Bi surfactant effects of Co/Cu multilayered films prepared by sputter deposition

The influence of a Bi surfactant layer on the structural and magnetic properties of Co/Cu multilayers grown onto Cu(1 1 0) buffer layer by RF magnetron sputtering has been studied. The results of X-ray diffraction revealed the initial deposition of a 2.0 Å-thick Bi layer onto the Cu buffer layer prior to the deposition of the Co/Cu multilayer yielded high-quality fcc-(1 1 0) oriented epitaxial films. The X-ray photoelectron spectra revealed that Bi was segregated at around the top of the surface. Therefore, Bi was concluded to be an effective surfactant to enhance the epitaxial growth of Co/Cu(1 1 0) multilayer. The maximum giant magnetoresistance and antiferromagnetic interlayer coupling ratios of the Co/Cu multilayers were increased by using the Bi surfactant layer.     

X-ray reflectivity study on gold films during sputter deposition

We performed in-situ X-ray reflectivity measurements of gold films during sputter deposition on polished silicon substrates. The measurements were performed at several substrate temperatures and under two argon pressures. The gold surfaces were also examined by scanning tunneling microscopy after deposition to obtain their real-space topographic images. These images were used to complement the X-ray reflectivity measurements in determining the effect of argon pressure on the gold surface and its height-height difference functions. An approximation for height-height difference functions was employed to analyze the X-ray reflectivity data. The measured interface width during growth followed a simple power law, consistent with recent theoretical results of dynamic scaling behavior. The scaling exponents, however, do not agree well with predictions based on some models in 2 + 1 dimensions.     

Modeling the reactive sputter deposition of Ti-doped VO_x thin films

In this paper an original numerical model,based on the standard Berg model,is used to simulate the growth mechanism of Ti-doped VOx deposited with changing oxygen flow during reactive sputtering deposition.Ti-doped VOx thin films are deposited using a V target with Ti inserts.The effects of titanium inserts on the discharge voltage,deposition rate,and the ratio of V/Ti are investigated.By doping titanium in the vanadium target,the average sputtering yield decreases.In this case,the sputter erosion reduces,which is accompanied by a reduction in the deposition rate.The ratio between V content and Ti content in the film is measured using energy-dispersive x-ray spectroscopy(EDX).A decrease in the vanadium concentration with the increasing of the oxygen flow rate is detected using EDX.Results show a reasonable agreement between numerical and experimental data.     

Reactive sputter deposition and metal–semiconductor transition of FeS films

FeS polycrystalline films were prepared on float glass by radio-frequency reactive sputtering. X-ray diffraction, scanning electron microscopy, Rutherford backscattering, and secondary ion mass spectroscopy were used to characterize the films. The effects of the deposition parameters, such as sputter power and substrate temperature, on the morphological structure and on the metal–semiconductor phase transition of FeS films were investigated. It has been found that the films show a substrate temperature dependent preferential orientation and phase-transition temperature. PACS 81.15.Cd; 68.55.Jk     

Characterization of a RF/dc-magnetron discharge for the sputter deposition of transparent and highly conductive ITO films

A RF-superimposed dc-magnetron sputter process for coating color filter materials with transparent and conducting ITO films was investigated. In this process, the sputtering cathode is excited simultaneously by dc- and RF-power (at 13.56 MHz). This work summarises the measured properties of the gas discharge. Some basic data of the deposited ITO films are given, also. The dependence of the RF portion of the total sputtering power on the discharge voltage has been monitored for different values of total power and process pressure. The ion energy distribution function of the positively charged ions approaching the substrate surface has been measured using a retarding field plasma analyser probe. It was shown that the mean energy of the ions increases with increasing RF portion of the total power. The electron temperature in the body region of the gas discharge has been derived from measurements of the optical emission of the excited species. Received: 3 November 1998 / Accepted: 8 March 1999 / Published online: 14 July 1999     

Magnetic properties and application of nanocomposite films

Some peculiar properties of magnetic nanocomposite films have been considered. It is shown that the physical limit of practical application of these materials, determined by their superparamagnetic transition, can be overcome using the effects of magnetic and exchange interactions between nanoparticles.     

Hybrid pulsed laser deposition and Si-surface-micromachining process for integrated TiC coatings in moving MEMS

