ICMCTF2002 Session B5-1: Hard Surfaces and Ion Beam Technologies

Wednesday, April 24, 2002 1:30 PM in Room Town & Country

Wednesday Afternoon

Start	Invited?	Item
1:30 PM	Invited	B5-1-1 Ion Beam Assisted Deposition of Ceramic Gradient Coatings M. Frietsch, V. Trouillet, M. Bruns, J. Goschnick (Forschungszentrum Karlsruhe GmbH, Germany) Ion Beam Assisted Deposition (IBAD) was applied to deposit coatings with a thickness gradient on a gas sensor microarray (GSMA) of high integrity which was developed at the Forschungszentrum Karlsruhe. The microarray is based on sputtered SnO₂ or WO₃ thin films, at elevated temperatures (> 200°C) the electrical conductivity of these metal oxides sensitively depends on the ambient gas composition. Parallel Pt electrode strips sputter-deposited on top of the metal oxide films, subdivide the latter, thus yielding a high number of sensor segments to form the GSMA (currently 38 on an area of 4 by 8 mm²) in one production step. In order to enable gas-recognition with the GSMA the initially identical sensor segments have to be differentiated regarding the selectivity of the gas response. This differentiation is achieved by coating the GSMA with a gradient membrane, a gas permeable film with a thickness variation across the sensor segments. The gradient membranes consisting of SiO₂ or Al₂O₃ were produced using phenyl-triethoxy-silane and aluminum-tri-sec-butylate as precursor in the IBAD process, respectively. With the aim of optimizing the gas selectivity variation of the sensor segments different shapes of the activating ion beam were employed to achieve different lateral variations of the current density of the ion bombardment. Thereby the thickness gradient of the coating can be adjusted since the deposition rate depends on the ion current density. Furthermore, the influence of different experimental conditions (precursor partial pressure, ion energy) on thickness gradient and film composition was investigated. Layers with a thickness variation of approximately 2 to 50 nm across the 8 mm wide microarray were examined as prepared and after annealing at 300°C using surface analysis by electron spectroscopy, optical investigations and nuclear analysis techniques. Auger electron spectroscopy (AES) and ellipsometry both with high lateral resolution were used to determine the thickness gradient of the coatings independently. Characterization with respect to the chemical state of the layer constituents was carried out by X-ray photoelectron spectroscopy (XPS). For quantification XPS and AES data were calibrated with absolute elemental concentrations obtained from n-RBS (non-Rutherford backscattering spectrometry).
2:10 PM		B5-1-3 Surface Treatment of Oxide and Carbide Powders by Ion Beam Techniques W. Ensinger (Philipps-University of Marburg, Germany) Powders are widely used in industry for various applications. Among the examples are chemical industry where powders serve as catalysts or catalyst supports or ceramic industry for fabricating sinter materials. Many of the properties of powders are determined by their surface. The latter plays an important role because the surface-to-bulk ratio is much higher for small par-ticles than for larger particles or bulk material. Therefore, surface modification techniques are a promising tool for modifying the properties of powder efficiently. Among them are ion beam techniques which offer a number of advantages such as controllability and versatility. However, the line-of-sight character of beam techniques is a major drawback. In order to treat powder with a maximum homogeneity, theoretically each side of each single powder grain has to be directly brought into the ion beam. For achieving this, more or less sophisticated devices for agitating the powder in the ion beam have to be used. In the present contribution, different facilities for ion beam treatment of powder (ion implantation, ion beam assisted deposition) are described, including the rotating wing-drum and the rotating spiral tube. Results on ion beam assisted sputter deposition of gold, platinum, and palladium on alumina, silica, silicon carbide and tungsten carbide are presented. By means of atomic absorption spectrometric measurements, the amount of deposited noble metals was determined. From scanning electron micrographs combined with electron microprobe the growth mode of the deposited material was identified. Electrochemical measurements were used to determine the electrocatalytic activity.
