Papers

ICMCTF2005 Session B5: Laser Assisted Coatings and Technologies

Monday, May 2, 2005 1:30 PM in Room Sunset

Monday Afternoon

Start	Invited?	Item
1:30 PM		B5-1 Remarkably Adherent, Thick and Tough Chromia (Cr₂O₃) Coatings on Steel Made by a New Process. A. Badzian, R. Roy (The Pennsylvania State University); P. Mistry (QQC Inc.); M.C. Turchan (Turchan Technologies) Beside chromium carbide and chromium nitride, chromium sesquioxide Cr₂O₃ is a new candidate for the hard and protective coatings. The microhardness of Cr₂O₃ is 29.5 GPa makes it the second among all oxides, even above sapphire. The ability to fabricate very hard, adherent and tough ceramic coatings on steel parts could be an obvious major goal for the surface coatings research community. We report here on a remarkable success on that goal. All coatings were prepared by the QQC team, based on their well known success of multiplexed laser synthesis of materials. All the characterization was done at Penn State. The output of the coating process on a 1.875" diameter rod of stainless steel is, typically, a dense, smooth coating approximately 0.4 mm thick. The X-ray diffraction pattern confirms that there is only one crystalline phase present: very well crystallized Cr₂O₃. Scanning Electron Microscopy revealed not only a lack of any pores of any size, but a most remarkable, inhomogeneous in size, microstructure. EDAX data show a homogeneous compositional distribution, with the presence of small amounts of Al and Si, and micron size islands of carbon. Transmission Electron Microscopy images show a wide distribution of sizes of crystal grains in the nanometer range and above. The shapes of these grains are completely irregular, and unlike any microstructure developed by sintering of powders.
1:50 PM		B5-2 Characterization of Hybrid Plasmas Produced by Laser Ablation and Pulsed DC Magnetron Sputtering J.G. Jones, C. Muratore, A.A. Voevodin, J.S. Zabinski (Air Force Research Laboratory) A hybrid deposition technique combining magnetron sputtering and pulsed laser ablation was shown to be an effective tool for the production of a high performance nanocomposite films for tribological applications. The formation of the film structure is critically influenced by the superimposition of the plasma streams from these two sources on the film condensation surface. This paper reports on the investigation of the hybrid plasma composition and chemistry in correlation to the properties of the composite films made of laser ablated yttria stabilized zirconium (YSZ) and pulsed DC sputtering of silver. Pulsed laser deposition (PLD) of materials produces a highly energetic plume, with laser pulse repetition rates of up to 50 Hz for an excimer laser. Each 248 nm laser pulse is typically of 15 nsec duration with the subsequent plume lasting for 10 to 15 usec depending on deposition conditions. Pulsed DC magnetron sputtering typically operates at a fixed frequency on the order of 100 kHz, with a 50% duty cycle; resulting in a deposition occurring for 5 usec durations with every 10 usec interval. YSZ/Mo films were deposited with various degrees of overlap of these two deposition fluxes through the use of a triggering oscilloscope and a programmable delay generator. In this manner the laser pulses were inserted at regular intervals while the pulsed DC magnetron sputtering continued. Concurrently, an intensified CCD camera (ICCD) was used to monitor the resulting optical emissions. Interaction effects between plasma pulses produced by magnetron and pulsed laser ablation are analyzed and correlated to the film chemistry and structure.
2:10 PM		B5-3 Laser-Arc-Module System for Industrial Series Deposition of Super Hard Coatings H.J. Scheibe (Fraunhofer USA, Inc.) Pulsed-laser and vacuum arc techniques are successfully applied for thin film deposition since more than 20 years, especially for the preparation of super hard amorphous carbon films (ta-C). The main advantage of both technologies is that the evaporated material is nearly complete ionized. Pulsed laser deposition (PLD) is a well controlled process, which can by used for deposition of nearly all materials (electrically non- and conducting), with a precisely micro- or nano-structure, but with a low efficiency. The vacuum arc deposition (VAD) is industrial used for hard coating deposition, but can only applied to conducting materials. To prepare films of a high quality, e.g. low roughness, low micro-particle content, low defect density etc., with VAD methods, the arc discharge has to be better controlled or filter technique has to apply. In the Laser-Arc process the arc discharge is guided on the cathode surface in a highly controlled manner by the position of the igniting laser pulses. A very regular erosion of the cathode material is achieved by the linear scanning of the laser beam and a simultaneously rotation of the cylindrical cathode. An overview about the basic Laser-Arc process, important parameters and the deposited ta-C film properties will be given. The need for coating of larger series of tools and components lead to the development of an industrial applicable deposition system. The result is the Laser-Arc-Module (LAM) technology, which can be combined with any conventional industrial used batch coater, irrespective of the manufacturer. The advantage of this LAM concept is that the whole equipment and all functions of the basic coater (e.g. vacuum production, sample planetary, cleaning technology, hard coating deposition and some more) can be used. Additionally a hard ta-C film can be deposited top-layer in the same batch cycle. Examples of realized LAM combinations with industrial deposition equipment are presented.
2:50 PM		B5-5 Pulsed Laser Deposition of Lanthanum Sulfide Thin Films S.B. Fairchild (Air Force Research Laboratory) Thin films of Lanthanum Sulfide (LaS) have been successfully depositied on Si substrates by pulsed laser deposition. The optimum deposition parameters (chamber pressure, substrate temperature, substrate-to-target separation, laser energy, laser repetition rate and spot size on target) are identified. The films are golden yellow in appearance with a mirror-like surface morphology and possess a sheet resistance around 0.1 W/square. X-ray diffraction analysis of micron thick films reveals successful growth of the cubic rocksalt phase with a lattice constant of 5.863 angstroms, which is close to the bulk LaS value. High resolution transmission electron microscopy reveals the films to be largely amorphous with nanocrystalline regions. The root-mean-square variation of film surface roughness measured over a 1 mm x 1 mm is found to be 1.74 nm by atomic force microscopy. These films have potential for semiconductor, vacuum microelectronics, and optoelectronics applications.
