Cluster-assembled Tb-Fe nanostructured films produced by low energy cluster beam deposition

Cluster-assembled Tb-Fe nanostructured films were prepared by the low energy cluster beam deposition method. The microstructure, magnetization and magnetostriction were investigated for the films. It is shown that the film is assembled by monodisperse spherical nanoparticles with average diameter of ～30?nm which are distributed uniformly. The cluster-assembled Tb-Fe nanostructured films exhibit good magnetization and possess giant magnetostriction with saturation value of ～1060 × 10(-6), much higher than that of the common Tb-Fe films. The origin of good magnetization and giant magnetostriction for the cluster-assembled Tb-Fe nanostructured film was discussed. The present work opens a new avenue to produce the nanostructured magnetostrictive alloy in application of a nano-electro-mechanical system.     

Glancing angle deposition of crystalline zinc oxide nanorods

Zinc oxide nanorod films produced by glancing angle deposition were fabricated within the parameter space defined by the process variables pitch (nanorod growth per substrate rotation), deposition rate, and throw distance to investigate the effect these parameters have on morphology and crystallinity. Statistical analysis was used to identify important relationships. Final film morphology depends on both pitch and deposition rate, where two growth regimes distinguished by deposition rate are observed and interpreted as arising from competition between geometric shadowing and crystalline growth kinetics. Optimal growth conditions for nanostructured films of isolated zinc oxide nanorods occurred for pitch values of approximately 1 nm to 10 nm. Pole-figure measurements confirm that the films consist of oriented single-crystal nanorods. Films deposited at all pitch values between 0.001 nm to 6.5 μm are crystalline and textured, and greater texturing is achieved for conditions of decreased surface diffusion.     

High-rate deposition of nanostructured SiC films by thermal plasma PVD

With ultrafine SiC powder as starting material, thermal plasma physical vapor deposition has been applied successfully to the deposition of SiC films on Si substrates. The control of processing parameters such as substrate temperature, powder feeding rate and composition of plasma gases, permits the deposition of SiC films on a wide area of around 400 cm² with a variety of microstructures from amorphous to nanostructured and with various morphologies from dense to columnar. For the nanostructured case, the crystallite size was between 3 and 15 nm and the maximum deposition rate calculated based on the actual deposition duty time reached 200 nm/s. The deposition mechanism is discussed briefly.     

Field emission from nanostructured AlN/GaN films on Si substrate prepared by pulsed laser deposition

Nanostructured AIN/GaN films with different thickness are synthesized on Si substrates by pulsed laser deposition (PLD). GaN and AIN single-layer films are also deposited for comparison. It is found that the turn-on field of the nanostructured AIN/GaN films is considerably decreased 2 orders of magnitude than that of single-layer films. The improvement of field emission (FE) characteristics is attributed to the quantum structure effects, which supplies a favorable location of electron emission and enhances tunneling ability. We show that by tuning the thickness of AIN/GaN, various FE characteristics can be obtained. It indicates that the optimal thickness of the nanostructured AIN/GaN films exists for their best field emission performance.     

Characterization of nanostructured hydroxyapatite prepared by Nd:YAG laser deposition

Pulsed laser deposition, under dry and water vapor conditions, was employed to synthesize nanostructured hydroxyapatite films by pulsed laser deposition (PLD) of chlorapatite target for the purpose of coating metallic bone implants by this material. A pulsed Nd:YAG laser operating at a wavelength of 1064 nm and emitting 9 ns pulses was used for deposition. AFM microscopy, FTIR spectroscopy, optical microscopy, adhesion and microhardness measurements were conducted to characterize the films. The in vitro test for the synthesized hydroxyapatite was performed using simulated body fluid (SBF). The results showed a successful transformation of the chlorapatite to hydroxyapatite films characterized by all the HAp peaks with 60 nm root mean square roughness, (80–327) nm grain size, and a microhardness of 512 HV.     

High-rate deposition of nanostructured SiC films by thermal plasma PVD

With ultrafine SiC powder as starting material, thermal plasma physical vapor deposition has been applied successfully to the deposition of SiC films on Si substrates. The control of processing parameters such as substrate temperature, powder feeding rate and composition of plasma gases, permits the deposition of SiCfilms on a wide area of around 400 cm² with a variety of microstructures fromamorphous to nanostructured and with various morphologies from dense to columnar. For the nanostructured case, the crystallite size was between 3 and 15 nm and the maximum deposition rate calculated based on the actual deposition duty time reached 200 nm/s. The deposition mechanism is discussed briefly.     

