ICMCTF1999 Session DP: DP Poster

Wednesday, April 14, 1999 5:00 PM in Room Atlas Foyer

Wednesday Afternoon

Time Period WeP Sessions | Topic D Sessions | Time Periods | Topics | ICMCTF1999 Schedule

DP-1 Wide Band Gap Silicon Carbon Nitride Films Deposited by Electron Cyclotron Resonance Plasma Enhanced CVD
K.H. Chen, J.-J. Wu (Institute of Atomic & Molecular Sciences, Academia Sinica, Taiwan); C.-Y. Wen (Natioanal Taiwan University, Taiwan); L.C. Chen, J.-W. Fan, P.-F. Kuo, Y.F. Chen (National Taiwan University, Taiwan); Y.-S. Huang (National Taiwan University of Science and Technology, Taiwan)
Ternary (Si, C)xNy phases with varying x and y (for brevity, SiCN) are attractive because of their potential for blue and uv optoelectronic applications. We report here the process of SiCN by electron cyclotron resonance plasma chemical vapor deposition possesses potential in facilitating SiCN nucleation. Continuous polycrystalline SiCN films with high nucleation density have been successfully deposited by this method. Rutherford Backscattering Spectrometry (RBS), Transmission Electron Microscopy (TEM), cathodoluminescence (CL), and piezoreflectance (PzR) were employed to characterize the composition, the structure, and the optical property of the films. Typical (Si; C) and N composition ratios of the films were around 0.75. The average grain size estimated from the TEM dark-field image was about 20 nm. For the SiCN film with 5 at. % of carbon content, all d- spacings of the film observed from TED pattern were similar to those of a-Si3N4 with 1-2% of shrinkage. From the RBS and the TEM results, we suggest the silicon carbon nitride films possess the same structure as a-Si3N4 with around 5 at. % of C substituting for Si. A strong and broad CL peak around 310 nm with uniform CL image was obtained from room temperature CL measurement. Analysis of the PzR spectrum indicated the direct band gaps of the SiCN film were around 3.15 and 4.7 eV at room temperature. Further optical property study by photoluminescence, photoconductivity and ellipsometry will be addressed.
DP-2 Effect of ion Bombardment on the Properties of B4C Thin Films Deposited by r.f. Sputtering
A. Lousa, E. Martinez, J. Esteve, E. Pascual (Universitat de Barcelona, Spain)
Boron carbide (B4C) is a good material for the application of very hard coatings. Sintered bulk B4C is one of the hardest known materials (40 GPa), with high Young's modulus and a very high chemical and thermal stability. The growth of B4C thin films is strongly influenced by both the stoichiometry of the film chemical composition and the ion bombardment during film growth; these affect the film structure and also the accumulated internal stress. We have used the tuned r.f. magnetron sputtering deposition, which is a powerful technique to grow thin films under controlled energy ion bombardment. The main feature of this technique is that the growing film bias voltage can be effectively controlled in a wide range of values by an external resonant circuit, and so the energy of ions impinging the growing film can be adjusted. We have used a sintered boron carbide target and several substrates: c-Si crystalline wafer, Corning 7059 glass and Cr-coated glass. The B4Cfilms are homogeneous and highly stoichiometric. Their mechanical properties: microhardness, Young's modulus, internal stress and adhesion, have been measured by the dynamical nanoindentation method, by the beam bending method and by the micro scratch method.
DP-3 Diamond Synthesis Via C-H-Metal System Under Sub-Atmospheric Pressure
H.K. Chang, C.A. Lu (National Dong Hwa University, Taiwan, ROC); M.S. Wong (National Dong Hwa University, ROC); Y. Liou (Academia Sinica, Taiwan, ROC)
The synthesis of metastable diamond from solid carbon via liquid metal process in hydrogen at sub-atmospheric pressures has been reported. The method combined some of the diamond growth mechanisms and methods of both HTHP (high temperature and high pressure) and low pressure CVD. It could be the third major method to produce diamond at large-scale and low cost. Here, we report a combined method including both catalysts- molten transition metals used in HTHP (high temperature and high pressure) and atomic hydrogen in low pressure (microwave and hot-wired) plasma enhanced CVD. The work is to study the metastable diamond synthesis from carbon powders mixed with transition metals (Ni, Co, Fe, Cu, Ag, and their alloys,etc) heated in hydrogen plasma at low pressures, to develop processes, to enhance the growth rate, and to understand the growth mechanisms. Different effects of transition metal catalysts on diamond growth, comparing with those catalysts used in HTHP method, were observed. The growth rate of metastable diamond via liquid-metal could be faster than that of CVD method. The new method could be used to grow diamond in the forms of powder, thin film or composite for a wide range of applications.
DP-4 Compositional and Structural Studies of DC Magnetron Sputtered SiC Films on Si(111)
Y.M. Lei, Y.H. Yu, C.X. Ren, S.C. Zou (Shanghai Institute of Metallurgy, Academia Sinica, China)
Polycrystalline SiC films were deposited on Si(111) by reactive DC magnetron sputtering using a 4 inch elemental silicon target. Composition of the deposited films was studied by AES and RBS which showed stoichiometric SiC could be obtained. Both AES depth profile and RBS indicated the existence of a transition layer. XRD analysis revealed the formation of polycrystalline SiC films at substrate temperature as low as 1123K, and the absence of other peaks in XRD patterns except the SiC(111) peak implied that the films were (111) oriented. Furthermore, the films were found to be consisted of columnar nanometer crystalites by cross section TEM study.
DP-5 Field Emission from Electrodeposited Diamond-Like Carbon Films
H. Kiyota, M. Iida (Kyushu Tokai University, Japan); H. Wang (Beijing Institute of Technology, Japan); T. Takida, T. Kurosu (Tokai University, Japan); K. Inoue, I. Saito (SONY, Japan); M. Nishitani-Gamo, I. Sakaguchi, T. Ando (CREST (c/o NIRIM), Japan)

