ICMCTF1998 Session F2: Nondestructive and In Situ Characterization

Monday, April 27, 1998 1:30 PM in Room San Diego

Monday Afternoon

Start	Invited?	Item
1:30 PM	Invited	F2-1 Electronic Structure and Chemical Characterization of Ultrathin Insulating Films J.M. Sanz (Universidad Autonoma de Madrid, Spain) The preparation and in-situ characterization of ultrathin films and layered structures is becoming increasingly important in thin film technology. In many cases, interface phenomena and strong interactions with the substrate lead to new metaestable phases that show up unique physical and chemical properties. Obviously, the ability to grow such materials with the desired properties requires some understanding of the growth mechanisms and the interfacial phenomena. Therefore, a complete characterization on a microscopic scale, during growth is of great importance. This can be achieved by electron spectroscopies to extract the chemical composition, the bonding and the electronic structure at different stages of the growth. In this article, the capabilities and limitations of conventional and synchrotron based electron spectroscopies in these kind of characterization problems are presented with the help of some selected examples. I will discuss experimental data on the synthesis of Zr₃N₄, by low energy nitrogen implantation, and its characterization (i.e. composition, bonding and electronic structure) using XPS and RPES. The data give evidence of the polar character of its bonding and its insulating characteristics. Other examples correspond to the characterization of oxide/oxide interfaces by ultrathin film growth of an oxide on a dissimilar oxide. In particular, the growth of TiO₂ on amorphous SiO₂ has been studied by in situ PES, RPES and XAS using synchrotron radiation. The results clearly indicate the formation of cross-linking Ti-O-Si bonds at the interface, which lead to strong modifications of the electronic structure when compared with thicker films. The growth of NiO on MgO (100) has been studied in terms of the Ni2p core line as determined by XPS. The Ni2p line shape shows a strong dependence on the film thickness (up to 2-3 monolayers) that can be used to study the interactions and coordination at the interface.
2:10 PM		F2-3 Investigation of the Roughness of Buried Interfaces Using X-ray Fluorescence B.W. Veal, I.V. Koshelev, A.P. Paulikas (Argonne National Laboratory) X-ray fluorescence has been used to probe the buried interface between film and substrate for films of various compositions and thicknesses. The films studied were AlO_x and SiO_x sputter-deposited onto polycrystalline nickel substrates, and aluminum oxide scales thermally grown on single-crystal NiAl. The intensity of Ni Kβ and Ni Kα x-ray fluorescence radiation, originating in the substrates, was measured as a function of the emission angle (relative to the planar surface) at angles near grazing. The ratio of the intensities (Ni Kβ)/(Ni Kα) can be used to probe the roughness of the buried interface. For the (nickel-free) films of SiO_x or AlO_x, the interface can be examined non destructively, usually in-situ, for film thicknesses up to several hundred nanometers or more.
2:30 PM	Invited	F2-4 Sharing of Spectral Data in Surface Chemical Analysis K. Yoshihara (National Research Institute for Metals, Japan); K. Yoshihar (National Research Institue for Metals, Japan) About 25 years has passed since surface analysis machines became available commercially. Since then, we have accumulated a lot of spectral data. However, this data has been scattered in the world, and is difficult to access. If we would collect this data and make a spectral database, this database would be useful to identify or analyze surfaces. At present, almost all the spectral data are obtained through computers. Therefore, we have to change the format to a common one. The energy and intensity scales are different from machine to machine, so we have to calibrate energy and intensity scales to share spectral data. As a part of the international collaborative reset of VAMAS, we have developed a PC-based system. Common Data Processing System (COMPRO), which integrates the spectral and physical data, peak position database, GUI query and analysis system. COMPRO Version 5.0 runs on Windows95, and is now distributed through the Internet (http.//sekimori,hrim.go.jp). This version can convert spectral data of ASCII format to the VAMAS Standard Data Transfer Format (ISO DIS 14976), and has an easy access interface to a Internet spectral database provided by the Surface Analysis Society of Japan (SASJ). COMPRO also has calibration systems for energy and intensity scales, and everybody can easily calibrate his/her analyzer. We can change our own spectral data to common ones with COMPRO. Since 1994, we have developed a network-oreinted database for surfaces chemical analysis such as AES and XPS spectra. SASJ provides spectral data, and controls its quality. Internet spectral data now has about 2,000 spectra of metals, semi-conductors and ceramics. The file structure of spectral data is based on ISO NP 14976 and ISO DIS 14975, which can carry the information on specimens, calibration and data-processing. This database has a GUI searching system, and the searching results are displayed on a client's PC, and a target spectrum can be downloaded to a client's PC through Internet.
