This site requires cookies for user logon accounts. Find out More

ICMCTF2007 Session FP: Symposium F Poster Session

Thursday, April 26, 2007 5:00 PM in Room Town & Country

Thursday Afternoon

Time Period ThP Sessions | Topic F Sessions | Time Periods | Topics | ICMCTF2007 Schedule

FP-1 Microstructure and Mechanical Properties of B4C Films Deposited by Ion Beam Sputtering M.J. Zhou, Q. Li (The Chinese University of Hong Kong) Boron carbide thin films were deposited on silicon substrates using ion beam sputtering at different substrate temperatures. The chemical composition and the microstructure of the films were analyzed by x-ray photoelectron spectroscopy, and transmission electron microscopy, respectively. Although all films are amorphous despite their deposition temperature, their radial distribution functions derived from the transmission electron diffraction pattern disclose difference in the short range order for films deposited below and above 350°C. The nanoindentation hardness of the films was measured using a nanoindentor. While the internal stresses of the films was evaluated using a profiler based on Stoney's equation. The experimental results suggest that the different hardness of the films is determined by the microstructure, rather than external factors.
FP-2 Resistive Switching Behavior in V-SrZrO₃ Sputter-Deposited Thin Films C.H. Lai (National United University, Taiwan); C.Y. Liu (National Kaohsiung University of Applied Sciences, Taiwan); C.H. Hsu (National United University, Taiwan); T.-Y. Tseng (National Chiao Tung University, Taiwan) V-doped SrZrO₃ sputtered films, formed in a metal-insulator-metal structure and exhibiting bistable resistive switching nature, were examined in this study. It was found that the low leakage state (L-state) conduction behavior can be well fitted by Frenkel-Poole transport model, while the variation of oxygen vacancy concentration can be used to explain the corresponding resistivity variations for L-states under different annealing ambience. The trapped level was estimated to be 0.5 eV from Arrehenius analysis at the temperature range of 298-403 K. Compared with data for H-state under thermal stress and endurance tests, the shorter heating duration and pulse width required for state switching revealed that L-state was the less stable state of bistable resistance switchability, and it required much less energy or power for L- to H-state transition than that for inverse state transition.
FP-3 Characteristics of Low-k SiOC(-H) Films Deposited at Various Substrate Temperature by PECVD using DMDMS/O₂ Precursor C.-Y. Kim, S.-H. Kim, R. Navamathavan, C.-K. Choi (Cheju National University, Korea); W. Y. Jeung (Korea Institute of Science and Technology, Korea) In the multi-layer wiring structure in microelectronic circuits, a bottleneck against high speed operation of elements is capacitance between wires. In order to decrease the capacitance between wires, it is necessary to reduce the dielectric constant (or relative dielectric constant) of an interlayer insulating film. Among the low dielectric constant films, SiOC(-H) films are important for application in advanced Cu interconnects. In this study, we report the influence of substrate temperature on SiOC(-H) thin films are deposited on p-type Si(100) substrate by using plasma enhanced chemical vapor deposition (PECVD) with dimethoxydimethlsilane (DMDMS) and oxygen gas as precursors. The films were deposited using different substrate temperature for rf power of 500 W and annealing of the film was carried out. FTIR spectroscopy studies were carried out in the absorbance mode in the range of 400 to 4000 cm^-1 which showed the various bonding configurations such as Si-O-Si(C), Si-CH₃, -OH, CH_n bonds in the films. As the deposition temperature increases, these Si-CH₃ and OH-related bonds are reduced. Consequently, the density of the film increase because of the decrease in the number of voids within the SiOC(-H) films. The X-ray photoelectron spectroscopic studies has been carried out to study the binding energies of Si-C, O-Si-O, C-H and C-O bonds in the SiOC(-H) films as a function of the substrate temperature. The refractive index of the SiOC(-H) film decreases with increase in the substrate temperature from 1.53 to 1.45 and that of annealed film also decreased from 1.45 to 1.36. The dielectric constant of the SiOC(-H) films were investigated using a metal insulator semiconductor (MIS, Al/SiOC(-H)/p-Si) structure at 1 MHz frequency and the lowest dielectric constant of the film deposited at 400°C achieved with DMDMS/O₂ precursor is found to be 2.12.
