Symposium F Poster Session

Tuesday, May 1, 2001 5:00 PM in Room Atlas Foyer

FP-1-1 Modified DLC and CN@sub x@ Films as a Basis for Biocompatible Surfaces
H.J. Steffen (Mannheim University of Applied Sciences, Germany); J. Degenhardt (CCR GmbH, Beschichtungstechnologie, Germany)
With the latest advances in artificial implants and medical devices there is an increasing need to design material surfaces that show fewer adverse effects regarding tissue and blood compatibility than the conventionally used materials. Among the recent developments of bioactive surfaces with antithrombogenic properties, heparinization of biomaterials is one of the traditional methods to enhance the haemocompatibility. Heparin is a polysaccharide and acts as a catalyst in the interruption of the blood clotting cascade. For a permanent immobilization of heparin it is necessary to covalently bond the heparin molecules to the surface using anchor groups like amine groups which are often created chemically. In this work an attempt was made to form reactive surface groups using a plasma process in order to avoid the usage of aggressive chemicals and solvents and to shorten the time for the heparin immobilization. The base material used was diamond-like carbon (DLC), which itself shows a good biocompatibility. DLC substrates were modified by treating them with either an ammonia, nitrogen/acetylene or an ammonia/acetylene plasma to produce the desired reactive anchor groups. The plasma-deposited films were characterized by infrared spectroscopy. Various nitrogen containing surface groups could be detected, which enable the heparin immobilization on these modified DLC films.
FP-1-2 Oxidation Characteristics of Protective Coatings of TiCrN on a Steel Substrate
S.C. Kwon (Korea Institute of Machinery & Materials, Korea); D.B. Lee (Sungkyunkwan University, Korea)
The oxidation behaviors of TiCrN coatings having compositions of Ti@sub 36@Cr@sub 26@N@sub 38@, Ti@sub 31@Cr@sub 35@N@sub 34@ and Ti@sub 14@Cr@sub 52@N@sub 34@ were studied by thermogravimetric technique between 700 and 1000@super o@C in atmospheric air. The oxidation kinetics approximately followed the parabolic rate law. The oxidation resistance of TiCrN coatings which were composed of TiN and CrN phases increased in the order of Ti@sub 36@Cr@sub 26@N@sub 38@, Ti@sub 31@Cr@sub 35@N@sub 34@ and Ti@sub 14@Cr@sub 52@N@sub 34@, implying that chromium within the coating played a decisive role in protection of steel surface from the oxidation. The oxides formed always consisted of TiO@sub 2@and Cr@sub 2@O@sub 3@. During oxidation, all the involved elements diffused either outwardly or inwardly, depending on the concentration gradients. The substrate elements diffused outwardly toward the oxide-gas interface, oxygen from the atmosphere diffused inwardly, and the coating elements diffused predominantly outward. The design of new coatings based on TiCrN will be discussed in view of high temperature application of coated tool.
FP-1-3 X-ray Reflectivity Technique for In-Situ Thin Film Characterization
A.M. Baranov (Research Institute of Vacuum Technique, Russia); P.E. Kondrashov, I.S. Smirnov (Moscow State Institute of Electronics and Mathematics, Russia); L. Parobek (AXIC, Inc.)
The thin film technology is developing in the direction of increasing in the number of materials which find application in the form of thin films. In the same time the thickness of layers decreases and complexity of the functional structures increases while advanced film structures require additional performance of layers. In this situation the traditional characterization techniques of thin films encounters the challenges. In this study an in-situ X-ray reflectivity technique is used to determine film thickness d, density r, and roughness s of thin-film coatings. The measurement is based on the registration of dynamic X-ray interference pattern which contains the information about current film parameters during deposition. The X-ray optical system of in-situ monitoring of reflectivity in the short range 0.5 - 2.2 A is developed. The system consists of X-ray tube, monochromator block and collimating system and X-ray detector which are located out of vacuum chamber. This method has some considerable advantages in comparison with ellipsometry and optical interference. In-situ X-ray reflectivity technique provides : - direct measurement of layer thickness without preliminary calibration for new material; - simultaneous measurement of the most important ultrathin film parameters (thickness, film density, and surface roughness); - dynamic presentation of parameters measured. The object of in-situ investigations were metal films obtained by magnetron sputtering and diamond-like carbon films deposited by rf-CVD. The obtained results are presented. The capabilities of X-ray reflectivity technique for the in-situ measurement and monitoring of ultrathin film thickness, growth rate, density and roughness in real time are presented. The perspectives of application of in-situ X-ray reflectivity in thin film technology are discussed. .
FP-1-4 Effect of Laser Irradiation on I-V Characteristics of Ag/Tl@sub 2@Ba@sub 2@Ca@sub 2@Cu@sub 3@O@sub 10@/CdSe Heteronano- Structures
S.H. Pawar, P.M. Shirage, D.D. Shivagan, L.A. Ekal, N.V. Desai (Shivaji University, India)
After discovery of high temperature superconductivity by Bednorz and Muller most of research is concentrated to bring these materials into applications by various ways. Hetrostructure devices could offer superior performance than conventional materials. So it is necessary to fabricate junction between metal, semiconductor and superconductor materials to bring it into large-scale applications like electronic devices, microelectronics devices and high power transmission. In the present investigation, we have been made an attempt to synthesize the Ag/Tl@sub 2@Ba@sub 2@Ca@sub 2@Cu@sub 3@O@sub 10@/CdSe heterostructure by using electrodeposition method. The processing parameters were studied and optimized. In this Tl@sub 2@Ba@sub 2@Ca@sub 2@Cu@sub 3@ alloy deposited onto silver substrate at constant potential -1.25 V vs. SCE. The alloyed films were oxidized electrochemically at potential + 0.7 V vs. SCE from 1N KOH solution. Semiconducting CdSe was deposited onto superconducting system at constant potential -0.6 V vs. SCE. Then the heteronano-structure is confirmed by studying XRD and applying Scherrer’s formula. The particle size was found to be in the range of 25-35 nm. Then the effect of Red He-Ne laser (@lambda@=632.8 nm) on the hetrostructure between Ag/Tl-2223/CdSe was studied by measuring I-V characteristics. The results obtained are discussed and reported in detail in this paper.
FP-1-5 Indentation Tests Applied to the Determination of Hardness and Toughness of Nickel Phosphorus Coatings
J. Lesage (UST Lille, IUT A, France)
Although mechanical properties of electroless Ni-P coatings have been extensively studied, the aim of this present work is to develop the understanding of indentation tests applied to toughness and absolute hardness determination of such coatings. Vickers indentation tests were performed on a Ni-P industrial coating with 10%P, previously heat treated at 300° and 600°C, respectively and loads varying between 1 N to 1300 N have been used. The absolute coatings hardness was determined by employing the most currently used models in the literature. The results have shown that the both Chicot and Lesage model and Korsunsky et al. models could give better description of the film and substrate contributions to the composite hardness if the influence of the load on the hardness number is taken into account. Average values of 9.8 GPa and 7.4 GPa were determined for the coating heat treated at 300°C and 600° respectively. The difference in hardness was assigned to the changing in the microstructural characteristics of the coating with heat treatment temperature. Since it was determined that the coatings cracked in Palmqvist mode during indentation, their toughness were determined by using one of the related equation proposed in the literature. The high spectrum of indentation loads has allowed the presence of two distinct zones which are distinguished in terms of primary cracks formed at the four tips of the indent and secondary cracks formed at the edges and around the indent. In order to take into account these two modes of cracking, an equivalent crack length is proposed which led to the representation of all the experimental data on the same curve. This is in accordance with the physical meaning that the energy per unit crack length associated with the cracking process is constant. Moreover, it was shown that the secondary cracking has appeared when the depth of the primary cracks in the cross section reach the thickness of the coating.
