ICMCTF2005 Session DP: Symposium D Poster Session

Thursday, May 5, 2005 5:00 PM in Room Town & Country

Thursday Afternoon

Time Period ThP Sessions | Topic D Sessions | Time Periods | Topics | ICMCTF2005 Schedule

DP-1 Surface Acoustic Wave Filter Devices on the Aluminum Nitride / Unpolished Nucleation Side of Hot Filament CVD Diamond J.-H. Song, J.-L. Huang (National Cheng-Kung University, Taiwan); H.-H. Lu (National Chin-Yi Institute of Technology, Taiwan); J.C. Sung (Kinik Company, and National Taipei University of Technology, Taiwan); M.-C. Kan (Kinik Company, Taiwan) High quality surface acoustic wave (SAW) filters devices base on the aluminum nitride (AlN) /diamond structure were prepared using the unpolished nucleation side of hot filament CVD diamond. The surface of hot filament CVD diamond films is quite rough and must be smoothed by mechanical polishing in order to favor the wave propagation and to fulfill the requirement of photolithograthic process. In this study, the substrates of SAW device were prepared using unpolished nucleation side of hot filament CVD diamond by removing from a silicon substrate by wet etching. The surface roughness of diamond substrate was less than 2 nm. The high C-axis oriented AlN as piezoelectric layer was deposited on diamond by RF sputter. The c-axis oriented AlN film would be deposited well on the diamond substrate due to lower lattice mismatch between (111) diamond and c-axis oriented AlN thin film. The center frequency of the AlN/diamond SAW filter device is 293.75 MHz (?=32µm), and the SAW velocity is 9400 m/s.
DP-3 Three Dimensional A-C:H Film Coating by Low Pressure Inductively Coupled Plasma Y.K. Koga (National Institute of Advanced Industrial Science and Technology, Japan) Three dimensional plasma CVD technique of a-C:H film has demonstrated using a new type high density volumetric plasma source with multiple low inductance antenna system.The uniformity of the film thickness and refractive index is within 2 percent for a-C:H films on hexagonal substrate holder in the pure toluene plasma with the pressure of 0.04 Pa. The films are duarable for the tribology test with a high load of 20 N up to more than 20000 cycles with low specific wear rate of 1.2x10-7 mm3/Nm and low friction coeeficient of 0.04.
DP-4 Effects of Ti- and Zr- Based Interlayer Coatings on the Hot Filament Chemical Vapour Deposition of Diamond on High Speed Steel R. Polini, F. Pighetti (Universita' di Roma Tor Vergata, Italy); M. Briac (National Institute for Optoelectronics, Italy); M. Amar, M. Ahmed (Manchester Metropolitan University, United Kingdom) The prospect of obtaining good adhesion of diamond films onto steel substrates is highly exciting because the achievement of this objective will open up numerous new applications in industry. However, the major problem with depositing diamond onto steel is high diffusion of carbon into steel at CVD temperatures leading to very low nucleation density and cementite (Fe₃C) formation. Therefore, the study of the nucleation and growth processes is timely and will yield data that can be utilised to get a better understanding of how adhesion can be improved. This work focuses on investigating the adhesion of thin diamond films on high speed steel previously coated with different interlayers such as ZrN, ZrC, TiC and TiC/Ti(C,N)/TiN. The role of seeding on nucleation density and the effect of diamond film thickness on stress development and adhesion will have been investigated using SEM, XRD and Raman spectroscopy.