Diamond and diamond-like carbon (DLC) are considered as promising materials for electron emitter applications such as flat-panel displays. These materials have usually been prepared by vapor-phase deposition techniques. We have carried out liquid-phase deposition of DLC films by an electrolysis of methanol and investigated the field emission properties from the electrodeposited DLC films.

The DLC films were deposited on Si substrate mounted on a negative electrode. A graphite rod was used as a positive electrode. The distance between the two electrodes was 10 mm. The current density was in the range of 10 to 20 A/cm2 when the high DC voltage was applied to the substrate. The field emission current from the deposited DLC film was measured by using a parallel plate configuration. Indium-Tin-Oxide coated glass plate was used as an anode whereas the deposited DLC film was a cathode.

The current - electric field characteristics shows a threshold field for electron emission as low as 1 V/µm. This threshold field is the lowest one for undoped DLC films ever reported, indicating that the electrodeposited DLC film has a potential advantage for the field emitter applications. We also find that that the emission properties can be explained by Fowler-Nordheim relationship based on the tunneling theory. To visualize the spatial distribution of the emission site, we observed a light emission from a fluorescent screen mounted at 200 µm above the DLC films. We found that the electrons are emitted from the isolated emission site within the DLC film and that a small portion of the surface area contributes to the field emission.

DP-7 CNx Thin Films Grown by Pulsed Laser Deposition: Raman, Infrared and X-Ray Photoelectron Spectroscopy Study
S. Trusso (Cnr - Messina, ITALY); F. Neri (Istituto Nazionale per la Fisica della Materia - University of Messina, ITALY); C. Vasi (CNR-MESSINA, ITALY)
Carbon nitride films have been deposited by pulsed laser ablation of graphite targets in a controlled nitrogen atmosphere. A 532 nm Nd:YAG pulsed laser beam (8 ns pulse width, 50-100 mJ pulse energy) was focused onto the target surface. The deposition chamber was filled with ultrapure nitrogen gas at pressures up to 20 mbar. Films were deposited on both c-Si and 7059 Corning glass substrates. The samples composition was determined by means of X-ray photoelectron spectroscopy. A study of the C 1s and N 1s core level photoemission bands evidenced, upon increasing nitrogen gas partial pressure, a systematic modification of the components related to both trigonal and tetrahedral CN bonding configuration. Nitrogen atomic contents exceeding 30%, with respect to carbon, were estimated. Raman and infrared spectroscopy results showed broad and featureless structures typical of an amorphous carbon phase, independently of nitrogen pressure. Moreover, in the Raman spectra, there is also clear evidence of the symmetric tetrahedral C-N bond stretching mode band around 1250 cm-1.
DP-8 Plasma Assisted Physical Vapour Deposition of BN by DC Pulsed Sputtering of a B4C Target
L.A. Gea, G. Ceccone, F. Rossi, P. Leray (European Commission, Joint Research Centre, Italy)
Boron nitride coatings were deposited on Si (100) polished crystals by DC pulsed magnetron sputtering of a B4C target with auxiliary microwave Distributed Electron Cyclotron Resonance (DECR) plasma. The substrates were biased by an independent R.F. source. A good control of the deposition parameters and in particular of the energy and flux of the ions during the film growth was obtained. Characterization of the plasma was undertaken as a function of the total pressure, the nitrogen gas content and the microwave power. The presence of the various species was identified with Optical Emission Spectroscopy. Mass Spectrometry was used to determine the ion energy distribution while the plasma potential and the plasma densities were measured with a single Langmuir probe. The influence of the deposition parameters on the coating microstructure and mechanical properties are reported.
DP-9 Field Emission Characteristic of Diamond Films Grown by Electron Assisted Chemical Vapor Deposition
H.K. Baik, J.Y. Shim (Yonsei University, Republic of Korea); E.J. Chi (Yonsei University, Republic of Korea)