FP-1-6 The Electrical Response of Evaporated Cobalt Phthalocyanine Thin Films on Exposure to NO@sub 2@
N.A. Ibrahim, R.D. Gould (Keele University, UK)
A comprehensive study has been performed to investigate the response of cobalt phthalocyanine (CoPc) thin films to the effects of ambient NO@sub 2@. Evaporated CoPc films were provided with interdigitated planar electrodes and exposed to NO@sub 2@ concentrations of 5-100 ppm. In all cases the samples showed ohmic behaviour at room temperature, with current levels at 10 V applied voltage typically varying between 30 nA in the absence of NO@sub 2@ to over 100µA when exposed to 100 ppm NO@sub 2@. The samples were also subjected to cycling of the NO@sub 2@ concentration, when the gas supply was alternately switched on and off for periods of 20 minutes. The response to a step increase in NO@sub 2@ concentration, as well as the response when the NO@sub 2@ was switched off were investigated. Initially the current increased rapidly, but this became slower after the exposure time increased. When the NO@sub 2@ was switched off a sharp derease in the current was observed, followed by a slower decrease. These results were interpreted by reference to earlier work@footnote 1@,@footnote 2@. The NO@sub 2@ was initially chemisorbed onto the surface of the NO@sub 2@ in the form of NO@sub 2@@super -@ ions, which later slowly diffused into the bulk of the material. It was observed that at room temperature an equilibrium concentration could not be obtained within the time period investigated. Adsorption appeared to follow a Freundlich-type power-law isotherm.
FP-1-8 Properties of Tantalum Nitride Films Synthesized by Reactive Magnetron Sputtering for Biomedical Applications
Y.X. Leng, H. Sun, P. Yang, J.Y. Chen, J. Wang, G.P. Wang, N. Huang (Southwest Jiaotong University, China); X.B. Tian, L.P. Wang, P.K. Chu (City University of Hong Kong)
Tantalum nitride films are synthesized by reactive magnetron sputtering with orthogonal design technology by optimizing the nitrogen partial pressure, substrate temperature, and sputtering current. The chemical composition of the films is assessed using Auger electron spectroscopy and x-ray photoelectron spectroscopy. X-ray diffraction is employed to identify the structure of the films. The mechanical properties are determined by microhardness and pin-on-disk wear tests. The results show that the adhesion between the film and substrate is affected mainly by the sputtering current and substrate temperature. The hardness of the TaN films is altered by the nitrogen partial pressure and can reach as high as HK4000. The blood compatibility of the films is evaluated by clotting time measurement and platelet adhesion test and compared to that of low temperature isotropic pyrolytic carbon (LTIC). Our data demonstrate that the blood compatibility of TaN is better than that of LTIC, suggesting that TaN is a potential artificial heart material.
FP-1-9 Hemocompatibility and Enhancement Mechanism of Ti(Ta+5)O@sub 2@ Film
J.Y. Chen (City University of Hong Kong); P. Yang, Y.X. Leng, H. Sun (Southwest Jiaotong University); X.B. Tian, L.P. Wang, P.K. Chu (City University of Hong Kong); N. Huang (Southwest Jiaotong University)
Blood contacting biomaterials have recently attracted much interest. The improvement of the antithrombogenic properties of the coating surface permits a hybrid design of layers for biomedical applications such as artificial heart valves and stents. Using magnetron sputtering technology, titanium oxide films doped with Ta+5 are fabricated to meet the challenge of enhanced hemocompatibility. The structure of the films is investigated by x-ray diffraction and x-ray photoelectron spectroscopy. The blood compatibility is evaluated by clotting time and platelet adhesion measurements. In-vitro experiments are also conducted. Our reesults show that Ti(Ta+5)O@sub 2@ films exhibit attractive blood compatibility exceeding that of low isotropic pyrolytic carbon. The existence of Ta+5 improves the blood compatibility. Materials characteristics such as the surface energy and semiconductivity also play important roles. Our results suggest that the smaller blood / film interfacial tension is partially responsible for the enhancement. In addition, the film possesses better hemocompatibility because its optical bandgap of 3.2eV is wider than that of fibrinogen which is 1.8eV. These factors result in thinner protein layers on the surface and less distortion as well as denaturing.
FP-1-10 Influence of the Growth Conditions of AlN Films by Laser Ablation
A Basillais, C Boulmer-Leborgne (Gremi, France); J Perriere (Gps, France)
The pulsed laser ablation of targets in vacuum or in a reactive ambient gas (especially for oxide layer) is a very popular method for growing thin films with complex compositions and various properties. But the reliability of the pulsed laser deposition technique needs a wider understanding of thin film growth for nitride films. In this study we report AlN thin film growth by pulsed laser ablation of Al target in N2 reactive ambient gas compared to laser ablation of AlN target in vacuum or N2 gas. An approach of AlN film grown on Si(100) and Al2O3 substrates is studied. The best experimental conditions are defined in relation with film quality deduced from surface analysis (RBS, NRA, XPS, XRD, MEB). The influence of process parameters such as nature of the target, laser energy density and nitrogen partial pressure on the composition, chemical nature and structure of the films has been investigated. The main problem in AlN film growth was the oxygen incorporation. The origin of this contamination and the mechanisms of incorporation were studied, and the crucial parameter was found to be the residual pressure during ablation. Due to the difference in chemical reactivity between O and N, it is necessary to increase the density of atomic nitrogen to obtain pure AlN films. Thus, a RF discharge device was added allowing a better nitrogen molecule dissociation. Finally the hexagonal AlN phase can be formed in the laser deposited films. Highly textured films presenting epitaxial relationships with (001) Al2O3 substrates can be grown with only 5% oxygen contamination. The plasma plume investigation by emission spectroscopy allows the reactive species kinetics study for AlN growth. A secondary discharge device is mounted on the substrate to study the dark zone where there is no more plasma plume emission.
FP-1-11 Study of W Films Derived from Silane Activation and TiN Barrier Integrity for W Volcano-Free Process
H.L. Chang (National Chiao Tung University, Taiwan); F.L. Juang (Silicon Integrated Systems Corp., Taiwan)
The silane activation to form a Si seed layer is used for W film deposition by a chemical vapor deposition system. The effects of silane activation time on W volcano formation are investigated. The experiment results indicate that long silane activation time catalysts and increases area density of W volcano. Use SEM to examine the W plugs formed in various silane activation time. In this study, higher step-coverage of W films occurs at a range of silane activation time. In additions, the step-coverage of W films is getting worse as the silane activation time increasing. The mechanisms of silane activation time related to W volcano formation and film step-coverage are examined. TiN barriers with different thickness are used to evaluate the effectiveness for process of W volcano-free. It is investigated that the W volcano-free process is in the limited ranges of TiN films thickness, and is a compromise between internal stress and TiN film thickness.
FP-1-12 Micro-Impact Testing: A New Technique for Investigating Fracture Toughness
B.D. Beake (Micro Materials Ltd., United Kingdom); M.J. Ibàñez (Instituto de Technología Cerámica); J.F. Smith (Micro Materials Ltd., United Kingdom)
The wear-resistance of surface-engineered systems is becoming routinely evaluated by nanoindentation and/or scratch testing. However, the results do not always correlate with actual coating performance, where coatings and thin films often fail by a fatigue process. Here, knowledge of fracture toughness of coatings is an important design parameter which can be used to optimise the final product performance. A novel micro-impact technique has been developed to simulate the repetitive contact conditions which many thin films and coatings experience in service. In this work we describe how the technique has been used to investigate the impact resistance of ceramic coatings of almost identical microhardness. There were very clear differences in impact behaviour between the coatings which correlated with measurements of their fracture toughness determined from crack inspection. Coatings with low fracture toughness values exhibited high wear rates and a marked susceptibility to brittle fracture. Notably, the high surface roughness of some of the ceramic samples precluded the determination of critical loads by scratch testing. In contrast, the micro-impact technique is less affected by roughness than scratch testing, and therefore is able to provide useful data on a wider range of materials. The micro-impact technique offers an important new method for the determination of the fracture toughness of thin films where methods involving the direct visualisation of cracks are impossible.
