ICMCTF2002 Session F2-1: Nondestructive and In-Situ Characterization

Friday, April 26, 2002 8:30 AM in Room San Diego

Friday Morning

Start	Invited?	Item
8:30 AM		F2-1-1 Monitoring and Control of Growth of Cr-B-N Nanocrystalline Coatings Using In-Situ Spectroscopic Ellipsometry S.M. Aouadi, T.Z. Gorishnyy, S. Varma, S.L. Rohde (University of Nebraska-Lincoln) In-situ spectroscopic ellipsometry (SE) in the energy range from 1.5 to 5.5 eV was used to monitor the deposition of monolithic Cr-B-N coatings deposited by ion-assisted reactive magnetron sputtering. This ternary material has a complex phase diagram, consisting of three different phases over a large portion of the available phase fields: a CrxB1-x phase, a CrxN_1-x phase, and BN. Additionally, the BN may be in the hexagonal or cubic form or a combination of both. A systematic study was conducted as a function of each of the following deposition parameters using in-situ SE: nitrogen flow rate, bias voltage, and target current. In-situ ellipsometry data, and the resulting optical constants, are correlated with changes in composition and structure. This technique has been used to provide in real-time information regarding the relative amounts of hexagonal and cubic BN during film growth. Samples were tested post-deposition using X-ray diffraction and Atomic Force Microscopy for structural characterization; X-ray Photoelectron Spectroscopy, Auger Electron Spectroscopy, and Rutherford Backscattering for chemical characterization; as well as ex-situ SE (visible and infrared) to support the in-situ optical property analysis. The mechanical properties (hardness and elastic modulus) of the coatings were also evaluated using nanohardness. The effect of grain size and elemental/phase composition on the performance of these coatings is considered.
8:50 AM		F2-1-2 In-situ Study of Phase Evolution in Planar Magnetron Sputtered Tantalum Thin Films S.L. Lee (US Army ARDEC); D. Windover, T.-M. Lu (Rensselaer Polytechnic Institute) The design and construction of an in-situ planar magnetron sputtering deposition system with a beryllium chamber for X-ray transmission has been accomplished for growth study of refractory coatings for wear and erosion. The system sits on top of a conventional laboratory theta-two theta X-ray diffractometer. Fast X-ray detection of the Debye rings during growth was possible by interfacing a 2-dimensional array sensor to the diffractometer instead of using conventional Si(Li) or one dimensional array detector. Tantalum films were sputter deposited onto the surface of glass slides in argon gas to monitor the growth of tantalum films. Real time phase evolution analysis of a 260-nm film deposited at 30 mTorr showed the formation of a thin fine-grained, near amorphous under-layer, followed by the growth of beta phase tantalum, followed by the growth of alpha phase tantalum. The FWHM of the Chi-plot of alpha tantalum (110) reflection decreases with time, indicating the growth of more textured coatings as time progresses. Ex-situ grazing incidence X-ray and pole figure analysis showed that in-situ planar magnetron sputtered tantalum film surface on amorphous glass exhibited (110) fiber texture.
9:10 AM		F2-1-3 In-situ Studies of AlCuFeCr Magnetron Sputtered Quasicrystalline Thin Films E.J. Widjaja, L.D. Marks (Northwestern University) Quasicrystals exhibit properties that are very different from conventional metallic materials. They have high hardness and stiffness, but low fracture toughness compared to conventional metals. They also have a very low coefficient of friction which can be exploited for various tribological applications. Since the elements involved are very prone to oxidation, scientific studies of initial stage of growth require both growth and characterization under Ultra-High Vacuum (UHV) conditions for definitive answers. In-situ studies have been done on thin films in the Al rich region of the AlCuFeCr quasicrystalline phase field. Thin films were grown by magnetron sputtering on atomically flat MgO (001) and Al₂O₃ (001). These films were subsequently studied by Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). High Resolution Electron Microscopy (HREM) shows that thin films (< 30 nm) grown at room temperature are essentially amorphous. Upon subsequent UHV annealing at 310°C, the amorphous films transform into quasicrystalline films. Further annealing results in grain growth. Hexagonal crystalline phase was identified as approximant to the decagonal phase. At higher temperatures (> 300°C), thin film growth is identified to have island mode.
9:30 AM		F2-1-4 Acoustic Phonon Propagation and Elastic Properties of Nano-sized Carbon Films Investigated by Brillouin Light Scattering M.G. Beghi, C.S. Casari, A. Li Bassi, C.E. Bottani (Politecnico di Milano, Milan, Italy); A.C. Ferrari, J. Robertson (Cambridge University, United Kingdom); P. Milani (University of Milan, Milan, Italy) Carbon materials having a structure at the nanometer scale are of paramount interest. Experimental tools for the mechanical characterization of such materials are still an open issue: techniques like indentation and laser induced ultrasonics become critical. Brillouin light scattering (BLS) by acoustic phonons has peculiar advantages: it is intrinsically contact-less and non destructive, it can operate in-situ and it is local (measurement is over a zone of tens of microns). The elastic properties can be derived from the measured acoustic properties. Two applications are discussed here. Tetrahedral amorphous carbon (ta-C) films of high density and stiffness can be deposited with thickness down to a few nanometers. Such coatings are crucial for the achievement of higher storage density in magnetic hard disks. We show that combining BLS and X-ray reflectivity the elastic properties of films can be measured for thicknesses down to 2 nm. We also measure the dependence of stiffness on thickness, the peculiar properties of thicker ta-C films being fully developed at a thickness of around 10 nm. Low energy cluster beam deposition allows the deposition of films characterized by granularity and porosity at scale lengths ranging from nanometers to micrometers. Different deposition conditions allow to obtain films that still support the propagation of acoustic phonons, and films in which such phonons are confined and/or overdamped. BLS discriminates well among the two cases; in the first one the elastic properties can be obtained, at wavelengths of hundreds of nm. It is thus shown that BLS has a peculiar potential for the characterization of films having structures at a nanometric size.
9:50 AM		F2-1-5 On the Oxygen Diffusion Process in Plasma-deposited In/Sn Films with Different Defect Structure M. Quaas, H. Steffen, R. Hippler, H. Wulff (University of Greifswald, Germany) Thin tin doped indium films were deposited by dc magnetron sputtering at different substrate voltages. The substrate voltage influences the film microstructure. Information on domain sizes, microstrains and dislocation densities was obtained from x-ray profile analysis using the Warren-Averbach and Krivoglaz-Wilkens method. Films with different defect structure were annealed within a high-temperature-chamber and studied by in-situ GIXRD. During the post deposition annealing crystalline indium tin oxide (ITO) forms in a diffusion limited process. A mathematical model was developed to derive the diffusion coefficients from the time dependence of the ITO(222) x-ray reflection integral intenstiy. From the temperature dependence of the diffusion coefficients the activation energies for the oxygen diffusion into the metallic films were calculated. The determined diffusion coefficients as well as the values of the activation energy depend on the different microstructure of the films influenced by the deposition conditions.