ICMCTF2005 Session FP: Symposium F Poster Session

Thursday, May 5, 2005 5:00 PM in Room Town & Country

Thursday Afternoon

Time Period ThP Sessions | Topic F Sessions | Time Periods | Topics | ICMCTF2005 Schedule

FP-1 A Novel Nanoacoustic Microscope in Study of Thin Films
O.G. Lysenko, N.V. Novikov, V.I. Grushko (Institute for Superhard Materials, Ukraine)
Nanoacoutic deals with the investigation of acoustic waves using AFM or STM techniques. We developed the nanoacostic microscope that includes a pulse laser as a source surface acoustic waves and two tunneling tips to detect phase and amplitude of the acoustic waves. Now we report an improved technique that can measure the surface oscillates in GHz frequency range. This technique makes it possible to measure acoustic waves parameters in thin films and calculate their mechanical properties including elastic modulus, shear modulus, and thickness. The method is non-destructive and offers some advantages with respect to other methods.
FP-2 Nano-Rod Structure of Ferroelectric Lanthanum-Doped Bismuth Titanate
C.I. Kim, K.T. Kim (Chungang University, South Korea); S.G. Lee (Seonam University, South Korea)
Nano-rod structure of ferroelectric Bi 3.25La 0.75Ti3O12 thin film have been accomplished during the heat treatment. These nano-rod crystallites were well-oriented instead of lying on the surface. The BLT Nano-rod structures are analyzed via FE-SEM, HR-TEM, XRD and AFM. The high-resolution transmission electron microscopy (HRTEM) images also show that each nano-rod is a single crystal with 100 nm in length and 20 nm in width approximately. These crystallites may be evolved from the interaction between the ferroelectric Bi 3.25La 0.75Ti3O12 thin film and the Pt/Ti/SiO2/Si substrates at elevated temperatures. These nano-rod provide promising materials for nanoscale nonvolatile memory application.
FP-3 X-Ray Scattering Studies of Sputter-Deposited Ba0.48√sub 0.52TiO3/LaNiO3 Artificial Superlattice on a SrTiO3 Substrate
K.-F. Wu (National Tsing Hua University, Taiwan); H.-Y. Lee, H.-J. Liu (National Synchrotron Radiation Research Center, Taiwan); C.-H. Lee (National Tsing Hua University, Taiwan)
Artificial superlattices consisting of ferroelectric Ba0.48√sub 0.52TiO3 and conductive LaNiO3 sublayers were epitaxial grown on SrTiO3 (001) single crystal substrates by a dual-gun RF magnetron sputtering system. X-ray reflectivity and high-resolution diffraction measurements were employed to characterize the microstructure of these films. Formation of a superlattice structure was confirmed from the appearance of Bragg peaks separated by Kiessig fringes in x-ray reflectivity curves and a diffraction pattern. The fitted specular reflectivity indicates that surface roughness of the superlattices increases with increasing thickness of sublayers, but the interfacial roughness of superlattices remains nearly constant at a value about 0.66 - 0.81 nm. The presence of oscillation fringe in the diffuse scattering indicates that the conformal relationship exists between the superlattice surface and the film/substrate interface in high temperature deposition.
FP-4 Surface Evolution and Dynamic Scaling of Heteroepitaxial Growth of (La,Ba)MnO3 Films on SrTiO3 Substrate by RF Magnetron Sputtering
Y.-C. Liang (National Tsing Hua University, Taiwan); H.-Y. Lee, H.-J. Liu (National Synchrotron Radiation Research Center, Taiwan); T.-B. Wu (National Tsing Hua University, Taiwan)
The evolution of (La,Ba)MnO3 surface morphology during heteroepitaxial growth on SrTiO3 substrate was investigated using high-resolution x-ray reflectivity and atomic force microscopy measurements. The epitaxial growth of (La,Ba)MnO3 films on the SrTiO3 substrates was divided into the initial stage heteroepitaxial regime, and the intermediate stage crossover regime. In the early stage of growth, highly strained planar (La,Ba)MnO3 films were grown. As the film thickness approaches an effective critical thickness, the growth gradually crosses over to the island growth. At the same time, the relaxation of the lattice strain begins and the growth front becomes rougher. The evolution of the surface roughness in the different regime can be described by the different dynamic scaling exponent values. The relationship between surface roughness and the degree of strain for the growth of epitaxial (La,Ba)MnO3 film on SrTiO3 substrate will also be discussed in details.
FP-5 Enhancement on Anti-Bacterial Performance of Photocatalytic TiO2 Thin Films Modified by Metal Plasma Ion Implantation
D.-Y. Wang, H.-C. Lin (Mingdao University, Taiwan)