FP-1-13 Adhesion Promotion of Cu on C by Cr Intermediate Layers Investigated by the SIMS Method
K.E. Mayerhofer (Vienna University of Technology, Austria); E. Neubauer (Austrian Research Centers Seibersdorf, Austria); C. Eisenmenger-Sittner, H Hutter (Vienna University of Technology, Austria)
Copper-carbon composites are candidate materials serving as heat sinks for high speed/high performance electronic components. They combine high thermal conductivity with low density and a tailorable Coefficient of Thermal Expansion (CTE). Because of the low wettability of carbon by copper, a thin layer of chromium can be deposited to promote both the adhesion and the thermal contact of copper with the carbon fibers. Therefore in a first step layers of Cr and Cu were deposited by magnetron sputtering on plane vitreous carbon substrates (Sigradur G) which serve as a model for carbon fibers. From pull-off-adhesion measurements an interlayer-thickness of Cr in the range of 2 - 10 nm was found to provide the optimal adhesion for 1 µm thick copper overlayers. To model the later serial fabrication of the composite which involves a hot pressing step following the deposition, the C/Cr/Cu-samples were heat treated at 800°C under vacuum for 1 hour. Adhesion on the heat treated samples was superior in comparison to the untreated ones. To obtain information about the adhesion mechanism Secondary Ion Mass Spectrometry (SIMS) investigations were done on the depth distribution of the main elements copper, chromium and carbon. Two samples, one as deposited and one subjected to heat treatment after deposition are compared in this investigation. It is found that heat treatment mainly modifies the distribution of Cr in the C/Cr/Cu-System.
FP-1-14 A Comparative Study of Adhesion Promotion of Cu on C by Cr-Interlayers and by Plasma Pre-Treatment of the C-Surface
E. Neubauer (Austrian Research Centers Seibersdorf, Austria); C. Eisenmenger-Sittner, H. Bangert (Vienna University of Technology, Austria); G. Korb (Austrian Research Centers Seibersdorf, Austria)
Metal Matrix Composites (MMCs) based on copper reinforced with carbon fibers are promising materials for an application as heat sink in electronic devices. Due to the lack of adhesion between both constituents an improvement of the copper/carbon interface is necessary. This can be achieved by the removal of contaminants and by increasing the surface roughness of the fibers which enhances the mechanical clamping (e.g. by using plasma pre-treatment) or by the deposition of an adhesion promoting intermediate layer such as Cr. We present a comparative study of these two approaches in respect to the adhesion of Cu on C. Plane substrates of glassy carbon were either coated with Cr interlayers of different thickness by DC-magnetron sputtering or subjected to a plasma pre-treatment of different lengths. The plasma was a DC-gas-discharge supported by a magnetic field. The Ar-pressure was 7 Pa, the average energy of the Ar+ ions was 1keV. Onto the Cr-coated or plasma-treated surface a Cu-layer of 1 µm thickness was deposited by DC-magnetron-sputtering. Macroscopic adhesion tests (pull-off tests) were performed and showed a positive influence on the adhesion of Cu in all cases. The adhesion-promoting effect of the different treatments can be ranked as follows: The smallest effect is achieved by simply depositing Cr as adhesion promoter. Subsequent heat treatment of C/Cr/Cu-samples significantly increases the adhesion of the Cu-overlayer up to the values which can be achieved by using a plasma pre-treatment. Considered the wide range of plasma-treatment types this way seems to be a promising approach to increase the mechanical as well as thermal contact of Cu on C.
FP-1-15 Study of Nature of Principal Scattering Processes in Vacuum Flash Evaporated Thin Films of Thermoelectric Alloy (Bi@sub 0.25@Sb@sub 0.75@)@sub 2@Te@sub 3@ by the Application of Jain-Verma Theory of Carrier Energy Dependent Relaxation Time
V. Damodara Das, R.C. Mallik (Indian Institute of Technology, Madras, India)
Importance of scattering mechanisms under operation in thermoelectric materials can be recognized due to the control of the efficiency of thermoelectric devices like thin film thermopiles and their arrays as the carrier energy dependence of scattering depends on the nature of principal scattering occurring in the thermoelectric material. Hence, it is advantageous to know about the principal and other scattering mechanisms under operation in a thermoelectric material at any given temperature and situation. Jain - Verma theory of carrier energy dependent relaxation time is useful in knowing the nature of energy dependence of the relaxation time, and hence, the nature of the principal scattering mechanism. @paragraph@Jain -Verma theory has been applied to the thermoelectric data of vacuum flash-evaporated and annealed polycrystalline thin films of (Bi@sub 0.25@Sb@sub 0.75@)@sub 2@Te@sub 3@ alloy of different thicknesses vacuum-deposited at room temperature on clean glass substrates to study the nature of principal carrier scattering mechanism in the thin films of the above thermoelectric material and also to know the extent of other scattering mechanisms simultaneously under operation in these films. @paragraph@It is found that the value of the energy dependent scattering index parameter lies between - 0.4 and - 0.3. This indicates that even though the principal scattering mechanism in the thin films of the above material is the normal lattice scattering, other scattering like "impurity" scattering and surface scattering and grain boundary scattering are significant in the present thin films of the alloy, which increase the value of the scattering parameter from the value for pure lattice scattering. It is found that the value of the scattering index parameter decreases with increase in temperature from about - 0.3 at 310 K to - 0.4 at 400 K.. This indicates that there is atomic diffusion and rearrangement during heating in the present alloy thin films at higher temperatures, which decreases the interstitial atom (i.e., "impurity atom") concentration, thereby decreasing the extent of scattering of charge carriers by the "impurity atom" scattering process. These results are discussed and compared with those of thin films of other composition alloys reported earlier.
FP-1-16 Application of Linear Ion Source for Surface Modification of Polimide Films
S. Hakamata, N. Yasui, A.M. Ektessabi (Kyoto University, Japan)
Ion beam irradiation is a potential technique to achieve good adhesion between polymer and metal, because of its controllability of ion energy and dose. However the ion source is rather expensive in general compared with a plasma source. We have tried to solve this problem by using a linear type ion beam source that has a slit type ion beam with a length of more than 300 mm and a width of more than a few mm. The beam width of this type of ion source can be extended, in principle, to as much as 2000 mm, and can modify wide polymer film continuously. Current and energy distribution of the linear ion source have been measured and the results show the good uniformity of the beam. Surface of polyimide film, which is a popular material for many electronic devices such as flexible printed circuit and liquid crystal display, have been modified by oxygen ion beam generated by the linear ion source. The result of X-ray photoelectron spectroscopy shows the equivalent modification quality to more popular electron cyclotron resonance (ECR) type ion source. Adhesion test between modified polyimide film and cupper thin film also show a fine result, which indicates a high probability to apply the linear ion source to mass production of such kind of metal-polymer complexes.