FP-4 Poisson's Ratio and Young's Modulus of Thin Films Measured using X-Ray Diffraction Associating Curvature Technique H.-Y. Chen (National Kaohsiung University of Applied Sciences, Taiwan); F.-H. Lu (National Chung Hsing University, Taiwan) Poisson's ratio and Young's modulus are the most import mechanical properties of thin films, but always have problematic in measurement. Hence, the X-ray diffraction was employed to measure the strain and then the residual stress was determined by using curvature technique. Finally, Poisson's ratio and Young's modulus are evaluated from the slope and intercept in the cos²αsin²ψ - strain plot using the measured strain and stress value. The titanium aluminum nitride (TiAlN) films were prepared by cathodic arc plasma deposition with a thickness of 200 nm. The as-deposited films had strong (111) preferred orientation and the composition was Ti_0.6Al_0.4N. The Poisson's ratio and Young's modulus were deduced from the present methodology to be 0.14 and 215 GPa. Another technique, nano-indentation method, is also used to verify the validity of present method.
FP-5 Luminescence Characteristics of Nano ZnGa₂O₄ Phosphor by Precipitation Method H.W. Choi, K.H. Kim, H.H. Yoon, S.J. Park, J.H. Cha, H.H. Kwak, S.J. Kim (Kyungwon University, Korea) Nano ZnGa₂O₄ phosphor was precipitated by dropping a mixed solution of zinc sulfate and gallium sulfate into aqueous NH₃ at a low temperature with stirring. And the precipitates were sintered at 600~1000°C for 1 hours in air ambient and cooled in furnance. The properties of the ZnGa₂O₄ phosphors were investigated by TG-DTA (Thermogravimetry and differential thermal analysis), SEM (Scanning electron microscopy), PL (Photoluminescence) and XRD (X-ray diffraction). The PL spectra was measured at room temperature using a spectrometer with a broadband incoherent ultraviolet light as an excitation source with a wavelength of 256nm. The PL spectra were a broadband ranging from 300nm to 500nm and its peak was at 420nm. The main peak at 1000°C was the highest. The phosphors formed spherical nanocrystallites in uniform size at less than 100nm. The results of XRD reveal that the powder start to be crystallized at 600°C and pure ZnGa₂O₄ phase was obtained at 1000°C, which corresponds well to the results measured by TG-DTA. In conclusion, nano ZnGa₂O₄ phosphor had the best characteristics at the sintering temperature at 1000°C.
FP-8 Structural Characterisation of Al-Au Based Intermetallic Coatings Prepared by Unbalanced Magnetron Sputtering I.M. Ross, J.C. Walker (University of Sheffield, United Kingdom); M. Moser (University of Leoben, Austria); P.H. Mayrhofer (Montanuniversität Leoben, Austria); R. Braun (DLR - German Aerospace Center, Germany); W.M. Rainforth (University of Sheffield, United Kingdom) Recent studies of Al-Au based intermetallic coatings have revealed promising high temperature properties such as good thermal stability and oxidation resistance. These properties lend themselves to potential applications such as oxidation resistant protective coatings for aerospace and automotive components. In this contribution, we detail the structural characterisation of a range of Al-Au intermetallic coatings with Al/Au <2, Al/Au =2 and Al/Au >2 prepared by unbalanced magnetron sputtering. We have applied advanced transmission electron microscopy, scanning transmission electron microscopy and associated analytical techniques to elucidate the coating structure, interface and surface morphologies. Coatings with an Al/Au =2 exhibited a single Al₂Au phase with a dense columnar structure. On the other hand, coatings with Al/Au <2 and Al/Au >2 displayed a bimodal (Al, Al₂Au) showing micro-segregation and a porous trimodal (Au, AlAu, Al₂Au) microstructure respectively. Earlier studies of the coatings micro-mechanical properties have shown that Al/Au <2 and Al/Au >2 films have a hardness of 2 and 4 GPa respectively compared to 8 GPa for the single phase Al/Au =2 coating. Moreover, the Al/Au <2 and Al/Au >2 films exhibited poor structural stability at elevated temperature due to the presence of low melting point Al and AlAu phases. On the basis of these findings the single phase Al/Au =2 film was selected for further investigation and coatings prepared on polished gamma Ti-45Al-8Nb-0.17C (TNB-V2) substrates. These coatings were subjected to cyclic oxidation testing at 750°C and 850°C (1 hour cycles) for 1000 hours in each case. By correlating the microstructure of the as-deposited films to those after cyclic oxidation the potential for single phase Al/Au =2 films as an oxidation protective coating on gamma titanium aluminide based substrates is discussed.
