Showing papers on "Evaporation (deposition) published in 2011"

Cu2ZnSnS4 thin film solar cells by fast coevaporation

Abstract: Solar cells based on kesterite-type Cu2ZnSnS4 (CZTS) were fabricated on molybdenum coated soda lime glass by evaporation using ZnS, Sn, Cu, and S sources. The coevaporation process was performed at a nominal substrate temperature of 550°C and at a sulfur partial pressure of 2–3 × 10−3 Pa leading to polycrystalline CZTS thin films with promising electronic properties. The CZTS absorber layers were grown copper-rich, requiring a KCN etch step to remove excess copper sulfide. The compositional ratios as determined by energy-dispersive X-ray spectroscopy (EDX) after the KCN etch are Cu/(Zn + Sn): 1.0 and Zn/Sn: 1.0. A solar cell with an efficiency of 4.1% and an open-circuit voltage of 541 mV was obtained. Copyright © 2010 John Wiley & Sons, Ltd.

Highly Sensitive Biosensing Using Arrays of Plasmonic Au Nanodisks Realized by Nanoimprint Lithography

Abstract: We describe the fabrication of elliptical Au nanodisk arrays as a localized surface plasmon resonance (LSPR) sensing substrate for clinical immunoassay via thermal nanoimprint lithography (NIL) and enhancement in the sensitivity of the detection of the prostate-specific antigen (PSA) using the precipitation of 5-bromo-4-chloro-3-indolyl phosphate p-toluidine/nitro blue tetrazolium (BCIP/NBT), catalyzed by alkaline phosphatase. Au nanodisks were fabricated on glass through an unconventional tilted evaporation, which could preserve the thickness of imprinted resists and create an undercut beneficial to the subsequent lift-off process without any damage to pattern dimension and the glass while removing the residual polymers. To investigate the optically anisotropic property of the LSPR sensors, a probe light with linear polarization parallel to and perpendicular to the long axis of the elliptical nanodisk array was utilized, and their sensitivity to the bulk refractive index (RI) was measured as 327 and 167 ...

Directly drawing self-assembled, porous, and monolithic graphene fiber from chemical vapor deposition grown graphene film and its electrochemical properties.

Abstract: Integration of graphene into macroscopic architectures represents the first step toward creating a new class of graphene-based nanodevices. We report a novel yet simple approach to fabricate graphene fibers, a porous and monolithic macrostructure, from chemical vapor deposition grown graphene films. Graphene is first self-assembled from a 2D film to a 1D fiberlike structure in an organic solvent (e.g., ethanol, acetone) and then dried to give the porous and crumpled structure. The method developed here is scalable and controllable, delivering tunable morphology and pore structure by controlling the evaporation of solvents with suitable surface tension. The fibers are 20–50 μm thick, with a typical electrical conductivity of ∼1000 S/m. The cyclic voltammetric studies show typical capacitive behavior for the porous graphene fibers with good rate stability and capacitance values ranging from 0.6 to 1.4 mF/cm2. Decorated with only 1–3 wt % MnO2, the graphene/MnO2 composites exhibit remarkable enhancement of c...

Tunable Localized Plasmon Transducers Prepared by Thermal Dewetting of Percolated Evaporated Gold Films

Abstract: Gold island films displaying localized plasmon properties were prepared by evaporation of just-percolated Au films onto glass substrates followed by annealing at ≥550 °C. Annealing induces depercolation and formation of large, single-crystalline, well-separated islands, partially embedded in the glass. Two dewetting mechanisms were identified, depending on the initial film morphology. The variability of island sizes and shapes provides effective means of tuning the position of the localized surface plasmon resonance (LSPR) band in a wide wavelength range. With an increase in the Au nominal thickness a transition occurs from transducers dominated by absorbance to ones dominated by scattering. Numerical simulations taking into account the shape and size distribution in actual island samples are in agreement with the experimental spectra. Refractive index sensitivity (RIS) measurements at a constant wavelength or at a constant extinction, tailored to the specific transducer, provide superior sensitivity to r...

