Nano Thin Films Research Articles

The Charge-Discharge Characteristics of Woody Carbon Modified with Fe<SUB>3</SUB>O<SUB>4</SUB> Nano Phase Using the Hydrothermal Method

Carbon materials decomposed by low temperature have a higher surface area and contain micro-holes and thus have a larger lithium storage space. In this study, the natural bamboo carbon powders were used as the experimental materials to process the hydrothermal method with the post-treatment. The results show that Fe3O4 thin films are formed on the surface of carbon particles. After charge-discharge testing, it was found that the powders not only increased the capacity, but also improved the irreversibility. With increasing the concentration (0:05� 0:25 M), the coating particles became coarse and the thickness of Fe3O4 nano thin films increased. Notably, the C-0.05Fe powder had a better charge-discharge cyclability. [doi:10.2320/matertrans.M2009312]

Flexible solar cells and modules

Flexible photovoltaic (PV) modules enable a wealth of applications in architecture, clothing integration, or other mobile power supplies. Moreover, a simple and cost-effective roll-to-roll manufacturing of thin film PV modules could in the long run compete with large area glass plate processing for the PV power market. Based upon the optimisation of amorphous, nano and protocrystalline silicon thin films, flexible solar cells grown at temperatures between 40°C and 110°C are described with power conversion efficiency up to 5%. A novel in situ series connection technique establishes monolithic integration of such cells into a PV module by locally masking thin film deposition, without any laser patterning or breaking of the continuous production flow. The first flexible modules from a non-optimised, single junction n-i-p structure demonstrate the function of the in situ series connection, and exhibit a total area efficiency of 3%, resulting from an average single cell efficiency of 3.3% and a total interconnection loss of only 15% over the 40 cm2 module area.

Characterization of optical properties of amorphous BaTiO 3 nanothin films

Amorphous barium titanate nanothin films were prepared by sol–gel dip-coating method. According to transmission spectrum, the refractive index and optical band gap of nanothin films have been determined. High transmission spectrum without any fluctuation in visible wavelength region was recorded. Experimental results indicated that the surface morphology of prepared nanothin films were improved and as a result of that, a better optical properties, less optical losses and higher band gap width were obtained in contrast with other reported data. It was found that optical propagation loss of BaTiO 3 nanothin film was much lower than normal polycrystalline BaTiO 3 thin film. It seems to us that, amorphous barium titanate nanothin films would be suitable for several applications.

Defects in nanothin crystalline layers and multilayer structures formed of them

Optical spectra of multilayer structures of nanothin films with nanocrystals of defined size and undoped crystals with given content of the impurities were compared. Relationships among the content of impurities, colloids and properties of the initial crystals, and multilayer structures were examined. The influence of surface effects on size-dependent properties of nanothin layers with LiF, CaF2, CdS and CdSe nanocrystals were investigated. Microstructure testing, optical absorption, photoluminescence and nonlinear optical experiments indicate that the possible origins of nanothin layers peculiarities are their purification and the metal excess accumulation in their boundaries.

Surface Modification of Titanium Using Nanothin Films of Copper for Biofouling Control

Biofouling is one of the major impediment in the use of titanium, which is otherwise excellent material with respect to corrosion resistance and mechanical properties, for seawater-cooled condensers of power plants. The routine chlorination treatment and sponge ball cleaning may not be successful to keep the titanium condenser tube clean over a period extending to years. This brings into focus the relevance of surface modification of titanium to improve the antimicrobial properties, which can effectively supplement the present treatment programmes. In this study antimicrobial thin film of copper (Cu) is developed on titanium surfaces, as copper is known to be very toxic to microorganisms and effectively kills most of the microbes by blocking the respiratory enzyme system. The preparation of nanocrystalline thin films of copper on titanium surfaces was done by pulsed DC magnetron-sputtering technique. Then this thin film was characterized using Glancing Incidence X-ray Diffraction (GIXRD) and Atomic Force Microscopy (AFM). Antimicrobial properties of these specimens were evaluated by exposure studies in seawater. Results showed two order decrease in the bacterial density on copper coated surface and epifluorescence micrographs depicted very few fluorescing cells and no biofilm formation clearly demonstrating the superior antibacterial capability of this nanocrystalline copper thin film.

