Papers

ICMCTF2008 Session B1-1: Sputtering Coatings and Technologies

Thursday, May 1, 2008 8:00 AM in Room Golden West

Thursday Morning

Start	Invited?	Item
8:00 AM		B1-1-1 Plasma-Enhanced Magnetron Surface Cleaning and Deposition for Smooth and Rifled Bore Applications S. Lee (US Army ARDEC-Benét Labs); R. Wei (Southwest Research Institute) In the plasma enhanced magnetron process, higher ion bombardment is achieved using an external filament to increase the plasma density and biasing to increase ion bombardment energy. Higher ion bombardment offers the advantages of effective pre-deposition surface cleaning for improved adhesion and the deposition of hard and dense coatings with reduced columnar structure, but increased residual stresses. In this work, plasma cleaning using argon, helium, nitrogen, and hydrogen plasma was tested. It was determined that sputter cleaning in argon was most effective in removing surface oxides and debris from target and substrate surfaces prior to deposition. Sputter cleaning using argon ions also will not encounter potential hydrogen embrittlement problem for tantalum coating deposition. The study of surface cleaning was performed using O18 oxidation for 3 hrs at 350°C to differentiate from native O16 surface oxidation. AES (Auger electron spectroscopy) and SIMS (Secondary Ion Mass Spectroscopy) analyses were performed. Plasma enhanced tantalum deposition was made on sections of 120mm smooth bore and 155mm rifled barrel sections. X-ray Diffraction analysis showed bcc Ta structure. Scan Electron Microscopy showed coatings were dense, uniform, and adhesive on 120mm smooth bore, and land and groove sections of 155mm rifled bore sections. However, the coatings on the walls of the rifled barrels were thinner with more columnar structure due to oblique angle deposition. Thick (148 µm and 286 µm) bcc Ta coatings deposited on 120mm smooth bore barrel sections gave excellent performance in Benet’s high temperature pulsed laser heating test and the VES (vented erosion simulator) in-door firing range test, simulating the thermal-mechanical-chemical environment of large cal barrel firing. The coatings showed excellent structure, no cracks, no damages, no degradation to the coatings or steel after 161 rounds of firing, while severely eroding four VES test fixtures made of bare steel.
8:20 AM		B1-1-2 Reactive Sputtering with Rotating Cylindrical Magnetrons D. Depla (Ghent University, Belgium); L. Xiuyan (Taiyuan university of Technology, China); J. Haemers, R. De Gryse (Ghent University, Belgium) For reactive magnetron sputter deposition several models can already be used to explain the behaviour of the deposition parameters as a function of the reactive gas flow. The authors have shown before the importance for a good description of the target processes during reactive magnetron sputtering. However, this work was focussing on planar magnetrons while on industrial level rotating cylindrical magnetrons are more popular due to the higher overall target consumption and the better stability during compound deposition. This contrast between the experimental and theoretical work on laboratory scale and industrial scaled magnetron sputter deposition is also noticed when looking for experimental data on reactive magnetron sputtering with a rotating cylindrical magnetron. Indeed, to have access to enough experimental data it was necessary to build a small scaled rotating cylindrical magnetron. Hence, the paper starts with a presentation of this home build rotating cylindrical magnetron which was used to perform a series of experiments. The most important conclusions from this experimental work will be presented. First, one should realize that to understand and to model the reactive magnetron sputtering with this type of magnetron, no steady state solutions can not be used because of the target rotation. Indeed, when the rotation speed is high enough, it is possible that the target processes occurring at a given part on the target are not finished when entering again in the plasma zone. The presented influence of the rotation speed on the reactive sputter behaviour of aluminium and titanium in an argon/oxygen plasma clearly demonstrated this. Another conclusion of the experiments, it is the importance of deposition of compound material on the target. This effect has never implemented before in models for magnetron sputtering. It will be shown that this has an important role on the interpretation of the reactive sputtering behaviour with this interesting magnetron sputter source.