There are increasing researches into use of carbon-based films as a field emitter material because it has many attractive properties such as low or negative electron affinity, high chemical and mechanical stability, and low field emission characteristics. There have been many reports to identify the origin of low field emission of carbon-based films. However, the low field emission behavior has not been clearly understood.

On the other hand, hydrogen in atomic and molecular states is a main constituent of the vapor phase of chemical vapor deposition (CVD) diamond growth process and the diamond films synthesized by CVD process contain typically up to a few at. %. Although hydrogen exists in diamond films with quite a small amount it can critically affect electrical conductivity of diamond films.

It is expected that the change of hydrogen content or hydrogen-related bond in diamond films can affect field emission property of diamond. It should be also considered that the grain size and surface morphology could change field emission property. Until now there has been no report on the effect of hydrogen in diamond on the field emission property.

In this study, in order to change the hydrogen content and structural property of diamond films, diamond films are grown at various bias conditions using an electron assisted CVD system. A comparison has been performed on the qualitative amount of hydrogen in the films grown at various bias conditions and diode current-voltage characteristics are investigated. Difference of the field emission property is discussed by comparing both hydrogen content and structural properties with electrical resistivity.

DP-10 Fabrication and Characterization of the Conic Diamond FEAs with a Pt Gated Structure
C.-F. Chen, H.-C. Wang (National Chiao Tung University, Taiwan, R.O.C.)
Applying a high electric field on field emits electrons from the tip of the FEAs. Among the characteristics that affect the power of field emitter arrays include the shape and work function of emission materials, the distance between tip and gate, and vacuum environmental conditions. However, the (111) plane of a diamond has a negative or very small electron affinity. Therefore, as widely recognized, the diamond is the most promising material for manufacturing a solid-state electron emitter. In this study, we successfully fabricate conic diamond field emitter array devices by applying an IC process capable of forming a metal-insulator-semiconductor (MIS) diode structure. The conic diamonds are then deposited and, ultimately, grow inside of the electric gates. In addition, the field emission current is measured when applying 1000V voltage on the anode in which the applied gate voltage is varied from 0 to 50 volts. Experimental results indicate that the threshold voltage of this device is about 12 V, and the field emission current is about 40 µA when the gate voltage is 30 V.
DP-11 Characterization of Interface of c-BN Film Deposited on Silicon(100) Substrate
J. Tian (Harbin Institute of Technology, P.R. China); L.F. Xia (Harbin Institute of Technology, P.R. C hina); X.X. Ma, Y. Sun (Harbin Institute of Technology, P.R. China)
The growth sequence of c-BN film deposited on single silicon substrate using Active Reactive Evaporation(ARE) have been investigated through ion thinning method, in which a combination of X-ray Photoelectron Spectroscopy(XPS) and FTIR were used for compositional and microstructural analysis. c-BN film was etched at size 4x4mm2 by argon ion in XPS equipment, by which elemental depth concentration profile and XPS B1s spectra were obtained. FTIR was alternately used to determine the microstructure of BN film at different etching depth. In conclusion, a thin h-BN layer grow on Si substrate prior to c-BN formation, which is supported by the compressive stress induced formation mechanisms of c-BN film.
DP-12 Structure and Photoluminescence Properties of Diamond Films Deposited on Porous Silicon
V. Baranauskas, B.B. Li, M.C. Tosin (Faculty of Electrical and Computer Engr., State University of Campinas, Brazil); A. Peterlevitz, S.F. Durrant (Feec, Unicamp, Brazil)
Porous silicon (PS) layers, made by anodic etching of crystalline Si wafers, have been completely coated by diamond films using the hot-filament chemical vapor deposition (CVD) technique. Ethanol diluted in hydrogen was used as the carbon source for diamond deposition. We observed that diamond nucleation occurs predominantly on the top of the PS spikes, creating individual islands of growth. The diamond nucleation depends on the PS formation parameters, such as pore diameter, surface roughness, structure and thickness. Depending on these parameters diamond deposition could not be achieved for all kinds of PS because of cracking and delamination of the PS layers. We observed that diamond nucleation can be enhanced by seeding the surface with diamond grains. The nucleation time seems to be homogeneous over the PS surface and the islands have an independent growth process until the complete coalescence of the diamond film. The deposited grains have an almost plane interface with the PS layer. The diamond film is of polycrystalline nature but is not columnar as is usual in diamond deposition on c-Si. The films have benn characterized by Auger and Raman Spectroscopy and X-Ray diffraction. The photoluminescence of the samples has also been investigated. The photoluminescence spectra showed an intense sharp peak at 738 nm, corresponding to vacancy defects in the diamond cubic structure, and a broad peak around 640 nm, which may be attributed either to diamond vacancy defects or to PS luminescence.