Preparation of nano-thin films from conducting polymer by chemical vapor deposition method and its application for light emitting diodes (LED) and organic solar cells

It was demonstrated that a series of copolymers consisting of p-phenylenevinylene (PV) and p-phenyleneethylene (PE) units could be prepared from a single monomer, p-(methoxymethyl)benzyl chloride, via chemical vapor deposition polymerization (CVDP) method. The composition of the copolymers can be varied by altering the monomer activation temperature; the higher the temperature, the lower the content of the PV units becomes. The sufficient incorporation of the PE units into the poly(p-phenylenevinylene) backbone caused a significant blue shift in both photoluminescence and electroluminescence. The luminescence properties of the copolymer strongly depend on the amount of the PE units incorporated. The external quantum efficiency of the electroluminescence devices having the configuration of ITO/PEDOT-PSS/copolymer/Al-Li increased as the content of the PV units increased in the copolymer, which can be ascribed to the improved confinement of excitons. For the solar cell based on PPV derivative, the effect of the PCBM concentration on the performance of the solar cell is investigated. The results show that there is no interaction between the MEH-PPV and PCBM phase and the photoluminescence of MEH-PPV is quenched by the incorporation of PCBM. With increasing PCBM concentration, the short circuit current density and the overall energy conversion efficiency of the solar cell have been strongly improved.

Minimization of the effect of temperature on thin-film nano- and microelectromechanical systems and pressure sensors based on them

Methods for minimizing the effect of temperature on thin-film nano- and microelectromechanical systems and pressure sensors based on them are summarized. Properties are provided and different methods are described. Conclusions are derived from analyzing the methods about requirements for their comprehensive use.

Thin-film nano- and micro-electromechanical systems – the basis of contemporary and future pressure sensors for rocket and aviation engineering

Ways of improving information converters are considered, in particular, primary information converters (sensors). Problems are described that arise during the use of sensors in space rocket and aviation engineering. Designs are presented for thin-film nano- and micro-electromechanical systems that are the basis of contemporary and future tensoresistive pressure sensors. Areas of research are determined with the aim of minimizing the effect of critical destabilizing factors (temperature, vibration) within these systems and pressure sensors based upon them.

Thickness-Dependent Electronic Structure of Intermetallic CeCo2 Nanothin Films Studied by X-ray Absorption Spectroscopy

We report the electronic structure study of intermetallic CeCo2 nanothin films of various thicknesses by X-ray absorption near-edge structure (XANES) spectroscopy at Ce L3-, Co K-, and L2,3-edges. The Ce L3-edge absorption spectra reveal that the contribution of tetravalent Ce component increases with the film thickness, and all investigated nanothin films exhibit intermediate valence nature. Variation of the spectral intensities observed at the Co K-edge threshold implies modification in the Co 3d states and the enhancement of 3d-4f-5d hybridization. The Co 3d and Ce 4f occupation numbers were estimated from these spectroscopic results. The present study brings out how the surface-to-bulk ratio and the charge transfer between Ce and Co ions affect the electronic structure of nanothin films.

Electrostatic deposition of nanothin films on metal substrate

Electrostatic deposition of nanothin films on metal substrateThin solid film has been deposited by electrohydrodynamic spraying (electrospraying) onto a metal substrate. Electrospraying is a low-energy physical process in which tangential stress exerted by electric field on the surface of a liquid flowing form a capillary nozzle causes jet elongation, and the Coulomb repulsive forces disintegrate of this jet into fine droplets. By this method TiO2, ZnO, MgO, or Al2O3particles of size from 20 to 100 nm electrosprayed from a colloidal suspension were deposited onto a stainless steel substrate. The advantage that electrospray has over other methods for thin solid film production is that the growth rate of the layer is relatively high, the process can be carried out in an ambient atmosphere, in air or other gas, and at low temperature, without the need for a complex reactor and vacuum systems.