Indium tin oxide nanowhisker morphology control by vapour-liquid-solid glancing angle deposition

A new growth technique for indium tin oxide nanowhiskers with increased control over feature size and spacing is reported. The technique is based on a unique combination of self-catalysed vapour-liquid-solid (VLS) growth and glancing angle deposition (GLAD). This VLS-GLAD technique provides enhanced control over nanowhisker morphology as the effect of typical VLS growth parameters (e.g.?flux rate, temperature) is amplified at large deposition angles characteristic of GLAD. Spatial modulation of the collimated growth flux controls trunk width, number and orientation of branches, and overall nanowhisker density. Here we report the influence of growth conditions (including deposition angle, flux rate, nominal pitch and substrate temperature) on nanowhisker morphology, with specific focus on the effect of large deposition angles. Sheet resistance and transmission of the films were measured to characterize their performance as transparent conductive oxides. Hybrid nanostructured films grown in this study include high surface area nanowhiskers protruding from a conductive film, ideal for transparent conductive electrode applications.     

Nanostructured nickel oxide films prepared by chemical vapor deposition and their electrochromic properties

The influence of the deposition conditions on the structural features and electrochromic properties of nickel oxide (NiO) films prepared by chemical vapor deposition has been investigated. NiO films have been prepared on fluorine doped tin oxide (FTO) coated glass substrates from nickel-acetylacetonate precursor and their electrochromic properties have been studied by cyclic voltammetry in a 0.1 M KOH solution at room temperature. Films exhibiting only the NiO phase were obtained at deposition temperatures higher than 450 degrees C in a wide range of reactor pressures (0.13 to 66.6 kPa). Particularly, NiO films prepared at 500-550 degrees C from 0.13 to 53.3 kPa are transparent in nature and exhibit a crystallite size varying from 10 to 60 nm. An appreciable anodic electrochromic change from transparent to black coloured resulted from a very porous surface morphology and film thickness of about 3.5 microm. The electrochromic change was maintained over 3000 switching cycles. Nanostructured 3.5 microm-thick NiO films showed a maximum difference in optical transmittance of about 40% in the near-infrared region. These results make the nanostructured NiO films comparables with those prepared by other deposition techniques.     

Reversible wettability of ZnO nanostructured thin films prepared by pulsed laser deposition

This work reports on the photoinduced wettability changes of high quality nanostructured ZnO films grown on Si by pulsed laser deposition (PLD) under different growth parameters. The wetting behavior of the resulting films can be reversibly switched from hydrophobic to hydrophilic, through alternation of UV illumination and dark storage. The kinetics of this wetting transition are studied by monitoring the time evolution of the corresponding contact angles. Finally, the influence of the film properties over the observed wetting response is discussed.     

Vacuum arc deposition of nanostructured multilayer coatings for biomedical applications

In recent years, the smart materials have attracted much attention due to their unusual properties such as shape memory effect and pseudoelasticity, being widely used for biomedical implants. These materials contain certain amounts of nickel, titanium and others which are not adequate for surgical implants and prosthesis. In the work reported here, two types of nonostructured multilayer coatings (TiN/ZrN, ZrN/Zr) used to prevent the ions release from shape memory alloys were investigated. For comparison, the TiN and ZrN monolayers were also examined. The films were deposited onto nickel-titanium based alloy (Ti-Ni-Nb) and Ni substrates by vacuum arc deposition technique under various deposition conditions. The concentrations of dissolved ions in Ringer solution for uncoated and coated Ni samples were determined to examine the benefic barrier effect of these coatings for ions release from shape memory alloys. In order to have a more complete characterization of the investigated coatings, other properties such as elemental and phase composition, morphology, texture, microhardness, and adhesion were studied. For all coatings, the concentrations of dissolved ions were lower that those measured in the case of the uncoated specimens. The nanostructured multilayer films exhibited the best mechanical and anticorrosive properties.     

One-minute microwave-assisted chemical bath deposition of nanostructured ZnO rod-arrays

Microwave-assisted chemical bath deposition (MACBD) is an emerging route for rapid synthesis of films and nanostructured particles. In this paper we report MACBD of ZnO rod-array films on bare glass substrates from an aqueous bath of tetra ammonium zinc complex. The deposition time is reduced to about 1 min as compared to around 60 min for conventional CBD. X-ray diffraction study shows that as-deposited films are uniaxially out-of-plane textured along the c-axis. Scanning Electron Microscopy reveals that the films consist of elongated elliptical tapered rods of diameters 250 to 350 nm. Atomic Force Microscopy shows that the films consist of about 350 nm grains. The RMS roughness is about 60 nm. The energy band gap is 3.27 eV as estimated from optical data. The films are n-type with electrical conductivity of 1 × 10^− 4 S/cm.     