DP-5 Photocurrent Analysis of Fluorine Doped Thin DLC Films for Electronic Applications S.C. Trippe (CenPRA - Centro de Pesquisas Renato Archer, Brazil); R.D. Mansano (University of San Paulo, Brazil); J.C. Madaleno, E. Pereira, L. Pereira (University of Aveiro, Portugal) Diamond Like Carbon (DLC) has been considered an interesting material for some optical and electronic applications. Together with a high value of microhardness, it exhibits a good optical transparency in a wide wavelength range, as well as high electrical resistivity and thermal conductivity. One of its potential applications involves field emitter devices and the possible application in displays. With a promising beginning, some questions remain unsolved. The growth conditions affect the defects that are electrically active and they strongly influence the final behavior. In order to improve the electrical properties of the films, many attempts of doping have been made. In this work fluorinated DLC films have been deposited in a reactive RF magnetron sputtering system with different concentrations of CF₄ on p-type Si substrates. The thicknesses of the DLC films (measured by perfilometry) range from 0.5 to 1.2 µm. Schottky diodes have been made by Al evaporation on both surfaces (DLC and Si) in a transverse geometry. The effects of fluorine concentration during growth have been studied by electrical DC and photoconductivity measurements. It has been found that the photocurrent in visible region can increase up to two orders of magnitude compared with dark conditions, lowering the activation energy associated with the ionization process (from 140 meV to less than 20 meV) and is dependent on fluorine concentration. The typical photocurrent densities under reverse bias are about 20 - 40 mA/cm² and the carrier density about 10¹⁷ cm³. Discreet photoconductivity shows the influence of two contributions, one in blue - green region (2.4 - 2.5 eV) and another in red - near IR region (1.6 eV). This last contribution appears to be dependent on fluorine concentration DLC growth. Finally a model to explain the photoelectrical properties is proposed.
DP-6 Thin Polycrystalline Diamond Films: Structural Characterisation and Related Electrical Properties J.C. Madaleno (University of Aveiro, Portugal); S.C. Trippe (CenPRA - Centro de Pesquisas Renato Archer, Brazil); L. Pereira (University of Aveiro, Portugal) Polycrystalline diamond films have properties that make them attractive to several applications, ranging from mechanical coatings to the use as electronic devices. Because polycrystalline films have some advantages over homoepitaxial ones, like larger deposition areas and lower costs, their morphological and physical properties have been intensely studied. The films’ structural nature stains the final electrical properties and the correct knowledge of this correlation helps a correct device development. In this work, diamond samples grown by Microwave Plasma Chemical Vapour Deposition have been used to fabricate Schottky diodes. The films’ final thickness ranges from 8 to 12 µm (determined from infrared spectroscopy). The rugosity, taken from AFM data, is 0.5 µm. Raman spectra taken both with HeNe and Ar lasers are presented. The correlation between the films microstructure and electrical DC properties is shown. A detailed study of the micro-Raman spectra reveals the presence of many non pure diamond phases like DLC, graphite, nanodiamond and hydrogenated carbon bonds at the grain boundary regions. The current - voltage data is strongly correlated with the diamond / non-diamond rate. The films’ electrical conductivity rises as the presence of the non-cubic phases increases (current densitites ranging from 1 mA/cm² to 50 mA/cm²), with the corresponding lowering of the rectifying factor. The ideality factor is close to 3. The activation energy for the ionization processes lies in the range 100 and 200 meV. The diamond / non diamond ratio shows that we can control the electrical carrier transport through the film when that ratio lies between 1.5 and 9. Outside these limits the devices become pure resistive or nearly insulating, which suggests that some structural defects are responsible for the major injection and carrier transport mechanisms. The possibility of controlling the structural defects in order to make the films suitable for electronic applications is discussed.