3:10 PM		F2-6 Photothermal Reconstruction of Thermal-diffusivity Depth Profiles in Ni-Alloy J. Garcia, A. Mandelis (Photothermal and Optoelectronic Diagnostics Laboratories, Canada); B. Farahbakhsh, I. Harris (Edison Welding Institute) The formulation of a generalized expression for the thermalwave field in an inhomogeneous thin solid layer deposited on a homogeneous semi-infinite substrate will be discussed. The resulting inverse problem theory is based on the Hamilton-Jacobi formulation of the laser-induced thermal-wave problem. A working algorithm to invert simulated photothermal frequency scan data in obtaining thermal diffusivity depth profiles using this technique has been developed. Experimental thermal-wave frequency-scan results from several thermal sprayed samples of 625 Ni alloy (Ni, Mo, Cr) of approximately 300-aem thicknes and 0.33% porosity on structural carbon steel substrates have been obtained using an intensity-modulated laser beam source and infrared photothermal radiometric detection. As a result, thermal-diffusivity depth profiles have been reconstructed. The data showed large variations in the range of the measured values of the thermal diffusivity depth profiles of some thin coatings. These variations were found to be correlated with the thin-coating deposition process, thus rendering out thermal-wave depth profilometric technique into a powerful non-destructive diagnostic methodology for thermal sprayed thin coatings on substrates. The effects of surface roughness and the procedure to noise in both simulated and experimental data on the depth profile reconstruction will also be discussed.
3:30 PM		F2-7 SAW Technique for the Characterization of Thin Silicate Films S.L. Hietala (TPL, Inc.); C.J. Brinker (Sandia National Laboratories); M.C. Liu, D.J. Taylor (TPL, Inc.) A commercial system utilizing a surface acoustic wave (SAW) technique is used to determine the surface area and pore size distributions of thin films, particularly those with mesoporous pore sizes (2-50 nm). With this non-destructive method, films can be deposited by almost any technique and are measured "as-deposited," which provides more accurate porosity data. With additional instrumentation, the SAW technique is used for determining stiffness changes and mass uptake in thin microporous silicate films during gas adsorption.
3:50 PM		F2-8 Optical Properties of Nitrogen Doped DLC Films: Study by Raman Spectroscopy and Ellipsometry V.V. Artamonov, N.I. Klyui (Institute of Semiconductor Physics, Ukraine); A. Perez-Rodriges (Universitat de Barselona, Spain); V.A. Semenovich (Institute for Superhard Materials, Ukraine); A.B. Romanyuk, M.Ya. Valakh (Institute of Semiconductor Physics, Ukraine); O.V. Vasilik (Institute of Semiconductor Physics, Ukraine) Diamond like carbon (DLC) films have been grown by plasma decompositions of CH₄-H₂ and CH₄-H₂-N₂ gas mixtures in parallel plate reactor. After deposition some of the films were implanted with nitrogen ions wi th the energy of 150 keV and at the dose up to 10^-17 cm^-2. Relationship between the optical properties of the films, growth conditions and regimes of post- growth treatments was obtained by Raman spectroscopy and spectroellipsometry. The rf (13,56 MHz) amplitude bias voltage and gas compositions have a marked influence on the properties of the prepared films. It was also shown that optical bandgap of a-C:H:N films strongly depends on nitrogen content in the gas mixture. The comparison of the results obtained by Raman spectroscopy and spectroellipsometry shows that in dependence on nitrogen content in the gas mixture and total gas pressure in the reaction chamber the nitrogen can stimulate the formation of sp²- (at low nitrogen content) or sp³-coordinated bonds (at high nitrogen content) in the films. After implantation the significant changes of Raman spectra accompanied by increasing of film hardness was observed. The effect mentioned is related to film disordering and ion-beam induced phase-structural transformation in the implanted region.