Morphology Dependence of the Lithium Storage Capability and Rate Performance of Amorphous TiO2 Electrodes

Abstract: Amorphous TiO2 film electrodes of controllable and reproducible nanostructure and porosity were grown via evaporation of titanium in an oxygen ambient (i.e., reactive ballistic deposition (RBD)). The cyclability, rate capability, and Coulombic capacity of the electrodes depended on their morphology and porosity, which varied with the angle of incidence of the evaporated titanium. When films are deposited via evaporation at a glancing angle of 80° with respect to surface normal, nanocolumnar arrays with high internal porosity, high surface area, and optimal pore size and connectivity can be prepared. The optimized films deposited at 80° exhibit a reversible lithium capacity of ∼285 mA h g−1 at a low cycling rate (0.2 C) and maintain a reversible capacity near 200 mA h g−1 at rates as high as 5 C. About 70% of the theoretical capacity (235 mA h g−1) was retained with indiscernible capacity decay after 100 cycles at 1 C. The total charge stored in the TiO2 RBD films involves both surface capacitive and diffu...

Applications of the matrix-assisted pulsed laser evaporation method for the deposition of organic, biological and nanoparticle thin films: a review

Abstract: The matrix-assisted pulsed laser evaporation (MAPLE) technique offers an efficient mechanism to transfer soft materials from the condensed to the vapor phase, preserving the versatility, ease of use and high deposition rates of the pulsed laser deposition (PLD) technique. The materials of interest (polymers, biological cells, proteins, …) are diluted in a volatile solvent. Then the solution is frozen and irradiated with a pulsed laser beam. Here, important results of MAPLE deposition of polymer, biomaterials and nanoparticle films are summarized. Finally, the MAPLE mechanism is discussed. A review of experimental and theoretical works points out that the simple model of individual molecule evaporation must be abandoned. Solute concentration, solubility, evaporation temperature of solvents, laser pulse power density and laser penetration depth emerge as important parameters to explain the morphology of the MAPLE-deposited films.

One-step self-assembly, alignment, and patterning of organic semiconductor nanowires by controlled evaporation of confined microfluids.

Abstract: Organic semiconductors, which have unique electronic and optical properties that differ from those of their inorganic counterparts, have attracted intense attention for potential applications in optoelectronic devices such as organic lightemitting diodes (OLEDs), 2] organic field-effect transistors (OFETs), organic solar cells (OSCs), and gas sensors. 11] Numerous reports have indicated that organic semiconductor molecules predominantly aggregate and selfassemble into one-dimensional (1D) nanowires or nanorods along the direction of p–p stacking or other directional intermolecular interactions. Owing to excellent performance in carrier transport, such one-dimensional nanostructures may serve as attractive building blocks in future organic electronic applications. However, to fabricate practical devices on a large scale, a major challenge is to design a method to deposit and align a large number of such nanowires in a desired position. In most cases, nanostructures selfassembled directly from solution tend to be distributed in a macroscopically random fashion on the substrate. Disordered alignment of organic semiconductors may significantly increase the overall cost due to material consumption and also result in poor performance of electronic devices. Therefore, a facile deposition and patterning method for organic semiconductor molecules is highly desirable. To date, several strategies for alignment of 1D nanowires have been investigated, including the Langmuir–Blodgett technique, electric or magnetic field assisted alignment, dip coating, electrostatic alignment, and so on. However, these methods usually require an external facility and are limited in producing large-area ordered patterns. In recent years, evaporation-induced self-assembly (EISA) has been reported to prepare well-ordered 2D patterns. The EISA method depends on the simple fact that a drop of colloidal solution always leaves a ringlike deposit at the perimeter. During the evaporation process, the loss of solvent mainly occurs at the contact line, and an outward capillary flow carries the solvent and dispersed solute from the interior to the contact line. Therefore, the key parameter to achieve well-ordered 2D patterns is an efficient method to control the contact line. Recently, Lin et al. reported a simple method for controlling droplet evaporation in a confined geometry, which leaves behind well-organized gradient concentric ring patterns. With a spherical lens on the substrate, the contact line is well controlled and hence gradient concentric rings are obtained. However, the asprepared patterns are usually amorphous and no specific nanostructures are formed because of the hard-to-crystallize materials used in evaporation process, such as polymer and inorganic quantum dots (QDs). On the other hand, organic semiconductor molecules can easily self-assemble into 1D nanostructures by evaporation. 44] We have developed a facile method to prepare aligned organic nanowires on a solid substrate or liquid/liquid interface based on the EISA method. 45] With the aid of solvent evaporation, selfassembly of molecules and alignment of as-obtained nanostructures can be combined to produce a large-area ordered pattern of organic nanowires or films. However, the method wastes a lot of solvent, and the contact line is not easy to control. We have now integrated the EISA method with the concentric ring patterns of Lin et al. , so that simultaneous self-assembly, alignment, and patterning of organic semiconductor nanowires can be achieved in one step. Here we demonstrate such a facile approach to fabricate large-scale concentric arrays of nanowires by solvent evaporation in a confined geometry. N,N’-Dimethylquinacridone (DMQA) was selected as a nonvolatile solute in this experiment. It is an industrially important red organic dye with intense fluorescence, which is widely used in photovoltaic and other organic electroluminescent devices. It was synthesized according to the reported procedure and was purified twice by vacuum sublimation. Concentric ring patterns of DMQA nanowires were prepared from chloroform solutions of DMQA with concentrations of 0.2, 0.1, and 0.05 mmolL . The confined [*] Z. L. Wang, R. R. Bao, X. M. Ou, Prof. J. C. Chang, Prof. X. H. Zhang Nano-organic Photoelectronic Laboratory and Key Laboratory of Photochemical Conversion and Optoelectronic Materials Technical Institute of Physics and Chemistry Chinese Academy of Sciences, Beijing (China) E-mail: xhzhang@mail.ipc.ac.cn