The anatase TiO2 depicts great potential in energy conversion, pollution control, electrolysis, and anti-bacterial applications due to its photocatalytic behavior under UV irradiation. Our current research emphasizes on the improvement of the photosensitivity of TiO2 under visible light by doping band gap materials such as Pt, Cu, V, and Pd by using metal plasma ion implantation process. Nanometric TiO2 coatings were synthesized by using sol-gel and spin coating technique. The pure anatase TiO2 phase was obtained after a 500°C calcination process in atmosphere. The anatase TiO2 thin film was then irradiated by using metal plasma ion implantation at 40 KV. Influences of the optical band gap of the metal-doped TiO2 were characterized by optical emission spectroscopy and quadrupole mass spectroscopy. The photocatalysis efficiency was characterized by decolor tests of the crystal violet. The integrity of the anatase TiO2 thin films deposited on medical glass was analyzed by electron microscopy, x-ray diffractometry, and nanotribology test standard.
FP-6 Magnetic Response of Cobalt Oxide Films Prepared by Pulsed Liquid Injection MOCVD
L.M. Apatiga, H. Boehnel, V.M. Castano (UNAM, Mexico)
Thin cobalt oxide films prepared by pulsed liquid injection metal-organic chemical vapor deposition (MOCVD) from a commercially-available cobalt (II) acetylacetonate compound, as the precursor, oxygen as the reactant and argon as the carrier gas, were deposited on Si (100) substrates at 650 °C in about 40 minutes. According to X-ray diffraction and atomic force microscopy, smooth and polycrystalline films, consisting of the Co3O4 phase only, were produced. Magnetic properties such as, saturation magnetization Ms, the remanence Mr, the coercivity Hc, the squareness ratio SQR, S* which is related to the slope at Hc, and the switching field distribution SFD were extracted from the hysteresis loop, which show cobalt oxide films with coercivities of 6.61 mT, squareness ratio of 0.2607 and saturation magnetization of 12.17 nAm2, corresponding to a soft magnetic material. All measurements were made at room temperature and longitudinally, with the magnetization parallel to the plane defined by the substrate/film surface.
FP-7 Properties of MoNxOyyThin Films as a Function of the N/O Ratio
J. Barbosa, L. Cunha, L. Rebouta, F. Vaz (Universidade do Minho, Portugal); E. Alves (ITN, Portugal); P. Goudeau, Jean-Paul Rivière (Universite Poitiers, France); S. Carvalho (Universidade do Minho, Portugal)
Metal oxynitride films show a wide variety of optical, electrical and mechanical properties providing some opportunities for technological applications. The main purpose of this work consists on the preparation of single layered molybdenum oxynitride, MoNxOy, thin films. Varying the oxide/nitride ratio allows tuning the band-gap, bandwidth, and crystallographic order between oxide and nitride and consequently electronic, mechanical and optical properties of the material. Films were deposited on steel substrates by dc reactive magnetron sputtering. The depositions were carried out from a pure Mo target varying the process parameters such as substrate bias voltage and flow rate of reactive gases. X-ray diffraction (XRD) results revealed the occurrence of face-centred cubic phases (γ-Mo2N type and MoN). The chemical composition was determined by Rutherford Backscattering Spectrometry (RBS). Residual stresses are compressive in the range from - 0.5 to - 3 GPa. All these results have been analysed and will be presented as a function of the deposition parameters, the chemical composition and the structure of the films.
FP-8 Effect of Sodium Lauryl Sulfate on Electrodeposition of Ni-P Layer as a Under Bump Metallization
Y.-C. Lin, J.G. Duh (National Tsing Hua University, Taiwan)
The nickel plating has been used as the under bump metallurgy (UBM) in the microelectronic industry. In this study, the electroplating process was demonstrated to be a favorable alternative approach to produce the Ni-P layer as UBM. The surface morphology and surface roughness in electroplated Ni-P was evaluated with the aid of both field emission scanning electronic microscope and atomic force microscope. The wettability of several commercial lead-free solders, including Sn-37Pb, Sn-3.5Ag, and Sn-3.5Ag-0.5Cu solder paste, on electroplated Ni-P with various phosphorous contents (6wt%, 9wt% and 13wt%) was investigated. The electrodeposition of Ni-P with sodium lauryl sulfate (C12H25OSO3Na) addition slightly increased the phosphorous contents of Ni-P deposit to 7wt%, 10wt%, and 14wt%, respectively. The surface morphology and the surface roughness of Ni-P layer were significantly enhanced with sodium lauryl sulfate adding. The improvement of surface morphology and surface roughness upgraded the wettability of electroplated Ni-P. In addition, the interfacial reaction between lead free solder and electroplated Ni-P UBM was also investigated.
FP-9 Effect of Surface Capping Molecules on the Electronic Structure of CdSe Nanocrystal Film
H.H. Park, H.J. Choi, J.K. Yang, S. Yoon (Yonsei University, South Korea); H.J. Chang (Dankook University, South Korea)