DP-13 Enhancement of Diamond Nucleation Using the Solid-Liquid-Gas Interface Energy
V. Baranauskas, M.C. Tosin (Faculty of Electrical and Computer Engr., State University of Campinas, Brazil); A. Peterlevitz (Feec, Unicamp, Brazil); G.I. Surdutovich (Faculty of Electrical and Computer Engr., State University of Campinas, Brazil); S.F. Durrant (Feec, Unicamp, Brazil)
Diamond nucleation on non-diamond substrates is a limiting process in the chemical vapor deposition (CVD) method. To enhance the nucleation density and to lower the nucleation time several techniques are usually employed, such as scratching the substrate surface or the seeding of the surface with diamond grains prior to deposition. For special applications of diamond, such as the use of diamond thin films in optics or microelectronics, scratching and seeding are not recommended because they increase surface roughness and the inhomogeneity of the growing film. We suggest in this work the enhancement of nucleation by the use of the equilibrium forces of the solid-liquid-gas interface on a substrate surface wetted by droplets of high vapor pressure liquids or reactive liquids, such as vacuum oils and acids. The wetting angle Θw between the liquid droplet and the substrate is characteristic of these materials and the probability of diamond nuclei formation depends on tethaw. Comparative experimental results of this technique to the scratching or seeding techniques will be presented.
DP-14 An Array of Inductively Coupled Plasma Sources for Large Area Plasma
S. Park, C. Kim, O. Beom (Inha University, Korea)
An array of 2x2 inductively coupled plasma(ICP) sources has been built by modifying the conventional RIE type LCD etcher. Each ICP has its own planar circular antenna and quartz dielectric window to the reaction chamber. One RF supply and only one matching network are used for delivering the power to all ICP sources in this system. Distribution of ion and electron densities and electron temperature are measured in terms of the number of acting ICP sources, chamber pressure and RF power. By adjusting the power distribution among the 4 ICP units, uniformity of oxygen plasma can be improved dramatically. The plasma density of about 10 10can also be obtained in the 620x620 mm2- chamber, which is one order of magnitude higher than that of the RIE plasma source. Photoresist removal by the oxygen plasma is performed on 320x400 mm+2glass plates.
DP-15 Optical Properties of Tetrahedral Amorphous Carbon Prepared by Filtered Cathodic Vacuum Arc Technique
L.K. Cheah (Nanyang Technological University, Singapore, Republic of Singapore); X. Shi, E. Liu, Z. Sun, B.K. Tay, J.R. Shi (Nanyang Technological University, Singapore)
Optical properties of tetrahedral amorphous carbon (ta-C) films deposited by filtered cathodic vacuum arc technique are reported. The optical band gap, optical absorption spectra and complex refraction index were determined by spectroscopic ellipsometry technique. The optical band gap of the ta-C films ranged from 2.0 to 2.6 eV depending on the sp3 content in the films. The optical band gap with 2.6 eV is correspondence with the ta-C film with maximum sp3 (~88%). It has been found that the optical band gap of the hydrogenated ta-C (ta-C:H) film increases to 3.0 eV as the H partial pressure reached 8x10-6 Torr. An analysis of the bonding configuration of the H in the ta-C:H has been performed by measuring the infrared spectra. Relative intensity of D and G peaks in Raman spectra was observed to decrease with the increasing of H partial pressure from 2x10-7 to 8x10-6 Torr. In order to study the effect of ion bombardment to the ta-C film during the deposition, the Ar+ with ion energy ranged from 50 to 500 eV was used. The optical band gap reduced from 2.6 to 1.5 eV as the Ar+ energy increased. The x-ray photoemission spectroscopic shows the increase in sp2 after the Ar+ bombardment. Therefore, we concluded that the high energy bombardment relaxed the sp3 to sp2 configuration. N is used to dope the ta-C (ta-C:N). Two methods have been tried. First method is by gas filling to the cathode arc region during deposition. Second method is the ion beam assisted deposition. It is observed that from the RBS that the ion beam assisted deposition has higher nitrogen incorporation compared to the background gas filling method. The optical band gap reduced as the nitrogen partial pressure increased
DP-16 Effect of Nitrogen Doping on the Morphology and Electrical Property of CVD Diamond
