ICMCTF2003 Session F3: Surface and Thin Film Analysis

Wednesday, April 30, 2003 8:30 AM in Room Royal Palm 4-6

Wednesday Morning

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8:30 AM		F3-1 A Multi-Technique Approach of Tribofilm Characterization C. Minfray, J.M. Martin (Ecole Centrale Lyon, France); C. Esnouf (INSA, France); T. Le Mogne (Ecole Centrale Lyon, France) The characterization of tribofilm has been already studied by various surface analysis tools since many years. The analytical techniques usually performed on this kind of sample are X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES) and X-ray Absorption Near-Edge Structure (XANES). XPS is interesting for chemical environment information. AES has a good spatial resolution (about 0.5 µm) permitting AES mapping or making AES linescan¹. With XANES, polyphosphate chain length can be characterized in case of ZDDP tribofilm. AES depth profile can although be performed in order to follow the composition of the tribofilm with depth. So, coupling XPS, AES and XANES² is interesting to clarify the different layers composition of the tribofilm. In this work, AES, XPS, Secondary Ion Mass Spectroscopy (SIMS) and Transmission Electron Microscopy (TEM) are carried out on tribofilm made by ZDDP additives. SIMS was also performed, using a Time of Flight spectrometer, which has a very high sensitivity and a very high mass resolution, it is now possible to have a molecular information without damage on the surface. This technique is sensitive from the first layer to a few nanometers. Our aim is to investigate also the film in its depth. Firstly, depth profiles (by AES and SIMS) were carried out. Secondly, a transverse section made by Focused Ion Beam (FIB) is observed by TEM. All results are discussed in order to give a better understanding of the tribofilm composition. This multi-technique approach could be extended to different kind of tribofilms. ¹ C. GROSSIORD, J.M. MARTIN, T. Le MOGNE and T. PALERMO, UHV friction of tribofilms derived from metal dithiophosphates, Tribology Letters, 6 (1999) 171-179. ² J.M. MARTIN, C. GROSSIORD, T. Le MOGNE, S. BEC and A. TONCK, The two-layer structure of Zndtp tribofilms Part I: AES, XPS and XANES analyses, Tribology International, 34 (2001) 523-530.
8:50 AM		F3-2 Quantitative Analysis of Thin Films by Radiofrequency-powered Glow Discharge Optical Emission Spectrometry: Hydrogen, d.c. Bias Voltage, Density Corrections J. Michler, M. Aeberhard, R. Payling (EMPA, Switzerland) Glow discharge optical emission spectrometry (GD-OES) has emerged as a major technique for surface and depth profile analysis, owing to the unique combination of fast sputtering rate, high depth resolution, excellent sensitivity and multi-element capability. Although direct current (dc) glow discharges are the most widely used GD-sources for the analysis of metallic coatings, the more recent radio frequency (rf) GD sources offer the advantage that both conducting and non-conducting samples can be analysed. Recently, an algorithm for rf-GD-OES has been developed for dc bias voltage, hydrogen and coating density correction. These corrections allowed to combine samples with different electrical characteristics in a single calibration and to obtain correct quantitative depth profiles of hard coatings on steel even in the presence of significant amounts of hydrogen in the coating. In this paper, quantitative depth profiles measured by rf-GD-OES are presented for a variety of thin films using these correction algorithms. It is shown that rf-GD-OES is a universal tool for fast depth-profiling: On the one hand Al₂O₃, CrN, TiC and TiN coatings on steel as well as Diamond and DLC films on silicon, on the other hand 50nm thick TiO₂ and Nb₂O₅ coatings on titanium as well as several nanometer thick oxide films on zinc coatings were successfully analysed. In all cases, the emission yields of different elements were found to depend on the hydrogen content within the specimen. By applying both dc bias voltage, density and hydrogen correction, correct depth profiles of were obtained.
