Synthesis, Characterization and Applications of Boron Nitride, Carbon Nitride and Fullerene Like Structures

Tuesday, April 11, 2000 8:30 AM in Room Royal Palm Salon 4-6

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8:30 AM D1-3-1 Nanoindentation and FEM Study of the Effect of Internal Stress on Micro/Nano Mechanical Property of Thin CNx Coating
M. Bai, K. Kato (Tohoku University, Japan)
Pursuit of ever-increasing storage density has lead to a steady reduction in head-disk separation which requires protective coating as thin as possible and as hard as possible. It has been found that the internal stress affects micro-tribological properties of CNx coating greatly. In this study, five kinds of thin hard CNx overcoats with different internal stress were synthesized by ion beam assisited deposition method. Nanoindentation was used to evaluate the micro/nano mechanical properties of CNx coating. The resultant load-displacement data was analyzed and it was found that the internal stress does affect the elastic modulus and hardness of CNx coating according to the magnitude and type of internal stress. A finite element method was used to simulate the nanoindentation process and to examine the dependence of hardness and modulus on internal stress. Experimental results were compared with calculation results. A calibration method was proposed according to FEM anlysis and contact mechanics anaylsis.
8:50 AM D1-3-2 Investigation of the Thermal Stability of Nitrogen-Rich Amorphous Carbon Nitride Films
W. Kulisch, C. Popov, L. Zambov (University of Kassel, Germany); M. Jelinek, J. Lancok, J. Bulir (Czech Academy of Sciences, Czech Republic); M.P. Delplancke-Ogletree (Université Libre de Bruxelles, Belgium)
A number of nitrogen rich amorphous carbon nitride films (N/(C+N) = 40-55%) has been prepared by different deposition methods. After thorough characterization by AES, XPS, Raman, FTIR, EELS and ellipsometry, each sample was cut into pieces which where annealed at different temperatures in the range between 200-600@super o@C. Thereafter, the samples were subjected to the same analysis methods. The aim of this study was twofold: First, the thermal stability of the samples should be investigated since nitrogen rich CN@sub x@ films were repeatedly reported to be thermally unstable. In addition, correlations of the changes of the spectra from the various analysis methods should contribute to the identification of spectral features (especially for FTIR and XPS) which are currently fiercely debated in literature. It was found that annealing up to 400@super o@C improves the film quality by desorption of contaminants, water and loosely bonded material but also by chemical reactions, thus leading to a densification. The nitrogen/carbon ratio is almost unaffected. Annealing at 600@super o@C, however, causes serious loss of material and a decrease of the relative nitrogen content. The remaining films possess nearly the same structure and composition, irrespective of the deposition method and the original structure. The second part of our contribution will be devoted to the discussion and identification of features in infrared, Raman and XPS spectra. For example, three bonding states were found with XPS for nitrogen as well as for carbon atoms which could be identified by correlating the changes of the spectra of the different analysis methods caused by each annealing step.
9:10 AM D1-3-3 Optical, Electrical and Mechanical Properties of Nitrogen-Rich Carbon Nitride Films Deposited by ICP-CVD
C. Popov, L. Zambov, M.F. Plass, W. Kulisch (University of Kassel, Germany)
An inductively coupled plasma utilizing chemical transport reactions has been used to deposit thin carbon nitride films with a high nitrogen content (N/C ratio at about 1 or higher). The basic properties of the CN@sub x@ films were thoroughly characterized by a variety of techniques: the composition by elastic recoil detection (ERD) analysis, wavelength dispersive (WDX) analysis, Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS); and the bonding structure by electron energy loss spectroscopy (EELS), Raman and Fourier transform infrared (FTIR) spectroscopies, and XPS. In this contribution we report on the characterization of the application relevant properties of these films, especially optical (refractive index, transmission), electrical (dielectric constant, resistivity) and mechanical characteristics (stress, hardness, wear resistance). The refractive index is in the order of 1.5 - 1.8 depending on the deposition conditions; furthermore, the films on fused silica substrates are highly transmitting for wavelengths above 600 nm. The C-V curves indicated the insulating character of CN@sub x@ films which was confirmed by I-V measurements yielding resistivities in the order of 10@super 11@ @OMEGA@ cm. Concerning the mechanical properties it was found that the layers possess almost no stress as measured by the bending method on silicon cantilevers. The hardness is in the range of 1 GPa and a resistance of 0.6 was determined by ball-on-disk test with stainless steel balls. The investigations showed that these films may suit especially for optical and electrical applications. Finally, we correlate these films characteristics with the basic properties and structure of the coatings.