Poly(oxyethylene) and ramie whiskers based nanocomposites: influence of processing: extrusion and casting/evaporation

Abstract: Polymer nanocomposites were prepared from poly(oxyethylene) PEO as the matrix and high aspect ratio cellulose whiskers as the reinforcing phase. Nanocomposite films were obtained either by extrusion or by casting/evaporation process. Resulting films were characterized using microscopies, differential scanning calorimetry, thermogravimetry and mechanical and rheological analyses. A thermal stabilization of the modulus of the cast/evaporated nanocomposite films for temperatures higher than the PEO melting temperature was reported. This behavior was ascribed to the formation of a rigid cellulosic network within the matrix. The rheological characterization showed that nanocomposite films have the typical behavior of solid materials. For extruded films, the reinforcing effect of whiskers is dramatically reduced, suggesting the absence of a strong mechanical network or at least, the presence of a weak whiskers percolating network. Rheological, mechanical and microscopy studies were involved in order to explain this behavior.

Solvent Evaporation Assisted Preparation of Oriented Nanocrystalline Mesoporous MFI Zeolites

Abstract: A solvent evaporation route to produce hierarchically porous zeolites with an oriented MFI nanocrystalline structure has been developed, and the method is scalable and low cost. In this method, hexadecyltrimethoxysilane is added to an ethanol solution containing zeolitic precursors. A dry gel is formed during the evaporation process. Subsequent hydrothermal treatments produce the hierarchically porous zeolite. High resolution transmission electron microscopy (HRTEM) studies suggest that misoriented zeolite nuclei are produced in the early stages of the hydrothermal treatment, but further reactions lead to single crystal-like aggregates composed of intergrowth nanocrystals with a mean interparticle pore diameter of 12 nm. Almost all Al atoms exist in tetrahedral sites, as confirmed by 27Al magic angle spinning nuclear magnetic resonance (MAS NMR). Variable temperature hyperpolarized (HP) 129Xe NMR spectroscopy suggests a fast molecular diffusion process from the interconnection between micro- and mesopores...

Tailored Single Crystals of Triisopropylsilylethynyl Pentacene by Selective Contact Evaporation Printing

Abstract: Organic semiconductors have great potential for application in numerous emerging low-cost and disposable electronic devices such as organic thin fi lm transistors (OTFTs), solar cells, memories, sensors, and fl exible displays. [ 1–3 ] One of the most urgent demands for the realization of such devices is the need to develop new organic semiconductors with a high carrier mobility as well as good and cost-effective processibility for highperformance devices. Chemically-modifi ed pentacene derivatives such as triisopropylsilylethynyl pentacene (TIPS-PEN) have received much attention, in particular in OTFTs. [ 4 , 5–14 ]

Surface Structures of Ultrathin TiOx Films on Au(111)

Abstract: Ultrathin films of titanium oxide were grown on (22 × √3)-reconstructed Au(111) surfaces by Ti evaporation in ultrahigh vacuum (UHV). Following Ti deposition onto room temperature Au substrates, the samples were oxidized at 600 °C in 10−6 Pa O2. Scanning tunneling microscopy (STM) images show that three different ordered TiOx film structures form as the amount of deposited Ti is increased. Auger electron spectroscopy (AES) was used to measure the stoichiometry of the films. The first structure occurs for Ti surface coverages of 0.5 ML Ti depositions and forms triangular shaped islands w...

