ICMCTF2007 Session D2-2: Diamond and Diamond-Like Carbon Materials

Thursday, April 26, 2007 8:00 AM in Room Sunset

Thursday Morning

Start	Invited?	Item
8:00 AM	Invited	D2-2-1 Laser Micro and Nanoprocessing of Diamond and Diamond-Like Carbon Films V. Kononenko, T. Kononenko, S. Pimenov, M. Komlenok, V. Konov (General Physics Institute, Russia) The aim of this work is to report the developed laser-based approaches and recent experimental results to micro and nanoprocessing of super hard diamond and diamond-like carbon (DLC) films. The results were obtained using micro-, nano-, pico- and femtosecond pulses of various laser sources, including KrF excimer laser, two harmonics of Nd:YAP laser, Nd-YAG laser and Ti:sapphire laser. The influence of laser pulse duration on the diamond ablation rates and crater quality has been investigated. It is found that microsecond regime is the most productive one, characterized by the ablation rates of up to 7 µm/pulse as compared to 0.2 µm/pulse for ns pulses and 0.05 µm/pulse for ps-fs pulses and by low roughness processed surface. Special attention was paid to the laser induced surface graphitization. The dependencies of the graphitized layer thickness on the radiation parameters will be discussed. The obtained data show that the graphitized laser thickness is close to the heat penetration depth in the materials and is controlled either by laser pulse duration. For single crystal diamond and DLC films the regime of the nanoscale laser ablation ("nanoablation") was revealed at fluencies below the graphitization threshold. The nanoablation rate was found about 10^-3nm/pulse in air and negligible in an inert gas atmosphere. Its temperature dependence is close to Arrhenius curve, that evidence in favor of the photochemical character of the nanoablation. Novel low coherence interferometric technique for local monitoring of the transparent plate thickness in the course of laser ablation will be presented. Its applications for real time control of laser polishing and shaping of CVD diamond will be demonstrated. The examples of pulsed laser fabrication of micro and nanostructures (CVD diamond diffractive optical elements, surface microstructuring to improve tribological systems) will be presented.
8:40 AM		D2-2-3 Comparative Studies of Influence of Acetylene to Argon Flow Rate Ratios on Amorphous Carbon Films Produced on Steel Substrates by Plasma Immersion Ion Implantation and Deposition M. Xu (Shanghai Jiao Tong University and City University of Hong Kong); X. Cai (Shanghai Jiao Tong University, Hong Kong); J. Zhao (Southwestern Institute of Physics); Q. Chen (Shanghai Jiao Tong University, Hong Kong); P.K. Chu (City University of Hong Kong) Amorphous carbon film is useful in many applications due to its favorable tribological and mechanical properties. It can be deposited by various techniques including ion beam deposition, chemical vapor deposition and so on. However, direct fabrication of a-C films on certain materials such as ferrous substrates still faces some technological difficulties thus hampering wider applications. Besides, the film and interfacial quality synthesized by conventional deposition techniques depend on the deposition conditions. Plasma immersion ion implantation and deposition has been utilized to produce a-C films recently and an interfacial region in which carbon and the substrate elements are well mixed can be achieved. Most reports have hitherto focused on the effects of the negative bias voltage on the properties of the films. In contrast, the impact of the flow rates, for example, the ratio of the acetylene to argon flow rates or the deposition pressure have not been investigated as much and based on our literature search, a systematic study on these effects has not been conducted. The objective of this study is to investigate the elastic and tribological properties of films directly prepared on steel substrates using various acetylene to argon flow rates. The main focus was the adhesion and deformation response of the films using the scratch test as the main experimental characterization tool. The film deformation response is studied to gain a better understanding of the mechanisms governing failure of the films. The nanoscratch test provides a simple versatile and rapid means of assessing the adherence of the film to the substrate. The nanoscratch apparatus used in this work can make fine and controlled low load scratches and provide coefficient of friction measurements as well as information about in situ surface elastic-plastic deformation depth during the test. Based on the experimental results, the cause and mechanism can be explained by the nucleation theory.
