ICMCTF1998 Session F3-2: Surface and Thin Film Analysis (2)

Friday, May 1, 1998 8:30 AM in Room San Diego

Friday Morning

Start	Invited?	Item
8:30 AM		F3-2-1 Hexagonal Ntride Coatings:Electronic and Mechanical Properties of V₂N, Cr₂N and MoN R. Sanjinés, P. Hones, C. Wiemer, F. Lévy (IPA,EPFL, Switzerland) It is reported in the literature that some hexagonal phase nitrides, such as Cr₂N, Ta₂N, V₂N, MoN, exhibit significantly higher microhardness values (28 to 37 GPa) compared to their polymorph fcc MeN nitrides. Of particular interest is the study of the electronic structure of these materials to obtain pertinent information about their specific properties. The aim of the paper is to present some results related to hexagonal V₂N_x, Cr₂N_x and MoN_y nitride thin films which have been prepared by RF magnetron sputtering. The V₂N_x and Cr₂N_x films crystallise in the hexagonal phase in a narrow stoichiometric composition range with 0.8
8:50 AM		F3-2-2 Surface- and Microanalytical Characterization of Silicon-Carbonitride Thin Films Prepared by Means of RF Magnetron Co-Sputtering M. Bruns, H. Lutz, H. Klewe-Nebenius (Forschungszentrum Karlsruhe GmbH, Germany); H. Baumann (University of Frankfurt, Germany) Carbonitridic and Silicon-Carbonitridic coatings, respectively, are of increasing interest for improving surface properties of materials for many applications. Due to the variety of materials for deposition and nearly no restrictions with respect to the substrate materials RF magnetron sputtering is the most versatile coating technique compatible to semiconductor technology. Therefore, Si-C-N thin films of various stoichiometries were reactively sputtered using ¹⁵N enriched N₂/Ar sputtering gas and Si/C co-sputtering targets with different Si/C areas resulting in defined and reproducible multicomponent systems using only a single sputtering cathode. The development of production methods for these new ternary systems needs information on depth distributions of the layer components as well as on stoichiometries and binding states of the layer constituents. Depth information were obtained from Rutherford backscattering measurements (RBS), nuclear reaction analyses (NRA), and Auger electron (AES) depth profiling; chemical binding states, however, can only be determined from surface analytical experiments like X-ray photoelectron spectroscopy (XPS). By means of standard samples the influences of the analytical methods were studied on composition and chemical bonding within the investigated layers. The nuclear methods RBS and NRA, enable to estimate XPS and AES sensitivity factors for all components for the used ESCALAB-5 spectrometer as well as argon ion sputtering yields for the new Si-C-N systems. In addition, the different substrate layers, i.e. SiO₂ and Si₃N₄, respectively, were used as internal standards to check the obtained sensitivity factors. Using these calibrations XPS surface analyses and AES depth profiles are directly suitable for characterization and quantification and allow for routine control of stoichiometry, vertical and lateral homogeneity, and reproducibility of such ternary layers.
9:10 AM	Invited	F3-2-3 Fundamental Characterization of Carbide and Nitride Coating Materials: Correlation of Surface Composition and Frictional Properties S.S. Perry (University of Houston) Metal carbides and metal nitrides represent an interesting class of materials with potential applications as wear resistant hard coatings. However many related issues dealing with composition, surface chemistry, and frictional properties remain unstudied or unresolved and must be addressed before being employed in high tech applications as coatings. In the present study, a number of surface analytical tools have been used to investigate the interfacial properties of single crystal titanium carbide, vanadium carbide, and titanium nitride. Scanning tunneling microscopy, atomic force microscopy, and low energy electron diffraction have been used to probe the structure of the (100) face of these materials. X-ray photoelectron spectroscopy, high resolution electron energy loss spectroscopy, and temperature programmed desorption have been used to investigate the chemical reactivity of these surfaces with atmospheric and model lubricant species. Finally, lateral force microscopy, performed under a range of environments, has been used to characterize the frictional properties of these materials. These studies demonstrate the way in which the correlated use of surface analytical and fundamental tribological techniques succeeds in providing a fundamental picture of the interfacial properties relevant to hard coating systems.
9:50 AM		F3-2-5 Corrosion of Titanium-nitride Encapsulated Silver Films Exposed to a Hydrogen-sulfide Ambient. D. Adams, B.A. Julies (University of the Western Cape, South Africa); J.W. Mayer, T. Alford (Arizona State University) Simultaneous preparation of both sides of a Ag film has been accomplished by exposing a Ag(19 at.% Ti) alloy on SiO₂ to an ammonia (NH₃) ambient. Annealing of the alloy at 600°C for 30 min in flowing NH₃ resulted in segregation of Ti to the surface and to the alloy/SiO₂ interface. At the surface a Ti-nitride (TiN) is formed, while at the interface Ti reacted with the SiO₂ to form a Ti-oxide/silicide bilayer structure. To evaluate the effectiveness of the TiN encapsulation as protection against corrosion of Ag, the nitrided structures were annealed at temperatures ranging from 100 - 500°C in a static hydrogen sulfide (H₂S) ambient. Scanning Electron Microscopy (SEM) in combination with Energy Dispersive X-ray analysis (EDX) as well as Atomic Force Microscopy (AFM) were used to study the corrosion products and evaluate the surface morphology. The surface and interfacial reactions were investigated with Rutherford Backscattering Spectrometry (RBS). These results will be discussed and a model presented for the corrosion mechanism of Ag via the TiN encapsulation.