8:40 AM		B1-1-3 Microstructural and Electrical Characteristics of Reactively Sputtered Zr-N Thin Films J.-L. Ruan (National Cheng-Kung University, Taiwan); D.-F. Lii (Cheng Shiu University, Taiwan); J.S. Chen, J.-L. Huang (National Cheng-Kung University, Taiwan) Zr-N thin films were deposited by DC reactive magnetron sputtering. The effects of nitrogen flow rate on the microstructure, chemical and electrical properties of the Zr-N films were investigated by means of x-ray diffraction, electron probe microanalyzer, atomic force microscopy, x-ray photoelectron spectroscopy and four point probe method. Results indicated that the stoichiometric Zr-N films, which showed a rock-salt crystal structure, were formed at nitrogen flow rate of 3 sccm. It exhibited a gold-like color and a minimum of electrical resistivity. The films became brownish and more electrically resistive with increasing nitrogen flow rate. XPS analysis results exhibited that the binding energy of Zr 3d electrons gradually shifted toward the higher value direction from the Zr-Zr binding state of pure metal to both the Zr-N binding state of stoichiometric and over-stoichiometric compound with increasing nitrogen flow rate.
9:00 AM		B1-1-4 Effect of Plasma Current Density on the Properties of Nanostructured Ti_xN_y Films Prepared by Reactive DC Magnetron Sputtering P.K. Barhai, N. Kumari, I. Banerjee (Birla Institute of Technology, India); S.K. Pabi (Indian Institute of Technology Kharagpur, India); S.K. Mahapatra (Birla Institute of Technology, India) Stoichiometric and non- stoichiometric of TiN films were deposited on steel by varying the plasma current density from 10mA/cm² to 40mA/cm², using DC magnetron sputtering. The colours of the films obtained were golden, pink, blue and green. At lower current density (~10mA/cm²), the film showed stoichiometric TiN, whereas, at higher current density (~20, 30 and 40mA/cm²) the films showed non stoichiometric TixONy. Crystallinity, thicknesses and atomic concentration of the films have been characterized by GIXRD, Auger Electron Spectroscopic (AES) and XPS techniques. The average thickness as determined from Auger Electron Spectroscopy of the film increased with plasma current from 775A0 to 996A0. The hardness, roughness and Young’s modulus of the films were analyzed by nano-indentation. Hardness of the TiN film was found to increase from 7.054 GPa to 17.49 GPa and Young’s modulus from 209.774 GPa to 257.586 GPa with increasing plasma current density. SEM and AFM images showed the grain size of the non- stoichiometric films to increase with increasing plasma current density. AFM image of TixNy films are found to have nanostructured grains. The durability and the quality of the film colour have been characterized by colorimetric analysis.
9:20 AM		B1-1-5 Investigation of Nanostructured CrN/Amorphous- Si₃N₄ Multilayer Thin Films J.-W. Lee, J.-S. Yang (Tung Nan University, Taiwan); L.-C. Chang (Huafan University, Taiwan) Nanostructured CrN/amorphous-Si₃N₄ multilayer coatings were deposited periodically by the bipolar asymmetric pulsed DC reactive magnetron sputtering technique. The structures of multilayer coatings were characterized by an X-ray diffractometer. The surface and cross sectional morphologies of thin films were examined by a scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. The surface roughness of thin films was explored by an atomic force microscopy (AFM). The nanohardness and elastic modulus of multilayer coatings were investigated by means of a nanoindenter. Nanoscratch and nanowear testers were used to evaluate the nanotribological properties of thin films. The fracture toughness of multilayer coatings was also explored. It is observed that the bilayer period of coatings ranges from 40 nm to 5 nm. The influences of the bilayer period on the microstructure and mechanical properties were investigated. The mechanisms of hardening and toughening of nanostructured multilayer films were also discussed.