DP-7 Effect of Amorphous Si Layer on the Reaction of Carbon and Silicon in the C/Si Multilayer by IBS under UHV C.K. Chung, M.Q. Tsai, B.H. Wu (National Cheng Kung University, Taiwan) Conventional diamond-like carbon (DLC), amorphous silicon (a-Si) and silicon carbide (SiC) films are prepared by magnetron sputtering or chemical vapor deposition at high vacuum at a base pressure of 10^-6 Torr. In this paper, another deposition technique is used to form carbon/silicon multilayers by ion beam sputtering (IBS) at room temperature under ultra high vacuum (UHV) at a base pressure of 10^-9 to 10^-10 Torr. Then, post vacuum annealing at 10^-6 Torr is performed to study the stability and reaction between carbon and silicon in the C/Si multilayer. Three kinds of structure ie single layer of C, two-layer C/a-Si and three-layer a-Si/C/a-Si are deposited on the single crystalline silicon (c-Si) (100) substrate to study the a-Si effect on the reaction of C and Si under vacuum annealing and characterized by Raman spectroscopy, grazing incident angle X-ray diffractometer (GIAXRD) and Auger electron spectroscopy (AES) depth profile. The as-deposited carbon is DLC with primary sp³ from Raman spectra and increasing sp2 bonding to form sp2-sp3 bonding of amorphous carbon as annealed at 900 ÂºC for one hours . There is no inter-diffusion between C and Si of single layer of C on c-Si substrate even annealed at 900°C for 1.5 hours but it results in the inter-diffusion between C and Si of two-layer C/a-Si annealed at 900°C for 1.5 hours as well as the a-Si transformation to polycrystalline Si shown in the GIAXRD. The grain boundary of polycrystalline Si is helpful to the inter-diffusion between C and Si. It becomes more obvious in the three-layer a-Si/C/a-Si structure. The a-Si transformation to polycrystalline Si begins at about 500°C and becomes obvious at 700°C and then great inter-diffusion occurs between C and Si at 900°C as well as SiC formation in the multilayer. The a-Si layer in C/Si multilayer enhances the inter-diffusion between C and Si and form the nanocomposite structure of C, Si and SiC phases.
DP-8 Effect of the Target Power Density on the Synthesis and Physical Properties of Sputtered nc-C Films H.S. Myung, Y.S. Park, A.R. Jeon, B.Y. Hong, J.G. Han, L.R. Shaginyan (Sungkyunkwan University, South Korea) Since first synthesized by Aisenberg and Chabot in 1971, there has been a continuous growth on the study of synthesis and properties of carbon based films for a period of two decades. These films have various industrial applications due to attractive properties such as high hardness, low friction coefficient, high infrared transparency, high electrical resistivity, good chemical inertness and low surface roughness, etc. In general, carbon based coatings prepared by plasma processing are described as an amorphic solid carbon composed of small sp² bonded graphitic clusters and sp³ coordinated carbon atoms. Therefore, high hardness of carbon based films usually linked with sp³ like bonds. However, sp²-dominated hard and conductive carbon based films are recently emerged. These films have the advantage which various industrial applications are possible owing to hard and conductive properties and have been studied consequently so that it is achieve. Therefore, in this study, we synthesized hydrogen free amorphous carbon (a-C) films with various graphite target power density and gas pressure using a closed-field unbalanced magnetron sputtering system (CFUBM) and attempt to find the relationship between the microstructure and physical properties of a-C films with variation of target power density and gas pressure. Power density of graphite target was varied from 10 to 30 W/cm² at a fixed Ar gas pressure of 0.4Pa, and the Ar gas pressure from 0.4 to 2 Pa at a constant power density of 30W/cm². The film structures were investigated in Raman spectroscopy, XPS and FESEM. Physical properties of a-C films were evaluated by nano indentation tester, 4-point probe and residual stress tester. a-C film deposited at target power density of 10 W/cm² and Ar gas pressure of 0.4 Pa exhibited maximum hardness and minimum electrical resistivity.
DP-9 Characterization of CVD Diamond Films by Cycling Gas Flow Rate T.-G. Kim, H.-S. Kim (Miryang National University, South Korea); S.-H. Kim (Silla University, South Korea); C.-W. Lee (Jinju National University, South Korea); M.-S. Song (Shinhan Diamond Industrial. Co., Ltd., South Korea) We deposited diamond films by using a MPECVD(microwave plasma enhanced chemical vapor deposition) system. To enhance the diamond nucleation densities and qualities, we apply cyclic on/off modulation methane and oxygen gas flow during the initial deposition stage as a function of the reaction time. Detailed process to enhance the diamond nucleation densities and qualities by applying cyclic on/off modulation of methane and oxygen gas flow was presented. Surface morphologies and diamond qualities of the films were investigated. The enhancement of the diamond qualities by the cyclic process was noticeable under the condition of the higher methane and oxygen gas flow on/off time ratio. Based on these results. We discussed the cause for the enhancement of the diamond nucleation densities and the diamond qualities as a function of methane and oxygen gas flow on/off time ratio.