Optoelectronic devices fabricated with CdSe nanocrystals synthesized by colloidal process have become the focus of much attention.1-2In these systems, during the fabrication process, CdSe nanocrystals are capped with Trioctylphosphine oxide (TOPO) as a capping organic molecule. As a result, the electronic structure of CdSe nanocrystals could be heavily affected by the covered TOPO with polar characteristic.

In this work, we demonstrate the effect of TOPO coverage on the electronic energy structure of CdSe nanocrystal film qualitatively and quantitatively. We have synthesized colloidal CdSe nanocrystals through an alternative route, known as greener approach using Cd(Ac)2, Se powder, stearic acid, TOPO, and TOP. CdSe nanocrystal films were prepared by spin casting deposition on glass or Si(100) substrate. TOPO concentration was controlled by varying the UV exposure time. We investigated the change of the electron energy state of TOPO-covered nanocrystal films with various covering rate of TOPO by near edge x-ray absorption fine structure and photoemission spectroscopy. Furthermore, PL and UV-visible spectra also showed optical properties of nanocrystal films.

1 M. Drndic, M. V. Jarosz, N. Y. Morgan, M. A. Kastner, and M. G. Bawendi, J. Appl. Phys. 92, (2002) 7498
2 R. Cohen, S. Bastide, D. Cahen, J. Libman, A. Shanzer, and Y. Rosenwaks, Optical Materials 9, (1998) 394.

FP-10 Influence of Calcination Temperature on the Electrochemical Performance of ZnO-Coated LiCoO4 by Cathode
T. Fang, J.G. Duh (National Tsing Hua University, Taiwan); S.-R. Sheen (Academia Sinica, Nankang, Taiwan)
Olivine type LiFePO4 catches considerable interest as a novel cathode for Li-ion batteries. Its relative high capacity, good cycleability, environmentally friendly constituent and low cost make it attractive to the power-storage market. However, because it is an intrinsically and electrically insulator, the capacity fading will abruptly deteriorate at a high current rate. To improve its conductivity, increasing the quantity of LiFePO4-carbon contact points is an effective approach. It is demonstrated that raising the amount of added carbon black can enhance the initial capacity and cycleability. However, the power density of derived cells will be reduced. In order to improve the rate capability and also to maintain the high power density, a uniformly distributed thin carbon layer on LiFePO4 surfaces is required. In this study, a unique coating technology with pH-controlled gelatin solution is introduced. The carbon-coated LiFePO4 powders are characterized by thermal calorimeter (TG/DSC) to confirm the amount of coated carbon. Distribution of carbon, detailed interfacial morphology and structural changes are revealed by FE-SEM and TEM. Furthermore, the impedance spectra and cycle-life test reaults verify that the electrochemical performance of LiFePO4 is improved by the novel coating method.
FP-11 Interface Control of Y2O3 Thin Film with Si(100) in a Metal-(Ferroelectric)-Insulator-Semiconductor Structure
H.H. Park, C.K Lee (Yonsei University, South Korea); S.K. Kwon, J.D. Kim (Electronics and Telecommunications Research Institute, South Korea)