FP-9 The Effect on the Microstructures of Electroless Nickel Coatings Initiated by Pulsating Electric Current C.-K. Lin, C.-T. Chen, T.-J. Yang (Feng Chia University, Taiwan) Conventional electroless Ni coating is prepared without additional electric current. The microstructures of the as-plated coatings will be influenced by its composition. Amorphous coating is obtained when phosphorus weight percent exceeds 8%, but a nanocrystalline one exhibits with less phosphorus amount. In the present study, pulsating electric current was applied during electroless Ni plating process. The applied current is controlled to avoid the occurrence of electric deposition. The effect on the microstructure of electroless nickel coating was investigated systematically by controlling the current density and duty cycle. The as-plated coatings were then investigated by atomic force microscopy, transmission electron microscopy, x-ray diffraction, synchrotron X-ray absorption spectroscopy, etc. The AFM results showed that pulsating electric current can initiate Ni nanocrystallization and accelerate electroless Ni deposition. TEM image confirmed that the grain size of precipitated Ni nanocrystals was ranged from 5 to 10 nm. Further microstructural investigations were performed by conventional X-ray diffraction and synchrotron X-ray absorption spectroscopy. A combination of various experimental results showed that a nanocrystalline coating was deposited successfully by pulsating electric current initiated electroless Ni plating process.
FP-10 Nickel Silicide Nanocrystals Embedded in SiO₂ and HfO₂ for Low Power Nonvolatile Memory Application F.M. Yang (National Chiao Tung University, Taiwan); T.-C. Chang (National Sun Yat-Sen University, Taiwan); P.-T. Liu (National Chiao Tung University, Taiwan); P.H. Yeh (National Tsing Hua University, Taiwan); Y.C. Yu, J.Y. Lin (National Yunlin University of Science and Technology, Taiwan); S.M. Sze, J.C. Lou (National Chiao Tung University, Taiwan) In this study, a nonvolatile memory device with NiSi₂ nanocrystals embedded in the SiO₂ and HfO₂ layer has been fabricated. A significant memory effect is observed through the electrical measurements. Under low operating voltage, 8V, is implemented and a significant threshold-voltage shift, 0.4V, is observed. The retention characteristics are tested to be robust. Also, the endurance of the memory device is not degraded up to 10⁶ write/erase cycles. The processing of the structure is compatible with the current manufacturing technology of semiconductor industry.
FP-11 Characterization of BaZrO₃ Films Prepared by a PVD and Hydrothermal Duplex Technique F.-H. Lu, H.-P. Deng, Y.-C Chieh (National Chung Hsing University, Taiwan) Dielectric barium zirconate (BaZrO₃, BZO) films was prepared by a novel physical vapor deposition and hydrothermal duplex technique. Zirconium nitride films were firstly deposited on Si substrates by unbalanced magnetron sputtering. Subsequently, ZrN-coated Si specimens (ZrN/Si) were soaked in Ba(CH₃COO)₂ and NaOH mixture alkaline solutions at temperatures below 100°C. X-ray diffraction results confirmed that cubic BZO films was successfully prepared on ZrN/Si. The crystallinity, preferred orientation, lattice parameter, and relative peak intensities were determined. Resultant BZO films exhibited a (111) preferred orientation. Moreover, the morphology of obtained BZO films was investigated by field-emission scanning electron microscopy. From micrographs, the thickness of formed BZO films was about 1 µm at 90°C for 8 hours and 2 µm at 90°C for 15 hours. The film thickness as well as morphology significantly depended on reaction temperatures and times. The dielectric properties of the Pt/BZO/ZrN/Si structure have been investigated by high-frequency capacitance-voltage (C-V) measurements. The obtained dielectric constant of resultant BZO films was remarkably higher than that of bulk BZO, was reported from the literature.