DP-10 Carbon Nanotubes Deposition by Atmospheric Pressure PE-CVD Using Nickel Catalyst S.J Kyung, C.W. Kim, Y.H. Lee, J.H. Lee, G.Y. Yeom (Sungkyunkwan University, South Korea) In the industrial plasma processes, low-pressure plasmas are dominant in the processing of the materials such as thin film deposition, etching, and surface treatment. However, to generate plasmas at low pressures, costly vacuum equipment and vacuum measurement tools are required, and the use of vacuum in the processing increases the fabrication cost and decreases throughput. If stable glow discharges can be realized under atmospheric conditions in large area, the expensive vacuum equipment and the measurement tools can be eliminated and the throughput can be also increased. Many studies concerning the growth of carbon nanotubes(CNT) using Fe,Co and Ni as the catalysts have been reported. In those reports, carbon nanotubes demonstrated different morphologies and internal structures due to the variety of nanotube growth parameters and catalysts used during the CVD. In this study, Ni were used as a catalysts. The effect of different gases used for the catalyst surface pre-treatment(N₂ or NH₃) was also analyzed. CNTs were grown by the atmospheric pressure PECVD. To generate atmospheric pressure plasmas, capillary electrode discharge which is a modification of conventional dielectric barrier discharge was used. Using the atmospheric pressure PE-CVD method, multi-walled carbon nanotubes with diameters of approximately 20-30 nm could be synthesized on glass substrates by the decomposition of acetylene. The structure and morphology of product was analyzed by a scanning electron microscope (SEM), a transmission electron microscope (TEM), and a Fourier transform Raman spectrometer (FT-Raman). This study provides a new method growing CNT at atmospheric pressure and low temperature, which has some specials advantages for scale-up production or applications.
DP-11 Effects of Patterned Catalysts on Structural and Field-Emissive Properties of Carbon Nanotubes Grown by ICP-CVD C.K. Park, J.P. Kim, S.T. Hong, H.S. Uhm, J.S. Park (Hanyang University, South Korea) Electron-emitters based on carbon nanotubes (CNTs) are purported to be promising candidates for the realization of cold cathodes and field-emission displays (FEDs) due to their remarkable properties. In particular, the high aspect ratio of CNTs can generate a large electric field enhancement to obtain electron emission at a low electric field. However, the electrostatic field-screening effect is observed when a great number of CNTs are in close proximity. It is also noted that the sizes or the patterns of catalyst dots may change the growth of CNTs, and hence seriously influence on their structural properties as well as the electron emission capabilities. However, this issue has failed to be profoundly investigated. We present experimental results regarding the effects of catalyst sizes and patterns on the structural and field-emissive properties of multi-wall CNTs which are grown by inductively-coupled plasma-CVD (ICP-CVD) using a gas mixture of C₂H₂/ NH₃. TiN films are deposited on SiO₂-coated Si substrates by DC magnetron sputtering and patterned to have disk cells with diameters between 5 µm and 200 µm. Ni catalysts are deposited on TiN layers by RF magnetron sputtering. The size and the pattern of catalyst dots are determined by the previously formed TiN layers. The electric biases are also applied to substrate during CNT deposition. For all the CNTs grown, their nanostructures and morphologies are analyzed in terms of Ni dot sizes by Raman spectroscopy, AFM, SEM, and TEM. It is observed that the height and the diameter of CNTs are increased with catalyst sizes, but both are rapidly decreased by increasing catalyst size greater than 100 µm. The critical dimensions of catalyst dots for better electron-emission capabilities of CNTs are induced from the measurement of electron-emission currents and threshold electric fields. Further experimental results regarding the effects of catalysts will be presented in more detail.