High-k oxide has been used as gate oxide for metal-insulator-semiconductor(MIS) structure and buffer layer for metal-ferroelectric-insulator-semiconductor(MFIS) structure. However, for applying a gate oxide to MIS structure and a buffer layer to MFIS structure, several issues such as leakage current, capacitance, crystallinity, chemical stability in contact with silicon, and other properties have to be considered. These issues are mainly dependent on the interfacial properties. Retaining the beneficial properties for high-k oxide has turned out to be very difficult because of the formation of interfacial SiOx layer. Therefore, the control of formation of interfacial SiOx layer at the first step of oxide deposition is very important issue for the high performance and reliability of M(F)IS structure.

In this work, we used Y2O3as high-k oxide gate because it shows several particularly relevant physical properties such as wide band gap (5.5 eV), relatively high dielectric constant (14-18), crystallographic stability up to 2325°C, and low lattice mismatch with Si substrate.1 We have focused on the controlling of interfacial layer by varying the annealing temperature of deposited Y-metal. Y-metal and Y2O3were deposited by dc magnetron reactive sputtering on Si substrates and the formation of interfacial SiOx layer was reduced by the deposition of Y-metal. The control of interfacial oxides was strongly dependent on the annealing temperature. The interface between Y2O3thin film and Si was investigated by using x-ray photoelectron spectroscopy. Surface morphology and thickness of the stack layer were observed with atomic force microscopy and ellipsometry. The electrical properties such as capacitance-voltage and current-voltage were discussed and related with the controlled interface property.

