Papers

ICMCTF1999 Session F2: Nondestructive and In-situ Characterization

Wednesday, April 14, 1999 1:30 PM in Room San Diego

Wednesday Afternoon

Start	Invited?	Item
1:30 PM		F2-1 X-Ray Diffraction Characterization of Metal, Nitride, and Oxide Epitaxial Films and Superlattices J. Birch (Department of Physics, Linköping University, Sweden); C. Engström, C.N.L Edvardsson, H. Fornander (Linköping University, Sweden) Non-semiconductor epitaxial films and superlattices are in general not structurally as perfect as their semiconductor counterparts. This often makes it necessary to use low resolution or medium resolution x-ray diffraction (XRD) with much higher intensities than high resolution XRD. In this paper three examples are given where strain relaxation of very thin Pd- and SrTiO₃-films, and thermal stability of Mo/NbN superlattices have been studied using an ordinary laboratory x-ray source with low and medium resolution optics. The coherency strain and particle size evolution with film thickness (0.5-20 nm) of magnetron sputtered and evaporated Pd films on MgO(001) substrates were characterized using low resolution grazing incidence XRD. The thinnest films consisted of epitaxial (001)-oriented islands strained to ~1% which, depending on growth temperature, gradually relaxed as the films became thicker. The sputtered films were less strained with somewhat larger islands. A combination of x-ray reflectivity, θ-2θ scans, and reciprocal space mapping was used to study the thermal stability of epitaxial (001)-oriented Mo/NbN superlattices grown on MgO(001). After annealing at 1000 deg. C for 3 h., an interfacial reaction transformed a Mo/NbN superlattice with modulation period Λ=1.4 nm to an epitaxial (001)-oriented tetragonal MoNbN film with some remaining compositional modulation. A superlattice with Λ=6.5 nm transformed into a mixture of polycrystalline MoNbN and (001)-oriented NbN. Reciprocal space mapping using a multilayer mirror monochromator and crystal optics was used to characterize the strain relaxation of epitaxial (001)-oriented SrTiO₃ grown on LaAlO₃ substrates by magnetron sputtering. All films, in the thickness range 9.3144.0 nm, were strained (2.8-0.3%) with a tetragonal distortion which decreased monotonically with increasing film thickness. Finally approaching an undistorted lattice parameter 0.6% larger than that of bulk SrTiO₃ indicating an off-stoichiometric film composition.
2:10 PM		F2-3 X-ray Stress Measurement of Ni-Al Coating Layer Prepared by Combustion Synthesis Reaction H.H. Hirose (Nanao Junior College, Japan); S.T. Takago, M.T. Tasaki, T.S. Sasaki (Kanazawa University, Japan) The self-propagating high-temperature synthesis (SHS) reaction is the material synthesis methods with good heat efficiency for the super alloy etc. An excellent joint can be expected between Ni-Al coating and the substrate material. However, in the other hand, it seems that residual stress was generated in their interface, because the difference of a mechanical property of the materials. The X-ray stress measurement method develops into this as one of effective experimenting mechanical techniques in field of the residual stress analysis. In this study, an X-ray method was applied, and the influences of the coating thickness and the property of substrate material on the residual stress in the Ni-Al coating layer were discussed. As a result, it is summarized that as follows; (1) An average state of the residual stress in the surface of Ni-Al coating film was clarified. (2) When the coating film was made, changing temperature generated residual stress due to the difference of thermal expansion coefficient between the substrate and the coating film. (3) The stress gradient of the coating film was measured from the nondestructive inspection.
2:30 PM		F2-4 In-Situ Analysis of Aluminum Enhanced Crystallization of Hydrogenated Amorphous Silicon (a-Si:H) By Using X-Ray Diffraction F.A. Khalifa, H.A. Naseem, J.L. Shultz, W.D. Brown (University of Arkansas) Aluminum enhanced crystallization of hydrogenated amorphous silicon a-Si:H is studied. Thin film samples of a-Si:H (5000 ⁰A)are deposited by using Plasma Enhanced Chemical Vapor Deposition (PECVD) on oxidized <100> silicon substrates. Aluminum is deposited on a-Si:H by using evaporation. The samples are analyzed by using In-Situ X-ray diffraction. Analysis is done in temperature controlled vacuum chamber at glancing angle by using thin film optics. Growth in <111> silicon peak is observed during annealing the samples at 200, 225, 250 and 275 ⁰C. Growth in area of <111> silicon peak with time is plotted for different annealing temperature. Rate of area growth is calculated for all plots and is used to find the activation energy. SEM and AFM are done on the samples before and after annealing to see the roughness difference between different samples. Results show that a-Si:H starts to crystallize during heating process. There is no change in crystallization when the samples are cooled. The activation energy is calculated as 1.12ev.
2:50 PM		F2-5 Raman Microprobe Analysis of Metal-Doped Diamond-Like Carbon Films G. Doll (Timken Research) Metal-doped diamond-like carbon films are comprised of nanocrystals of metal carbide embedded in a matrix of hydrogenated amorphous carbon (aC:H). The composite structure provides these films with ceramic-like hardnesses, and polymer-like elasticities and surface energies. Ti, W, and Cr doped films grown by a closed field, unbalanced magnetron sputtering process have been examined using a microscopic Raman scattering process. By varying the power of the excitation laser, the thermal stability of the composite microstructure of metal-doped diamond-like carbon is examined. At low laser powers, the Raman signature of the films is typical of that of undoped diamond-like carbon. But at higher laser powers (temperature), the Raman spectra show that the aC:H matrix graphitizes, and scattering from the metal carbide particles dominates. These results are correlated with measurements of the mechanical and tribological properties of these films.