High efficiency low temperature grown Cu(In,Ga)Se2 thin film solar cells on flexible substrates using NaF precursor layers

Abstract: We report a total-area efficiency of 15.9% for flexible Cu(In,Ga)Se2 thin film solar cells on polyimide foil (cell area 0.95 cm2). The absorber layer was grown by a multi-stage deposition process at a maximum nominal process temperature of 420°C. The Na was added via evaporation of a NaF layer prior to the absorber deposition leading to an enhanced Voc and FF. Growth conditions and device characterization are described. Copyright © 2011 John Wiley & Sons, Ltd.

In-situ observation of non-hemispherical tip shape formation during laser-assisted atom probe tomography

Abstract: It is shown by SEM imaging of the tip and by observing the emission pattern of the evaporated atoms that laser assisted evaporation in an atom probe can lead to nonhemispherical tip shapes and time-dependent nonuniform emission. We have investigated this nonuniformity by observing the change in field of view when using laser wavelengths of 515 nm and 343 nm on silicon. The change is monitored in situ by 0.5 nm thick silicon oxide. We demonstrate that the field of view can easily be changed by more than 10 nm and that the apparent oxide layer thickness can deviate substantially from its correct value. The dependence of the tip shape deformations and the reconstruction artifacts on the laser wavelength are explained through simulations of the laser-tip interaction and nonhomogeneous heating effects.

Laser damage study of nodules in electron-beam-evaporated HfO 2 /SiO 2 high reflectors

Abstract: A reactive electron beam evaporation process was used to fabricate 1.064 μmHfO2/SiO2 high reflectors. The deposition process was optimized to reduce the nodular density. Cross-sectioning of nodular defects by a focused ion-beam milling instrument showed that the nodule seeds were the residual particles on the substrate and the particulates from the silica source “splitting.” After optimizing the substrate preparation procedure and the evaporation process, a low nodular density of 2.7/mm2 was achieved. The laser damage test revealed that the ejection fluences and damage growth behaviors of nodules created from deep or shallow seeds were totally different. A mechanism based on directional plasma scald was proposed to interpret observed damage growth phenomenon.

Self-assembly of virus particles on flat surfaces via controlled evaporation.

Abstract: Dynamic self-assembly of nonvolatile solutes via controlled solvent evaporation has been exploited as a simple route to create a variety of hierarchically assembled structures. In this work, two glass slides were used to form a confined space in which a solution of a rodlike nanoparticle, tobacco mosaic virus (TMV), was evaporated to create large-scale stripe patterns. The height and width of the stripes are dependent on the TMV concentration. The large-scale-patterned surfaces can be applied to control surface hydrophobicity and direct the growth of bone marrow stromal cells. We systematically studied the effects of stripe width and height on surface hydrophobicity using optical microscopy, atomic force microscopy, and contact angle measurements. This technique offers a facile approach to form 2D patterns on a large surface from a wide range of proteins as well as other biomacromolecules.

Thermally evaporated SnS:Cu thin films for solar cells

Abstract: Cu-doped tin sulphide (SnS) films with a thickness of about 300 nm have been grown on glass substrates by thermal evaporation technique. Different Cu-doped SnS films were obtained by controlling the Cu evaporation time to roughly alter Cu-doping concentration in SnS films (from 5.7 to 23 atom ). Then they were annealed at a temperature of 250 C and a pressure of 5.0 10 -3 Pa for 90 min. The structural, optical and electrical properties of the films were characterised by X-ray diffraction, atomic force microscopy, ultraviolet visible near infrared spectrometer and Hall-effect measurement system. All the films are polycrystalline SnS with orthorhombic structure, and the crystallites in the films are all exclusively oriented along (111) direction. Annealing can optimise the crystallinity of all the films. With the increase of Cu-doping concentration, the grain size of the films becomes larger and larger, but the roughness decreases. Meanwhile, the evaluated direct bandgap E g of the SnS:Cu films initially decreases, reaches a minimum value of 1.38 eV with 15 atom Cu and then increases thereafter. The carrier concentration of the films increases sharply, while the resistivity of the films decreases straightly. All the films are of p -type conductivity. Using the optimised conditions, it is possible to prepare SnS:Cu thin films suitable for absorbers of thin film solar cells.