1 R.J. Gaboriaud, F. Pailloux, P. Guerin, F. Paumier, J. Phys. D: Appl. Phys. 33 (2000) 307.

FP-13 Silicon Effects on Oxide Coatings on Aluminium Alloys
X. Nie, L. Wang (University of Windsor, Canada)
Electrolytic plasma process (EPP) can be used to cleaning, coating, carburizing, nitriding, and oxidizing. Electrolytic plasma oxidizing (EPO) of aluminium alloys is an advanced technique to deposit a thick and hard ceramic coating on some aluminium alloys. However, the EPO treatment on Al-Si alloys with a high Si content has rarely been reported. Particulrly, there is a lack of study on the influence of silicon content and silicon mophology on the properties of the EPO coating. In this research, a systematic investigation was conducted in terms of the effects of silicon on the EPO coating formation, microstrcurure, and mechanical and tribological properties. Cast hypereutectic 390 alloys (17% Si) and hypoeutectic 319 alloys (7% Si) before and after T6 heat treatment were choosen as substrates. X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray analysis system (EDX) were employed to investigate phase-structure and morphologies of the EPO coatings on those substrates. Nanoindentation with AFM imaging was used to measure nanohardness and elastic modulus of coated and uncoated substrates. A pin-on-disc tribometer and surface profilometer were occupied to study tribological behaviors of the coatings. Keywords: Coating, Al-Si alloy, nanoindentation, wear.
FP-14 The Pore Distribution Control of Chemical Vapor Infiltrated SiC Whisker on the Porous SiC Body.
B.I. Joo, W.S. Park, D.J. Choi (Yonsei University, South Korea); H.D. Kim (Korea Institute of Machinery and Materials, South Korea)
As the industry application of nano materials is increased, it is very important to research nano pore structure material. Therefore we researched modified pore structure by growing of whisker. The SiC whisker was deposited using hot-wall type furnace at 1100°C -1300°C . The MTS(Metyltrichlorosilane) was used as source gas. The input gas ratio α [H2/MTS] was varied from 40 to 90. SEM observations were conducted to examine the microstructure of whiskers, which had two different deposition type such as film and whisker. The pore size distribution was examined by mercury porosimeter. And we made an analysis of a specific surface area in order to observe the density of whisker. Our result showed that a whisker growth through a simple CVI process formed effective pore size below 10µm. Controlling the distribution of pore size using the whiskering seems to have the advantage of minimizing pressure drop and increasing mechanical strength. Particularly, compressive strength was increased about 100%. Therefore our whiskering process will be a promising method to apply for advanced filter materials.
FP-16 Chemical Bonding Investigation of Amorphous Hydrogenated Si-N Alloys Deposited by Plasma Immersion Ion Implantation
L.G. Jacobsohn, I.V. Afanasyev-Charkin, R.K. Schulze (Los Alamos National Laboratory); L.L. Daemen (Manuel Lujan Jr. Neutron Scattering Center); M. Nastasi (Los Alamos National Laboratory)
Amorphous hydrogenated Si-N (a-SiNx:H) alloys were deposited by plasma immersion ion implantation with a negative pulsed bias of -4 kV applied to the substrates at 5 kHz, with a pulse width of 20 ms (10% duty cycle) and a working pressure of 10 mTorr of mixtures of SiH4 and N2. Films with N/Si ratios from 0.58 to 1.18 were obtained, as determined by Rutherford backscattering (RBS) and elastic recoil detection analysis (ERDA). A total H content of 9 at. % was nearly the same in all films. Chemical bonding was investigated by infrared, Raman and x-ray photoelectron (XPS) spectroscopies. They revealed a complex environment with several different chemical bonds that changed for different N/Si ratios. In Si-richer films, the presence Si aggregates could be inferred, while the increase of the Si content lead to the formation of Si-N bonds and the preferential attachment of H to N. Moreover, Raman measurements revealed increasing structural ordering for N/Si values approaching the stoichiometric value of 1.33. Film hardness, that ranged from 11 to 15 GPa as determined by nanoindentation, was correlated with the structural changes.
FP-17 The Stoichiometric and Bonding Characterization of Si-C-O-H Films Deposited using Remote PECVD
S.H. Cho, Y.J. Lee, D.J. Choi (Yonsei University, South Korea); T.S. Kim (Korea Institute of Science and Technology)