9:40 AM		B1-1-6 Synthesis and Characterization of Sputter-Deposited Nanocrystalline Nanolaminates A.F. Jankowski (Texas Tech University) Nanocrystalline nanolaminates are widely used in fundamental studies of material behaviours and in a variety of industries with applications that include Bragg diffractors for x-ray telescopes and advanced lithography, magnetic recording, as well as hard wear-resistant surfaces for cutting tools. The nanocryslline nanolaminate can be synthesized by diffusion process evolution through phase decomposition. However, in general, the more interesting physical behaviours appear when the nanolaminate structures are artificially synthesized as, for example, through physical vapour deposition methods such as sputtering. The physical properties are dependent upon the specifics of the nanostructural arrangements of atoms at grain boundaries and of atoms within the constituent layers. Nanolaminates can be: 1-D nanocrystalline, i.e. an artificial crystal with a composition modulation of amorphous layers; 2-D nanocrystalline with one component layer crystalline as is typical for Bragg diffractors; or 3-D wherein all the layers are nanocrystalline. The specific structural features available for characterization are chemical bonding states, composition gradients, and atomic structure that reveals crystalline phase and lattice distortions. As such, not all nanocrystalline nanolaminates are created equal, and consequently, can display very different physical behaviours than their constituent counterpart microstructures. For the case of sputter deposition, the energetic parameters of the synthesis process are keys to defining the details of the nanocrystalline nanolaminate structure and behaviour. 3-D nanolaminates of metals and ceramics will be reviewed with a focus on systems such as that display grain boundary and/or interlayer distortion effects. Mechanical properties to be reviewed are tensile behaviour, and surface nanohardness with accompanying structural characterization through x-ray diffraction and high resolution electron microscopy.
10:20 AM		B1-1-8 Microstructure Evolution of CrAlSiN/W₂N Superlattice Coatings Deposited by DC Magnetron Sputtering Y.Z. Tsai, J.G. Duh (National Tsing-Hua University, Taiwan) CrAlSiN/W₂N nano-layered coatings were prepared by DC magnetron sputtering. The modulation periods of multilayer coatings were controlled in the range from 3 to 20nm. From the low angle X-ray diffraction and high angle XRD satellite peaks, the superlattice structure of these coatings was evidenced. The detailed layered structure was further investigated by HRTEM. Owing to the dense and smooth nano-layered microstructure, the CrAlSiN/W₂N multilayer films showed excellent microhardness. With an appropriate modulation period of 8nm, the hardness reached a maximum around 40GPa. The strengthening mechanism of the multilayer coatings was proposed and discussed. In addition, CrAlSiN mono-layer coatings exhibited distinct oxidation resistance. The anti-oxidation property of CrAlSiN/W₂N multilayer films with different bilayer periods was also investigated.
10:40 AM		B1-1-9 Xrd and Ftir Analysis of Ti-Si-Con Coatings for Biomedical Applications C. Oliveira, B.G. Almeida, S. Carvalho, M. Henriques, M. Susano, R. Oliveira (Universidade do Minho, Portugal); R. Escobar (ICMM,Instituto de ciencia de Materiales de Madrid -CSIC, Spain); F. Vaz (Universidade of Minho, Portugal) Ti-Si-C-ON films were deposited by DC reactive magnetron sputtering using different partial pressure ratio of oxygen (pO2) and nitrogen (pN2). The films structure was studied by X-ray diffraction. Fourier transform infrared spectroscopy (FTIR) was used in order to characterize their chemical properties and determine their characteristic vibrational modes. Compositional analysis revealed the existence of two different growth zones for the films; one zone deposited under low pO2/pN2 and another zone deposited under high pO2/pN2. For the samples deposited under low pO2/pN2 it is possible to identify a fcc type structure and there is a tendency for an increase in the peak intensity ratio I(111) /(I(111)+I(200) with increase in pO2/pN2, indicating a preferential crystalline growth change. It is difficult to unequivocally identify which phases are formed. Carbon and oxygen substitution of regular nitrogen positions to formed fcc Ti(C,O,N) phase, once the nitrogen content decreases, could be possible. The samples that were deposited at high pO2/pN2 presented a significant loss of crystallinity, with the sample with highest oxygen content found to be amorphous. Tanking account the application of these coatings (biomedical application), preliminary results showed, that samples deposited with higher ratios of pO2/pN2 presented lower values of biofilm formation, indicating that the increase of oxygen leads to biomaterials less susceptible to be colonized by Staphylococcus epidermidis. Correlation between the structural and biological behaviour will be discussed.