B.--J. Lee (Korea Institute of Science and Technology, also Korea Advanced Institute of Science and Technology, Korea); B.-T. Ahn (Korea Advanced Institute of Science and Technology, Korea); Y.-J. Baik (Korea Institute of Science and Technology, Korea)
Morphology variation and electrical property of diamond with the addition of nitrogen are investigated. Microwave plasma chemical vapor deposition is used for diamond deposition. Methane and nitrogen concentrations are varied up to 5% and 400 ppm respectively. In order to observe the habit change of diamond with the addition of nitrogen, both isolated particles and film are grown respectively. Comparison between two shape changes are used for clarifying the texture formation mechanism in the case of nitrogen addition. With the variation of nitrogen, the isolated particle shape changes between octahedron and cubo-octahedron. Texture orientation of the films follows the evolutionary selection rule. The electrical conductivity, observed in the diamond film grown without nitrogen, disappears completely when coating diamond with the nitrogen. This is very essential for the application of diamond film as an insulating layer. Crystal analysis using Raman spectroscopy and nitrogen concentration measurement in the film are also performed.
DP-17 Synthesis of Diamond Thick Film by Direct-Current Plasma Assisted CVD Process
W.S. Lee, Y.-J. Baik, K.Y. Eun (Korea Institute of Science and Technology, Korea)
4-inch diamond film with thickness over several hundred micrometers have been synthesized by a parallel-plate type direct-current plasma assisted CVD process. The pulsed dc voltage was supplied to the cathode and the substrate was grounded. The methane and/or alcohol mixed with hydrogen was used as precursor gas. The temperature of cathode and substrate was monitored by optical pyrometer. The cathode temperature was maintained around 1200-1300oC. The substrate temperature was 1150-1300°C. The reaction gas pressure was100-140 torr. The cathode and substrate was made of Mo. The interelectrode distance was 15-40mm.The dc plasma was stabilized by optimizing cathode temperature, frequency and duty of input pulsed dc volatage.Long-term deposition over one hundred hours was achieved. The film was characterized by Raman spectroscopy and SEM. The plasma was characterized by optical emission spectroscopy. The effect of process parameters, such as hydrocarbon content, interelectrode distance, gas pressure, on the film property and uniformity will be discussed.
DP-18 Study on the Effects of Substrate Modification on Carbon Nitride Thin Films Prepared by Direct Ion Beam Depostion
D.Y. Lee, Y.H. Kim, D.J. Choi, D.W. Han, I.K. Kim, H.K. Baik (Yonsei University, Korea)
The carbon nitride thin films were uniquely synthesized by using positive nitrogen ion beams and negative carbon ion beams. Its energy was 125eV and 80eV respectively. The effects of substrate modification on the synthesis of carbon nitride thin films were evaluated by the variation of deposition time. Silicon Nitride and (100) oriented Si wafer were used as a substrate for the deposition of carbon nitride thin films. We investigated the plasmon energy loss and the chemical bonding as a characterization of bulk atomic density and the surface properties. The variation of structural properties of carbon nitride thin films from the interface to the bulk site was investigated by using x-ray photoelectron spectroscopy and auger electron spectroscopy and the atomic arrangement of interface was studied by high resolution transmission electron miscroscopy.
DP-19 Analysis of Carbon Nitride Thin Films by the Plasmon Energy Loss Feature and the Deconvoluted Results of Core C1s X-ray Photoelectron Spectroscopy Peak Shifts
Y.H. Kim, D.J. Choi, H.K. Baik (Yonsei University, KOREA)
The carbon nitride thin films were synthesized by direct dual ion beam deposition method. The structural and compositional properties of the deposited CN films were evaluted from the plasmon energy loss and the deconvoluted results of XPS core 1s peak shifts. From the C1s deconvolution results, we can make a relaton between the value of plasmon energy loss and a function of deconvoluted constituent of sp, sp2 and sp3 hybridized component. Even though we can not find a relation between the atomic concentration of each carbon and nitrogen component and the value of plasmon energy loss, we can obtain the information of atomic density and the deconvoluted each hybridized components from the value of plasmon energy loss. These plasmon energy loss and C1s deconcoluted results were compared with the deconvoluted Raman spectra results.
DP-20 Direct Ion Beam Deposition of Diamond-like Films from RF Inductively Coupled (IC) Plasma Source: Mechanical, Electrical and Optical Properties
B. Druz (Veeco Instruments, Inc); I. Zaritsky, K. Williams, A. Hayes (Veeco Instruments Inc.); V.I. Polyakov, A.V. Kchomich (Institute of Radio Eng. & Electronics, Russia); X. Li, B. Bhushan (The Ohio State University)