Silicon carbide is a very attractive candidate for microsystems applications because of its mechanical strength, chemical inertness, and other properties. Si-C-O-H films were deposited on (100) silicon wafer using Hexamethyldisilane(HMDS) as a precursor by remote plasma enhanced chemical vapor deposition (RPE-CVD) system. The flow rate of HMDS source was fixed at 14 sccm and H2 gas was used as a carrier gas. The deposition temperature was in the range of 300 ~ 400°C. The plasma power was varied from 200 to 400W. The stoichiometric and bonding properties of deposited films were investigated using FTIR spectrometer and X-ray photoelectron spectroscopy(XPS). The SiCOH film showed similar properties with SiOH-like film and the growth rate of SiCOH film increased with temperature however had no relation with RF-power. It is showed that the temperature dependency of SiCOH film growth rate was related with the carbon contents of the film by FTIR analysis.
FP-18 The Characterization of SiC:H Films Deposited using HMDS Precursor with C2H2 Dilution Gas by Remote PECVD System
S.H. Cho, D.J. Choi (Yonsei University, South Korea); T.S. Kim (Korea Institute of Science and Technology, South Korea)
Silicon carbide is a very attractive material for its mechanical strength, chemical inertness, and other properties for microsystems applications. SiC:H films were deposited on (100) silicon wafer by remote plasma enhanced chemical vapor deposition (RPE-CVD) system in the temperature range of 50 ~ 450°C. Hexamethyldisilane(HMDS) and H2 gas were used as a precursor and a carrier gas, respectively. The flow rate of HMDS source was fixed at 12 sccm and the input rate of C2H2 dilution gas was fixed at flow rate of 3 sccm in order to study the carbon effect on the film stoichiometric and bonding properties. The plasma power varied from 200 to 400W. The stoichiometric and bonding properties of deposited films were investigated by the FTIR spectrometer and the X-ray photoelectron spectroscopy (XPS). The thickness of deposited films was measured using ellipsometer. We showed that the carbon content in the film deposited with C2H2 diluent gas was more than 30% for all deposition conditions. The growth rate of SiC:H films decreased with the increase of temperature from 250 to 400°C however increased again at 450°C. The growth rate of film increased with the plasma power for all deposition conditions.
FP-19 The Effect of Bias on the Structure and Property of ZrN Thin Film Deposited by UBM Sputtering
Y.-W. Lin, J.-H. Huang, G.-P. Yu (National Tsing Hua University, Taiwan)
Nanocrystalline ZrN films were deposited on Si substrates using an unbalanced magnetron (UBM) sputtering system. The effect of bias on the microstructure and properties of zirconium nitride (ZrN) film was investigated. A negative bias voltage ranging from -20V to -130V was applied to the substrate. Effects of substrate bias were related to the energy and momentum of the deposited particles. Deposited energy may enhance the mobility of the adatoms to stable site on the substrate surface, but arriving ions with high energy and momentum may induce radiation damage to the growing film and produce lattice defects. Thickness (100 nm ~ 450 nm), texture, roughness, packing factor, and resistivity are correlated to the momentum and the total energy delivery with different substrate bias. Hardness of ZrN films were ranging from 20~40GPa. The hardness increases with increasing packing factor. Nanocrystalline structures of ZrN thin film indicate that strength of hardness is due to grain boundary strength. The packing factors of ZrN films were obtained by Rutherford backscattering spectrometer (RBS), and the N/Zr ratio also can be calculated. Resistivity decreases from -20V to -90V and then increases from -90V to -130V. Residual stress correlated to the momentum is ranging from -2~-13 GPa.
FP-20 Nanoindentation and Residual Stress Measurements of Yttia-Stablised Zirconia Composite Coatings Produced by Electrophoretic Deposition
X.J. Lu, X. Wang, P. Xiao (University of Manchester, United Kingdom)
Nano-identation and fluorescence spectroscopy have been used to measure the mechanical properties and residual stresses in yttria stablized zirconia (YSZ) coatings, respectively. The YSZ coating was produced using plasma spraying, electron beam physical vapour deposition (EBPVD) and electrophoretic deposition (EPD). The load-displacement plots obtained from nanoindentation were related to microstructure of the coating, i.e. porosity, cracks and texture orientations of the coating. Meanwhile, measurements along the coating cross-section gave a decreasing hardness and Young's modulus with increase in distance from the coating/substrate interface. In addition, residual stress increased with increase in distance from the interface. These phenomena should be related to the microstructural features of the coating.
FP-21 Measurement of Yield Strength and Ultimate Strength of Hard Coatings.
S. Kamiya, S. Amaki (Nagoya Institute of Technology, Japan); H. Hanyu (Osg Corporation, Japan)