9:10 AM		F3-3 Atomic Environment and Interfacial Structural Order of TiAlN/Mo Multilayers C.J. Tavares, L. Rebouta (Universidade do Minho, Portugal); J.P. Rivière, T. Girardeu, Ph. Goudeau (Université de Poitiers, France); E. Alves (ITN, Portugal); N.P. Barradas (Instituto Tecnológico e Nuclear, Portugal) Multilayered TiAlN/Mo coatings were deposited by dc reactive magnetron sputtering on a custom-made chamber. In order to access the composition of these coatings a combined study of X-Ray Diffraction (XRD), Extended X-Ray Absorption Fine Structure (EXAFS) and Rutherford Backscattering Spectrometry (RBS) experiments were performed. Through the simulation of the EXAFS spectra, giving the local atomic environment of the titanium atoms inside the nitride (TiAlN), a cubic phase has been evidenced with aluminium atoms occupying titanium sites. For modulation periods in the range of 3.5-11.1 nm, RBS simulations on these multilayers enabled also the determination of the level of intermixing that occurred at the interfaces as a function of the negative bias voltage. This intermixing width can be as high as 2.4 nm for the roughest samples (larger periods) or as low as 0.6 nm for those with the sharpest interfaces (smaller periods).
9:30 AM		F3-4 Surface and Interfacial Structures for Sputter-deposited TiNi Films on Various Substrates Y.K. Fu, H.J. Du, S. Zhang (Nanyang Technological University, Singapore) Shape memory alloy (SMA) films have the potential to become a primary actuating candidate for MEMS (micro-electro-mechanical system) applications. However, there are few studies on surface, interfacial structures and chemistries of TiNi films on different substrates, such as silicon, silicon dioxide, silicon nitride and poly-silicon, etc. These substrates or interlayers are widely used in MEMS technology as thermal and electric insulating layers. In this study, TiNi films were prepared on the above-mentioned substrates by co-sputtering TiNi and another Ti target. Surface chemistry and effects of substrate effects on interfacial structures were characterized using X-ray photoelectron spectroscopy (XPS). As soon as TiNi film was exposed to the ambient atmosphere, oxygen and carbon quickly adsorbed on the surface. The dominant elements on film surface were C, O and Ti, while the level of Ni peak was very low. XPS depth profiling was used to study the chemical states of different elements changing with depth for both surface and interfacial layers. For TiNi films on different substrate studied, there were thin reaction layers formed between TiNi films and substrates, which affected shape memory and phase transformation behaviors. Si₃N₄ interlayer was found to be a good diffusion protective layer compared with other substrates.
9:50 AM		F3-5 Characterization of Physical Vapor Deposited Platinum/Tantalum Nitride Thin Films on Silicaon Dioxide Substrate H. Hung, B.-S. Chiou (National Chiao Tung University, Taiwan, ROC) Platinum/Tantalum nitride (Pt/TaN_x) thin films have been prepared by physical vapor deposition. The dependence of film properties such as resistivity, elemental concentration depth profiles and microstructures on annealing temperature is studied. Mapping image of Pt was obtained by electron-probe microanalyzer (EPMA). Secondary ion mass spectrometry (SIMS) was employed to analyze the concentration profile of the samples. The microstructure of the deposited films was analyzed by grazing angle X-ray diffraction(XRD). Crystallization of Pt film, showing Pt(111) and Pt(200) textures, and enhancement of TaO₂(211) of TaN_x film occurred at annealing temperatures of 800°C for 30min in a nitrogen ambient. It was determined that Pt/TaN_x thin film is thermally stable on silicon dioxide (600°C for 30min in a nitrogen ambient), preventing the exposure of TaN_x films. Keyword: thermal stability, tantalum nitride, physical vapor deposition, platinum, crystallization.