Control of morphology and optical properties of PbS nanostructured thin films by deposition parameters: study of mechanism

PbS thin films were grown on glass substrates by chemical bath deposition (CBD) using lead nitrate, thiourea and sodium hydroxide in aqueous solutions at three different temperatures (22, 36 and 50?°C). The microstructure and morphology evolution of the films were investigated using X-ray diffraction, scanning electron microscopy and atomic force microscopy. Optical properties were studied using UV–Vis–IR spectroscopy. The results indicate that temperature plays an important role in controlling the morphology and optical properties of nanostructured PbS thin films through changing deposition mechanism. The active deposition mechanism changed from cluster to ion-by-ion mechanism with an increase in deposition temperature from 22 to 50?°C, and consequently, film properties such as morphology, optical absorption and preferred orientation changed completely.     

Chemical vapour deposition of coatings

Chemical Vapour Deposition (CVD) of films and coatings involve the chemical reactions of gaseous reactants on or near the vicinity of a heated substrate surface. This atomistic deposition method can provide highly pure materials with structural control at atomic or nanometer scale level. Moreover, it can produce single layer, multilayer, composite, nanostructured, and functionally graded coating materials with well controlled dimension and unique structure at low processing temperatures. Furthermore, the unique feature of CVD over other deposition techniques such as the non-line-of-sight-deposition capability has allowed the coating of complex shape engineering components and the fabrication of nano-devices, carbon-carbon (C-C) composites, ceramic matrix composite (CMCs), free standing shape components. The versatility of CVD had led to rapid growth and it has become one of the main processing methods for the deposition of thin films and coatings for a wide range of applications, including semiconductors (e.g. Si, Ge, Si_1-xGe_x, III-V, II-VI) for microelectronics, optoelectronics, energy conversion devices; dielectrics (e.g. SiO₂, AlN, Si₃N₄) for microelectronics; refractory ceramic materials (e.g. SiC, TiN, TiB₂, Al₂O₃, BN, MoSi₂, ZrO₂) used for hard coatings, protection against corrosion, oxidation or as diffusion barriers; metallic films (e.g. W, Mo, Al, Au, Cu, Pt) for microelectronics and for protective coatings; fibre production (e.g. B and SiC monofilament fibres) and fibre coating. This contribution aims to provide a brief overview of CVD of films and coatings. The fundamental aspects of CVD including process principle, deposition mechanism, reaction chemistry, thermodynamics, kinetics and transport phenomena will be presented. In addition, the practical aspects of CVD such as the CVD system and apparatus used, CVD process parameters, process control techniques, range of films synthesized, characterisation and co-relationships of structures and properties will be presented. The advantages and limitations of CVD will be discussed, and its applications will be briefly reviewed. The article will also review the development of CVD technologies based on different heating methods, and the type of precursor used which has led to different variants of CVD methods including thermally activated CVD, plasma enhanced CVD, photo-assisted CVD, atomic layer epitaxy process, metalorganic assisted CVD. There are also variants such as fluidised-bed CVD developed for coating powders; electrochemical vapour deposition for depositing dense films onto porous substrates; chemical vapour infiltration for the fabrication of C-C composites and CMCs through the deposition and densification of ceramic layers onto porous fibre preforms. The emerging cost-effective CVD-based techniques such as electrostatic-aerosol assisted CVD and flame assisted CVD will be highlighted. The scientific and technological significance of these different variants of CVD will be discussed and compared with other vapour processing techniques such as Physical Vapour Deposition.     

Low-temperature growth of nanostructured diamond films

Nanostructured diamond films are grown on a titanium alloy substrate using a two-step deposition process. The first step is performed at elevated temperature (820 degrees C) for 30 min using a H2/CH4/N2 gas mixture to grow a thin (approximately 600 nm) nanostructured diamond layer and to improve film adhesion. The remainder of the deposition involves growth at low temperature (< 600 degrees C) in a H2/CH4/O2 gas mixture. The continuation of the smooth nanostructured diamond film growth during low-temperature deposition is confirmed by in situ laser reflectance interferometry, atomic force microscopy, micro-Raman spectroscopy, and surface profilometry. Similar experiments performed without the initial nanostructured diamond layer resulted in poorly adhered films with a more crystalline appearance and a higher surface roughness. This low-temperature deposition of nanostructured diamond films on metals offers advantages in cases where high residual thermal stress leads to delamination at high temperatures.     