The most fundamental parameters to represent the mechanical strength were evaluated in this study for a number of coatings on substrates, which are the yield strength and ultimate strength of coatings. Conventional techniques, e.g., scratch test, evaluate the strength of coatings in mixture of many factors that influence the fracture behavior such as film thickness, residual stress, etc. Contrary to this ambiguity, independent measurement of strength-related physical parameters is the key for the possible design of coating-substrate systems and to ensure their integrity. From this point of view, a series of techniques had already been developed by the authors to evaluate the strength of coatings in terms of toughness and adhesive toughness, which represent the physical resistances against crack extension in the coatings and the interfaces between the coatings and the substrates. In order to fill out the missing part of the necessary parameter set, the resistances of the coatings against applied stresses were newly evaluated in this study by developing new techniques.

With the aid of numerical simulation, systematic evaluation of these two parameters was enabled independent of the other factors that influence the apparent deformation behavior. Yield strength was evaluated so as to fit the simulated indentation load-displacement relation to the result of experiment. Ultimate strength was also independently determined by taking the effect of residual stress into account in the simulation. The knowledge of newly evaluated strength in combination with the formerly obtained information on toughness opens a new possibility for the quantitative discussion on the aspects of materials science such as the size of hidden defects. These parameters were accumulated for various hard coatings and examined to give a new figure of the strength of coatings.