3:30 PM		F2-7 Historical Aspects and Current Status of Thermal Conductivity Measurement of Diamond and Diamond-like Thin Films P. Kuo (Wayne State University)
4:10 PM		F2-9 Sputtering Target Arc Detection Using Acoustic Emission A. Leybovich (Tosoh SMD Inc.); R.M. Ferdinand (On-line Digital Technologies, Inc.) A method of sputtering target arc detection using acoustic emission has been developed. The method is based on acquiring acoustic emission signals generated by arcing events. Acoustic signals are acquired by utilizing a high frequency, piezo-acoustic sensor attached to the target, the source flange, or to any other acoustically-prone sputtering source component. The sensor converts the acoustic signal into an electric signal which is processed by the arc counting unit. The operation of the acoustic emission sensor is synchronized with the DC power supply source in such a way that the power supply switching transients are completely eliminated from the data acquisition stream. The acoustic noise, generated by system pneumatic switching elements, is also eliminated by windowing and synchronizing the data acquisition time with the wafer deposition intervals. Changing duration and delay of the time window makes it possible to acquire the only arc-related acoustic signals and only during the wafer deposition. To improve the acoustic resolution and to suppress the occasional low frequency acoustic noise, the high-pass acoustic sensor is used. Laboratory testing confirmed that the method objectives had been achieved.
4:30 PM		F2-10 High Frequency INPL Scanning Acoustic Microscopy - A Novel Non-Destructive Surface Analytical Tool for Assessment of Coating Specific Elastic Moduli and Tomographic Study of Subsurface Defects D. Rats, J. von Stebut (Ecole des Mines, France); J.M. Saurel (Université de Montpellier II, France) Scanning acoustic microscopy is a surface analytical technique which has had relatively limited scientific impact in the past. In an inter-comparison study within the European Standards Measurements and Testing programme FASTE it has been shown that in the analytic "acoustic signature mode" this technique is well suited for the determination of coating specific elastic constants (Young's modulus and Poisson coefficient) with a precision of better than 1%. Owing to very quick translation tables as well as powerful control and data exploitation software the present instrument is especially versatile and user friendly. With high operating frequencies (up to 1 GHz) the surface acoustic waves (SAWs) are entirely confined in the coating and the corresponding wave velocity is coating specific. When varying the operating frequency dispersion curves can be established allowing for non destructive determination of coating thickness. In the acoustical imaging mode the elastic interaction of the SAWs with stress discontinuities in the surface can be exploited to establish the corresponding subsurface images. In the present paper we present a case study of various coatings generally deposited on steel substrates : - Magnetron sputtered TiN as compared to commercially available coatings - DLC deposited by CVD, - MoST deposited by a commercial supplier by unbalanced magnetron sputtering, - polycrystalline CVD diamond coatings on SiC substrates, - magnetron sputtered quasi crystalline films, - TiO₂ and N-doped stainless steel films realised by magnetron sputtering, - electronic connector boards. In all of these cases the elastic moduli are determined and cracking failure in 3 point bending and high load indentation is revealed. This way hertzian cracking can be clearly distinguished from lateral cracking and interfacial adhesive failure.
4:50 PM		F2-11 Evaluation of Thermal Spray Recovered Turbine Shafts by the Advanced Ultrasonic Technique Time of Flight Diffraction H. Figueroa (PDVSA, Intevep, S.A., Venezuela); D. Castillo (Insermerca C.A., Venezuela) One of the most common applications of thermal spray in the oil industry, in the rec9overy of worn mechanical components of rotative equipment, such as turbine shafts. In this case, the presence of disbonding or lack of good contact between the substrate and the metallic coating, reduces the lifetime of the component, causing in some cases, an adhesive failure of the piece. Due to the lack of existence of a standard that allows to quantify the coating quality using a non-destructive method, it has been necessary to device an inspection procedure to ensure the quality of the components being recovered. At Intevep, we have applied several ultrasonic techniques such as pulse echo, phase change, and Time of Flight Diffraction (TOFD) to the interface evaluation of a 1 mm thick coating, applied by flame thermal spray and HVOF to steel cylinders 4" in diameter. Several types of defects were induced during the coating preparation. Out of those techniques, we found pulse echo to be the least reliable, whereas phase change and TOFD provided unequivocal signatures of the presence of disbonding and oxide layers. This is due to the fact that pulse echo solely relies on the intensity of the reflected beam to identify the presence of a defect. As is well known, the intensity of the signal detected can be affected significantly by a series of factors other than disbonding itself, such as the type of surface preparation, type of couplant used, pressure applied to the transducer on the surface to be inspected, etc. Phase change and TOFD on the other hand, are less prone to providing false data, since these techniques rely very strongly on the wavelike properties of ultrasound, which are less sensitive to the factors listed above. In this paper, we present the procedure developed to inspect turbine shafts.