ZnO nanostructured film deposition using the separated pulsed laser deposition (SPLD) assisted by electric and magnetic drift motion

We have developed the separated pulsed laser deposition (SPLD) technique to prepare high quality ZnO based films exhibiting uniform and droplet-free properties. This SPLD consists of an ablation chamber and a deposition chamber which can be independently evacuated under different ambient gases.The gas species and the pressures in both chambers can be arbitrarily chosen for the specific deposition such as nanostructured films and nanoparticles. The ablation chamber is a stainless steel globe and the deposition chamber is a quartz tube connected to a metallic conic wall with an orifice. We used a KrF excimer laser with λ = 248 nm and 25 ns pulse duration. The different gas conditions in two chambers allow us to realize optimal control of the plasma plume, the gas phase reaction and the film growth by applying the bias voltage between the conic wall and the substrate under the magnetic field. We can expect that at appropriate pressures the electric and magnetic field motion (E × B azimuthal drift velocity) gives significant influences on film growth.We have deposited ZnO thin films at various pressures of ablation chamber (Pab) and deposition chamber (Pd). The deposition conditions used here were laser fluence of 3 J/cm², laser shot number of 30,000, Pab of 0.67-2.67 Pa (O₂ or Ar), Pd of 0.399-2.67 Pa (O₂), and substrate temperature of 400 °C. Particle-free and uniform ZnO films were obtained at Pab of 0.67 Pa (Ar) and Pd of 1.33 Pa (O₂). The ZnO film showed high preferential orientation of (002) plane, optical band gap of 2.7 eV, grain size of 42 nm and surface roughness of 1.2 nm.     

Fabrication of scandium stabilized zirconia thin film by electrostatic spray deposition technique for solid oxide fuel cell electrolyte

A cost-effective and promising simple deposition method, electrostatic spray deposition (ESD), was used to fabricate dense scandium stabilized zirconia (ScSZ) thin films. The effect of solvent mixtures on their surface morphology was investigated. The films deposited using a mixed ethanol-butyl carbitol solvent with high boiling point showed higher smoothness compared with those deposited using ethanol and a mixture of ethanol and ethylene glycol, respectively. Single-phase ScSZ dense films were formed within 2 h at a low deposition temperature of 450 °C. Analysis of as heat-treated films using scanning electron microscope and atomic force microscope also indicated the formation of the uniform, smooth and dense thin films even at a low densification temperature. Furthermore, the ScSZ film deposited under the optimal condition showed the maximum in electrical conductivity of approximately 0.33 S cm^− 1 at a low operating temperature of 800 °C.     

Microwave irradiation-assisted method for the deposition of adherent oxide films on semiconducting and dielectric substrates

We report a method for the deposition of thin films and thick coatings of metal oxides through the liquid medium, involving the microwave irradiation of a solution of a metal-organic complex in a suitable dielectric solvent. The process is a combination of sol-gel and dip-coating methods, wherein coatings can be obtained on nonconducting and semiconducting substrates, within a few minutes. Thin films of nanostructured ZnO (würtzite) have been obtained on Si(100), glass and polymer substrates, the nanostructure determined by process parameters. The coatings are strongly adherent and uniform over 15 mm × 15 mm, the growth rate ∼ 0.25 μm/min. Coatings of nanocrystalline Fe₂O₃ and Ga₂O₃ have also been obtained. The method is scalable to larger substrates, and is promising as a low temperature technique for coating dielectric substrates, including flexible polymers.     

Influence of the deposition parameters on the morphology and electrical conductivity of PANI/PSS self-assembled films

The influence of deposition parameters, namely polymer concentration and pH of the deposition solution, cleaning, and drying steps on the morphology and electrical characteristics of polyaniline and sulfonated polystyrene (PANI/PSS) nanostructured films deposited by the self-assembly technique is evaluated by UV–Vis spectroscopy, optical and atomic force microscopy, and electrical resistance measurements. It is found that stirring the cleaning solution during the cleaning step is crucial for obtaining homogenous films. Stirring of the cleaning solution also influences the amount of PANI adsorbed in the films. In this regard, the drying process seems to be less critical since PANI amount and film thickness are similar in films dried with N₂ flow or with an absorbent tissue. It is observed, however, that drying with N₂ flow results in rougher films. As an additional point, an assessment of the influence of the deposition method (manual versus mechanical) on the film characteristics was carried out. A significant difference on the amount of PANI and film thickness between films prepared by different human operators and by a homemade mechanical device was observed. The variability in film thickness and PANI adsorbed amount is smaller in films mechanically assembled.     

Optical fiber sensor based on oblique angle deposition

The technique of oblique angle deposition has been extended to the fabrication of nanostructured metal coatings on the tips of standard silica optical fibers by thermal evaporation. The coatings are initiated as metal island films, which grow into extended rodlike structures as the deposition continues. The nanorod coatings demonstrate excellent surface-enhanced Raman scattering performance with variability of less than 10% as shown by direct measurements off the fiber tip with thiophenol as a test analyte. However, in the remote sensing configuration, the nanorod structures perform no better than thin metal island films. This appears to be mainly due to reduced transmission when nanorod lengths exceed ~100 nm. Moreover, the variability of remote measurements is increased to 18%. This is believed to be due to variations in coupling efficiency.