Electrical properties of strained nano-thin 3C–SiC/Si heterostructures

The effects of strain on the conduction mechanism in heterostructures consisting of strained nano-thin 3C–SiC films on Si are reported. These films exhibit significantly different electrical behaviours than the bulk material. Strained nano-thin 3C–SiC films were grown on n-type Si substrates by gas source molecular beam epitaxy. Reflection high-energy electron diffraction patterns show that these films are about 3% strained relative to the SiC lattice constant. In order to investigate the electrical properties of thin film structures, Al, Cr and Pt contacts to a nano-thin film 3C–SiC were deposited and characterized. The I–V measurements of the strained nano-thin films demonstrate back-to-back Schottky diode characteristics and the band offsets due to the biaxial tensile strain introduced within the 3C–SiC films were calculated and simulated. Based on the experimental and simulation results, an empirical model for the current transport in the heterostructures based on strained nano-thin films has been proposed. It was found that due to the band alignment of this structure, current is constrained at the surface which allows use of nano-thin films as surface sensors.

Preparation and characterization of nano and microcrystalline ZnO thin films by PLD

Nano and microcrystalline ZnO thin films were prepared on glass substrates using pulsed laser deposition technique under a vacuum of 3 × 10 −7 Torr at different laser power density. Composition analyses show that the films deposited at low laser power density have more structural defects than the film deposited at high laser power density. It confirms that the content of Zn in free-state decreased greatly at high laser power density. Atomic force microscopy analysis shows that the surface roughness of the deposited films increases with an increase in laser power density. X-ray diffraction analyses show that all the films are oriented along (0 0 2) direction independently on the laser power density applied. The structural quality increases with an increase in laser power density. It is due to the fact that the increase of laser power density leads to the enhancement of peak intensity. The increase of laser power density reduces the film transmission in the visible range of the spectra. The optical band gap value is found to be in the range from 3.42 to 3.39 eV. It shows that the optical band gap value decreases with an increase in laser power density. FTIR analysis shows that the hydrated oxide content in the deposited films decreases with an increase in laser power density.

Elastic Properties of Nano–Thin Films by Use of Atomic Force Acoustic Microscopy

AbstractAtomic force acoustic microscopy (AFAM) is a non-destructive method able to determine the indentation modulus of a sample with high lateral and depth resolution. We used the AFAM technique to measure the indentation modulus of film-substrate systems Msam and then to extract the value of the indentation modulus of the film Mf. The investigated samples were films of silicon oxide thermally grown on silicon single crystal substrates by use of dry and wet oxidation methods. The thickness of the samples ranged from 7 nm to 28 nm as measured by ellipsometry. Our results clearly show that the values of Msam obtained for the film-substrate systems depended on the applied static load and the film thickness. The observed dependency was used to evaluate the indentation modulus of the film. The values obtained for Mf ranged from 77 GPa to 95 GPa and were in good agreement with values reported in the literature.

Fabrication of InP nano inner cladding fiber and its amplification propertg based on quantum size effect

We uses improved chemical vapour deposition and drew fibres with InP nano thin films. Based on the hydrogen atom model, we calculate the corresponding size of the InP particle aB=8313 nm. By the quantum size-effect, we calculate the change of the energy band of particles with different sizes and the corresponding light absorption wavelength. From the system testing, the fibres have gain at 906—1044 nm, 1080—1491 nm and 1524—1596 nm. The results showed that the energy level of inner cladding materials creates a red shift when the thickness of thin-film is 5—50 nm. The fibre creates optical amplification.

Molecular assembled crosslinked self-doped polyaniline nano-thin films in application of electrochromic devices

Crosslinked self-doping polyaniline (SPANI) nano-thin films were prepared by using the molecular assembly process coupled with the copolymerization of aniline (AN) with the self-doping monomers DABSA (2,5-diaminobenzenesulfonic acid). DABSA were also used as surfactants and the di-amino groups rendered as chain extension/crosslinked sites in the simultaneous copolymerization and molecular assembly process. TEM and SEM results indicated that the morphology changes from micelles to nano-films. This SPANI nano-film is promising for the application in electrochromic devices.