9:00 AM		D2-2-4 Successful CVD Diamond Integration with GaN for High Power Electronics Applications F. Faili, C. Engdahl, E. Francis (Crystallume) This paper presents an updated overview of the latest development in hot filament assisted CVD diamond growth and diamond integration with electronic materials. In this investigation, we study the successful demonstration of GaN on diamond and review and compare the results with that of silicon on diamond (SOD). The effects of process conditions on the characteristics such as stress and thermal conductivity are described. The as-deposited diamond films were characterized by stress and morphology. The GaN on diamond stack were evaluated optically and electrically. A steady-state technique was used to measure the thermal conductivity of the deposited and free standing diamond and the GaN/Diamond layers.
9:20 AM		D2-2-5 The Electrical Properties of Amorphous Carbon at High Electric Field Using the Sandwich and Coplanar Structure Y. Miyajima, J.M. Shannon, S.J. Henley, D.C. Cox, S.R.P. Silva (University of Surrey, United Kingdom) Carbon is a unique material with four valence electrons forming three different types of hybridisations like sp³, sp² and sp¹ hybridised bonding. Hence, the carbon related material covers a wide range from semiconductor to semi-metallic or polymeric depending on the hybridisation type and the hydrogen content. This implies that amorphous Carbon (a-C) or hydrogenated amorphous Carbon (a-C:H) can be tuned to change their properties by changing the hybridised bonding ratio or the atomic ratio of carbon and hydrogen etc. Usually, the electrical properties of a-C are measured using two terminal devices like the sandwich and the coplanar structures. The length of these two terminal devices was over tens of nanometres for the sandwich structure and over micrometers in the past. We use 100 nanometres coplanar electrodes fabricated using Focused Ion Beam (FIB) system to measure the electrical properties of a-C in this study. Pulsed laser deposition is used to deposit a-C film with different sp³ fraction. The results are compared with the electrical properties of a-C measured using sandwich structure. Both, structures show Pool-Frenkel conduction at high electric fields. Values between three and five were found for the dielectric constant of low sp³ fraction a-C film which was evaluated using a model based on the Poole-Frenkel conduction. When this value is compared to the optically measured data there is a good fit. Further analysis on the evolution of defect densities as a function of sp³ content is presented in this paper and strategies for fabricating three terminal device structures in low mobility amorphous semiconductors.
9:40 AM		D2-2-6 Structure, Electronic Characterisation and Applications of Nanostructured Carbon Thin Films J.D. Carey, S.J. Henley, S.R.P. Silva (University of Surrey, United Kingdom) Thin films of disordered carbon are produced by pulsed laser ablation in different pressures of an inert gas, argon. At low pressures, hard mirror smooth films are produced, however, on increasing the background pressure of gas, first nodular and then filamentary carbon films with a large surface area are produced. The electronic properties show that the visible Raman spectra and the room temperature photoluminescence are correlated and are interpreted in terms of the clustering of the sp2 carbon phase. Electron spin resonance data show that there is delocalization of the wavefunction in the sp² cluster. At high pressures it is possible to decorate the surface with silver atoms using laser ablation and to use the resulting surfaces as scaffolds for surface enhanced Raman spectroscopy (SERS). High resolution transmission electron microscopy show clustering of the metal atoms. Evidence of SERS from nanostructured silver islands coated with thin carbon layers down to 0.5 nm is also observed.
10:00 AM	Invited	D2-2-7 Anti-Inflammatory, Antiallergic and Anticancerogenic Properties of NCD K. Mitura, S. Mitura (Technical University of Lodz, Poland) Different medical implants are covered by carbon coatings. The coatings form a diffusion barrier between an implant and the human environment. The research on carbon coatings proved that layers are biocompatible with the living organism^{1, 2, 3}. Nanocrystalline Diamond Coatings (NCD) were manufactured by RF PCVD and RF/MW PCVD methods⁴.Contact allergy on metal implants is very popular subject of biomedical engineering. Different medical implants are covered by Nanocrystalline Diamond Coatings. NCD form the diffusion barrier between an implant and the human environment. The research on NCD proved that diamond layers are antiallergic for living organism. We examined the mechanical and biological properties of interlocking nail with NCD after two years exposition in human environment. Nanocrystalline Diamond Coatings (NCD) were manufactured by RF PACVD method⁴.The first results indicate that NCD coating is a barrier diffusion between metal ions. We have not observed corrosion. Biological examinations indicate that the tissues around the implant have not the congestion, inflammatory process and proliferation of fibrous connective tissue. Diamond Powder Particles (DPP) form an extended surface of NCD. In examinations in vitro with CCRF-CEM, acute T lymphoblastic leukemia cell line and HL60, human promyelocytic leukaemia cell line we proved that diamond powder has anticancerogenic properties. Clinical research with DPP proved antiallergic and anti-inflammatory properties. ¹A.H.Lettington, Carbon Vol. 36, No 5-6, (1998), 555-560. ²R.Butter, M.Allen, L.Chandra, A.H.Lettington, N.Rushton, Diamond and Related Materials, 4 (1995) 857-861. ³D.P.Dowling, P.Kola, K.Donelly, T.C.Kelly, K.Brumitt, L.Lloyd, R.Eloy, M.Therin, N.Weil, Diamond Rel. Materials, 6, (1997) 390-393. ⁴K.Mitura et all, Surface Coatings Technology, 2006, in press. K.Bakowicz, S.Mitura, Journal of Wide Bandgap Materials, Vol. 9, No. 4 (2002) 261.
