Showing papers on "Sputter deposition published in 2008"

Transparent conductive zinc oxide : basics and applications in thin film solar cells

Abstract: ZnO and Its Applications.- Electrical Properties.- Optical Properties of ZnO and Related Compounds.- Surfaces and Interfaces of Sputter-Deposited ZnO Films.- Magnetron Sputtering of ZnO Films.- Zinc Oxide Grown by CVD Process as Transparent Contact for Thin Film Solar Cell Applications.- Pulsed Laser Deposition of ZnO-Based Thin Films.- Texture Etched ZnO:Al for Silicon Thin Film Solar Cells.- Chalcopyrite Solar Cells and Modules.

Reactive Sputter Deposition

Abstract: Simulation of the Sputtering Process.- Electron Emission from Surfaces Induced by Slow Ions and Atoms.- Modeling of the Magnetron Discharge.- Modelling of Reactive Sputtering Processes.- Depositing Aluminium Oxide: A Case Study of Reactive Magnetron Sputtering.- Transport of Sputtered Particles Through the Gas Phase.- Energy Deposition at the Substrate in a Magnetron Sputtering System.- Process Diagnostics.- Optical Plasma Diagnostics During Reactive Magnetron Sputtering.- Reactive Magnetron Sputtering of Indium Tin Oxide Thin Films: The Cross-Corner and Cross-Magnetron Effect.- Reactively Sputter-Deposited Solid Electrolytes and Their Applications.- Reactive SputteredWide-Bandgap p-Type Semiconducting Spinel AB2O4 and Delafossite ABO2 Thin Films for "Transparent Electronics".- Oxide-Based Electrochromic Materials and Devices Prepared by Magnetron Sputtering.- Atomic Assembly of Magnetoresistive Multilayers.

Synthesis of vanadium dioxide thin films and nanoparticles

Abstract: Thin-film materials with 'smart' properties that react to temperature variations, electric or magnetic fields, and/or pressure variations have recently attracted a great deal of attention. Vanadium dioxide (VO2) belongs to this family of 'smart materials' because it exhibits a semiconductor-to-metal first-order phase transition near 340 K, accompanied by an abrupt change in its resistivity and near-infrared transmission. It is also of great interest in condensed-matter physics because it is a classic strongly correlated electron system. In order to integrate vanadium dioxide into microelectronic circuits, thin-film growth of VO2 has been studied extensively, and studies of VO2 nanoparticles have shown that the phase transition is size-dependent. This paper presents a broad overview of the growth techniques that have been used to produce thin films and nanoparticles of VO2, including chemical vapor deposition, sol–gel synthesis, sputter deposition and pulsed laser deposition. Representative deposition techniques are described, and typical thin-film characteristics are presented, with an emphasis on recent results obtained using pulsed laser deposition. The opportunities for growing epitaxial films of VO2, and for doping VO2 films to alter their transition temperature and switching characteristics, are also discussed.

Size effect of Ag nanoparticles on surface plasmon resonance

Abstract: This work studies the effect of the sized silver (Ag) nanoparticles on the optical property of SPR. Nanoparticles were prepared on fluorine-doped-tin-oxide (FTO) coated glass substrates by RF magnetron sputtering with various deposition times and the subsequent rapid thermal annealing (RTA) to control the particle size. To make the Ag films, Ag films of different thicknesses were first deposited on either glass or FTO substrate by a vacuum sputtering technique. Some of the samples founded nanoparticles by rapid thermal annealing. The substrates with and without nanoparticles were then sensitized by immersing them in a 0.2 mM N719 dye solution. Finally, the effect of the absorption coefficient was investigated by adsorbing it on fine silver Ag islands. The surface plasmon resonance enhanced the absorption by the sample with Ag nanoparticles above that of the sample without nanoparticles. In this study, the peak position of the surface plasmon characteristic absorption increased with the grain size of the nanoparticles in a red-shift. The structure and the quantity of Ag particles were very critical to the surface plasmon resonance effect.

