Avi Bendavid

Review of the filtered vacuum arc process and materials deposition

The problem of removing macroparticle contamination from cathodic arc deposition technology has been addressed by several techniques. These techniques have been sufficiently successful that in recent years improved coatings have been developed and advanced applications are starting to appear. The present paper is a review of these advances and the properties of new materials synthesised using different filtered cathodic arc configurations.

Deposition and modification of titanium dioxide thin films by filtered arc deposition

Abstract Thin films of titanium dioxide have been deposited on glass substrates and conducting (100) silicon wafers by filtered arc deposition (FAD). The influence of the depositing Ti − energy, substrate types and substrate temperature on the structure, density, mechanical and optical properties have been investigated. The results of X-ray diffraction (XRD) showed that with increasing substrate bias, the film structure on silicon substrates changes from anatase to amorphous and then to rutile phase without auxiliary heating, the transition to rutile occurring at a depositing particle energy of about 100 eV. However, in the case of the glass substrate, no changes in the structure and optical properties were observed with increasing substrate bias. The optical properties over the range of 300–800 nm were measured using spectroscopic elliosometery, and found to be strongly dependent on the substrate bias, film density and substrate type. The refractive index values of the amorphous, anatase and rutile films on Si were found to be 2.56, 2.62 and 2.72 at a wavelength of 550 nm, respectively. The hardness and elastic modulus of the films were found to be strongly dependent on the film density. Measurements of the mechanical properties and stress also confirmed the structural transitions. The hardness and elastic modulus range of TiO 2 films were found to be between 10–18 and 140–225 GPa, respectively. The compressive stress was found to vary from 0.7 to 2.6 GPa over the substrate bias range studied. The composition of the film was measured to be stoichiometric and no change was observed with increasing substrate bias. The density of the film varied with change in the substrate bias, and the density ranged between 3.62 and 4.09 g/cm 3 .

Structural and optical properties of titanium oxide thin films deposited by filtered arc deposition

Abstract Thin films of titanium oxide have been deposited on conducting (100) silicon wafers by filtered arc deposition (FAD). The influence of the depositing Ti + energy on the structure, optical and mechanical properties of these films has been investigated. The results of X-ray diffraction showed that with increasing substrate bias the film structure changed from an anatase to rutile phase at room temperature with the transition occurring at a depositing particle energy of about 100 eV. The optical properties over the range of 300 to 800 nm were measured using spectroscopic ellipsometry and found to be strongly dependent on the substrate bias. The refractive index values at a wavelength of 550 nm were found to be 2.6 and 2.72 for the anatase and rutile films, respectively. The optical band gap as a function of the substrate bias was also determined and was found to be 3.15 and 3.05 eV for anatase and rutile phases, respectively. Hardness and stress measurements also confirmed the structural transitions. The hardness range of TiO 2 films was found to be between 11.6 and 18.5 GPa and the compressive stress was found to vary over the range of 0.7–2.6 GPa. Studies carried out in this paper showed that the properties of the FAD-deposited TiO 2 are sensitive to the energy of depositing Ti + .

The properties of TiN films deposited by filtered arc evaporation

Abstract Titanium nitride films were deposited on steel and silicon substrates using a filtered arc evaporation process. The microhardness, crystallite size, residual stress, adhesion, surface roughness and crystallographic orientation of the films were studied as a function of substrate bias over the range 0 to -400 V. The mechanical and structural properties were found to depend upon the degree of substrate bias. The spectral reflectance in the region between 250 and 2500 nm was measured and compared with Kr + ion-assisted deposited TiN films. In addition, the electrical resistivity and the superconducting transition temperature of the filtered arc deposited TiN films were measured to be 20 μΩ cm and 4.3 K respectively.

Composite yarns of multiwalled carbon nanotubes with metallic electrical conductivity.

Unique macrostructures known as spun carbon-nanotube fibers (CNT yarns) can be manufactured from vertically aligned forests of multiwalled carbon nanotubes (MWCNTs). These yarns behave as semiconductors with room-temperature conductivities of about 5 x 10(2) S cm(-1). Their potential use as, for example, microelectrodes in medical implants, wires in microelectronics, or lightweight conductors in the aviation industry has hitherto been hampered by their insufficient electrical conductivity. In this Full Paper, the synthesis of metal-CNT composite yarns, which combine the unique properties of CNT yarns and nanocrystalline metals to obtain a new class of materials with enhanced electrical conductivity, is presented. The synthesis is achieved using a new technique, self-fuelled electrodeposition (SFED), which combines a metal reducing agent and an external circuit for transfer of electrons to the CNT surface, where the deposition of metal nanoparticles takes place. In particular, the Cu-CNT and Au-CNT composite yarns prepared by this method have metal-like electrical conductivities (2-3 x 10(5) S cm(-1)) and are mechanically robust against stringent tape tests. However, the tensile strengths of the composite yarns are 30-50% smaller than that of the unmodified CNT yarn. The SFED technique described here can also be used as a convenient means for the deposition of metal nanoparticles on solid electrode supports, such as conducting glass or carbon black, for catalytic applications.