Titanium carbide (TiC) is one of the preferred coatings for improving the performance of macroscopic moving mechanical components due to its established wear-resistance. Pulsed laser deposition (PLD) is an excellent method for depositing TiC, because unlike any other deposition process for TiC, PLD offers the capability of producing high-quality films even at room temperature. Using a modified PLD technique, especially designed for the deposition of particulate-free films, TiC coatings have been deposited at room temperature on silicon (Si) and on several types of thin films typically employed for fabricating microelectromechanical systems (MEMS). Our results demonstrate that TiC coatings also offer a high wear-resistance to Si surfaces, which in turn has led to our application of TiC to “moving” Si MEMS devices. The performance of moving Si MEMS devices is limited by their poor operational lifetimes, which have been attributed to the excessive wear at sliding Si interfaces. The work presented here describes a hybrid process, whereby PLD is used in conjunction with a user-friendly Si surface micromachining scheme for inserting wear-resistant TiC coatings between critical sliding Si interfaces in MEMS devices. This paper describes the properties of PLD-TiC for MEMS and the hybrid PLD-surface micromachining process for the integration of TiC coatings into Si MEMS. Received: 23 January 2003 / Accepted: 8 February 2003 / Published online: 28 May 2003 RID="*" ID="*"Corresponding author. Fax: +1-310/563-7614, E-mail: gouri.radhakrishnan@aero.org     

Vacuum versus gas environment for the synthesis of nanocomposite films by pulsed-laser deposition

Nanocomposite films formed by Cu nanocrystals (NCs) with sizes <10 nm embedded in an amorphous Al₂O₃ host have been grown by alternate pulsed-laser deposition both in vacuum and in a buffer gas (Ar) up to pressures of 0.1 Torr. The dimensions, dimension distributions, and shape of the NC produced in vacuum and in Ar up to pressures of 5᎒^-3 Torr follow a similar trend as a function of the Cu areal density. This allows us to conclude that the nucleation and growth of the NC are dominated by processes occurring at the substrate surface rather than in the gas phase. For Ar pressures ̓᎒^-2 Torr, the anisotropy of the NC is enhanced, the deposition rate decreases abruptly and a significant amount of the buffer gas is incorporated into the host, thus leading to the formation of a porous material.     

Formation of Ti and TiN ultra-thin films on Si by ion beam sputter deposition

Ultra-thin titanium and titanium nitride films on silicon substrate were obtained by ion beam sputtering of titanium target in vacuum and nitrogen atmosphere, using argon ions with energy of 5 keV and 15 μA target current. Elemental composition and chemical state of obtained films were investigated by X-ray photoelectron spectroscopy with using Mg-Kα X-ray radiation (photon energy 1253.6 eV). It was shown that it is possible to form both ultra-thin titanium films (sputtering in vacuum) and ultra-thin titanium nitride films (sputtering in nitrogen atmosphere) in the same temperature conditions. Photoelectron spectra of samples surface, obtained in different steps of films synthesis, detailed spectra of photoelectron emission from Si 2p, Ti 2p, N 1s core levels and also X-ray photoelectron spectra of Auger electrons emission are presented.     

Texturing effects in molybdenum and aluminum nitride films correlated to energetic bombardment during sputter deposition

Molybdenum films sputter-deposited at low pressure show a (110) to (211) texture turnover with increasing film thickness, which is accompanied by a transition from a fiber texture to a mosaic-like texture. The degree of (002) texturing of sputtered aluminum nitride (AlN) films strongly depends on nitrogen pressure in Ar/N₂ or in a pure N₂ atmosphere. For the understanding of these phenomena, the power density at the substrate during sputter deposition was measured by a calorimetric method and normalized to the flux of deposited atoms. For the deposition of Mo films and various other elemental films, the results of the calorimetric measurements are well described by a model. This model takes into account the contributions of plasma irradiation, the heat of condensation and the kinetic energy of sputtered atoms and reflected Ar neutrals. The latter two were calculated by TRIM.SP Monte Carlo simulations. An empirical rule is established showing that the total energy input during sputter deposition is proportional to the ratio of target atomic mass to sputtering yield. For the special case of a circular planar magnetron the radial dependence of the Mo and Ar fluxes and related momentum components at the substrate were calculated. It is concluded that mainly the lateral inhomogeneous radial momentum component of the Mo atoms is the cause of the in-plane texturing. For AlN films, maximum (002) texturing appears at about 250 eV per atom energy input. Received: 23 June 2000 / Accepted: 12 December 2000 / Published online: 3 April 2001     

VO2-WO3 nanocomposite thin films synthesized by pulsed laser deposition technique

Pure VO₂ and VO₂-WO₃ composite thin films were grown on quartz substrate by pulsed laser deposition (PLD) technique. The influence of varying WO₃ molar concentration in the range from x = 0.0 to x = 0.4 on structural, electrical and optical properties of VO₂-WO₃ nanocomposite thin films has been systematically investigated. X-ray diffraction studies reveal the single crystalline monoclinic VO₂ phase (m-VO₂) up to 10% of WO₃ content whereas both m-VO₂ as well as h-WO₃ (hexagonal WO₃) phases were present at higher WO₃ content (0.2 ≤ x ≤ 0.4). Optical transmittance spectra of the films showed blue shift in the absorption edge with increase in WO₃ content. Temperature dependence of resistivity (R-T) measurements indicates significant variation in metal-insulator transition temperature, width of the hysteresis, and shape of the hysteresis curve. Cyclic Voltammetry measurements were performed on VO₂-WO₃ thin films. A direct correlation between V/W ratio and structure-property relationship was established. The present investigations reveal that doping of WO₃ in VO₂ is effective to increase the optical transmittance and to reduce the semiconductor to metal phase transition temperature close to room temperature.     

