triton X-100 (TX-100), Polyoxyethylene lauryl ether (PLE) or Pluronic PE6400 during 5 min at 60 °C. The film was characterized by contact angles, FT-IR, XPS and AFM. The film was totally composed of octadecanethiol and was influenced by the surfactant in the thickness and tilt angle. The anti-tarnishing ability of the film on the silver was evaluated by electrochemical measurements in 0.5 mol/L NaCl solution containing 10 mmol/L Na₂S. The protection efficiency reached 91.9% The electro-oxidation reaction process was reduced substantially in 0.5 mol/L NaOH solution. EIS data proved that the inhibition of the monolayers was marked and the coverage of the film was more than 94.5%. The color, gloss and reflectance of silver with SAMs were almost similar to the bare silver. It was found that after 48 h accelerated tarnishing test, the protection of the thiol film remained efficient. The film controlled markedly the transfer of ion to the surface and the sulfuration rate of silver was reduced substantially.     

Enhanced optical modulation due to SPR in gold nanoparticles embedded WO3 thin films

Surface plasmon resonance (SPR) phenomenon of metal-dielectric composite thin films formed by embedding the noble metal nanoparticles in a dielectric matrix offers a high degree of flexibility and enables many applications such as surface enhanced spectroscopes, numerous biological and chemical sensing fields. A remarkable enhancement in optical modulation after embedding the gold nanoparticles in a reticulated mesh like matrix of WO₃ thin films was observed. WO₃ films were prepared onto the conducting ITO coated glass substrates by a novel pulsed spray pyrolysis technique (PSPT). A reticulated mesh like morphology of WO₃ was achieved by optimizing the deposition parameters of PSPT and the gold nanoparticles were embedded in the WO₃ matrix by a drop casting method. Enhancements in electrochromic properties of WO₃ in terms of optical modulation (ΔOD), coloration efficiency (η) and response times (t_c and t_b) were attributed to the assistance of SPR in gold nanoparticles during coloration and electric field induced quenching of SPR during bleaching.     

Corrosion Protection of Electro-Galvanized Steel by Ceria-Based Coatings: Effect of Polyethylene Glycol (PEG) Addition

A cerium oxide thin layer was deposited onto galvanized steel by cathodic electrodeposition from 0.1 M concentrated cerium nitrate solution. In this work, the influence of polyethylene glycol (PEG) addition on the composition and morphology of the deposits is examined. The results showed that the addition of PEG to the cerium nitrate solutions leads to a decrease in the cracks in the deposits by decreasing the hydrogen reduction reaction and by decreasing the film thickness which provided enhanced corrosion protection. Moreover, the substrate dissolution reaction is inhibited.     

Transparent conductive thin films based on chemically assembled single-walled carbon nanotubes

Transparent conductive thin films were fabricated by the chemical assembly of carboxylated single-walled carbon nanotubes (ca-SWNTs) onto aminosilane-modified glass plates. The ca-SWNTs were deposited with multilayer structures by amidation reaction between the carboxylic acid groups of ca-SWNTs and amino groups of linker molecules with the aid of coupling agents. Unlike the chemically assembled SWNT layers reported thus far, these SWNT assemblies have high-density structures and excellent surface adhesion due to direct chemical bonding to their substrates, which results in high electrical conductivity. The covalent bonds of the SWNT thin film were characterized by X-ray photoelectron spectroscopy, and the structures of SWNTs in the conductive thin film were analyzed by Raman spectroscopy. Imaging by scanning electron microscopy shows that the SWNT thin film has a uniform morphology with high-density multilayer structure over large areas, and UV–vis spectroscopy analysis shows that the transmittance of SWNT thin film in visible light region is excellent and further improved to greater than 90% upon thermal treatment at 250 °C. The electrical resistivities of the ca-SWNT thin film were found to be 5–10 Ω cm, which was improved to 0.2–0.4 Ω cm by the thermal treatment. The work function measured by photoelectron spectroscopy in air was found to be 5.12 eV.     