Well-Aligned Cone-Shaped Nanostructure of Polypyrrole/RuO2 and Its Electrochemical Supercapacitor

Abstract: A new well-aligned cone-shaped nanostructure of polypyrrole (WACNP) has been successfully grown on Au substrate by using a simple, one-step, reliable, and template-free anodic deposition method. The formation mechanism of WACNP is proposed, in which the hydrogen bonding introduced from phosphate buffer solution (PBS) promotes the formation of a well-aligned nanostructure of polypyrrole (PPy), while the steric hindrance effect arisen from high concentration of pyrrole (Py) boosts its vertical alignment and further forms a cone-shaped nanostructure. The 3D, arrayed, nanotubular architecture coated with an ultrathin layer of RuO2 by the magnetron sputtering deposition method was tailored to construct a supercapacitor. The unique structure and design not only reduces the diffusion resistance of electrolytes in the electrode material but also enhances its electrochemical performance. The modification of RuO2 on WACNP results in a capacitance higher than that of WACNP by three times. The specific capacitance of...

A study of the oxidation behavior of CrN and CrAlN thin films in air using DSC and TGA analyses

Abstract: Freestanding CrNx and Cr1 − xAlxN films with two different Al atomic percentages with respect to the metal sublattice (x = 0.23 and x = 0.60) were produced by pulsed closed field unbalanced magnetron sputtering (P-CFUBMS). The dynamic oxidation behavior of the films has been characterized by thermal analysis using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The structure of the films at different thermal-annealing temperatures were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) in an effort to understand different phase transitions and oxidation reactions observed on the DSC curves. The peak temperatures of the main exothermic/endothermic oxidation reactions in the DSC signals at different heating rates were applied to the Kissinger model for determination of activation energies. The mechanical properties of the films at different heat-annealing states were measured by nano-indentation. It was found that the CrNx films oxidized in air after 600 °C by the dissociation of fcc (face center cubic)-CrN to h(hexagonal)-Cr2N and nitrogen and, after 900 °C by the dissociation of h-Cr2N to Cr and nitrogen in the film. The addition of Al to CrN film can further improve the oxidation resistance, especially for the high temperature above 800 °C. The oxidation degradation in two Cr-Al-N films started with dissociation of fcc-CrAlN to h-Cr2N and nitrogen in the film. The presence of thermally stable Al–N bonding in the fcc-CrAlN structure can suppress the reduction of nitrogen in the film. A dense (Cr,Al)2O3 layer (either amorphous or crystalline) formed at early oxidation stage (

Bottom-Gate Zinc Oxide Thin-Film Transistors (ZnO TFTs) for AM-LCDs

Abstract: In this paper, high-performance bottom-gate thin-film transistors (TFTs) with transparent zinc oxide (ZnO) channels have been developed. The ZnO film for active channels was deposited by RF magnetron sputtering. The crystallinity of the ZnO film drastically improved when it was deposited on a doublelayer SiOx/SiNx gate insulator. In order to achieve a ZnO TFT back-plane for liquid-crystal display (LCD) with the required pattern accuracy, dry etching of the ZnO film in an Ar and CH4 chemistry has been developed. The etching rate and tapered profile of the ZnO film could be controlled by the Ar content in the etching gases of Ar and CH4. The saturation mobility (musat) of the ZnO TFT strongly depended on a gate voltage. A musat of 5.2 & cm2 .(V .s)-1 at VGS = 40 V and VDS = 10 V, and an on/off-current ratio of 2.7 x 107 were obtained. A drain-current uniformity of plusmn7% was achieved within a radius of 20 mm from the substrate center. A 1.46 -in diagonal LCD with 61 600 pixels has been driven by the ZnO-TFT back-plane. A moving picture image was available on fabricated LCD driven by the ZnO TFTs.