9:30 AM D1-3-4 Characterization of CN@sub X@ Thin Films Prepared by Hot Filament CVD
R. Kurt, A. Karimi (Swiss Federal Institute of Technology (EPFL), Switzerland)
This paper describes a hot filament CVD process for carbon nitride thin films without hydrogen additions. The concentration of the nitrogen precursors NH@sub 3@ and N@sub 2@ relatively to methane has been systematically varied in order to analyze the influence of nitrogen incorporated into the CN@sub X@ films for the structure formation. Additionally total pressure and total gas flow rate were changed within a large scale. Various substrate temperatures between 1800 and 2300@super o@C were applied with the aim to improve the deposition. But during one experiment the temperature of the carborized W filament was kept constant. It is a well-known fact that the substrate temperature and substrate bias voltage are further important parameter in chemical vapor deposition. Several materials such as (100) and (111) Si, SiO@sub 2@, quartzglas, and Ni, were used as substrates in order to study their influence on nucleation and growth of the CN@sub X@ films. As a result we succeed in screening of the possible range for CN@sub X@ film deposition. @paragraph@ The chemical composition and the structure of the deposited CN@sub X@ films were studied by RBS, TEM, and SEM. From the FTIR and Raman spectroscopy the vibrational properties were observed. From the results conclusions to the chemical bonding states are drawn. The structure of the films was analyzed by means of X-ray and electron diffraction using a transmission electron microscope for the latter. Additional STM investigations reveal cluster like microstructure of the film surface. @paragraph@ The mechanical properties of the CN@sub X@ thin films were investigated using nanoindentation measurements. From the load-displacement curve the hardness and the Young's modulus of the films were calculated. The results will be compared with reactively sputtered CN@sub X@ films containing different amount of nitrogen up to 42 at.%N.
9:50 AM D1-3-5 Microwave and DC-plasmajet CVD Synthesis of Si-C-N Coatings
P. Supiot (Laboratoire de Génie des Procédés d’Interaction Fluides Réactifs-Matériaux, U.S.T. Lille I, FRANCE); A. Wank (Institut of Composite Materials, Chemnitz Univ. Of Technology, Germany); C. Dupret (Laboratoire de Génie des Procédés d’Interaction Fluides Réactifs-Matériaux, U.S.T. Lille I, France); C. Vivien (Laboratoire de Génie des Procédés d’Interaction Fluides Réactifs-Matériaux , U.S.T. Lille I, France); J. Wilden (Institut of Composite Materials, Chemnitz Univ. Of Technology, Germany); L. Pawlowski (Laboratoire de Génie des Procédés d’Interaction Fluides Réactifs-Matériaux, U.S.T. Lille I, France)
Silicon carbide has excellent properties for wear protection applications even at elevated temperatures. The similar system Si@-@C@-@N is expected to have moreover an excellent thermal shock resistance. DC torch used for Vacuum Plasma Spraying (VPS) was previously applied to manufacture pure Si@-@C@-@N coatings. The present work is concerned with an alternative way of synthesis of this material using a microwave plasmajet. The plasma is ignited in molecular nitrogen in a fused silica tube and accelerated through a nozzle with linearly conical shape. Powers up to 3kW are transferred to the plasma at pressures ranging from 100 to 2000 Pa. Subsequently, a large set of experimental conditions is used to test the deposition process. The precursors, either hexamethyldisiloxane or hexamethyldisilazane, are evaporated immediately after introduction into reactor and the vapors are injected into the plasmajet. The molecular fragments and atoms resulting from the interaction between the jet and the precursor are accelerated and gradually condense on the surface of substrate. The resulting temperature of the latter is monitored during the deposition process. The deposits are characterized by Fourier Transform Infra Red Spectroscopy (FTIR), Scanning electron microscope (SEM) and Energy Dispersive X-ray (EDX) techniques. Additionally a scratch energy density test is used to estimate the adhesion of the coating. A comparison of the results obtained by both DC torch and microwave setups is carried out and used for discussion.