Absence of superconductivity in Nd_(0.8)Sr_(0.2)NiO_x thin films without chemical reduction

The recently reported 9-15 K superconductivity in Nd_(0.8)Sr_(0.2)NiO_2/SrTi03 heterostructures that were fabricated by a soft-chemical topotactic reduction approach based on precursor Nd_(0.8)Sr_(0.2)NiO_3 thin films deposited on SrTiO_3 substrates,has excited an immediate surge of research interest.To explore an alternative physical path instead of chemical reduction to realizing superconductivity in this compound,using pulsed laser deposition,we systematically fabricated 63 Nd_(0.8)Sr_(0.2)NiO_x(NSNO) thin films at a wide range of oxygen partial pressures on various oxide substrates.Transport measurements did not find any signature of superconductivity in all the 63 thin-film samples.With the oxygen content reducing in the NSNO films by lowering the deposition oxygen pressure,the NSNO films are getting more resistive and finally become insulating.Furthermore,we tried to cap a 20-nm-thick amorphous LaAlO_3 layer on a Nd_(0.8)Sr_(0.2)NiO_3 thin film deposited at a high oxygen pressure of 20 Pa to create oxygen vacancies on its surface and did not succeed in obtaining higher conductivity either.Our experimental results together with the recent report on the absence of superconductivity in synthesized bulk Nd_(0.8)Sr_(0.2)NiO_2 crystals suggest that the chemical reduction approach could be unique for yielding superconductivity in NSNO/SrTiO_3 heterostructures.However,SrTiO_3 substrates could be reduced to generate oxygen vacancies during the chemical reduction process as well,which may thus partially contribute to conductivity.     

钢筋腐蚀监测的光纤传感技术

采用电化学方法制备了用于混凝土结构钢筋腐蚀监测的光纤传感器,该方法基于电沉积于光纤纤芯上的敏感膜能够将腐蚀信息传递给光纤内传导的光波,从而获取腐蚀信息,实现腐蚀监测。证明了采用光纤传感技术监测混凝土结构筋腐蚀是可行的。     

铁表面四苯基卟啉蒸汽沉积膜形成和结构研究

在铁表面进行四苯基卟啉蒸汽沉积处理,获得了具有一定耐蚀性的膜层。采用ＸＰＳ,ＳＥＭ和ＳＴＭ技术对成膜过程及膜的结构成进行了研究,发现在铁表面上进行Ｈ２蒸汽沉积处理形成沉膜时,首先在样品表面形成比较均匀覆盖的基础层。     

Poly(N-vinylcarbazole) (PVK) deposited by evaporation for light emitting diodes thin films structures

The sandwich structures have been obtained by deposition of organic thin films on commercial tin oxide. Then the organic films were covered by a thin aluminium film. All the films were deposited by evaporation. The organic component was either a thin (150 nm) poly(N-vinylcarbazole) (PVK) film or a bilayer constituted of a thin PVK layer covered with a 8-hydroxyquinoline, aluminium (Alq₃). When PVK is deposited by classical thermal evaporation there is a shortening effect of the chain length, however, the main properties of the vinyl-carbazole molecules are preserved. These films are photoluminescent with blue light emission. The I–V characteristics of the sandwich structures are typical of such organic sample. They exhibit a rectifying behaviour, with a forward polarisation when the SnO₂ electrode is positively biased. They also exhibit electroluminescence. When a single PVK film is used, the signal is quite faint. It is improved when an organic bilayer is used. However, simultaneously there is a red shift of the signal.     

Microstructures and electrical conductance of silver nanocrystalline thin films on flexible polymer substrates

Using sputtering technique, silver nanocrystalline thin films were deposited on two different polymer substrates, namely pretreated nylon and polyester fabrics, under identical conditions. It is found that the difference of the electrical conductance between the two samples is quite large. The highest conductivity obtained from the coated nylon fabric is 2.4 × 10⁷ Sm^− 1, indicating the feasibility to fabricate wearable electrodes using silver coated fabrics. However, the electrical conductance of the coated polyester fibre is found to be lower by six orders of magnitude. Transmission electron microscopy reveals that the silver grains coated on the polyester fibre are spatially separated while the silver grains coated on the nylon fibre are connective. The pre-deposition surface conditions of the fibres are suggested to be responsible to the remarkable differences in the electrical conductance and microstructures of the silver nanocrystalline films.