2:30 PM		B5-1-4 Optimising the Nitrogen Ion Implantation of PVD TiN; Mechanical Properties and Mechanisms S.J. Bull (MMME, University of Newcastle, United Kingdom); A.J. Perry (AIMS Consulting, Switzerland); M. Klingenberg (CTC) The use of nitrogen implantation to improve the properties and performance of PVD and CVD TiN coated cutting tools is well documented. However, the mechanisms by which this improvement comes about are still the subject of considerable debate. Our recent work has shown no evidence for the existence of an amorphous TiN phase, suggested by some as the origin of the good performance, although the presence of an amorphous carbon deposit on the tool surface cannot be discounted. A factor which is often ignored in explaining performance is the high dose of nitrogen that is needed to improve properties (often 4x10¹⁷N/cm²). At this high dose the predicted nitrogen content in the films is much greater than 50%. Inspection of the TiN phase diagram reveals no higher nitrogen content phases than TiN so it expected that the excess nitrogen is present as bubbles. In this study we have looked at the effect of nitrogen dose and dose rate on the structure and mechanical properties of PVD TiN. Very low load nanoindentation analysis indicates a soft surface layer is produced which is associated with bubble formation rather than amorphisation. Localised exfoliation of the implanted layer occurs in order to release pressure in these bubbles. The effect of these structural changes on tribological performance will be discussed.
2:50 PM		B5-1-5 A Study on Texture Evolution of Transition Metal Nitride C.H. Ma (University of Illinois at Urbana Champaign); J.-H. Huang (National Tsing Hua University, Taiwan, ROC); H. Chen (University of Illinois at Urbana Champaign) The thin film's textures are strongly related to the deposition parameters and the substrates. In this study, highly textured TiN, VN and CrN are prepared by ion beam assisted deposition method (IBAD). The preferred orientations of the films were controlled mostly by ion beam incident directions. However, for different ion beam energy and flux, the substrate temperatures had influences in different degrees for the texture evolutions. In plane texture and fiber texture were the two textures studied here. Their evolution by increasing ion beam energy, ion beam flux and substrate temperature were illustrated by pole figure measurement. In the same time, the residual stresses were measured by the new developing cosin squire alpha sin squire phi plot method, which is a modified sin squire phi method using glazing incident angle setting. The residual stresses and texture evolutions were combined and gave a better explanation on the film's nano-hardness changes.
3:30 PM		B5-1-7 Influence of Carbon Plasma Ion Implantation on CrN Coatings for Packaging Molding Applications D.-Y. Wang (Mingdao University, Taiwan (ROC)); M.L. Li (National Chung Hsing University, Taiwan, ROC) Packaging molding is recognized as the essential finishing step of the semiconductor manufacturing process. The packaging process requires precision molding to ensure the exact positioning of the IC chip and the lead frame. In addition to resist corrosion and erosive wear from filler compounds, die materials need to remain inert to the molding epoxy, which flows at about 180⁰C, to reduce excessive production down time due to mold cleaning. CrN and CrC_x coating have been demonstrated as viable replacements for hard chrome plating currently selected as the standard protection method for packaging dies. In this study, a multilayered CrN coating, deposited by cathodic arc evaporation, was post-treated by a carbon plasma ion implantation process. Dispersively distributed CrC_x phase were identified within the CrN matrix at near-surface area. The influence of the CrC_x inclusion on mircrohardness enhancement will be investigated by mechanical and microstructural analyses. The improvement on the mold releasing capability due to the presence of CrC_x phase within CrN coatings will be examined by surface energy analysis as well as direct field test.
3:50 PM	Invited	B5-1-8 Production of Cr-N Films by the Ion Beam-Assisted Deposition Technology: Experiment and Computer Simulation A.G. Guglya (National Science Center "Kharkov Institute of Physics and Technology", Ukraine); I.G. Marchenko (Scientific Center of Physical Technologies, Ukraine); D.G. Malykhin, I.M. Nekludov (National Science Center "Kharkov Institute of Physics and Technology", Ukraine) The paper presents the experimental and theoretical study into the deposition of Cr-N films by the IBAD method. The investigations were performed at various film deposition rates and ion beam energies. The ion energy varied from 10 to 100 keV. Computer simulation methods were used to calculate the parameters of film irradiation with nitrogen ions for obtaining homogeneous chemical composition. The ion energy and film deposition rates were determined to produce transition layers of different phase composition. The electrophysical properties of films produced were investigated experimentally. It is found that at initial stages of film deposition the electrical resistivity of films irradiated with nitrogen ions is about 200 times higher than the one in nonirradiated films. As the film thickness grows, this difference falls down to a factor of 6. The X-ray diffraction analysis has revealed that a nanocrystalline structure is formed in the films under irradiation. A rise in the temperature up to 500^oC leads to an increase in the microcrystallite size up to 200 nm. Variations in the lattice parameter of deposited films under nitrogen ion bombardment were measured. The present results are discussed in the framework of the concepts about the influence of radiation defects on the structure of the resulting films.