Structural and electrochemical characterization of Ni nanostructure films on steels with brush plating and sputter deposition

Layers of nickel were coated on low carbon steel substrates applying both brush plating and DC magnetron sputtering techniques. X-ray diffraction analysis showed a preferential orientation along (1 1 1) for both sputter deposited and brush plated Ni nanostructure coatings. The sputtered Ni film showed better crystallinity as observed from XRD compared to brush plated Ni film on steel on account of the favorable conditions for grain growth in sputtering. SEM analysis indicated that the coatings are very regular without pores, with columnar structure for the sputter deposited Ni coatings. AFM was also applied for surface topography examination. Microhardness value was found to be higher for sputtered Ni film. Corrosion performance of these nanostructured Ni coatings were evaluated using electrochemical techniques and observed that the corrosion resistance of brush plated Ni film sample was significantly higher than that of the sputtered Ni film.     

Study of the plasmas produced during the deposition of TiC/SiC thin films in a hybrid magnetron-laser system

Time- and spatially-resolved optical emission spectroscopy was performed to characterize the plasma produced in a hybrid magnetron-sputtering-laser deposition system, which is used for TiC or SiC thin films preparation. A graphite target was ablated by a KrF excimer laser (λ=248 nm,τ=20 ns) and either Ti or Si targets were used for DC magnetron sputtering in argon ambient. Spectra were measured in the range 250–850 nm. The evolution of the spectra with varying magnetron powers (0–100 W) and argon pressures (0.3–10 Pa) was studied. Spectra of the plasmas produced by a) the magnetron alone, b) the ablation laser alone, and c) the magnetron and the ablation laser together, were recorded. Spectra (a) were dominated by Ar atoms and Ar⁺ ions. Emission lines of Ti and Si were detected, when Ti target and Si target was used, respectively. Spectra (b) revealed emission of C, C⁺, C₂, Ar, Ar⁺. Spectra (c) showed presence of all previously mentioned species and further of Ti⁺ ions emission was detected. The research was supported by Grant Agency of the Czech Republic No. 202/06/02161, GA ASCR project number A1010110/01 and Institutional Research Plan AV CR No. AV0Z 10100522.     

The luminescence and optoelectrical properties of ITO films prepared by a sputter type negative metal ion deposition

Transparent conducting indium tin oxide (ITO) thin films were prepared on glass substrates by a magnetron sputter type negative ion source which requires cesium (Cs) vapor injection for surface negative ionization on the ITO target surface. Although the film was prepared at 70 °C, it attained high optical transmittance, 88% and low resistivity, 2.03 × 10⁻⁴ Ω cm, at an optimized Cs partial pressure of P_Cs = 1.7 × 10⁻³ Pa. The as-deposited ITO films have a poly-crystalline structure with (2 1 1), (2 2 2), (4 0 0), (4 1 1) and (4 4 0) reflections.Also, ITO films prepared at P_Cs = 1.7 × 10⁻³ Pa were post-deposition vacuum annealed at 300 °C for 30 min. The films had a resistivity of 1.8 × 10⁻⁴ Ω cm and a transparency of 89.2%. The post-deposition vacuum annealed ITO film was used as an anode for a transparent organic light emitting diode (TOLED). A maximum luminance of 19,000 cd/m² was obtained.     

Pulsed-laser deposition of particulate-free TiC coatings for tribological applications

Hybrid bearings comprising ceramic or ceramic-coated steel balls and steel raceways can provide good fatigue life and resistance to wear. One of the coating materials that has received serious consideration in hybrid systems is titanium carbide (TiC). At present, the commercially available process for the deposition of TiC involves the heating of steel substrates to fairly high temperatures (>900 °C). The high-temperature process involves considerable costs and complexities that are associated with the post-deposition heat treatment and repolishing of the coated steels for bearing applications. Pulsed-laser deposition (PLD) is ideally suited to deposit TiC coatings on bearing steels at room temperature. However, it is well known that codeposition of particulates has been one of the most challenging problems of PLD. This is especially of concern when dealing with hard coatings for tribological applications. Here we describe a novel and extremely simple method of depositing high-quality, particulate-free TiC coatings on bearing steel surfaces that uses PLD. The method relies on a new non-line-of-sight deposition that uses a permanent magnet and prevents particulates from arriving at the substrate. The surface roughness of TiC films deposited on steels by way of this technique has an extremely low root mean square value of 1.6 nm. The TiC films have been extensively characterized for their morphology, chemical composition, and mechanical properties with scanning electron and atomic force microscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and nanoindentation. Time-resolved emission has been used for the in situ characterization of the laser-ablated TiC plume and has resulted in the identification of various plume species as a function of laser parameters. The spectroscopic results are correlated to film growth and to our modified PLD method.