10:40 AM		D2-2-9 Low-Friction Diamond-Like-Carbon (DLC)-Layers for Humid Environments W. Tillmann, E. Vogli, F. Hoffmann (University of Dortmund, Germany) Even though amorphous diamond-like-carbon (DLC) coated tools with their low friction and high wear resistance are well established in a wide field of industrial applications, their employment into humid environments is limited. Responsible for this behavior are the so-called "Dangling" o-bonds at the carbon surface, which in humid environment adsorb a thin water layer. Due to this, the structure of the surface will be changed, associated with increase of friction coefficients and unfavorable wear resistance properties. This work is focused on the development of a DLC-system with high wear and friction resistance even at humid environment. Using the Physical Vapor Deposition (PVD)-process different DLC-coating systems have been deposited, in which the layer properties have been designed related to the humidity conditions. Coating parameters, layers microstructure and layer properties have been systematically analysed with special emphasis on tribological properties. Correlations between layer structure and corresponding wear as well as friction properties have been scrutinized.
11:00 AM		D2-2-11 Deformation Behaviour of DLC Coatings on (111) Silicon Substrates A.J. Haq (University of New South Wales, Australia); P.R. Munroe, M. Hoffman (New South Wales, Australia); P.J. Martin, A. Bendavid (CSIRO Industrial Physics, Australia) The deformation mechanisms operating in diamond-like carbon (DLC) coatings on silicon substrates have been investigated using focused ion beam microscopy (FIB) and cross-sectional transmission electron microscopy (XTEM). A hydrogenated amorphous carbon coating of ~500 nm thickness was deposited by radio-frequency plasma-assisted chemical-vapour deposition onto a (111) oriented silicon substrate. Indentations were performed on the coatings using a spherical indenter with a radius of 5 µm for various loads up to a maximum of 150 mN. The coatings exhibited substantial elastic recovery on unloading. Pop-ins were observed even at loads of 100 mN and a distinct pop-out was observed in the unloading curve following indentation to 150 mN. Focused ion beam microscopy of the cross-section through the indentations revealed localized plastic compression of the coating beneath the indenter and bending at the coating-substrate interface. Although the coating was free from cracking or delamination, the substrate showed evidence of median cracks and lateral cracks for loads above 100 mN. XTEM investigation of indentations revealed cracks in the coating as well as cracks, defects and a transformation zone in the silicon substrate. These observations have been correlated with the deformation behaviour of the coating-substrate composite.
11:20 AM		D2-2-10 Effect of Residual Stress in P Doped Microcrystalline Silicon Carbide (mc-SiC) Films Grown by Hot-Wire Chemical Vapor Deposition (HWCVD) B.P. Swain (University of Cape Town, South Africa) P type doped microcrystalline silicon carbide (mc-SiC) films were deposited by Hot Wire Chemical Vapor Deposition (HWCVD) technique using SiH₄, C₂H₂, B₂H₆ and H₂ gas flow. Both the R factor and conductivity decreases with increase of C₂H₂ flow rate. The corresponding decrease in grain size with increase in C₂H₂ flow rate reflects from XRD and AFM measurements. Stress measurements were carried out by the X-ray powder diffraction technique known as the "osin2theta methodâ". For p type mc-SiC films show homogeneous biaxial stresses ranging from -150 MPa (compressive) to +125 MPa (tensile) as a function of C₂H₂ flow rate. The deposition parameters that could be expected to give unstressed films by this technique, which are shifted to small carbon content, and the ability to measure stresses in randomly oriented mc-SiC layers by this technique are shown in this paper.