FP-1-17 The Surface Reaction of SrBi@sub 2@Ta@sub 2@O@sub 9@ Thin Films Using Cl@sub 2@/CF@sub 4@/Ar Gas Chemistries
D.P. Kim, C.I. Kim (Chung-Ang University, Korea)
In recent years, non-volatile ferroelectric random access memory (FRAM) has been attracted great attention for the applications with fast switching speed, low operating voltage, and high radiation hardness. FRAM comes to be used where high performance and power efficiency are required, in such as communication products, portable applications, logic IC, and smart cards. For highly density FRAM, one transistor and one capacitor structure (1-T/1-C) was proposed. Pb(Zr@sub 1-x@Ti@sub x@)O@sub 3@ (PZT), SrBi@sub 2@Ta@sub 2@O@sub 9@ (SBT) and Bi@sub 3.25@La@sub 0.75@Ti@sub 3@O@sub 12@ (BLT) have been challenged as dielectric materials of capacitor. Among them, SBT thin films have been attracted because SBT thin films show high dielectric constant, long data retention and fatigue endurance up to 10@super 11@ switching cycles. A few papers have been reported about etching mechanism and electrical properties during SBT thin film etching. Therefore, SBT thin films were etched in CF@sub 4@/Cl@sub 2@/Ar by performing measurements of etch rates at different etching parameters such as gas mixing ratio, rf power, dc bias voltage, and chamber pressure. The chemical reactions on the etched surface were investigated with x-ray photoelectron spectroscopy and secondary ion mass spectrometry. Higher etch rate was obtained in CF@sub 4@/Cl@sub 2@/Ar plasma rather than in Cl@sub 2@/Ar plasma. Atomic force microscopy (AFM) was used to investigate the surface morphology of etched SBT thin films. High-resolution transmission electron microscopy (TEM) and auger electron spectroscopy (AES) were evaluated in order to investigate surface morphology. Electrical properties were characterized by measuring leakage current.
FP-1-18 Fabrication of YBCO Superconducting Film With CeO@sub 2@/BaTiO@sub 3@ Double Buffer Layer
S.Y Lee (Yonsei University, Korea); C.H Hur (University of Korea)
We have fabricated good quality superconducting Yba@sub 2@Cu@sub 3@O@sub 7@-x(YBCO) thin films on Hastelloy(Ni-Cr-Mo alloys) metallic substrates with CeO@sub 2@ and BaTiO@sub 3@ buffer layers in-situ by pulsed laser deposition in a multi-target processing chamber. YBCO film with CeO@sub 2@ single buffer layer shows Tc of 71.64 K and the grain size less than 0.1 mm. When BaTiO3 is used as a single buffer layer, the grain size of YBCO is observed to be larger than that of YBCO/CeO@sub 2@ by 200 times and the transition temperature of the film is enhanced to be about 84 K. CeO@sub 2@/BaTiO@sub 3@ double buffer layer has been adopted to enhance the superconducting properties, which results in the enhancement of the critical temperature and the critical current density to be about 85 K and 8.4 x 104 A/cm@super 2@ at 77 K, respectively mainly due to the enlargement of the grain size of YBCO film.
FP-1-19 Recovery of Plasma-Induced Damage in PZT Thin Film With Additive N@sub 2@ Gas
M.G. Kang, C.I. Kim (Chung-Ang University, Korea)
Lead zirconate-titanate (PZT) ferroelectric thin films are known for their possible application in non-volatile random access memories (NVRAMs) as well as dynamic random access memories (DRAMs). In order to gain high device performance, minimization of plasma-induced damage is needed. In this study, in order to investigate the etching damage effects of device performance, we etched PZT thin films with inductively coupled Cl@sub 2@/Ar plasma varying etch parameters such as gas mixing ratio, rf power, dc-bias voltage, chamber pressure. Also, we investigated the effects of damage recovery according to addition of N@sub 2@ gas. An N@sub 2@ plasma treatment for the etched samples effectively removed the etch-induced defects and damage on the surface, leading to improved surface morphology and electrical property in PZT. Plasma-induced damage was evaluated by electrical characterization and surface analysis. Electrical property is characterized by measuring leakage current. Surface morphology is investigated by atomic force microscopy (AFM) and scanning electron spectroscopy. .
FP-1-20 DC Conductivity in RF Magnetron Sputtered Gold-Silicon Nitride-Gold Sandwich Structures
R.D. Gould (Keele University, United Kingdom); S.A. Awan (University of Keele, United Kingdom)
Following our recent work@footnote 1@ on RF magnetron sputtered silicon nitride thin films, this has been extended to include the effects of gold electrodes on the electrical conductivity. The sandwich structure films were RF sputtered from a silicon nitride target at a power of 100 W using N@sub 2@ as the sputtering gas. In agreement with the results for samples with Al electrodes, the capacitance was independent of the applied voltage, indicating that Schottky barriers were absent at the interfaces and that Au provided an ohmic contact to the silicon nitride films. Measurements of capacitance as a function of inverse thickness showed a geometric variation, with a relative permittivity value of 6.8, slightly higher than for Al electrodes. When dc voltages exceeding approximately 2 V were applied there was a decrease in the current and the establishment of differential negative resistance behaviour. This is typical of electroforming, a process which is known to appear in thin film insulators having electrodes of a noble metal@footnote 2@. At low voltages Ohm's law was obeyed, followed by a field-lowering process, with coefficient @beta@ ~ 1.95 x 10@super -5@ eV m@super1/2@ V@super -1/2@. This was identified with Poole-Frenkel emission, since ohmic contacts rather than Schottky barriers were used. Such behaviour was in contrast to that observed in sputtered silicon nitride films with Al electrodes which showed space-charge-limited conductivity, but had similaritiesto results for ion-implanted silicon nitride films @footnote 3@, where the measured field-lowering coefficient was also smaller then the theoretical value. @paragraph@@footnote 1@ S.A. Awan, R.D. Guld and S. Gravano, Thin Solid Films 355/356, 456 (1999). @footnote 2@A.K. Ray and C.A. Hogarth, Int J. Electron. 57, 1 (1984). @footnote 3@A.D. Yadav and M.C. Joshi, Thin Solid Films 102, 187 (1983); Corrigendum 103, L49 (1983).
FP-1-21 Composition, Structure, Morphology, and Mechanical Properties of CrN@sub x@ Thin Films Deposited by dc Reactive Magnetron Sputtering
G.H. Wei, A. Rar, J.A. Barnard (The University of Alabama)
Thin films of CrN@sub x@ (0<= x <=1) were deposited on silicon (100) by dc reactive magnetron sputtering using a wide range of N@sub 2@ partial pressures (pN@sub 2@ ranged from 0 to 40 %). The chemical composition and crystal structure of the resulting CrNx thin films were determined by x-ray photoelectron spectroscopy and x-ray diffraction, respectively. X-ray reflectivity was used to measure the film thickness. Scanning electron and atomic force microscopy were used to evaluate the growth and surface morphology of the films. Nanoindention hardness and modulus were measured using a Hysitron nanomechanical properties system. The deposition rate was found to initially increase with increasing pN@sub 2@ up to about 4.0% and then decreased beyond this value. The presence of Cr, Cr@sub 2@N and CrN (and mixtures of these phases) has been identified and related to the average film composition. Pure Cr@sub 2@N was obtained for pN@sub 2@ in the range of 8.0 ~ 9.0 %, while pure CrN was obtained for pN@sub 2@ > 22%. AFM plan view studies showed that the roughness of CrNx decreased with increasing nitrogen content until Cr@sub 2@N was obtained, at which point the roughness increased. The highest hardness was obtained for pN@sub 2@ in the range 7.3 ~ 10.1 %. The effects of sputtering bias and annealing treatments on the growth mode and nanomechanical behavior of CrN@sub x@ are also reported.
FP-1-22 Young's Modulus and Hardness Calculations from Depth-Sensing Indentation Tests with a Knoop Indenter
L. Riester (Oak Ridge National Laboratory); A.C. Fischer-Cripps (CSIRO, Australia); P.J. Blau, E. Lara-Curzio (Oak Ridge National Laboratory)
Measuring hardness and Young's modulus with a Nanoindenter using a Knoop indenter tip may be useful for assessing mechanical properties of materials where a long, slender indenter geometry or shallow penetrations depths are preferred. This study attempts to find a relationship between contact stiffness, Young's modulus and hardness for the Knoop indenter. Experimental data from materials with known mechanical properties serve as basis for defining this relationship which will allow calculation of Young's Modulus and hardness for any material using a Knoop Indenter. A method to calibrate a Knoop indenter tip shape based on load vs. displacement data will also be presented.
