Papers

ICMCTF2002 Session D2-2: Synthesis and Characterization of Diamond, Ternary Phase and other Carbon-based Materials

Wednesday, April 24, 2002 1:30 PM in Room Royal Palm Salon 1-3

Wednesday Afternoon

Start	Invited?	Item
1:30 PM		D2-2-1 Nano-structuring of a-C for Electronic Applications S.R.P. Silva (University of Surrey, United Kingdom)
2:10 PM		D2-2-3 Carbon-based Films with Nano-sized Transition Metals W.Y. Wu (National Cheng Kung University, Tainan, Taiwan, ROC); J.M. Ting (National Cheng Kung University, Taiwan, ROC) Transition metal containing carbon thin films were grown using a reactive sputtering technique under argon and methane environments. A number of growth parameters, including argon to methane ratio, working pressure, substrate temperature, post-growth heat treatment, and growth time, were examined. It was found that the metallic elements might present in the resulting films as uniformly-distributed nanoparticles, depending on the metal type and growth parameters. Atomic percentages of metals were also determined to increase with argon to methane ratio. Crystallinity and microstructure of the nanoparticles, the interface between the nanoparticles, and the carbon films were examined using both scanning electron microscopy (SEM), transmission electron microscopy (TEM), micro-Ramam microscopy, and x-ray diffractometry. The resulting carbon-based thin films were also examined for electrical conductance using a four-point probe technique, optical properties using an n/k analyzer, and energy band gap using a photoluminescence technique.
2:30 PM		D2-2-4 Diamond Like Carbon Films Prepared by Facing Target Sputtering J.R. Shi (Data Storage Institute, Sinagpore); J.P. Wang (Data Storage Institute, Singapore) Diamond like carbon films were prepared by facing target sputtering technique with different Ar pressures. The films were characterized by using atomic force spectroscopy, Raman spectroscopy, nanoindenter and ellipsometer. All films have a smooth surface morphology with RMS roughness less than 0.2 nm over an area of 1µmm². The Raman spectra show a G peak around 1560 cm^-1 and a D peak around 1400 cm^-1. The intensity ratio of D peak to G peak, I_D/I_G increases monotonously from 0.90 to 1.80 as the Ar pressure increases from 2 mTorr to 10 mTorr. The Tauc optical band gap decreases from 2.1 eV to 1.7 eV with increasing Ar pressure. Both Raman and ellipsometric results show that there is a high fraction sp³-bonded carbon in the films. The films have a quite high hardness, which varies from 24 GPa to 18 GPa.
2:50 PM		D2-2-5 Silicon Carbonitride Compounds: Combined R.F. Magnetron Sputtering and Ion Beam Synthesis H. Lutz (Forschungszentrum Karlsruhe GmbH, Germany); M. Rudolphi, H. Baumann (Universitaet Frankfurt/Main, Germany); M. Bruns (Forschungszentrum Karlsruhe GmbH, Germany) Carbonitride as well as silicon carbonitride thin films have been the subject of great interest in recent years due to the expected improvement of surface properties for a lot of applications. R.F. magnetron sputtering as well as ion implantation enable us to achieve ternary systems of more than 52 at.% nitrogen content, e.g. the stoichiometric Si₂CN₄. But in case of high carbon content the sputtered films in general have a lack of nitrogen. The respective preparation via ion beam synthesis likewise leads to sub-stoichiometric films, too. A very promising approach to carbon rich compounds (i.e. SiC₂N₄) synthesis is the combination of R.F. magnetron co-sputtering and ion implantation. Defined and reproducible Si/C ratios within the films can be obtained using co-sputter targets of different Si/C areas and argon sputter gas. In a second step surface modification by high fluence implantation of ¹⁵N ions into these Si-C films results in suitable nitrogen content up to the theoretical amount. The chemical composition of the Si-C-N films was characterized by means of X-ray photoelectron spectroscopy (XPS). In case of the buried implanted layers chemical binding states were attainable after sputter etching using 300 eV Ar⁺ ions of a projected range minimized to a negligible part of the XPS information depth. Non-Rutherford backscattering spectrometry (n-RBS) was used to calibrate XPS and AES sputter depth profile data with absolute concentration values. Resonant nuclear reaction analysis (NRRA) provides non-destructive depth profiles of the layer constituents ¹⁵N and ¹³C, respectively.