FP-12 Experimental Studies on Epitaxially Grown TiN, VN and TiN/VN Coatings K. Kutschej, B. Rashkova, J. Shen, C. Mitterer, G. Dehm (Montanuniversität Leoben, Austria) It has recently been shown that alloying of hard coatings based on TiN with V drastically decreases the high-temperature friction coefficient due to the formation of lubricious Magnéli phase oxides on the coating surface. Although the effect of V on the tribological properties has been well described, the atomic processes controlling the necessary outward diffusion of V are not well understood. For the investigation of surface and interface structures as well as mechanical properties and, subsequently, diffusion mechanisms through differently oriented coatings, well-defined epitaxial model systems are necessary. To elucidate the maximum epitaxial thickness available, TiN and VN single-layer as well as TiN/VN bi-layers were grown on (100) and (111) MgO substrates using unbalanced magnetron sputtering from Ti and V targets in Ar/N₂. Films have been investigated by X-ray diffraction (XRD), electron back-scattering diffraction (EBSD), transmission electron microscopy (TEM), atomic force microscopy (AFM), and nanoindentation. XRD and EBSD results demonstrate a high orientation correlation of the films to the differentially oriented MgO substrates. Nanonindentation measurements showed hardness values up to 27 and 17 GPa for TiN and VN, respectively. The maximum epitaxial thicknesses obtained for the single-layer systems were used to synthesize epitaxial TiN/VN bi-layers with (100) and (111) orientation. Currently, TEM studies are performed to analyse growth defects of the TiN and VN single-layer films, and the interface structure of the bilayer films.
FP-13 Temperature Dependence of Microstructure and Residual Stress Properties of Nickel Coating on Silicon T.F. Young, Y.K. Chao, Y.C. Chiou (National Sun Yat-sen University, Taiwan); C.C. Ting (National Taipei University of Technology, Taiwan) Ni as an important magnetic material can be applied in many devices, s. a. sensors, storage media,, and also as actuator in MEMS. For advanced application in MEMS, the microstructure and residual stress properties of Ni play an important roll. In this work we have studied the properties of Ni thin film deposition on Si by means of FTIR, in si-tu temperature scanning XRD and nano indentation. Ni thin film was deposited on Si by means of r. f. sputtering at varied temperatures and with different thickness. Compared to other experimental conditions, we observed an unordenarily large IR absorption of the Ni/Si film deposited at 230°C for 15 min. to 30 min. Further investigation with nano indentation we studied the mechanical properties of Ni deposited on Si, and the in si-tu XRD has performed to study the phase change in dependence of temperature for Ni/Si after deposition Ni on Si at room temperature. Finally, we conclude that Ni deposited on Si at 230°C reveals a maximum residual stress for Young's modulus of 550 GPa and hardness of 5.5 Gpa respectively in Ni film and in Si substrate with the film thickness of about less than 40 nm. For deposition at higher temperature and thicker films the residual stress in Ni and in Si becomes less and constantly.
FP-14 Enhanced Performance Thin-Film-Transistor Passivated with a Low Dielectric Material for AMLCD T.S Chang, T.-C. Chang (National Sun Yat-Sen University, Taiwan); P.-T. Liu (National Chiao Tung University, Taiwan); S.W. Tsao (National Sun Yat-Sen University, Taiwan); F.S. Yeh (National Tsing Hua University, Taiwan) Spin-on low-k passivation is achieved on inverted-staggered back-channel-etched hydrogenated amorphous silicon thin-film transistors. The low-k passivation material has been investigated for different process temperature. The performance is improved with the temperature decreased. In 300 hydrogen bonds of the low-k film assist the hydrogen incorporation to eliminate the density of states between back channel and passivation layer. The characteristics of low-k passivated TFT have been studied in this work.