3:10 PM		B5-6 Reduction of Particulates and Stress in c-BN Films Prepared by Ion-Assisted Pulsed Laser Deposition G. Reisse, S. Weissmantel (University of Applied Sciences Mittweida, Germany); D. Rost (University of Applied Sciences Mittweida) Recently, we have demonstrated the deposition of cubic boron nitride (c-BN) films at high growth rates by means of ion-assisted pulsed laser deposition [1]. It was also shown that well-adherent films can be obtained on Si and WC hard metal substrates by using special h-BN intermediate layers. The maximum thickness of 0.5 µm, however, was limited by the accumulation of particulates in the films. For that reason and as the incorporation of particulates in pulsed laser deposited films is still a general problem of the method we have investigated the possibilities to eliminate them during the deposition of c-BN films by using either inhomogeneous magnetic fields or pulses of a second laser beam synchronized with those of the ablating laser beam. The basic idea of the first method is the separation of the ablated ions from the massive particulates by deflecting the film forming ions by 90° in an inhomogeneous magnetic field and simultaneously using a particulate stop in the direct line between ablation spot and substrate. Various arrangements of permanent magnets and coils used for the generation of the magnetic fields will be presented and discussed. Moreover, the experimental results will be compared to theoretical considerations and the properties of the c-BN films prepared in this way will be shown. The second method is based on the idea to evaporate the particulates on their way to the substrate by a second laser beam. First results will be presented considering especially the parameters necessary, such as time delay between the pulses and laser fluence. [1] S. Weissmantel, G. Reisse, Diam. Relat. Mater. 10, 11 (2001) 1973.
3:30 PM		B5-7 Industrially-Scaled Large-Area and High-Rate Tribological Coating by Pulsed Laser Deposition J.M. Lackner (Joanneum Research, Austria) This lecture addresses the techniques of the industrial scale-up and the potential applications of the Pulsed Laser Deposition (PLD). In the last decades the PLD has emerged as a unique tool with which to grow high quality films of complex chemical compounds - e.g. more than 800 different materials were deposited up to now. Hence, the PLD technique is accounted as a well-established laboratory coating technology. But the missing of PLD coating systems, which fulfil the requirements for industrial applications - mainly, high rate and large-area deposition - , is considered as one of the main obstacles for an industrial breakthrough of the PLD. First industrial successes in the application of the PLD coatings were achieved in the last years in the fields of superconducting materials, multilayers for X-ray optics, tribological materials and coating of polymer materials. The history of the industrially-used PLD is shown using the example of the industrially-designed PLD coater built at Laser Center Leoben of JOANNEUM RESEARCH in Austria. To allow pointing out future prospects and potentialities of the industrially-used PLD technique, the "HybridPLD" technique connecting PLD with sputtering and PACVD is introduced.
4:10 PM		B5-9 Adhesion of Superhard Pulsed Laser Deposited ta-C films with Low Internal Stress on Silicon, WC-Hard Metal and Steel S. Weissmantel, G. Reisse (University of Applied Sciences Mittweida, Germany); D. Rost (University of Applied Sciences Mittweida) Superhard tetrahedral amorphous carbon films with low internal stress were prepared by a combination of pulsed laser deposition and pulsed laser annealing. It will be shown that several µm thick ta-C films with up to 80 to 85 % sp³ bonds and a hardness of up to 60 to 90 GPa can be prepared by that method. In order to optimize the adhesion of those ta-C films, the influence of the various substrate materials, the pre-treatment of the substrate surface prior to deposition and the use of adhesion improving layers were investigated and will be presented. It will be shown, in particular, that adhesion on WC-hard metal and steel can be improved significantly by using Cr, Ti and TiN intermediate layers. Moreover, the influence of the pulsed laser annealing process, applied alternating to the deposition process and resulting in stress reduction and the preparation of nearly stress-free ta-C films, on the adhesion will be discussed. In a final part, examples of coated tools and the effect of the films on wear and friction will be shown.
4:30 PM		B5-10 Hard Zirconium Carbide Thin Films Grown by Pulsed Laser Deposition V. Craciun, J. Woo, G. Bourne (University of Florida); D. Craciun (National Institute for Laser, Plasma, and Radiation Physics, Bucharest) Thin films of zirconium carbide were deposited by the pulsed laser deposition technique on Si, quartz, and sapphire substrates. Structural information for the films was obtained by symmetrical and grazing incidence x-ray diffraction, and transmission electron microscopy. The thickness, density and interfacial and surface roughness were investigated by x-ray reflectivity and atomic force microscopy. Chemical composition and bonding was obtained by x-ray photoelectron and Auger electron spectroscopy. Analysis of the structural and chemical data was completed and compared to the mechanical properties of films determined from nanoindentation measurements. Crystalline zirconium carbide films exhibiting low surface roughness and mass densities close to the tabulated value were deposited only at substrate temperatures in excess of 600°C and laser fluences around 9 J/cm². On Si(100) substrates ZrC films grew epitaxially, with the (001) axis perpendicular to the substrate, whereas on sapphire the films grew with the (111) axis perpendicular to the substrate. On quartz and Si(111) substrates the grown films were highly textured along the (001) axis. Therefore, it was possible to measure the mechanical properties of ZrC along different crystalline axis.