3:10 PM		D2-2-6 On the Properties of Nanocomposite Amorphous Carbon Films Prepared By Off-Plane Double Bend Filtered Cathodic Vacuum Arc B.K. Tay (Nanyang Technological University, Singapore); P. Zhang (Nanyang Technological University, Sinapore) It is known to deposit hard thin films, such as tetrahedral amorphous carbon (ta-C), using a filtered cathode arc (McKenzie et al 1991, Fallon et al 1993, Martin et al 1988). These ta-C films have interesting and useful properties, such as extreme hardness (~70 GPa), thermal stability, high electrical resistivity, wide Tauc optical band gap (~2.5 eV), smooth surface and low friction, and transparency in wide spectral range because of the high sp³ fraction of carbon atoms (up to 87%) in the film. However, the high internal stress in the films can limit their applications, especially when it is desired to deposit a relatively thick film, as the film may flake away from the substrate. In order to reduce the internal stress of the ta-C films and in an attempt to improve adhesion of thick films of this type, different modifications have been made such as metal incorporation into the films. Nanocomposite amorphous carbon (a-C:Me) films were deposited by filtered cathodic vacuum arc (FCVA) technique using metal-carbon composite target. Atomic force microscopy (AFM), Raman, and X-ray photoelectron spectroscopy (XPS) were used to characterize the morphology and structure of the films. Nanoindenter and surface profilometer were used to determine the hardness, Young's modulus, and internal stress. The same metal content targets for different elements results in different metal content in the corresponding a-C:Me films. We attribute this observation to the dynamic balance deposition (DBD) effect of the FCVA deposition process. The influence of elements and the content in the target of each element on the structural and mechanical, properties were studied. The incorporation of elements in to the films results in the decrease of sp3 C fraction, internal stress in the deposited films, but the hardness and Young's modulus remains at high level. Keywords: Diamond-like carbon, a-C:Me films, Filtered Cathodic Vacuum Arc, Stress, Hardness Novelty: New carbon nanocomposite materials prepared by an off-plane double bend filtering arc technique
3:50 PM		D2-2-8 Synthesis and Characterization of ta-C/ta-C:Si Nanoscale Multilayers by Using Hybrid Filtered Vacuum Arc Process. C.S. Lee (Korea Institute of Science and Technology and Yonsei University, Korea); K.-R. Lee, K.Y. Eun (Korea Institute of Science and Technology, Korea); K.H. Yoon (Yonsei University, Korea) Tetrahedral amorphous carbon (ta-C) films, with outstanding mechanical, chemical and tribological properties have attracted much attention. However, high residual compressive stress is great limitation of the application of ta-C films. It was reported that small silicon addition to ta-C films (ta-C:Si) was an effective method to reduce the residual stress without deteriorating hardness ¹. In this work, ta-C/ta-C:Si nanoscale multilayers were deposited by hybrid filter vacuum arc (FVA) with simultaneous silicon magnetron sputtering. The mechanical properties were investigated as a function of the thickness and composition of ta-C:Si layers in the multilayer. The residual stress and hardness were evaluated by using the laser deflection method and nanoindentation technique respectively. The details of the atomic bond structures of multilayers were characterized by RBS, XPS, AES, Raman spectroscopy. The friction behaviors of the multilayers were also investigated and compared with ta-C and ta-C:Si single layer. ¹ C.S. Lee et al, Diamond Related Mater., 2001 in press.
4:10 PM		D2-2-9 Preparation And Characterization of Tetrahedral Amorphous Carbon Ultra Thin Films by Pulsed Filtered Vacuum Arc Deposition Hao Wang, Ning Ke, Haijing Peng, Wingyiu Cheung, Yun Gao, Wingfai Lau, Saipeng Wong (The Chinese University of Hong Kong, China) Tetrahedral amorphous carbon (ta-C) ultra thin films, with film thickness in the range of 3 to 11 nm, have been prepared on Si (100) substrates by pulsed filtered vacuum arc deposition using an off-plane double bend magnetic filter. Various negative bias voltage ranging from -20 to -300 V have been applied to the substrates. The films are characterized by non-Rutherford backscattering spectrometry, elastic recoil detection, Raman spectroscopy, spectroscopic ellipsometry, and atomic force microscopy. The intrinsic compressive stress in the films is determined by photoelasticity method. High sp³ content larger than 80% has been achieved in the films, as well as a small amount of hydrogen has been detected. The compressive stresses are in the range of 2 to 5 GPa, the refractive indexes are in the range of 2.4 to 2.7, the extinction coefficients are in the range of 0.0 to 0.2, the optical band gaps are around 2.5 eV. These films have promising potential applications as protective overcoats on ultra high-density hard disks and read-write heads.