10:30 AM D1-3-7 Preparation of Silicon Carbonitride Phases by Means of RF Magnetron Sputtering and Ion Implantation
M. Bruns, H. Lutz (Forschungszentrum Karlsruhe GmbH, Germany); F. Link, H. Baumann (Universitaet Frankfurt, Germany)
A continuing interest in carbonitride has persisted since the prediction of its structure by Liu and Cohen due to the expected improvement of surface properties for a lot of applications. However, an Si-C-N ternary system may be preferred and could exhibit all useful characteristics of the binary compound. Very promising approaches to silicon carbonitride synthesis are RF magnetron sputtering and ion implantation techniques providing tailored stoichiometries at high purity. Si-C-N thin films were reactively sputtered using @super 15@N enriched N@sub 2@/Ar sputtering gas and co-sputter targets with different Si/C areas resulting in defined and reproducible Si/C ratios at constant nitrogen concentrations. Alternatively, surface modification by sequential high fluence implantation of C and N ions into silicon allows for tuning the atomic fraction of all elements over a wide range. However, the implanted layers of interest are some ten nanometer below the surface. Both preparation techniques along with post-treatment procedures are discussed with respect to the attainability of stoichiometric phases, e.g. Si@sub 2@CN@sub 4@. @paragraph@ The chemical composition of the ternary systems were characterized by means of X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and Fourier transform infrared spectroscopy (FTIR). In case of the buried implanted layers chemical binding states, however, only can be determined from XPS after Ar@super +@ ion sputter etching. Therefore, it is necessary to reduce the Ar@super +@ ion energy drastically (< 400 eV) in order to minimize the projected range for the etching ions to a negligible part of the XPS information depth. For quantification XPS and AES data were calibrated with absolute concentration values from n-RBS (non-Rutherford backscattering spectrometry). Furthermore, both preparation techniques have the advantage that @super 15@N and @super 13@C isotopes can be introduced into the layers enabling non-destructive nuclear reaction analysis (NRA) for depth profiling.
10:50 AM D1-3-8 Depositions and Characterizations of Boron Nitride Thin Films
G.L. Doll (Timken, Inc.)
Deposition parameters greatly affect the phase, microstructure, and chemical bonding of boron nitride thin films grown by ion-assisted PVD processes. BN films that have been grown by an ion-assisted pulsed laser deposition process, have been examined by many characterization techniques, including infrared absorption, Auger electron spectroscopy, NEXAFS, and transmission electron microscopy. Elemental bondings and crystallinities of BN coatings grown in three nitrogen ion energy regimes: high (2500 eV), low (700 eV), and without ions (0 eV) are examined, and the results interpreted within the frameworks of several theoretical models for cBN film growth. In addition, other results are reported in which post-deposition ion implantation into sp2-bonded BN films which are under compression, is found to result in amorphous, sp3-bonded BN.