FP-15 Characterization of Thermoelectric Behavior of Composite Bismuth Telluride Thin Films Deposited by Pulsed UBM Sputtering D-Y. Wang, N.-H. Wang (Mingdao University, Taiwan) Thermoelectric materials provide advantages of thermal-electric energy conversion and environmental-benign as well as precise temperature control for various cooling applications. Presently, Bi-Te alloy exhibits the promising thermoelectric property of high Seebeck coefficient at medium temperature range (T<450°C). In this study, the bismuth telluride based thermoelectric thin films were synthesized on glass substrates with RF bias by using pulsed unbalanced magnetron sputtering. The deposition system consists of multiple sputtering cathodes, which provide tunable control of the incident flux of Bi and Te plasma. Both monolithic and multilayered Bi₂Te₃ thin films were deposited. The ionization of both metallic species was significantly enhanced by the unbalanced magnetic field design to allow improved crystallization and then film microstructure. The influence of the deposition parameters on thermoelectric properties will be revealed by FESEM, TEM and XRD analysis. To increase the Seebeck coefficient of Bi₂Te₃, various composition design schemes for a composite Bi-Te multilayer were investigated. The influence of the composition and the microstructure on the thermoelectric properties of the composite Bi-Te thin films was analyzed by Seebeck coefficient measurements. Keywords: thermoelectric, Bi₂Te₃, sputtering.
FP-16 Oxygen-Adsorption Characterization of Activated Non-Evaporable TiZrV Getter Films by Synchrotron Radiation Photoemission Spectroscopy C.-C. Li, J.-L. Huang (National Cheng-Kung University, Taiwan); R.-J. Lin (Intellectual Property Exchange Limited, Taiwan); D.-F. Lii (Cheng Shiu University, Taiwan) The non-evaporable getter (NEG) materials of various compositions, such as titanium or titanium alloys, have been widely used in vacuum-type devices to upgrade and to sustain the vacuum environment inside the cavity of the device by the chemical interaction between getters and gases. NEG can be used for efficient pumping of low-aperture and micro-miniature vacuum sealed-off devices or construct getter pumps as a complement of conventional pumping equipment. Oxygen gas is one of the main gaseous species that the getters absorb. Some studies have shown that the pumping capacity and speed of the NEG to the gases strongly depend on the geometrical area, the real surface area and the porosity of the getter after the activation of the NEG materials. We report the effects of oxygen-adsorption on the surface layer of the activated dense and porous TiZrV films on Si which are consecutively exposed in oxygen gas in a ultra-high-vacuum chamber using the in-situ characterization of synchrotron radiation photoelectron spectroscopy. Dense and porous TiZrV films were grown by the dc magnetron sputtering method with glancing angle of zero and 70° between substrate and target, respectively. The dense and porous TiZrV films have similar composition and thickness, and their specific surface areas are 2 m²/g and 13 m²/g, respectively. Before oxygen-exposure, the TiZrV films were activated to almost pure metallic state at 350°C for 30 min. Then, both-type TiZrV films were consecutively exposed in the oxygen atmosphere of 20 L, 50 L, and 100 L at room temperature. The oxidized degree of surface layer of the both-type films is similar after oxygen exposure. The composition of surface layer of the films gradually changes with the increase of the oxygen exposure. The detailed results of photoemission spectra of the oxygen-exposure TiZrV films and discussion of evolution of oxidized surface during consecutive oxygen-adsorption processes will be presented.
FP-17 Alternating Current Measurements of Thermally Evaporated Triclinic Lead Phthalocyanine Thin Films T.S. Shafai (Staffordshire University, United Kingdom); R.D. Gould (Keele University, United Kingdom) Electronic properties of thermally evaporated thin films of triclinic lead phthalocyanine were investigated employing symmetric gold ohmic electrodes in the frequency range of 100-20 kHz. At low temperatures ac conductivity was identified to be via a hopping type mechanism whereas at higher temperatures free-band model is considered to be the major cause for electronic transitions. Measurements on the dependence of capacitance on frequency (100-20 kHz) indicates that the capacitance is strongly frequency dependent, decreasing with increasing frequency at low frequency and less rapidly at higher frequencies. This is quantitatively interpreted using an equivalent circuit model. Oxygen doping was found to increase the capacitance of PbPc. The phenomenon was understood in terms of reduction in the value of device internal resistance induced by oxygen absorption.