Properties of Ti1-xSixNy films deposited by concurrent cathodic arc evaporation and magnetron sputtering

Abstract A new technique is described in the synthesis of thin films of Ti 1 −x Si x N y based on the concurrent reactive deposition of Ti produced by a cathodic arc source and Si produced by a d.c. magnetron sputter source. The technique permits the controllable doping of TiN with silicon over the range of 1–16 at.%. The films were found to have a microhardness of 70 GPa with a compressive stress of 5.5 GPa when deposited with a magnetron power of 220 W and a bias voltage of −150 V, and a maximum hardness of 58 GPa and stress values of approximately 3.3 GPa when deposited using 280 W magnetron power and −50 V bias. The hardness and stress of TiN was found to be 26 and 3.5 GPa, respectively, when deposited in the absence of the magnetron.

Modelling and finite element analysis of ultra-microhardness indentation of thin films

Abstract High stresses and complex deformations usually develop in thin films during indentation tests. Understanding the stresses and deformations in thin films is beneficial for the development of sound mechanical and thermomechanical components. This paper investigates the stress field and deformations in thin films under microindentation using finite element analysis. The features of the distribution of stress and strain are described. The change of the stress distribution as a function of Youngs modulus to the equivalent yield stress ratio (E/σoy) of the film is presented. The effects of the thickness of the film and the radius of the indenter on the stress are investigated. The results from the finite element analysis are found to be in a good agreement with experimental data and can be used to develop a reliable mechanical design methodology.

Influence of thickness and substrate on the hardness and deformation of TiN films

Titanium nitride films with thickness ranging from 0.2 to 1.4 μm were deposited by an ion-assisted filtered area vapour deposition system onto single-crystal silicon, sapphire and a tool steel at room temperature. Precision force-displacement measurements of Berkovich indentations to various loads and depths of penetration were made on all the films. The film thickness was particularly critical for indentations on the softer substrates (silicon and tool steel) whereas for the films on the sapphire virtually no influence was detected. Analysis of the force-displacement data indicated a strong load dependence of the hardness and modulus for the films on the softer substrates. The deformation about and beneath the films was also examined with scanning electron microscopy observations of cross-sections. There was virtually no evidence of plastic deformation of the film.

The deposition of TiN thin films by filtered cathodic arc techniques

A filtered cathodic arc source has been used to deposit thin films of titanium nitride. The properties of the films are influenced by the nature of the condensation process. TiN films may be deposited directly onto heated substrates in a nitrogen atmosphere or onto unbiased substrates at ambient temperature by condensing the Ti/sup +/ ion beam under 500 eV N/sub 2//sup +/ nitrogen ion bombardment. In the latter case, the film stoichiometry was varied from an N:Ti ratio of 0.8 to 1.2 by controlling the relative arrival rates of Ti and nitrogen ions. Simple models are used to describe the evolution of compressive stress as a function of arrival ratio and the composition of the N/sub 2//sup +/ ion-assisted TiN films.

Optical properties and stress of ion-assisted aluminum nitride thin films.

The optical properties and stress in thin films of aluminum nitride have been studied as a function of ion energy and the ion-to-vapor arrival ratio (J(i)/J(v)) for the N(2)(+) ion-assisted deposition of aluminum. The ion energy was varied between 75 and 1000 eV. The refractive index was found to depend on the ion energy and flux. The highest index was 2.10 at 633 nm. The films were found to be highly transparent over the wavelength region 275-800 nm. The films were found to be free of major oxide contamination, and x-ray photoelectron spectroscopy studies revealed the presence of excess nitrogen in films prepared at high J(i)/J(v) values. The film stress was also found to be related to the ion energy, and an anomalously high compressive stress of -5.0 GPa was found for 100-eV N(2)(+)-assisted depositions. By comparison, films prepared by magnetron deposition were found to have lower refractive indices (1.97-1 99, n633) and higher stress (-8 to -12 GPa) when deposited in pure nitrogen.