FP-1-23 Effect Of Heat Treatment For Residual Stress On TiCN Thin Films
T. Sasaki, M.G. Gotoh, S.T. Takahashi, Y. Hirose (Kanazawa University, Japan)
Titanium Carbon Nitride (TiCN) coating was aimed to improvement of wear resistance for metal cutting tool and punch dice. The use environment of the TiCN coating material should measure the change in the mechanical property in high temperature. @paragraph@ The X-ray diffraction technique was able to measure the internal stress within X-ray penetration depth, and an effective method of texture analysis for thin film material. @paragraph@ In this study, applied to heat treatment for TiCN coating material, which evaporated by physical vapor deposition method on steel substrate. We considered to influences of heat treatment temperature, for residual stress and texture characterization were using X-ray diffraction method.
FP-1-24 Study on Stress Measurement of Ti-Al Intermetallic Compound Prepared by SHS Method
T.M. Murotani, R. Okada, T. Sasaki, Y. Hirose (Kanazawa University, Japan)
Ti-Al system intermetallic compound have a high strength under the high temperature, and low weight material, use is advanced heatproof material. The self-propagating high-temperature synthesis (SHS) reaction is the material synthesis methods with good heat efficiency for intermetallic compound material. @paragraph@ Residual stress was generated in their interface, due to the difference of a mechanical property between materials. An X-ray stress measurement technique develops into this as one of effective experimenting mechanical techniques in field of the residual stress measurement.Specimen of this study as the Ti-Al system intermetallic compound was evaporated on cast iron substrate, using SHS method. @paragraph@ In this study, an X-ray diffraction technique was applied, and the influences of a coating temperature and a property of substrate material on a residual stress in the Ti-Al coating layer were discussed.
FP-1-25 Elastic Constants of ITO films
J. Jorzick, H. Seitz, B. Schröder, K. Jung (Universität Kaiserslautern und Schwerpunkt Materialwissenschaften, Germany); B. Hillebrands (Universitaet Kaiserslautern, Germany); T. Wittkowski (Universität Kaiserslautern und Schwerpunkt Materialwissenschaften, Germany)
Tin doped In@sub 2@O@sub 3@ is a commonly used material for technical applications requiring transparent and electrically conducting films. Of actual interest are ITO coatings on flexible substrates, for example as EMI shielding. Especially for this purpose the knowledge of the elastic properties of the film material is of importance. The present study uses the Brillouin light scattering (BLS) technique to determine several independent constants of the elastic tensor. The films were deposited by reactive d.c.-sputtering from an ITO target at a substrate temperature of 150 °C. In the BLS spectra the Rayleigh mode and up to four higher-order Rayleigh-like modes in the discrete part of the mode spectrum were detected. In order to determine the dispersion curves of the surface modes completely, six films of different thickness were investigated. This allows one to detect variations of the elastic properties with increasing film thickness. The elastic constants are deduced in a fit procedure to represent the experimental data. The full description of the elastic properties is achieved using a model of hexagonal symmetry with the zonal axis aligned parallel to the surface normal. The results of ITO on HF-etched crystalline silicon will be presented in detail, supplied with results of complementary analytical methods. The elastic constants of the film material are given and discussed in comparison to ITO films on other substrate materials. Work supported by the Deutsche Forschungsgemeinschaft.
FP-1-26 Influence of Residual Stress on Wear Property for Ni-Co-P/ Si@sub 3@N@sub 4@ Composite Film
S.T. Takago, J.S. Sakaguchi, S.T. Sasaki, Y. Hirose (Kanazawa University, Japan)
Materials which Ni-Co-P/Si@sub 3@N@sub 4@ coated material film is excels in the wear resistance. They are consists of metal and ceramics, which called as the metal matrix composite. Residual macro- and microstress generated due to the difference of mechanical properties. Since residual stress controlled the strength of materials, it is significant to evaluate the micro- and microstress accurately. @paragraph@ In this study, phase strains were measured using X-ray diffraction technique. Phase stress was determined from the diffraction elastic constant. Influence of the film thickness, the grain size and the volume fraction of Si@sub 3@N@sub 4@ particles on residual stress was discussed. The plane stress analysis and the triaxial stress analysis were performed. Furthermore the wear property was investigated by scratch test. @paragraph@ It was found that residual compressive stress in the Ni-Co-P phase decrease with the film thickness. Obtained stress calculated from plane stress analysis does not agree with that of triaxial stress analysis. The wear-resistance of film improved with compressive stress in the Si@sub 3@ N@sub 4@ phase.
FP-1-27 Residual Stress of PVD-TiN Film Using Image Plate
Y. Hirose, J.H. He, H.Y. Yoshida, T. Sasaki (Kanazawa University, Japan)
Residual stress of PVD-TiN (titanium/nitride) film using X-ray diffraction technique is measured actively. The PVD-TiN film coated materials have the [111] oriented texture. In this study, we measured stress using Image Plate (IP) as a 2D detector that was developed recently. TiN film evaporated by PVD was measured at @psai@=39, 75 deg. The results of experiment were compared with those by the diffractometer (0D detector) method using the parallel beam optics. @paragraph@ It was found that the stresses obtained by the both method agree well with each other. Moreover, this method was able to be shortening of measurement time by IP. In addition, the X-ray incidence angle was adjusted, the relationship between the substrate material (Fe) and TiN film was clarified.
FP-1-28 Abrasion Mechanism Investigations of Tantalum Thin Film in Colloidal Silica Slurry
S.Y. Chiu (National Chiao Tung University, Taiwan, ROC); J.W. Hsu (National Tsing Hua University, Taiwan, ROC); Y.L. Wang (Taiwan Semiconductor Manufacturing Company Ltd., Taiwan, ROC); J.F. Chen (National Chiao Tung University, Taiwan, ROC); M.S. Tasi (National Nano Device Laboratories, Taiwan, ROC); H.C. Shih (National Tsing Hua University, Taiwan, ROC); M.S. Feng (National Chiao Tung University, Taiwan, ROC)
Chemical mechanical polishing (CMP) has become the most viable process for obtaining global planarization on the manufacturing of multi-level metallization, Under intensive investigation for ULSI, copper has emerged as an attrative, and alternative choice for future interconnects applications. The challenge on Cu CMP process is the surfacer non-planarity after polishing, i.e. metal dishing and oxide erosion. It is strongly dependent upon the removal selectivity between Cu, barrier metal and dielectric layer. Slurry formulation, both abrasives and other additives, would be the key for the control of removal selectivity. Tantalum and its nitrides are known to be effective adhesion promoter and diffusion barrier for Cu metallization. Tantalum exhibits extreme chemical inerness because a protective oxide film is formed in an aqueous solution. The polishing rate of Ta is much lower than that of Cu in various slurry chemistries reported in earlier works. It makes the Cu/Ta selectivity become critical issues in determine the yield and throughput of Cu CMP. In this study, we focus on the abrasion mechanism of tantalum thin film in colloidal silica slurry. The slurry used in the experiments is colloidal silica slurry with iodate and hydrogen peroxide as an oxidant. The characteristics of these slurry chemistries have been inveastigated by electrochemical measurements, zeta-potential measurements, x-ray photoelectron spectroscopy. The surface morphology is determined by atomic force microscopy. The results demostrate that the abrasion mechanism of Ta would depend upon complexing actions with given chemistries and the electrostatic interactions with abrasives.
FP-1-29 Bias Effect on the Ion-Plated Zirconium Nitride Film on Si (100)
W.-J. Chou, G.-P. Yu (National Tsing Hua University, Taiwan, ROC); J.-H. Huang (National Tsing Hua University, Taiwan, R.O.C.)