Diamond-like carbon (DLC) films were deposited on various substrates using highly reproducible direct ion beam deposition from an RF IC CH4 plasma source 1. Combinations of gases such as CH4, CH4 -N2 were used to form plasma. The mechanical, electrical and optical properties of the films were examined as a function of deposition conditions and N2 content in gas composition. A small amount of N2 (6-8 sccm) did not markedly change hardness and stress, while electrical conductivity was significantly increased. In addition, a small amount of N2 improved tribological performance of the films reducing amount of debris and wear track size. Introduction of high N2 flow into the system significantly deteriorates value of these parameters. It was found that N2 essentially increases absorption coefficient, and reduces optical band gap. Analysis of the experimental results shows that observed effects can be explained by incorporation of N2 into carbon-strained network that induces structural changes and, in turn, leads to an increase of sp2 fraction in the DLC films. For investigation of the bulk and surface electrically active defects, the deep level transient spectroscopy (DLTS) was used. The density, activation energies and capture cross-sections of the bulk and surface defects in the DLC films with different N2 content were found. The role of the point defects in the DLC films is discussed.

1 B. Druz et al., Diamond and Related Materials 7 (1998) 965 - 972.

DP-21 Characterization of Hydrogen-free Diamond-like Carbon Films Deposited by Pulsed Plasma Technology
D.Y. Wang, C.L. Chang (National Chung Hsing University, Taiwan, ROC); W.Y. Ho (Surftech Corp., Taiwan, ROC)
Diamondlike carbon (DLC) films demonstrated significant advantages in cutting and forming of non-ferrous materials. The ultra-low friction coefficient and high surface hardness make DLC one of the most promising surface technologies for processing of advanced structure materials. In this study, hydrogen-free DLC films were synthesized by unbalanced magnetron sputtering of graphite targets. The high inherent stress of DLC thin films were dissipated through the application of a compound interface consisting of a series of Ti, TiN, and TiCN graded interlayers. The target poisoning problem was resolved with a 2 kHz medium-frequency DC power supply. In addition, a 20-100 kHz variable-frequency DC power supply was used for substrate biasing. Influences of pulsing parameters on film qualities were investigated by SEM/EDS, XRD, XPS, Raman, and Tribo-testers. Results demonstrated an improved DLC thin film with superior microhardness and tribological behaviors over the conventional DLC deposited by PECVD processes.
DP-22 Hardness, Nitrogenation and Optical Properties of the DC Magnetron Sputtered Amorphous Carbon Nitride Coatings
F. Fendrych, L. Jastrabik, L. Pajasova (Institute of Physics, Academy of Sciences, Czech Republic); T. Wagner (Laser-Optik-Technologie ORIEL, Darmstadt, Germany); L. Soukup, D. Chvostova (Institute of Physics, Academy of Sciences, Czech Republic); K. Rusnak (University of West Bohemia, Czech Republic)