DP-12 Growth of Aligned CNTs using MPCVD System without Applying Bias Y.M. Lu, C.M. Lo (Kun Shan University of Technology, Taiwan) Most studies of carbon nanotube are focused on how to synthesis high orientation products recently. In this study, the sputtered nickel film was used as the catalyst to grow carbon nanotubes. The reactants, the mixture of methane and hydrogen gases, were introduced into the microwave chemical vapor deposition (MPCVD) system. The effect of methane concentration on the growth of aligined carbon nanotube was studied. The result shows that high alignment carbon nanotubes can be obtained with 2.5sccm methane flow rate at relative low temperature (≤500°C) without any bias being applied. From the I-V measurement, it is found that the minimum turn-on voltage is 1.4V/µm and dependence on the orientation of CNTs. The aspect ratios is another factor to determine the turn-on voltage of CNTs.
DP-13 Thermogravimetric Analysis of Cobalt-Filled Carbon Nanotubes Deposited by Chemical Vapour Deposition B.P. Ramesh, W. Blau (Trinity College, Ireland); P.K. Tyagi, D.S. Misra (Indian Institute of Technology, India); N. Ali, J. Gracio, G. Cabral, E. Titus (University of Aveiro, Portugal) The preparation of great amounts of high purity carbon nanotubes is a major issue in carbon nanotube (CNT) research. Many of the CNT applications are sensitive to the amount of impurities present in a batch of nanotubes. The main impurities are ferromagnetic additives, which are essential for the growth of CNT and carbonaceous materials, such as carbon nanoparticles, amorphous carbon and nanofibers, which are formed during synthesis. In this work, we have attempted the separation and purification of carbon nanotubes using ultrafiltration method. The growth of CNTs was performed using Microwave Plasma Chemical Vapor Deposition (MPCVD) technique. Different characterization techniques were exploited inorder to analyze the purity of the tube. FTIR (Fourier Transform Infrared) studies were carried out in the range 400-4000cm^-1 to study in detail the attachment of defective elements in carbon nanotubes. TGA measurements were carried out under argon flow to obtain information on the decomposition and the burning properties of carbon nanotubes and impurities present in it. Thermal analysis was performed in the range from room temperature to 9000°C. Raman spectroscopy and X-Ray diffraction were employed to study the purity and defects present in CNT.
DP-15 Mechanical Properties of Hard Si-C-N and Si-B-C-N Films Z. Soukup, J. Vlcek, S. Potocky, J. Cizek, M. Kormunda (University of West Bohemia, Czech Republic); V. Perina (Academy of Sciences, Czech Republic) The ternary and quaternary materials containing Si, B, C and N have been attracting great interest due to their new features which can be used in coating and microelectronics technologies. Si-C-N and Si-B-C-N films were deposited on Si substrates by dc magnetron co-sputtering using a composed C-Si and C-Si-B (a fixed 20% boron fraction in the erosion track area) target, respectively, in nitrogen-argon mixtures. Film properties were controlled by the Si fraction in the magnetron erosion track area, the Ar fraction in the gas mixture, the substrate temperature and the substrate bias voltage. The films, typically 1.0 to 2.0 microns thick, were found to be amorphous with a very smooth surface, low compressive stress and good adhesion to substrates. Increasing the silicon fraction in the target area leads to a significant rise in the friction coefficient (from 0.24 to 0.53 for Si-C-N and from 0.33 to 0.85 for Si-B-C-N films under the investigated conditions) at almost constant values of the hardness (around 25 GPa for both the films at a higher substrate bias voltage and temperature) and its growing values (from 17 to 32 GPa for the Si-B-C-N films prepared without a substrate bias and ohmic heating). The lowest wear rates were achieved for the Si-C-N films with the highest carbon content and for the Si-B-C-N films with a high Si content. Increasing the argon fraction in the gas mixture results in a progressive increase in film hardness (up to 35 GPa for Si-C-N films and 50 GPa for Si-B-C-N films) at almost constant values of the friction coefficient (0.40-0.46) for Si-C-N films and its high values (0.60-0.81) for Si-B-C-N films.