FP-22 Electron Microscopy Evaluation of Interfacial Reaction in Lead-Free Solder and Sn-Pb Solder with Ni/Cu Under-Bump Metallization
L.-Y. Hsiao, J.G. Duh (National Tsing Hua University, Taiwan)
Electronic packaging is a technology of manufacturing electronic products that are composed of IC chips and electric devices. Ni/Cu under-bump metallization (UBM) for flip-chip application is widely used in electronics packaging. Eutectic SnPb-based solder are the most common materials in electronic industry. However, due to the toxicity of lead element, the investigation of alternative Pb-free solder is necessary. Currently, eutectic Sn-Ag solder are being developed as the lead-free solder. It is important to characterize the interfacial reaction of the eutectic Sn-Pb and Sn-Ag solders with Ni/Cu UBM after reflows for the reliability in solder joints. Transmission electron microscopy (TEM) analysis is employed in this study to reveal the morphology and identified the structure for intermetallic compounds (IMCs) between the solders and Ni/Cu UBM. The IMCs formed at the interface between solders and Ni/Cu UBM during reflowing are mainly (Ni, Cu)3Sn4 and (Cu, Ni)6Sn5. The composition distribution of Sn, Cu and Ni was further evidenced by energy-dispersive X-ray spectroscopy (EDS). It is aimed to investigate the detailed interfacial reaction and related diffusion behavior of Cu, Sn and Ni atoms between solders and Ni/Cu UBM during reflowing. On the basis of electron microscopy results, the evolution of the phase transformation between (Ni, Cu)3Sn4 and (Cu, Ni)6Sn5 was proposed.
FP-23 Behavior of Tin Whisker Growth on Surface Finish in the Lead-Free Solder Plating
K.S. Kim (Yeojoo Institute of Technology, South Korea); K.T. Kim (SeoJeong College, South Korea); C.H. Yu (Electronics and Telecommunications Research Institute, South Korea); H.I. Kim (University of California, Los Angeles)
Tin plating on component finishes may grow whiskers under certain conditions, which may cause failures in electronics equipment. To protect the environment, "lead-free" among component finishes is being promoted worldwide. Whisker behavior at various surface treatment conditions of pure Sn plating is presented. The temperature cycling test was performed in the temperature range of 55 - 125 °C and the ambient storage test at 25°C/ambient RH was also performed. In the temperature cycling test, bent-shaped whisker was observed on matte and semi-bright Sn plating, and flower-shaped whisker on bright Sn plating. The whisker on the bright Sn plating was tinier than those that on types of Sn plating, and the whisker growth density per unit area were lower. After 6 months under ambient condition, some part of showed only nodule(the nucleus state which was not grown to whisker) growth, but Cu leadframe showed horn-shaped whisker. After 600 cycles, the ~0.25 microm thin Ni3Sn4 formed on the Sn-plated FeNi42. However, we observed the amount of 0.76~1.14 microm thick Cu6Sn5 and ~0.27 microm thin Cu3Sn intermetallics were observed between the Sn and Cu interfaces. Therefore, the main growth factor of a whisker is the intermetallic compound in the Cu leadframe, and the coefficient of thermal expansion mismatch in FeNi42. This result showed that for the FeNi42 leadframe, the whisker growth rate of whisker depended on the number of cycles in the temperature cycling test and Cu leadframe on temperature. Also, whisker's growth and shape varied with the type of surface treatment and grain size of plating.
FP-24 The Comparison Study of CVD Process for Triso Coated Fuel through Computational Simulation and Actual Experiment
E.S Kum, J.H Jun, D.J. Choi, S.S Kim, H.L Lee (Yonsei University, South Korea); Y.W Lee, J.Y. Park (Korea Atomic Energy Research Institute, South Korea)
TRISO(tri-isotropic) coated particle fuel is one of the most important materials for H2 production through VHTR(Very High Temperature Gas Reactor), due to its high efficiency and inherent safety. It is composed of three isotropic layers : inner PyC(pyrolitic carbon), SiC, outer PyC layer and generally deposited by FBCVD(fluidized bed CVD) process. In this study, we adapted the process and thermodynamic simulation at various gas velocities and temperature profiles. The process simulation results showed that there is great deviation between hot zone temperature of simulation data and that of general horizontal hot wall reactor. The thermodynamic simulation results was nearly equal to experimental data of general FBCVD condition. We have performed the actual experiment using horizontal hot wall reactor and ZrO2 ball instead of UO2 kernel in order to compare simulation and experimental data. In the next study, we will present the mechanical and structural properties of coated ZrO2 ball and compare simulation data and experimental results.
FP-26 Residual Stresses Within High-Temperature Coatings
X.C. Zhang, B.S. Xu, H.D. Wang, Y.X. Wu (Shanghai Jiaotong University, China)
The thermo-mechanical integrity and operating reliability of coated components under high temperature conditions are strongly influenced by the residual stresses in coatings. However, due to the materials mismatch of coating and substrate, the residual stresses are commonly generated because the coating/substrate composite is resistant to the changed temperature. The role of residual stresses on the thermo-mechanical integrity of metal-based coatings has been discussed in the present paper. It complements five articles: one on the sources of residual stresses, which included thermal stress, quenching stress, and intrinsic stress, a second on the numerical solution of thermal residual stress that is independent of the number of layers based on the classical beam bending theory, a third on the stress redistribution due to the physical discontinuities (e.g.bending, edges and cracks), a fourth on the application of a method combining moiré interferometry and incremental hole- drilling (MIIHD) on the measurement of residual stresses in coatings, a fifth on the principle of fail-safe thermo-mechanical design.
FP-27 The Universal Nanomechanical Tester (UNAT) - A New Concept for the Characterization of the Mechanical Properties of Surfaces and Thin Films
T. Chudoba, V. Linss (ASMEC GmbH, Germany)
Nanoindentation has become an established technique for the measurement of mechanical properties of surfaces and thin films such as hardness and Young's modulus. While the mentioned mechanical properties can be determined on a small scale by nanoindentation this is not the case for tribological or wear properties. Up-to-date nanoindentation cannot be used to imitate the mechanical contacts in real applications where besides normal forces also lateral forces due to sticking and sliding friction play an important role. Often scratch tests are carried out additionally to indentation experiments to measure the adhesion of coatings. However, common scratch tests act more in a micro than in a nano scale and the results depend on the conditions during the test and the geometry (coating thickness, radius of the indenter, material of the indenter, scratch speed and so on). Thus, results obtained at different test conditions are often not comparable and cannot be used as input parameters for modeling with analytical or finite element methods. Therefore, the ASMEC GmbH (Germany) has developed a new device concept, the universal nanomechanical tester (UNAT). The instrument allows measuring lateral force-displacement curves additional to and with the same accuracy as normal force-displacement curves. This offers a wide range of new measurement principles. Nearly anything between pure (nano) indentation experiments and pure (nano) scratch experiments can be realized between one or several thousand load cycles. The conventional diamond tip can be replaced by any other solid material. The use of spherical indenters with forces at which elastic or beginning plastic deformation takes place makes it easier to combine the measurements with analytical stress calculations (for instance with Elastica®) and to derive critical stresses as material parameters. Further, the device can be used as micro and nano tensile tester. The poster contribution will introduce the working principle of the new device and give an overview over its applications.
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