Amorphous hard CNx coatings were deposited by DC magnetron sputtering in pure N2 atmosphere. Increase of the samples nitrogenation x = N/C was controled by: a) increase of working gas N2 pressure, b) decrease of DC magnetron current. These technologigal condition changes led to monotonous ( with systematic trend ) decrease of plastical microhardness of the investigated CNx coatings sequence.

Evaluation of optical properties combining the spectroscopic ellipsometry (1.5-4 eV) and the VUV reflection spectroscopy (4-14 eV) by means of Kramers-Kronig analysis showed increase of the π-plasmon resonance peak, which indicates enhancement of amount of π-bonded electrons. It is linked with increase of sp2 hybridization. The optical energy gap extrapoled by Tauc's plot indicates more semimetallic properties of the CNx coatings due to nitrogenation. A shift in the ε2(ω) maximum corresponding to σ-σ* electron transitions in carbon demonstrates deeper band structure changes in higly nitrogenated CNx films.

DP-23 Modeling of the Load Bearing Capacity and Fracture of Hard Coatings Using Spherical Indentations
J. Michler, E. Blank (Swiss Federal Institute of Technology (EPFL), Switzerland)

Hard coatings (as diamond or diamond-like carbon layers) are widely used as protective coatings on metal substrates. The performance of the composite depends on material parameters like the layer's Hardness, film fracture toughness, interface toughness between layer and substrate or the yield strength of the substrate. Residual stress in the layers and geometrical design parameters like the layer thickness, the tribology of the system and the loading conditions are of similar importance. Ideally, one would like to know all these parameters and their influence on coating failure. This implies an absolute measure of the materials parameters involved and a knowledge of the failure mechanisms.

Failure mechanisms of the substrate/coating composite are studied in this paper by a rigorous elastic-plastic finite element analysis. The common load case considered here is the indentation of spherical bodies into a layered surface, which typically would represent the mechanics in a ball bearing or penetration of wear debris in a layered surface.

For diamond-like carbon on steel and diamond on steel the onset of plastic deformation in the substrate and the coating fracture, dependent on the Young's modulus of the layer, the yield stress of the steel, the fracture stress of the layers and the indentor radius and coating thickness is calculated. Indentation experiments are carried out parallely to identify the failure mechanisms experimentally. Asymptotic analytical solutions are also discussed which allow extrapolating the results to other substrate coating systems. The results are summarized in form of a failure mechanism map, that allow to determine the optimal coating and coating thickness for a special load case, described by indentor radius and indentor force.

DP-24 Residual Stress in Heteroepitaxial Diamond Films on Silicon: Modelling and Origins
J. Michler, E. Blank (Swiss Federal Institute of Technology (EPFL), Switzerland)

This paper reports on the evolution of stress with the layer thickness in the case of heteroepitaxial diamond layers on silicon [001] substrates. It is shown by finite element calculations that the thermal stresses developing in the films can be treated analytically by plate theory. The calculated thermal stress, however, differs from the by Raman spectroscopy measured stress, because higher compressive stresses at small layer thickness, lateral stress gradients in the layers, stress inhomogeneities within single grains and plastic deformation of the substrate were found experimentally.

By the aid of finite element calculations and transmission electron microscopy (TEM), these differences are attributed to clear physical origins, i.e. temperature inhomogeneities during growth, the layer morphology (island growth, surface roughness) and microstructural sources as coherency strains and disclination formation. Temperature gradients during deposition induce radial stress gradients in the layer, which leads to more compressive stress at the edge of the specimen and stresses in free standing membranes. Creep of the substrate during deposition can be induced by temperature gradients and stresses due to the microstructure. In case of a noncontinuous layer or an important surface roughness finite element calculations show that an important part of the stress can be relaxed elastically. Finally, disclinations found by TEM investigations explain stress inhomogeneities within single grains.