Zirconium nitride (ZrN) films were produced by hollow cathode discharge ion-planted (HCD-IP) technique. The deposition conditions for the film with stoichiometric composition were chosen, and the thickness of ZrN films was also controlled. The bias was selected as a controlling parameter covering the range from floating to -250 volts. The purpose of this study is to minimize the noise to investigate the effect of bias on the properties of ZrN film. After deposition, the thin film structure was characterized by X-ray diffraction (XRD), cross-sectional transmission electron microscopy (XTEM), and high-resolution scanning electron microscopy (SEM). N/Zr ratios of the thin film were determined using both X-ray photoelectron spectrometer (XPS) and Rutherford backscattering spectrometer (RBS). From the results of RBS, packing factors of the ZrN films can be obtained. The resistivity of ZrN film was measured by four-point-probe. The hardness of the thin film was obtained from nanoindentation. Atomic force microscope (AFM) was used to measure the roughness of the thin film. The brightness and color of ZrN were determined using the Cielab calorimetric system. The results showed that (111) is the dominant preferred orientation in the ZrN film for all of the specimens and without exception. Hardness of ZrN film with excellent values were 22~32 GPa. The packing factor showed that the ZrN film was dense and close to the bulk material. Resistivity increased with increasing bias and decreasing packing factor. The surface morphology of ZrN films was smooth, the roughness for full series of specimens were lower than 4nm. The brightness of ZrN film decreased with increasing bias. The relationship between ZrN film properties and structure were correlated successfully.
FP-1-30 Characterization of Electrical and Structural Properties of Thin VO@sub x@ Films
S. Im, K.M. Park, W.H. Ha (Yonsei university, Korea); S. Yi (Korea Institute of Industrial Technology, Korea)
VO@sub X@films deposited on SiO@sub 2@and n-Si by reactive r.f. sputtering at room temperature were characterized for the purpose of MIS capacitors, because VO@sub X@films have high dielectric constant (@epsilon@= 13.84 for V@sub 2@O@sub 5@at R.T) compared to thermally grown SiO@sub 2@films, and also because the film possibly forms at low temperatures under 300°C. The working pressure was 5mTorr, adjusted by Ar and O@sub 2@flow 7:1. The r.f. power applied to the cathode was 300W. Post annealing was performed at the temperatures of 200°C, 300°C, 400°C, and 450°C in N@sub 2@ambient. The phase and properties of films were characterized by X-ray diffraction (XRD) and resistivity measurements. Then, approximately 3000Åthick Au-dots (300µm-dia) were deposited on VO@sub X@films for other electrical measurements.@paragraph@Resistivity decreases with the increase of annealing temperature due to the phase transition from V@sub 2@O@sub 5@to V@sub 2@O@sub 3@, characterized by X-ray diffraction (XRD). Atomic Force Microscope (AFM) shows that the surface roughness and cluster size of VO@sub X@films increase with the annealing temperature. According to the results from capacitance-voltage (C-V), most of all films have much higher capacitance than a reference SiO@sub 2@film by about 4 times when experimentally compared. However, current-voltage (I-V) characteristics show that the current leakage from VO@sub X@films are much larger than that from the SiO@sub 2@film. The leakage basically increases with the annealing temperature. In the present report, the correlation between the electrical and structural properties of thin VO@sub X@films will be further discussed in detail based on the results from XRD, AFM, I-V, and C-V measurents.
FP-1-31 Plasma Diagnostics of Diamond-like Carbon Films Deposited by Unbalanced Magnetron Sputtering
M.C. Chiu, D.Y. Wang (National Chung Hsing University, Taiwan, ROC)
Diamond-like carbon (DLC) films posses superior mechanical, optical, thermal, and electrical properties for advanced eng ineering applications. DLC films have been synthesized by various PECVD and PVD processes. In this study, DLC consisting of n on-hydrogenated amorphous carbon with very high microhardness was deposited by using unbalanced magnetron sputtering (UBMS). H ighly ionized carbon plasma was generated from pyrolitic graphite targets by UBMS. The reaction mechanism including carbon dis sociation and deposition was examined by plasma diagnostics. A Langmuir probe was installed to analyze the plasma potential, i on density, electron temperature, and electron energy distribution. A quadrupole mass spectrometer was installed to analyze th e mass spectra of neutrals, radicals as well as positive and negative ions. An optical emission spectrometer was installed to monitor the density of ionic species. The diagnosis provides a clear insight into the correlation between deposition parameter s and DLC properties. Accordingly, the further modification of DLC films such as stress reduction, hardness enhancement, and microstructure evolution via plasma alteration can be based upon.
FP-1-32 Effects of Si Surface States on the Epitaxially Grown Al@sub 2@O@sub 3@ Thin Films
S.W. Whangbo, Y.K. Choi, K.B. Chung, H.K. Jang, C.N. Whang (Yonsei University, Korea)
The Al@sub 2@O@sub 3@ films were epitaxially grown on clean and oxidized Si(111) substrates by ionized beam deposition. Al solid source and O@sub 2@ gas were used as a source materials. Reflection of high energy electron diffraction (RHEED), High resolution electron microscopy (HREM), and Atomic-force microscopy (AFM) results revealed that the Al@sub 2@O@sub 3@ thin films grown on the oxidized Si(111) surface had better crystalline qualities and surface flatness than the films grown on the clean Si(111) surface. The epitaxial temperature of the Al@sub 2@O@sub 3@ films was 830°C and the stoichiometry was found to be similar to that of sapphire used as a reference material.
FP-1-33 Characterization and Properties of SiO@sub x@ Films Deposited on p-Si by Thermal Evaporation of SiO Powders
H.S. Bae, S. Im (Yonsei University, Korea); J.H. Song (Korea Institute of Science and Technology, Korea)
Silicon oxide (SiO@sub x@) layers have usually been deposited onto Si substrate by PECVD and reactive RF-sputtering as a potential thin film for the Si-based optoelectronics.@@In the present study, the SiO@sub x@layers were fabricated by thermal evaporation of SiO powders onto p-type Si (100) substrates at 200@degree@C. The background pressure was ~10@super -5@Torr. The layer compositions and the thickness were determined by Rutherford backscattering Spectrometry (RBS). The thicknesses of oxide layers were 560@Ao@and 1000@Ao@and the@Ao@compositions were of x=1.4 ~ 1.6 respectively. After deposition, the samples were annealed in N@sub 2@ambient for 2 hours at 500@degree@C and 900@degree@C. The photoluminescence (PL) of the samples is observed in the violet region. Using an atomic force microscope (AFM), we have observed that the surface roughness of SiO@sub x@films increases with the annealing temperature. The thicknesses and surface roughness of the films were also characterized by X-ray diffraction (XRD). Then, metal-insulator-semiconductor (MIS) structure for electro-luminescence (EL) and current-voltage (I-V) measurements were prepared using Au layers and ITO layers as front electrodes with a dot diameter of 300@micron@. As a result, the red electroluminescence (EL) due to radiative defects from the SiO@sub x@samples was observed near 730 nm under a reverse bias. Current-voltage (I-V) measurement shows that there is little leakage current under the reverse bias.@@In the present work, it will be further discussed the effects of thermal annealing on the surface roughness, the electrical properties and emitting properties of SiO@sub x@layers.