Density functional theory study on stacking faults and twinning in Ni nanofilms

The energies of stacking and twinning faults in nanofilms of Ni with 7, 13 and 19-layers of (1 1 1) planes were determined using first-principles density functional theory total energy calculations. The ratios of energy barriers relevant to nucleation of dislocations and twinning as obtained from the generalized planar fault energy curves suggest an enhanced tendency for extended partial dislocation formation and twinning in the nano-thin films vis-a-vis the bulk.

Cubic SiC Nano-Thin Films and Nano-Wires: High Vacuum Metal-Organic Chemical Vapor Deposition, Surface Characterization, and Application Tests

Single-crystalline and epitaxial cubic silicon carbide (beta-SiC) nano-thin films have been deposited on Si(100) substrates at a sample temperature of approximately 900 degrees C using single source precursors by the thermal metal-organic chemical vapor deposition (MOCVD) method. Diethylmethylsilane and 1,3-disilabutane, which contain Si and C atoms in the same molecule, were used as precursors without any carrier or bubbler gas. Upon increasing the deposition temperature from 900 to 950 degrees C, beta-SiC nano-thin films with relatively small crystals and smoother surfaces were created on Si(100) substrates. Moreover, beta-SiC nano-wires with 40 approximately 100 nm in diameter have also been grown selectively on nickel catalyzed Si(100) substrates with dichloromethylvinylsilane by the MOCVD method. The deposition temperature in this case was as low as 800 degrees C under the pressure of 5.0 x 10(-2) Torr. It is worth noting that the initial growth rates of deposited beta-SiC nano-thin films and nano-wires strongly depend on the deposition temperature rather than the time. In order to test the possibility of applications of these materials for electronic components such as field emitter, MEMS, and high-power transistor, we fabricated the nanoelectronic devices using both beta-SiC nano-wires and nano-thin films. With these preliminary application tests, it is expected that SiC nanowires can be used as field emitter and nanoelectronic high-power transistor, and application of the SiC nano-thin films to MEMS is promising as well.

Optimization of growth conditions of ZnO nano thin films by chemical double dip technique

Zinc oxide (ZnO) nano thin films have been deposited by the chemical double-dip technique using aqueous ZnSO4 and NaOH solutions. The ZnO films were characterized in terms of surface morphology by x-ray diffraction, energy-dispersive x-ray analysis (EDX), the use of a scanning electron microscope (SEM) and atomic force microscope (AFM) for surface morphology. The films exhibited a smooth morphology. The chemical states of oxygen and zinc in the ZnO nano thin films were also investigated by x-ray photoelectron spectroscopy (XPS). In the present investigations, highly textured ZnO thin films with a preferential (002)-orientation were prepared on glass substrates. The deposition conditions were optimized to obtain device-quality films for practical applications.

The size and strain effects on the electric-field-induced domain evolution and hysteresis loop in ferroelectric BaTiO 3 nanofilms

The electric-field-induced evolution of stripe domains in BaTiO 3 nano-thin films is studied using molecular dynamics simulation method based on a shell model. The evolution of the 180° period stripe domains under a changing electric-field perpendicular to the film surface is investigated. It is found that both the thickness and the in-plane strain can influence the polarization distribution pattern and the domain switching process, and therefore affect the shape of hysteresis loop, which may be used to explain the discrepancy among existing experimental studies on the correlation between the thickness and the coercive field. Moreover, this simulation on the atomic-level domain evolution provides the microscopic insight of the domain switching, which can help us better understand the behaviors and properties of the ferroelectric thin films.

Interface and surface effects on ferroelectric nano-thin films

The effects originating from the interface or surface of a ferroelectric nano-thin film are accounted for in the phase field model devised. Two-dimensional simulations of domain structures and hysteresis loops were carried out. The simulation results show that transformation from an irregularly spaced to a regularly spaced 180° stripe domain structure occurs owing to competition and cooperation of the elastic and depolarizing energy in ferroelectric nano-thin films. This result is in agreement with recent experimental observations. The remnant polarization was found to decrease with decreasing film thickness, and the “actual” hysteresis loop, which was first studied by Bratkovsky and Levanyuk [Bratkovsky AM, Levanyuk AP. Appl Phys Lett 2006;89:253108.], was plotted to characterize the domain structures of ferroelectric nano-thin films and the imperfect screening effects of the electrodes.