DP-16 Photoconductivity and Transport Properties of Amorphous Silicon Carbon Nitride Thin Film and its Application for Deep UV Detection C.W. Chen, Y.Y. Lin (National Taiwan University, Taiwan); C.H. Shen (Academic Sinica, Taiwan); L.C. Chen (National Taiwan University, Taiwan); K.H. Chen (Academic Sinica, Taiwan) Photoconductivity of amorphous silicon carbon nitride (a-SiCN) thin films deposited by the microwave plasma-enhanced chemical vapor deposition (MW-CVD) method has been studied. A MSM (metal-semiconductor-metal) photodetector device based on the a-SiCN thin film demonstrates excellent selective UV sensing features with a relative quantum efficiency (RQE) about 103 for the incident light in the UV region than in the visible light region, providing the potential application for low-cost UV detection. A model based on the heterogeneous structure in a-SiCN thin films which consists of π-π^* bands and σ-σ^* bands was introduced to described the observed photoconductive and carrier transport properties. r; optical properties.
DP-17 Comparative Study Between Ammonia and Nitrogen as the Reactive Gas used for the Production of Silicon Carbonitride Thin FIlms by r.f. Magnetron Sputtering C.A. Achete, R.T. Britto, L.F. Senna, R.A. Simao, M. Michel (Coppe - UFRJ, Brazil); C.M. Lepienski (Catholic University of Parana, Brazil) Spectroscopy Silicon carbon nitride films have been successfully synthesized by reactive magnetron sputtering using a target of SiC and N₂ + Ar as reactive gases. However, it remains open the discussion about the role of each gas on the deposition process and films properties. In this work we present the results obtained using either nitrogen or ammonia as reactive gas to produce SiCN by r. f. magnetron sputtering. The films were prepared using a sintered SiC target and nitrogen / argon or ammonia / argon mixture gas. Different gas range flows were used to describe the properties. Fourier Transform Infrared Spectrometer (FTIR) was used to characterization of the films. The results revealed different chemical bonds in the film, such as CN, C=N, CN, Si'N and SiC, when different gases were used. We also observed a influence of deposition condition over deposition rates, hardness and internal stress. Atomic Force Microscopy (AFM) was used to describe differences in surface morphology of the deposited films in order to understand the variation in the measured of internal stress. Auger (AES) was used to sputter depth profiles.
DP-18 Thermal Stability of Hard Si-B-C-N Films Prepared by Reactive Magnetron Sputtering J. Kalas, J. Vlcek, S. Potocky, S. Hreben, R. Cerstvy (University of West Bohemia, Czech Republic); V. Perina (Academy of Sciences, Czech Republic); P. Zeman (University of West Bohemia, Czech Republic) The Si-B-C-N films were deposited on Si substrates by dc magnetron co-sputtering using a composed C-Si-B and B₄C-Si target in nitrogen-argon mixtures. Elemental compositions of the films (determined by WD-XRF and ERD), their bonding structure and mechanical properties (hardness, elastic recovery and effective Young's modulus), together with their oxidation resistance in air (measured using TGA up to 1300°C), were controlled by the Si fraction in the magnetron erosion target area, the Ar fraction in the gas mixture, the rf induced negative substrate bias voltage and the substrate temperature. The total pressure and the discharge current on the magnetron target were held constant at 0.5 Pa and 1A, respectively. Thermal stability of the elemental composition of the films and their properties was investigated by a post-annealing of the deposited films in argon at the temperatures up to 1100°C .