FP-1-34 Stress Profiles for Chromium Nitride Coatings Deposited by PVD Methods
M.A. Djouadi, C. Nouveau (ENSAM, France); O. Banakh, R. Sanjines (IPA, EPFL, Switzerland); L. Imhoff (Universite de Bourgogne, France); F. Levy (IPA, EPFL, Switzerland)
In previous works, the cubic and hexagonal phases of chromium nitride had been synthesised by magnetron and triode sputtering techniques [1, 2] and successfully applied in wood machining [2]. Indeed, it had been shown that the coated knives behave better than the uncoated ones. Nevertheless, the limiting factor for an optimal use of these films is their adhesion. The bad adhesion of the PVD films is related to their high level of compressive stress. Therefore we performed a deep study of the intrinsic stress of CrN and Cr2N films. The first results show that for both structures (hexagonal and cubic) the stress is no longer homogeneous with the film thickness. As it was not possible for us to perform in situ stress measurements, we decided to perform dynamic stress profile by following the variation of the substrate curvature with the deposition time, all the other parameters were kept constant. In addition to the stress measurements, composition and structural properties of the film versus thickness were obtained by XPS, XRD and AFM characterization. The results will be presented and the stress behavior will be discussed and compared with stress profiles obtained by Brillouin light scattering spectroscopy. 1 P. Hones, R. Sanjines, F. Levy, Surf. Coat. Technol. 94-95 . 1997 398-402. 2 M.A. Djouadi, P. Beer, R. Marchal, A. Sokolowska, C. Nouveau, Surf. Coat. Technol. 116-119. 1999 508-516. .
FP-1-35 Characterization of Thin Film Elastic Properties Using X-Ray Diffraction and Mechanical Methods: Application to Polycristalline Stainless Steel
P.O. Renault (Laboratoire Metallurgie Physique -UMR6630-CNRS, France); P. Villain (University of Poitiers, France); P. Goudeau (Universite de Poitiers, France); K.F. Badawi, C. Coupeau (Laboratoire Metallurgie Physique -UMR6630-CNRS, France); V. Pelosin (ENSMA, France); B. Boubeker (University of Ben M'Sik, Morocco)
Sputter deposited thin films are widely used for mechanical and tribological properties improvement of bulk material surface. Because of the particular microstructure (defects) which develops during thin film growth, the thin film elastic constants may differ from the bulk material one (when this material exists in the bulk state). The Young modulus and Poisson's ratio of reduced thickness layers are generally unknown whereas modelisation of mechanical behavior of thin film/substrate systems or stress determination by X-ray diffraction cannot be done in an accurate way without the knowledge of these values.@paragraph@This communication is devoted to measuring the mechanical properties of polycrystalline thin films. We will present three types of experiments which have been developed in our laboratory for determining elastic constant in polycrystalline thin films elaborated by ion beam sputtering:@paragraph@A vibrating reed device which allows in static mode to measure in situ the variation of the total stress in the film as a function of temperature up to 760K and thus to extract the bi axial modulus of the film for different annealing temperatures when the dilatation coefficients of the film and the substrate are known,@paragraph@In situ tensile deformation in a diffractometer which allows, in a simple way, Poisson's ratio determination in thin films and multilayers,@paragraph@Atomic Force Microscopy analysis of spontaneous buckling geometry of thin films presenting large compressive residual stresses which allows to extract the flexion modulus when the average in-plane stress is known.@paragraph@Results obtained for 304L stainless steel metallic thin films (300 nm thickness) will be discussed as well as the future developments of such experiments..
FP-1-36 Adhesion and Thermal Contact Resistance of Gold and Copper Films on Alumina Substrates
D. Sakami (Ecole Polytechnique de l'Université de Nantes, France); A. Lahmar, Y. Scudeller, F. Danes (Ecole Polytechnique de l'Université de Nantes)
This work deals with a comparative study between the Au/Al@sub 2@O@sub 3@ and Cu/Al@sub 2@O3 films. The first one is obtained by evaporation, while the second one is obtained by sputtering magnetron technique. The evolution of the thermal contact resistance (Rc) with respect to the film thickness is significant in both cases. Correlation between Rc values and the adhesion were developed from a detailed analysis of the interface. Observation with X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (MEB) have shown the formation of a new Compound in the interface region in the case of Au/Al@sub 2@O@sub 3@. However, the thermal and mechanical evolution may be attributed to change in structure, composition, and formation of constraints in the film during the production.
FP-1-37 Ti-Al System Intermetallic Compound Coating on Dual-phase Stainless Steel by SHS Method
T.K. Kondoh, T.G. Goto (Aichi Institute of Technology, Japan); H.H. Hirose (Kinjo University, Japan); T.M. Murotani, T. Sasaki (Kanazawa University, Japan)
Dual-phase stainless steel was remarking for structure material of chemical plant with excellent corrosion resistance. Whereas, Ti-Al system intermetallic compound have a high strength under the high temperature, and low weight material, use is advanced heatproof material. The self-propagating high-temperature synthesis (SHS) reaction is the material synthesis methods with good heat efficiency for intermetallic compound material. @paragraph@ In this study, an SHS method was applied, and Ti-Al system intermetallic compound was evaporated on dual-phase stainless steel substrate with surplus heat of reaction. Influences of a coating temperature in the substrate material property, and the Adhesion strength were discussed.
FP-1-38 Conductivity Variations in Lead Phthalocyanine Thin Films on Exposure to Ambient Air
T.S Shafai (Staffordshire University, United Kingdom); R.D. Gould (Keele University, United Kingdom)
Recent work on the basic conduction processes in evaporated lead phthalocyanine (PbPc) films with aluminium electrodes@footnote 1@ has been extended to include the effects of exposure to air ambient in Au-PbPc-Au and Al-PbPc-Au sandwich structures. These structures were fabricated by sequential evaporation at a pressure of 1.3 x 10@super -3@ Pa or below. Under vacuum Au-PbPc-Au sandwich structures showed ohmic conductivity followed by space-charge-limited conductivity (SCLC) dominated by trap levels located at a discrete energy level. When measured in air after storage for 24 hours, there was a significant increase in current in both the ohmic and the SCLC regions. Furthermore, conductivity in the SCLC region was now dominated by an exponential distribution of traps of typical concentration 4.5 x 10@super 23@ m@super -3@ as a result of the ambient storage. Conversely under forward bias (gold positive) Al-PbPc-Au samples showed a marked decrease in current density after exposure to air for a period of 24 hours. There was no significant change in current density values after further exposure of up to 1 week. Under reverse bias (aluminium positive) there was a significant change in the current density-voltage (J-V) characteristics which showed a linear dependence of logJ on V@super 1/2@, indicating Schottky emission. Derived values of the field-lowering coefficient @beta@ after this exposure to air were closer to the theoretical values than in samples unexposed to air. It was concluded that the formation of Schottky barriers are encouraged by air exposure, possibly forming an Al@sub 2@O@sub 3@ layer as previously suggested for triclinic PbPc@footnote 2@, whose effect would also be to reduce current levels in forward-biassed samples as observed. @footnote 1@R.D. Gould and T.S. Shafai, Thin Solid Films 373, 89 (2000). @footnote 2@A. Ahmad and R.A. Collins, Physica Status Solidi (a) 126, 411 (1991.
FP-1-39 Preparation Dependence of Photoluminescence From Ion-Beam-Mixed SiO@sub 2@/Si/SiO@sub 2@ Thin Films
K.H. Chae, J.H. Son, S.W. Shin, S.H. Kim, T.G. Kim, G.S. Chang, M.C. Sung, K. Jeong, S. Im, C.N. Whang (Yonsei University, Korea); J.H. Song (Korea Institute of Science and Technology, Korea)
The properties of photoluminescence from ion-beam-mixed SiO@sub 2@/Si/SiO@sub 2@ thin films depending on the deposition methods and heat treatments have been studied. SiO@sub 2@/Si/SiO@sub 2@ thin films having the structure of a few nanometer of Si embedded in SiO@sub 2@ layers were fabricated by the sputter-deposition and the electron-beam evaporation methods. The samples deposited by the sputter-deposition shows a 700 nm luminescence after ion-beam mixing and subsequent annealing at high temperature. But the samples deposited by electron-beam evaporation show no spectra after ion beam mixing and subsequent annealing at high temperature. On the other hand, the samples deposited by the electron-beam evaporation show a 420 nm luminescence when the samples were preannealed at high temperature before ion-beam-mixing and subsequent annealing at high temperature. Electron spin resonance, Raman spectroscopy, and transmission electron microscopy were performed to study the difference of photoluminescence depending on the deposition methods and thermal treatment.