10:10 AM		F3-2-6 Break
10:30 AM		F3-2-7 Sputter Deposited Chromium Nitride Based Ternary Compounds for Hard Coatings P. Hones (EPFL-Institut de physique appliquée, Ecole Polytechnique Fèdèrale de Lausanne, Switzerland); R. Sanjinés (IPA, PFL, Switzerland); F. Lévy (IPA, EPFL, Switzerland) Ternary transition metal nitride thin films on chromium nitride basis Cr_1-xMe_xN_y (Me = Mo, Ti, Nb, W) were deposited on silicon and HSS-steel substrates by reactive magnetron sputtering. For each alloy Me, x was varied between 0 and 1. The phase, texture and lattice parameter were determined by X-ray diffraction analysis. The morphology was examined by cross sectional scanning electron microscopy. The chemical composition was measured by electron probe microanalysis. For each compound, the cubic phase was observed in wide ranges of composition as a function of the deposition parameters (e.g. Cr_1-xMo_xN_y for 0≤x≤1 and 0.55≤y≤1) . Thin films grown at high substrate temperatures (T_S ≥ 400K) exhibit larger grain sizes of up to 20 nm. The real and imaginary parts of the pseudo-dielectric function were determined by spectroscopic ellipsometry in the photon energy range of 1.5 to 5.0 eV. The core levels and the valence band were analyzed using X-ray photoelectron spectroscopy. Hardness values, obtained by nanoindentation, strongly vary with the alloy Me and the Cr/Me ratio.
10:50 AM		F3-2-8 Atomistic Simulations of the Generation of a New Kind of Hydrocarbon Thin Film Through Molecular Cluster-Solid Surface Collisions L. Qi, S.B. Sinnott (University of Kentucky) Thin film growth through the impact of energetic organic molecular clusters with a diamond (111) surface in vacuum has been studied using molecular dynamics simulations. A second-generation version of the reactive empirical bond-order potential for hydrocarbons developed by Brenner, that has been modified to include long-range van der Vaals interactions, is used in the simulations. The velocities considered are in the hyperthermal region and are comparable to those that can trigger shock-induced chemistry in energetic materials. The outcome of the scattering event is monitored as the reactivity of the molecular cluster and surface are varied, and the dependence of the chemistry on the incident cluster velocity and the position of the reacting molecules within the cluster is examined. The resulting film structure appears to be significantly different from diamond, graphite, or diamond-like, amorphous-carbon thin films. The evolving film morphology will be discussed in detail.
11:10 AM		F3-2-9 Change in Residual Stresses of TiN Films with Annealing Treatments. T. Matsue (Niihama National College of Technology, Japan); T. Hanagusa (The University of Tokushima, Japan); Y. Ikeuchi (Niihama National College of Technology, Japan) The structure and residual stresses of TiN film deposited on steel substrate were investigated by X-ray diffraction. TiN films approximately 4 micro-meter thick was deposited on one side of substrates with the multi-arc(M-A) PVD method and the CVD method. The TiN film deposited with the PVD method exhibited high {111} orientation. The ones deposited with the CVD method exhibited high {100} orientation. Residual stresses in the TiN films were evaluated by the two-exposure method with measuring lattice strains in the directions determined by crystal orientation of the film. The TiN film deposited with the PVD method revealed very high compressive residual stresses of about -10GPa which are one order larger than the thermal residual stress expected from the thermal strain mismatch between the film and the substrate. On the other hand, the TiN films deposited with the CVD method had compressive residual stresses of about -2.0GPa. In case of the TiN films deposited with the PVD method, residual stresses in the TiN films decreased with increasing the annealing temperature, and got finally to the level of the thermal residual stress after annealing at temperatures below 1073K. On the other hand, the residual stresses in the TiN film deposited with the CVD method didn't change after annealing at temperatures below 1073K. After annealing at the temperatures above 1073K, residual stresses in the TiN film deposited by the PVD as well as the CVD method were almost the same with the thermal residual stresses. X-ray photoelectron spectroscopy(XPS) was used to determine the ratio of nitrogen to titanium(N/Ti) after the annealing treatment. The results of the XPS analysis showed that the initial value of N/Ti was about 1.08 in the as-deposited TiN films with the PVD method. The value of N/Ti didn't change after annealing at temperatures below 1073K. However, the value of N/Ti decreased to 1.00 after annealing at temperatures above 1073K. This tendency is the same with the TiN film deposited with the CVD method.
11:30 AM		F3-2-10 Effect of External Magnetic Field on c-Axis Orientation and Residual Stress in AlN Films K. Kusaka, T. Hanagusa, K. Tominaga, T. Ao (Tokushima University, Japan) Crystal orientation and residual stress development in AlN films deposited on borosilicate glass (the thermal expansion coefficient of which is nearly equal to that of AlN) substrates were investigated by X-ray diffraction method. The AlN films were prepared by a planar magnetron sputtering system with two facing targets under the condition of constant substrate temperature, various nitrogen gas pressure between 0.26 Pa and 2.6 Pa and various external magnetic field between 63 Gauss and 126 Gauss. The AFM surface observation of obtained AlN films were performed. We found that the large tensile residual stress was observed at high nitrogen gas pressure and large external magnetic field. With decreasing nitrogen gas pressure or external magnetic field, the tensile residual stress was decreased. We also found that they were closely connected between c-axis orientation and film surface form.