Evaluation of Nitrogen Doping of Tungsten Oxide for Photoelectrochemical Water Splitting

Abstract: Thin films of tungsten oxide were fabricated by reactive RF magnetron sputtering for applications related to the direct solar splitting of water. To investigate band gap reduction by nitrogen doping, films were deposited with nitrogen introduced into the sputtering ambient at partial pressures in the range of 0−6 mTorr N2. For dilute doping (pN2 3 mTorr), the diffraction pattern shows the evolution of a new phase that shows an increase in scattering power relative to the pure WO3. For these samples, a reduction of the optical band gap to <2.0 eV is measured. However, the photocurrent density under AM1.5G illumination showed a degradation from 2.68 mA/cm2 for pure WO3 to 0.67 mA/cm2 for the nitrogen doped sample (6 mTorr). The poor photocurrent fo...

Epitaxial nanotwinned Cu films with high strength and high conductivity

Abstract: We report on the synthesis of epitaxial (single-crystal-like), nanotwinned Cu films via magnetron sputtering. Increasing the deposition rate from 1 to 4 nm/s decreased the average twin lamellae spacing from 16 to 7 nm. These epitaxial nanotwinned Cu films exhibit significantly higher ratio of hardness to room temperature electrical resistivity than columnar grain (nanocrystalline), textured, nanotwinned Cu films.

Influence of substrate bias, deposition temperature and post-deposition annealing on the structure and properties of multi-principal-component (AlCrMoSiTi)N coatings

Abstract: Nitride films are deposited from a single equiatomic AlCrMoSiTi target by reactive DC magnetron sputtering. The influence of the substrate bias and deposition temperature on the coating structure and properties are investigated. The bias is varied from 0 to − 200 V while maintaining a substrate temperature of 573 K. And the temperature is changed from 300 to 773 K whilst maintaining a substrate bias of − 100 V. From X-ray diffraction analysis, it is found that all the as-deposited coatings are of a single phase with NaCl-type FCC structure. This is attributed to the high mixing entropy of AlN, CrN, MoN, SiN, and TiN, and the limited diffusion kinetics during coating growth. Specific aspects of the coating, namely the grain size, lattice constant and compressive stress, are seen to be influenced more by substrate bias than deposition temperature. In fact, it is possible to classify the deposited films as large grained (~ 15 nm) with a reduced lattice constant (~ 4.15 A) and low compressive residual stresses for lower applied substrate biases, and as small grained (~ 4 nm) with an increased lattice constant (~ 4.25 A) and high compressive residual stresses for applied biases of − 100 V or more. A good correlation between the residual stress and lattice constant under various deposition conditions is found. For the coatings deposited at − 100 V, and at temperatures above 573 K, the hardness could attain to the range of 32 to 35 GPa. Even after annealing in vacuum at 1173 K for 5 h, there is no notable change in the as-deposited phase, grain size or lattice constant of the coatings but an increase in hardness. The thermal stability of microstructure is considered to be a result of the high mixing entropy and sluggish diffusion of these multi-component coatings. For the anneal hardening it is proposed that the overall bonding between target elements and nitrogen is enhanced by thermal energy during annealing.

Processing effects on the stability of amorphous indium gallium zinc oxide thin-film transistors

Abstract: Amorphous oxide semiconductors are attracting much attention due to their high electron mobility even when processed at low temperatures. One such material is indium gallium zinc oxide (IGZO). At a temperature of 175 °C, an IGZO thin-film transistor (TFT) is demonstrated to exhibit an incremental channel mobility (μinc) of ∼17 cm2 V−1 s−1 and a turn-on voltage (Von) of ∼1 V. Given this performance, IGZO seems well-suited for TFT applications. We report on how decreasing oxygen partial pressure and increasing RF power during the sputtering deposition decreases Von towards 0 V and increases mobility. Two types of stability, constant bias testing conditions and idle shelf life, are explored and it is found that stress test stability is closely correlated to the initial value of Von, with an initial Von of 0 V resulting in improved stability.

Transparent Al-Zn-Sn-O Thin Film Transistors Prepared at Low Temperature

Abstract: We have fabricated transparent bottom gate thin film transistors (TFTs) using Al-doped zinc tin oxide (AZTO) as active layers. The AZTO active layer was deposited by rf magnetron sputtering at room temperature. The AZTO TFT showed good TFT performance without postannealing. The field effect mobility and the subthreshold swing were improved by postannealing below 180 °C. The AZTO TFT exhibited a field effect mobility (μFET) of 10.1 cm2/V s, a turn-on voltage (Von) of 0.4 V, a subthreshold swing (S/S) of 0.6 V/decade, and an on/off ratio (Ion/Ioff) of 109.