11:30 AM D1-3-10 A Concept for the Deposition of Adherent Cubic Boron Nitride Films
A. Klett, R. Freudenstein, M.F. Plass, W. Kulisch (University of Kassel, Germany)
Applications of cubic boron nitride films are, despite their promising properties, hitherto prevented by their poor adhesion. Two reasons are responsible for this: the high compressive stress caused by the ion bombardment which is necessary for c-BN deposition, and the low adhesion strength at the complex c-BN/substrate interface consisting of a layered sequence substrate/amorphous mixing layer/textured h-BN nucleation layer/c-BN film. Starting from a theoretical discussion of both problems, which are supported by experimental results, we will present a concept for the deposition of adherent c-BN films. Theoretical considerations suggest that low stress values can be obtained using high ion energies and low Ar/N@sub 2@ ratios of the bombarding ions. Experimental investigations show indeed that with both measures the stress can be reduced by a factor of approximately 4 down to 4-5 GPa. However, in order to facilitate c-BN nucleation, high Ar/N@sub 2@ ratios should be used in the initial phase of the process. On the other hand, the h-BN nucleation is from a mechanical point of view the weakest link of the complex nucleation structure and should thus be avoided or at least reduced to a minimum thickness. Our results show that this is possible by means of a graded interface layer B --> BN. c-BN films with such interfaces possess indeed an improved adhesion. Thus, the following process for the deposition of adherent c-BN films emerges: a) deposition of a B --> BN interlayer; b) rapid nucleation of c-BN under severe ion bombardment; c) growth of c-BN using moderate ion bombardment.
11:50 AM D1-3-11 Cubic Boron Nitride Deposition in Large Scale Reactor Investigation of Deposition Conditions
M. Hock, A. Neuffer (University of Stuttgart, Germany); T. Fischer (University of Sttutgart, Germany); L. Ulrich, A. Lunk (University of Stuttgart, Germany)
In plasma enhanced physical vapor deposition (PEPVD) of cubic boron nitride (c-BN) films the deposition parameter range for c-BN growth is strongly restricted. Therefore in large scale deposition devices systematically investigations are necessary to find out the parameter range for growth over a large area with nearly constant deposition rate and c-BN content. @paragraph@ Investigations are performed in a hollow cathode arc evaporation device (HCAED) in a power range of 2 - 5 kW. In the first step plasma parameters (electron density, mean energy of electrons, plasma potential) were measured spatially resolved in the substrate area of the deposition chamber. Gas species used are argon and nitrogen. In the second step the spatial resolved boron deposition rate was measured as function of HCAED-power. By evaluation of the data from plasma parameter and boron deposition rate measurements the ratio of ion to boron flux rate can be achieved. The ratio of ion to boron flux in dependence on ion energy is one crucial parameter in PEPVD of c-BN film nucleation and growth. Both flux rates to the substrate surface are strongly depending on the position of the substrate in the deposition chamber and on outer parameters such as pressure, power and gas mixture. Typical values of these outer parameters are: pressure of 0.6 Pa, power of 5 kW and ratio of argon to nitrogen of about 3:1. A simulation shows large area (>300mm) where c-BN film growth with nearly constant deposition rate is possible. The size of these area depends on the distance of the evaporator to the substrate surface. Experiments confirm the simulation. The c-BN content of the films was measured in situ and ex situ by IR reflection spectroscopy.
12:10 PM D1-3-12 Growth of Cubic Boron Nitride Films by Triode Sputtering and IBAD : Development of Intrinsic Stress
M.A. Djouadi (ENSAM, France); V. Mortet ( ENSAM, France); S. Khandozhko, M. Ben El Mekki (ENSAM, France); D. Bouchier (Université Paris-Sud, France)
In the present work, attempts were made for deposition of c-BN films on unheated silicon substrates by IBAD technique and also Triode sputtering system. The films were characterized by infrared and Raman spectroscopy. High-resolution cross sectional TEM is used to confirm the optical results. Films with c-BN content up to 85% were obtained at temperature of 200@super o@C and in a pure nitrogen discharge. It's well known that the development of intrinsic stress hinders the deposition of thick c-BN films. So, the intrinsic stress in the deposited films was studied and in order to better understand this stress behaviour in depth stress profiles have been performed by three different procedures. After the description of the procedures, the obtained results may be discussed in relation with the different process parameters. @paragraph@ Finally it has been found that on condition to change the ion flux or energy during growth it's possible to get less stressed films. This assumption was checked and cubic boron nitride films with stress values of 5 GPa and relatively good adhesion were obtained.