11:00 AM		B1-1-10 Characterization of Bi_0.5Sb_1.5Te₃ Thin Films Prepared by RF Magnetron Sputtering K.-J. Kang, H.-J. Lin (National United University, Taiwan); Z.-D. Huang, H.-S. Chu (ITRI, Taiwan) Thermoelectric thin films of Bi_0.5Sb_1.5Te₃ were prepared on SiO₂/Si substrates by radio-frequency (RF) magnetron sputtering. The casting Bi0.5Sb1.5Te3 alloy was used as target. In order to enhance the transport properties of thin films, annealing in argon ambient at atmospheric pressure was carried out for 30 min in the temperature range from 150 to 350^oC. The effects of annealing temperature on surface morphology, crystallinity and electrical transport properties were investigated. The morphology, composition and structure of these films were analyzed by field-emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). We confirmed that as-deposited Bi_0.5Sb_1.5Te₃ thin films have a homogeneous structure. At higher annealing temperature, the crystallinity of the films was improved. However, excessive high annealing temperature caused porous thin films due to the evaporation of tellurium. The transport properties of thin films, in terms of the electrical resistivity and Seebeck coefficient were determined at room temperature. It was proved that the performance of thin films could be enhanced by optimizing the annealing temperature. The change of Seebeck coefficient from positive to negative value was observed after annealing.
11:20 AM		B1-1-11 Reproducible Resistive Switching Behavior in Sputtered CeO₂ Polycrystalline Film C.-Y. Lin, S.-Y. Wang, C.-C. Lin, T.-Y. Tseng (National Chiao Tung University, Taiwan) Sputter-deposited CeO₂ film in metal-insulator-metal structure exhibits repeatable resistive switching behavior under voltage bias. Based on the X-ray diffraction patterns and the cross-sectional scanning electron microscope image, the CeO₂ film is polycrystalline structure with columnar grains perpendicular to the bottom electrode. Moreover, due to the symmetric device structure, the resistive switching behavior is independent of bias polarity so that both positive and negative voltages can switch the device from high conducting state (ON-state) into low conducting state (OFF-state), and then back to ON-state. The resistance ratio between two memory states is about five orders of magnitude, which is stable over 10⁴ s at 0.3 V stress. In addition, the resistance ratio decreases as an increase in the compliance current during forming process. The stability of ON-state, OFF-state, and Origin-state (the state before performing forming process) against temperature is also investigated in this study, showing that the OFF-state is less stable.
11:40 AM		B1-1-12 Electrical and Optical Properties of ITO Thin Films Deposited by ICP-Assisted Magnetron Sputtering K.S. Shin, N. Britun, M.J. Keum (Sungkyunkwan University, Korea); Y. Setsuhara (Osaka University, Japan); J.G. Han (Sungkyunkwan University, Korea) Tin-doped indium oxide (ITO) films are widely used for transparent electrodes in display devices among other materials such as zinc oxide, indium oxide and their compounds. Although ITO is used for transparent electrodes because of high optical transmittance and low resistivity, it should be improved to meet the properties of transparent electrode due to having high resistivity in the low temperature process using polymer substrate. ITO thin film has amorphous phase when it was deposited by conventional magnetron sputtering in the low temperature. As film thickness is increased in the low temperature process, ITO films having crystallity are synthesized. However, film thickness is restricted by application of organic light emitting diodes (OLED). The densities of ions and electrons in ICP-assisted plasma are much higher than conventional magnetron sputtering. We investigated effect of plasma density on change of film microstructure. To investigate interrelation between plasma parameters and structure of thin films, we employed plasma diagnostic method such as Langmuir probe, OES, RGA and so on. Also, optical and electrical properties of ITO thin films were analyzed by UV/Vis spectrometer and hall measurement. Surface morphology and microstructure was estimated by AFM and XRD. The detailed results will be presented.