Development of multifunctional photoactive self-cleaning glasses

Abstract: Glasses for architecture must have many functions in addition to their transparency. For example, the glasses with the functions, of self-cleaning, light control, UV reduction, anti-bacterial, energy conversion, and so on, will be used in buildings in the near future. This paper reviews some results on multifunctional photoactive glasses based on multi-layer coatings containing TiO2 film and other functional coatings developed by us recently. The self-cleaning of glasses can be realized by coating the photoinduced super-hydrophilic nanoporous thin films based on TiO2 photocatalysts via sol–gel route. A new method to enhance the photocatalytic activity of TiO2 thin films direct coated on soda-lime glass was developed by treating the films in acidic solutions. The films also have good photoinduced anti-bacterial properties. The doping of a small amount of silver into the TiO2 porous film can enhance its anti-bacteria effect without UV light irradiation. The TiO2 thin films by appropriate heat-treatment can operate as self-cleaning glass in the visible light region. The UV reduction self-cleaning glasses are prepared by magnetron sputtering two layers of TiO2–CeO2 and TiO2 thin films on soda-lime glasses. The TiO2–CeO2 thin films can cut all of UV light through adjusting the ratio of TiO2 and CeO2. The TiO2/TiN/TiO2 type multi-layer coated on glass substrate can act as low-E self-cleaning glass. The potential water-repellent coating based on TiO2 is discussed finally.

Thickness dependence of structural, electrical and optical behaviour of undoped ZnO thin films

Abstract: Undoped ZnO thin films of different thicknesses were prepared by r.f. sputtering in order to study the thickness effect upon their structural, morphological, electrical and optical properties. The results suggest that the film thickness seems to have no clear effect upon the orientation of the grains growth. Indeed, the analysis with X-ray diffraction show that the grains were always oriented according to the c (0 0 2)-axis perpendicular to substrate surface whatever the thickness is. However, the grain size was influenced enough by this parameter. An increase in the grain size versus the thickness was noted. For the electrical properties, measurements revealed behaviour very dependent upon thickness. The resistivity decreased from 25 to 1.5×10 −3 Ω cm and the mobility increased from 2 to 37 cm 2 V −1 s −1 when the thickness increased from 70 to 1800 nm while the carrier concentration seems to be less affected by the film thickness and varied slightly remaining around 10 20 cm −3 . Nevertheless, a tendency to a decrease was noticed. This behaviour in electrical properties was explained by the crystallinity and the grain size evolution. The optical measurements showed that all the samples have a strong transmission higher than 80% in the visible range. A slight shift of the absorption edge towards the large wavelengths was observed as the thickness increased. This result shows that the band gap is slightly decreases from 3.37 to 3.32 eV with the film thickness vary from 0.32 to 0.88 μm.

Pt- and Pd-nanoclusters functionalized carbon nanotubes networked films for sub-ppm gas sensors

Abstract: A gas chemiresistor, fabricated onto alumina using multi-walled carbon nanotubes (MWCNTs) networked films grown by radiofrequency plasma enhanced chemical vapor deposition (RF-PECVD) technology, is described for high-performance gas detection, at an operating temperature of 200 °C. Functionalizations of MWCNTs tangled bundle-films with nominally 5-nm thick Pt- and Pd-nanoclusters, prepared by magnetron sputtering, provide higher sensitivity for significantly enhanced gas detection of NO2, H2S, NH3, CO, up to a low limit of sub-ppm level. The measured electrical conductance of the functionalized MWCNTs upon gas exposures is modulated by charge transfer with p-type semiconducting characteristics. Pt- and Pd-nanoclusters functionalized MWCNTs gas sensors exhibited better performances compared to unfunctionalized MWCNTs, making them promising candidates for air-pollutants environmental monitoring. Simple electronic interface for the chemiresistor has been developed with a voltage output of the sensor signal.