FP-1-40 Microtopographic Characterization of Molybdenum Doped Aluminum Oxide Coatings for Application on Solar Absorbers
M.F. Costa, V. Teixeira, A. Monteiro (Universidade do Minho, Portugal); C. Nunes (Instituto Nacional de Engenharia e Tecnologia Industrial, Portugal)
The development of new efficient solar energy collectors either for thermal conversion is deserving a new strong attention on view of our days ecological problems. A number of PVD coatings can be successfully employed in thermal converters. Multilayered molybdenum doped aluminum oxide coatings show very positive characteristics. Its energy conversion efficiency depends on its chemical and physical structural characteristics and related optical properties like reflectance, emittance, absorptance and transmittance. The roughness and topographic characteristics of the produced coatings will greatly condition its relevant properties. Thus a careful evaluation of the coatings’ roughness and its microtopographic inspection is performed with the MICROTOP.03.MFC microtopographer. Preliminary results will be presented and discussed.
FP-1-41 Characterization of Chromium Nitride Films Produced by PVD Techniques
A. Barata, L. Cunha, C. Moura (Departmento de Fisica - Universidade do Minho, Portugal)
Chromium nitride thin films have been deposited on stainless steel substrates, by r.f. reactive magnetron sputtering. The influence of process parameters such as substrate temperature, substrate bias and partial pressure of reactive gas have been investigated. The characterization of microstructure in these coatings was performed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). These studies allow us to analyse the influence of deposition parameters in crystal phase and crystal orientation. The relation between surface defects, and their characteristics, with deposition conditions will be also taken into account. The presence of oxygen on coatings surface, due to atmospheric contamination, is analysed by means of Raman spectroscopy (RS). This optical technique can be used for the characterization of the surface oxides at different stages of oxidation. The changes observed in Raman spectra can be correlated with process parameters.
FP-1-42 Performance of Chromium Nitride and Titanium Nitride Coatings During Plastic Injection Moulding
L. Cunha, M. Andritschky (Universidade do Minho, Portugal); A. Zarychta (Silesian University of Technology, Poland); K. Pischow, Z. Wang (Savcor Coatings Oy, Finland); A.S. Miranda, A.M. Cunha (Universidade do Minho, Portugal)
Monolithic coatings of chromium nitride and titanium nitride and multilayer titanium/chromium nitride coatings were produced by r.f. and d.c. reactive magnetron sputtering in order to determine their potential to be used as protective coatings for machinery parts of plastic injection moulding or extruding machines. Tribological and mechanical properties like hardness, Young’s modulus, and wear rate were measured. Monolithic coatings showed higher hardness and lower wear rate when compared with multilayer coatings. The corrosion performance in certain environments was also studied and the behaviour of multilayer coatings was significantly better than the behaviour of monolithic coatings. Multilayer coatings avoid the penetration of chemically aggressive agents through pinholes or pores. The performance of the coatings during plastic processing was tested in an injection moulding machine. The wear rate of the nitride based coatings was more than two orders of magnitude better then some traditional ways of protecting the surfaces like electrodepositing hard chromium or nitriding the steel surface.
FP-1-43 High Temperature Self Lubricant Quasicrystalline Composite Coatings
A. Agüero, F.J. García de Blas, F. Longo, A. Román, A. Sánchez (Instituto Nacional de Técnica Aeroespacial, Spain)
Lubrication at temperature extremes is difficult and can only be achieved by employing self lubricant solid films. The PS100-300 generations of composite coatings develop by NASA constitute one of the best examples of the few coating materials that are effective at temperatures as high as 1000°C and that are also wear resistant. These coatings are deposited by atmospheric plasma spray (APS) and comprise a hard component such as CrC, solid lubricant additives such as Ag and the BaF2-CaF2 eutectic on a NiCr matrix1. Another family of materials with promising tribological properties is that of quasicrystalline alloys (QC), which in general are hard (700 HV0.@footnote 1@), have low friction coefficients and high chemical stability@footnote 2@. Thick composite coatings based on the QC material AlCoFeCr, NiCr, NiCr-Co, WS2, Ag and BaF2-CaF2 have been deposited by APS, low pressure plasma spray (LPPS) and high velocity oxy fuel spray (HVOF). Preliminary results will be presented including characterization by means of SEM-EDS and XRD, microhardness measurements and high temperature pin-on-disc testing to determine friction coefficients as a funciotn of temperature as well as wear resistance. The HVOF deposited coatings have a hardness of 635 HV0.2 and are uniform and dense, presenting less deffects such as oxidation along splat boundaries than the equivalent coatings deposited by APS (200 HV0.2). @footnote 1@ C. DellaCorte and J.A. Fellenstein, Tribology Transactions, v. 40, p.639 (1997). @footnote 2@ D.J. Sordelet and J.M. Bubois, MRS Bulletin, v. 22, p. 34 (1997).
FP-1-44 A Study of Neon-Nitrogen in DC Glow Discharges by Optical Emission Spectroscopy.
J.C. Avelar-Batista, A.D. Wilson, A. Davison, A. Leyland, A. Matthews, K.S. Fancey (University of Hull, United Kingdom)
Although plasma-based surface treatment and coating deposition systems commonly use inert gas-based discharges, considerations of cost combined with useable characteristics tends to limit selection of the inert gas to argon. The need for such a gas to perform as little more than a buffer agent appears to be rarely considered. Nevertheless, the presence of argon in a discharge can influence charge exchange and dissociation behaviour with commonly used process gases such as nitrogen [1]It has been known for many years that metal vapour, present as a minority species in an argon-based discharge, can be significantly ionised by argon metastables (Penning ionisation)[2]; the effect also occurs in neon-based discharges [3]. Of particular interest, is that neon can also Penning ionise nitrogen: preliminary investigations through the deposition of TiN coatings by reactive ion plating have suggested that neon can enhance nitrogen reactivity [4]. In this paper, we report on the use of spatially resolved optical emission spectroscopy to investigate mechanisms within the cathode sheath and plasma regions of dc glow discharges. Results will be used as evidence to suggest that neon may provide key benefits over the use of argon in a plasma processing environment. [1] K S Fancey, Vacuum, 46, 695 (1995). [2] J W Coburn and E Kay, Appl Phys Lett., 18, 435 (1971). [3] D Serxner, R L Smith and K R Hess, Appl Spectrosc., 45, 1656 (1991). [4] K S Fancey, A Leyland, F M Badow and A Matthews, Mat Sci Eng., A262, 227 (1999).
FP-1-45 Ion Plating Discharges: Initial Studies With a Mass-Energy Analyser
A. Davison, A.D. Wilson, J.C. Avelar-Batista, A. Leyland, A. Matthews, K.S. Fancey (University of Hull, United Kingdom)
To understand and improve plasma-based treatment and coating deposition processes, it is important to acquire information on the characteristics of species bombarding the surfaces being processed. To this end, a mass spectrometer/energy analyser system has been installed to sample species arriving at the cathode (substrate) of a dc ion plating system. The analyser can detect species with incident energies of up to 1 keV and the mass detection capability is 2500 amu. The latter feature has a vital role in the detection of species arriving as atomic clusters. For example, there is evidence to suggest that thermal evaporation sources (such as vapour emission by electron beam heating) produce clusters of vapour atoms in an ion plating discharge, with cluster sizes being of the order of tens of atoms per unit charge [1]. In this paper, we report findings from preliminary studies with the analyser, which will provide further elucidation of the vapour and gas bombardment characteristics at the substrate from discharges used in ion plating. [1] K S Fancey and A Matthews, App Phys Lett., 55, 834 (1989).