DP-19 Influence of Deposition Parameters on Si-C-N Thin Films Produced by PVD Techniques: Raman Analysis J. Leme, C. Moura, L. Cunha (Universidade do Minho, Portugal); E.J. Liang (Zhengzhou University, PR China) Silicon carbon nitride (Si-C-N) thin films have been deposited by reactive magnetron sputtering. The constant deposition conditions were Argon and Nitogen flows (100 sccm and 10 sccm, respectively), the substrate temperature (300°C) and the source power apllied to Si an C targets (100 W and 500 W, respectively). The substrate bias voltage varied from 0 V up to -100 V. The as-deposited films were analyzed by Raman spectroscopy (RS) using the 488 nm excitation line and by Electron Probe Microscopy/wavelength dispersive spectroscopy (EPMA/WDS). The main features observed in the RS are the two broad bands at ~1360 cm^-1 (D-band) and ~1580 cm^-1 (G-band), characteristic of amorphous carbon materials. The change of the D and G band position, FWHM and its relative intensity with respect to the G band,I_D/I_G, indicates the changes in carbon and nitrogen configuration in the films (mixed sp³-sp² hybridization). The WDS analysis indicates that the composition in carbon and silicon increases with the increase of negative bias voltage.
DP-20 Comparison of Raman Spectroscopy on Amorphous Carbon Nitride Prepared from Graphitic-Like and Diamond-Like Carbon Matrixes A. Champi, F.C. Marques (IFGW/UNICAMP, Brazil) Raman spectroscopy of amorphous carbon nitride, prepared under the condition graphitic-like and diamond-like carbon are obtained, is reported. The films were deposited by glow discharge in methane (CH₄) plus nitrogen (N₂) atmosphere, under low bias, -200 V (for diamond-like matrix) and high bias, -800 V (for graphitic-like matrix). XPS and nuclear reaction analysis were performed for determining the nitrogen concentration. Carbon-hydrogen, carbon-nitrogen and nitrogen-hydrogen bonds were investigated through FTIR spectroscopy. Raman measurements were performed using two excitation energy named: visible (514nm) and ultra-violet, UV (244nm). These study focused on the investigation of the vibration energy and energy shifts associated with the G (~1580 cm-1) and D (~ 1350 cm-1) bands. It was observed that the intensity, the energy position and the shift of these two bands depend on the excitation energy. The difference in energy between the visible and UV, the so called dispersion parameter, was investigated for both set of films. This parameter brings additional information concerning the structure of the films regarding size and concentration of graphitic clusters, and qualitative information on the sp²/sp³ concentration. These results were also correlated with other mechanical properties, such as hardness, stress and elastics constants, and optical properties. In addition to the G and D bands, UV Raman presents an additional band at ~2200nm associated with sp bonds (CN), which increases with nitrogen concentrations to both matrixes.
DP-22 Fatigue Properties of a SAE 4340 Steel Coated with TiCN by PAPVD E.S. Puchi-Cabrera (Universidad Central de Venezuela); D.T. Quinto (Balzers, New York); C.J. Villalobos-Gutierrez, J. La Barbera-Sosa, M. Moreno-Castillo, L. Cabezas-Hernandez (Universidad Central de Venezuela); G. Mesmacque (University of Lille, France) The fatigue behavior of quenched and tempered SAE 4340 steel has been investigated, both in air and in a NaCl solution, before and after coating the material with a film of TiCN deposited by PAPVD. The samples were coated industrially at Balzers with a film of BALINIT® B of approximately 3 microns in thickness and the fatigue tests were carried out under rotating bending conditions, at alternating stresses in the range of 539-695 MPa, depending on the condition of the material. In this way, it was possible to determine the Wahler curves for the uncoated and coated samples, in order to evaluate the effect of the TiCN film on the fatigue and corrosion-fatigue properties of the substrate. However, prior to fatigue testing, the static mechanical properties of the uncoated and coated material were evaluated by means of tensile testing. The results of such an evaluation indicated that the presence of the film gives rise to a slight increase of about 10% in the yield strength of the steel but also a slight decrease of about 12% in its tensile strength, in comparison with the uncoated substrate. It has been observed that the presence of the film also gives rise to a significant increase in the fatigue life of the coated specimens, when these are tested in air. Such an increase varies between 135-175%, depending on the alternating stress applied to the material. Also, the fatigue limit of the steel was observed to increase by 6% after coating. On the contrary, under corrosion-fatigue conditions at alternating stresses in the range of 539-696 MPa, the fatigue life either decreased slightly or remained unchanged in relation to the uncoated samples. The fractographic analysis conducted on selected samples tested both in uniaxial tension and fatigue, indicated that the coating remains well adhered to the substrate even under the most severe conditions of testing, as well as a high fracture strength.