10:30 AM		F3-7 Characterisation of Graded Composite Coatings Based on Cr-Cr₂O₃ and TiN_yO_x Prepared by Magnetron Sputtering C. Nunes (National Institute of Industrial Engineer and Technology (INETI), Portugal); V. Teixeira (University of Minho, Portugal); M.L. Prates (National Institute of Industrial Engineer and Technology (INETI), Portugal); N.P. Barradas, A.D. Sequeira (Instituto Tecnológico e Nuclear, Portugal) Thin selective absorber coatings are widely used in conversion of solar radiation into thermal energy. Since an efficient solar photothermal conversion benefits from spectrally selective absorber surfaces it is necessary to use advanced deposition techniques to improve the selectivity by developing new coating concepts Selective cermet thin films were produced by D.C. magnetron sputtering of metallic Chromium and Titanium targets at constant target current, constant substrate bias and temperature. These films are graded cermets, with a decreased gradient of metal concentration, from the substrate to the surface. Basically, these films, are formed with one cermet layer rich in metal, one or more cermet layers with less metal fraction than the first one, and the last is only ceramic layer (the antireflection layer). The metallic component, was deposited by D.C. non-reactive sputtering, while ceramic component, was deposited by D.C. reactive sputtering in an Argon and Nitrogen atmosphere or Argon an Oxygen. The metallic and ceramic components of the cermets, were deposited in a sub-layer system, consisting in alternating metallic and nitride or oxide sub-layers.The sub-layers thickness was changed in a way, to change the metal volume fraction from the bottom to the top of the film. The effect in the optical properties of the metallic fraction in the layers and the number of sub-layers in the film is discussed. For films based on Chromium, the optimum film selectivity achived was a solar absorptance of 94% and a thermal emitance oh 6%, at 82 degrees. For Titanium based films, the best selectivity achived was a solar absorptance of 91% and a thermal emitance of 4%. The microstructure and thickness were studied by scanning electron microscopy (SEM). The surface microtopography was analysed by atomic force microscopy (A.F.M.) and the metal concentration profile by Rutherford Backscattering Spectrometry (R.B.S.).
10:50 AM		F3-8 Phase Transition Studies in Barium Zirconium Titanate Thin Films Deposited by Sol-gel Technique A. Dixit, S.B. Majumder, P. Dobal, R.S. Katiyar (University of Puerto Rico) The phase transition behavior of BaZr_xTi_1-xO₃(x= 0.0 to 0.40) thin films has been investigated.The films were prepared on platinum substrate using sol-gel technique.The structure and preferred orientation of the resulting films were examined by x-ray diffraction measurements.Electrical properties of thin films were measured and their ferroelectric nature was confirmed for 0.0c~ 350K. The dielectric measurements confirm this observation.Above 15% the dielectric constant measurements show a broad maximum at the transition temperature.For Zr concentration above 30% the material shows relaxor properties. This work was supported in parts by NASA NCC5-518 , NSF INT0097018 and DOD-N00014-02-1-0215 grants.
11:10 AM		F3-9 Ion Beam Analysis of Multilayer X-ray Mirrors, Possibilities and Peculiarities V. Egorov, E.V. Egorov, A.S. Kondakov (Russian Academy of Science, Russia) Multilayer X-ray mirror presents a specific planar thin film structure where the strict sequence of light and heavy material hyperfine layers (sublayers) takes place. The thickness of every sublayer's couple must be maintain with best accuracy over a thickness of all multilayer structure. Size of the couple is the structure period or the spacing of unidimentional pseudocrystal. X-ray testing of the structure allows to define of it's spacing but they can not enable to describe sublayer's thickness in couples and to detect the contaminations content in the mirror. This problems can be solved by ion beam analysis application. The work is devoted to study of multilayer planar structures (W/C)_n and (W/Si)_n deposited on Si substrates by using of Rutherford backscattering of H⁺ and He⁺ ions. Investigations were carried out in RBS chamber of Ion Beam Analytical Complex Sokol-3 IPMT RAS [1]. Measurements which data presented were carried out in the standard scattering geometry and in one at almost beam sliding incidence. Total thickness of multilayer structures, depth profiles of absolute element concentrations and some peculiarities of it's sublayer constitution were determinated experimentally. Data obtained permit to define argon concentration in the structure and unhomogeneity of sublayer thickness over a depth of studied multilayer structures, without damage of mirrors. They were used for optimization of the procedure mirror preparation. [1] A.F. Vyatkin, V.K. Egorov, E.V. Egorov, Mat. Res. Soc. Symp. Proc., v585, 2000, MRS, pp. 183-189.