FP-18 Structural and Textural Analyses of Si-C and Carbon CVD Coatings by Raman Microspectroscopy G. Chollon (LCTS, France) The high temperature structural performances of carbon and ceramic CVD coatings are directly related to the control of their nature, i.e., their chemical composition and microstructure. Besides the crystal structure and the crystalline state, the texture at long range (i.e., the crystallite main orientation in the material) is of great interest as it may significantly influence the mechanical and thermal behavior of materials (e.g., toughness, creep, thermal conductivity, permeability). In the present study, the polarization properties of the Raman scattering have been specifically utilized for the texture analysis of Si-C and carbon coatings processed by CVD. A polarized Raman scattering analysis of the optical phonons was conducted to identify the SiC polytype(s) present in the coatings and evaluate the possible preferential orientation of the SiC crystallites. This approach was applied through the Raman mapping of SiC-based coating cross-sections, for various structural materials such as CVD-monofilaments and HTR-nuclear fuel particles. The CVD-monofilaments were found either stoichiometric, or free silicon (or carbon)-rich. The SiC crystallites were predominantly cubic with variable amounts of stacking faults along the [111] axis. The large interlocked -SiC crystallites of the HTR particle form an isotropic texture at long range whereas the submicrometric and faulted crystallites of the CVD-monofilaments give rise to a preferential orientation of their stacking faults axis parallel to growth. The structure of pyrolytic carbon (pyrocarbon) significantly differs from that of ideal graphite. Such heavily faulted structures (turbostratic and highly distorted) give rise to broad and/or unexpected Raman features. These bands however display significant polarization effects which have been used to assess the preferential orientation of the graphene layers (i.e., the anisotropy) in pyrocarbon coatings.
FP-19 TEM Analysis of Alumina Coating Deposited by AC Inverted Magnetron Sputtering A. Aryasomayajula (University of Arkansas); S. Canovic (Chalmers University of Technology, Sweden); D. Bhat (University of Arkansas); Mat Halversson (Chalmers University of Technology, Sweden) Thin films of alumina were deposited by AC inverted magnetron sputtering on stainless steel substrate. Chromium oxide was used as a template layer because lattice mismatch between ±-chromium oxide and±-alumina is very small. This makes ±-chromium oxide suitable to be used as a template layer to grow ±-alumina at low temperatures. The XRD peak values (2) of ±-Chromium oxide and ±-alumina are very close. So it is very difficult to analyze the phase from the XRD. TEM was used to analyze the phase formation as a function of thickness, power and oxygen partial pressure. These results will be discussed in detail in this paper.
FP-20 Hot Corrosion Behaviour of Ti-6Al-4V in Molten Salt Environments R.A Mahesh, R. Jayaganthan, S. Prakash (IIT Roorkee, India) Ti-6Al-4V alloy is a potential material for structural and biomedical applications due to its high strength to weight ratio, superior corrosion resistance, and good fatigue, and biocompatibility. A thorough understanding of high temperature corrosion behavior of Ti-6Al-4V is very essential to propose this material as a viable alternative to the conventionally used lightweight materials, which are sensitive to corrosion in air craft components and power generating equipments. It is found that a study on hot corrosion behavior of Ti-6Al-4V is very scarce in the literature. The present work is focused to study the hot corrosion behavior of Ti-6Al-4V in molten salt environments simulating the actual conditions prevailing in the aforementioned applications. The influence of microstructural features and compositions on its corrosion behavior ought to be thoroughly analyzed. The nature, composition, and thickness of the protective oxide layer formed on the titanium alloys are heavily dependent on the complex corrosive environment they are subjected to during service conditions. Hot corrosion study on both as prepared and heat treated Ti-6Al-4V samples is carried out in air and molten salt environments i.e. 50%Na₂SO₄ - 50%NaCl and 40% Na₂SO₄- 60%V₂O₅ at 750°C under cyclic conditions in the present work. Thermogravimetric technique is used to establish the kinetics of corrosion. XRD, SEM/EDAX, and EPMA techniques are used to analyze the corrosion products formed on the Ti-6Al-4V. The alloy suffered severely in 40% Na₂SO₄- 60%V₂O₅ environment. The degradation mechanism of the alloy is discussed in detail.

Time Period ThP Sessions | Topic F Sessions | Time Periods | Topics | ICMCTF2007 Schedule