DP-25 Hard Carbon Films With Graphitic Nanostructure
C.F. Meyer, B. Schultrich, H. Ziegele, A. Luft (Fraunhofer - Institut f|r Werkstoff- und Strahltechnik, Germany); H.-J. Scheibe (Fraunhofer - Institut f|r Werkstoff und Strahltechnik, Germany); H. Banzhof (Technische Universitdt Dresden, Germany)
The Laser-Arc technique has been well proved for the deposition of superhard amorphous carbon. With dominating fraction of sp3 bonds. It is based on the controlled ignition of pulsed vacuum arc discharges by short laser pulses. The deposition of such mainly diamond-like bonded material requires complete ionization and high ion energy and low deposition temperature. By modifying the deposition conditions graphitic inclusions inside an amorphous material can be prepared. Especially they can be produced in the form of concentric shells of graphene lamellae. The dense and smooth carbon films with such onion-like structures are very hard reflecting the high interlayer strength of graphite and show a very high elastic recovery, whereas heir optical properties resembles graphite-like materials. The influence of various deposition parameters such as substrate temperature and noble gas doping on the nanoscaled heterogeneous structures is discussed.
DP-26 Characterization of Ion-Assisted Pulsed Laser Deposited Cubic Boron Nitride Films
G. Reisse, S. Weissmantel (University of Applied Sciences Mittweida, Germany)
Cubic boron nitride films were deposited by pulsed laser deposition from a boron nitride and a boron target using a KrF-excimer laser, where the growing films were bombarded by a nitrogen or a nitrogen/argon ion beam. The variation of the microstructure of the films with laser and ion beam parameters and substrate temperature has been investigated by infrared spectroscopy, cross-section and plan-view high-resolution transmission electron microscopy including diffraction, electron-energy-loss spectroscopy and in-situ ellipsometry. It will be shown that c-BN films with high phase purity can be prepared at sufficiently strong ion bombardment as well as substrate temperatures above 160 °C. The c-BN phase was found to grow exclusively on top of the well-known hexagonal interlayer with c-axis orientation parallel to the substrate surface. Two preferred orientations of c-BN crystallites were observed, the first characterized by {111} and the second by {100} lattice planes growing parallel to the (002) lattice planes of the initially formed h-BN layer. Pure c-BN films were prepared at maximum growth rates of 16 nm /min. Additional uv-photon irradiation of the growing films results in distinct modifications of the microstructure of the BN films. Using laser pulse energy densities on the substrate surface above 200 mJ/cm2 the laser irradiation leads to the formation of turbostratic h-BN even though the unirradiated film regions of the same sample show the cubic structure. In contrast, films irradiated at 100 to 160 mJ/cm2 are cubic. Electron microscopic observations show that in this range the mean diameter of crystallite in the excimer laser irradiated regions increased by a factor of 2 in comparison with unirradiated regions of the same sample. The experimental results will be discussed in context with the results of temperature field calculations.
DP-27 Deposition of Low Cost DLC Coatings by Medium Frequency PACVD
A. Hieke, K. Bewilogua, I. Bialuch, T. Michler (Fraunhofer Institute for Surface Engineering and Thin Films, Germany)
For engineering applications diamond like carbon films (DLC) are the most suitable coatings, if high wear resistance and low friction is needed. The most common method to deposit DLC films is radio frequency PACVD (RF, 13.56 MHz), which is technically difficult and expensive to scale up to industrial dimensions. During the last two years our institute had tested different methods for plasma excitation with a great potential for upscaling. In this paper the deposition of DLC coatings by bipolar-pulsed (22kHz) and sine wave form (87kHz) medium frequency (MF) PACVD compared to RF PACVD will be presented. The parameters are very similar to the well known and industrialized plasma nitriding process. The experiments were carried out in a commercially available plasma nitriding plant. The substrate temperature during the deposition process was lower than 200°C. Methane (CH4) and a mixture of Argon/Hydrogen were used to deposit DLC films. The mechanical properties of the films such as hardness, Young's modulus and wear resistance were studied as a function of the process parameters. But pure DLC is only one kind of coating which can be created by MF PACVD. By doping the DLC network with other elements like silicon, fluorine, oxygen or nitrogen it is possible to influence the surface energy of the deposited modified DLC coatings. The properties of the DLC and modified DLC coatings are absolutely comparable to those deposited by RF PACVD.
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