DP-23 Adherent Diamond Coatings on Cemented Tungsten Carbide Substrates with New Fe/Ni/Co Binder Phase R. Polini (Universita' di Roma Tor Vergata, Italy); M. Delogu, G. Marcheselli (Fabbrica Italiana Leghe Metalliche Sinterizzate (FILMS) SpA, Italy) WC-Co hard metals continue to gain importance for cutting, mining and chipless forming tools. Cobalt metal currently dominates the market as a binder because of its unique properties. However, there are also detrimental properties of this binder metal due to its hexagonal close-packed structure. Moreover, the price of cobalt has been relatively unstable during the last years. This was a major incentive in the development of pre-alloyed powders which contains less than 40 % cobalt and, consequently, are less sensitive to cobalt price fluctuations. In this paper we first report the results of extensive investigations of WC-Fe/Ni/Co hard metal sintering, surface pre-treating and deposition of adherent diamond films by using an industrial Hot Filament CVD (HFCVD) reactor. In particular, CVD diamond was deposited onto WC-Fe/Ni/Co grades which exhibited the best mechanical properties. Prior to deposition, the substrates were submitted to surface roughnening by Murakami's etching and to surface binder removal by aqua regia. The adhesion was evaluated by indentation tests and compared to the adhesion of diamond films grown onto Co-cemented tungsten carbide substrates, whiche were submitted to similar etching pretreatments and identical deposition conditions.
DP-24 Using Thermal Annealing to Correlate Substrate-Stress with Diamond Nucleation on Coarse and Micro-Grain Cemented WC-Co Substrates G. Cabral, N. Ali (University of Aveiro, Portugal); R. Polini (Universita' di Roma Tor Vergata, Italy); E. Titus, V.F. Neto, J. Gracio (University of Aveiro, Portugal) This work focuses on establishing a possible correlation between substrate-stress and diamond nucleation onto coarse (6 µm) and micro-grain (0.8 µm) cemented WC-Co substrates. The diamond deposits were produced on the WC-Co substrates using three CVD processes, namely, conventional CVD, bias-enhanced-growth (BEG) and time-modulated CVD (TMCVD). The substrate-stress was characterised using the full width at half maximum (FWHM) values of the tungsten carbide (WC) X-ray diffraction (XRD) peaks. Thermal annealing in vacuum conditions was carried out at different temperatures and for different time durations in order to develop different levels of stress in the substrates. It was generally noted that the substrate-stress decreased with thermal annealing and annealing time. This enabled us to compare firstly, the stress relaxation behaviours observed in micro- and coarse grain WC-Co substrates. In addition, the thermal annealing made it feasible to deposit diamond particles onto substrates that were under different magnitudes of stress. The experiments of this study enabled us to correlate substrate-stress with diamond nucleation density. In addition, it was noted that the TMCVD and the BEG processes produced nano-scale diamond deposits, which displayed superior uniformity and coverage compared to similar deposits produced using the conventional diamond CVD approach. The diamond carbon phase quality of the deposits was characterised using micro-Raman spectroscopy. In addition, the densities and the morphologies of the diamond deposits nucleated on the WC-Co surfaces after the CVD processes were characterised using AFM and SEM.

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