ICMCTF2010 Session HP: Symposium H Poster Session

Thursday, April 29, 2010 5:00 PM in Golden Pacific Ballroom

Thursday Afternoon

Time Period ThP Sessions | Topic H Sessions | Time Periods | Topics | ICMCTF2010 Schedule

HP-1 Cobalt Nanocrystals Embedded in Silicon Oxide Fabricated by Incorporating Oxygen Elements During Sputtering Process
Chih-Wei Hu (National Chiao Tung University, Taiwan); Ting-Chang Chang (National Sun Yat-Sen University, Taiwan); Chun-Hao Tu (National Chiao Tung University, Taiwan); Yu-Hao Huang (National Tsing Hua University, Taiwan); Chao-Cheng Lin (National Chiao Tung University, Taiwan); Min-Chen Chen (National Sun Yat-Sen University, Taiwan); Fon-Shan Huang (National Tsing Hua University, Taiwan); S.M. Sze, Tseung-Yuen Tseng (National Chiao Tung University, Taiwan)

In the experiment, the CoSi2 thin film deposited by sputtering in O2 ambient has been studied to fabricate the Co nanocrystals memory device. Based on the difference of the oxidation free energy between the Co and Si elements, a selective oxidation process during the thermal annealing enhance the formation of cobalt nanocrystals embedded in silicon oxide. The charge-storage ability of the formed Co nanocrystals has also been studied by fabricating the capacitance structure. In addition, more factors such as annealing temperature and oxygen flow rate are discussed for the nanocrystals formation. It is found that the Co nanocrystals show a larger size and lower density at high temperature annealing. The size and density distribution of nanocrystals affect the performance of the memory device. In the study of oxygen content, the XPS analyses have confirmed that the compositions of nanocrystals were changed by different oxygen flow rate during sputtering process. An inappropriate oxygen flow causes the in-complete oxidation or over-oxidation, which degenerate the charge storage ability of the Co nanocrystals device.

HP-2 High Power Impulse Magnetron Sputtering of Zirconium
Jiri Rezek, Jan Lazar, Jaroslav Vlcek (University of West Bohemia, Czech Republic)

High power impulse magnetron sputtering of zirconium was investigated at a high average target power density in a period, being approximately 100Wcm-2. The depositions were performed using an unbalanced circular magnetron with a directly water-cooled planar zirconium target of 100mm diameter. The repetition frequency was 500Hz at duty cycles ranging from 4 to 10% and an argon pressure of 1Pa. Time evolutions of the discharge characteristics were measured to provide information on absorption of energy in the discharge plasma and on transfer of arising ions to a substrate (located 100mm from the target) at an average target power density in a pulse up to 2.22kWcm-2. Time-averaged mass spectroscopy was performed at the substrate position. High fractions (21-32%) of doubly charged zirconium ions were found in total ion fluxes onto the substrate at decreasing fractions (from 23 to 3%) of singly charged zirconium ions when the average target power density in a pulse increased from 0.97 to 2.22kWcm-2. It was shown that ion energy distributions are extended to high energies (up to 100eV relative to ground potential) under these conditions. The rise in the values of the average target power density in a pulse resulted in a decrease of the deposition rate of films from 590 to 440nm/min.

HP-3 Impact of Strain Engineering on InGaAs NMOSFET with a InGaAs Alloy Stressor
P.-H. Sun, Shu-Tong Chang, C.-C. Lee (National Chung Hsing University, Taiwan)

Strain engineering has been widely adopted to extend scaling limits and the device performance of MOSFETs. To sustain further enhancement in device performance, new materials and novel device structures are needed. The high electron mobility of III–V compound semiconductor makes them an attractive candidate as MOSFET channel material for high-speed applications beyond the sub 32 nm technology node. National University of Singapore (NUS) research group had reported the first demonstration of a strained InGaAs with In mole fraction of 0.53 channel n-MOSFET featuring in situ doped InGaAs with In mole fraction of 0.4 source/drain (S/D) stressors (Please refer to a conference paper by Prof. Yee-Chia Yeo at Symposium on VLSI Technology Digest, pp. 244-245, 2009). To realize the full potential of the III–V compound-based MOSFETs, channel-strain engineering will be an important direction. The effect of strain on electron transport in many III–V compound-based semiconductors, e.g., gallium arsenide (GaAs) and indium gallium arsenide (InGaAs), is need to further study. However, the integration of the process-induced strain in III–V compound-based MOSFETs to exploit the effect of local stressors, such as the lattice-mismatched S/D for mobility enhancement, is also needed to explore. In this work, we report the results of electron mobility calculations and device simulations for novel InGaAs with In mole fraction of 0.53 NMOSFETs with InGaAs S/D stressors using In mole fraction of 0.4 under various geometry structures. The lattice mismatch between InGaAs alloy S/D and InGaAs channel is exploited to induce tensile strain in the channel for mobility enhancement. The stress distribution in the InGaAs channel regions in NMOSFETs with various lengths and widths were studied using 3D ANSYS simulations. The mobility enhancement was found to be dominated by the tensile stress along the transport direction and compressive stress along the growth direction in wide width devices. Stress along the width direction was found to have the least effect on the drain current in wide length and width cases. Impact of width on performance improvements such as the drive current gain was also analyzed using 3D TCAD simulations.

HP-4 Ir Nanocrystals Lying on Asymmetric SiO2/Si3N4 Tunnel Barrier With Large Memory Window for Nonvolatile Memory Application
Terry Wang, Chao-Jui Chen, I-Ju Teng, Chien-Min Liu (NCTU, Taiwan); Cheng-Tzu Kuo (Min Dao University (MDU), Taiwan)

Recently, metallic nanocrystals have been widely investigated for high programming/erasing (P/E) efficiency and low power consumption nonvolatile memory application [1-2]. Metallic nanocrystal nonvolatile memory has many advantages, such as smaller operating voltage, a wide range of available work functions, and larger charge capacity. In addition, for possibility breaking the scaling limits of thickness of the tunnel oxide, multi-stacked tunneling layer has been also extensively studied [3-5] . Multi-stacked tunneling layer provided asymmetric tunnel barrier (ATB) and it could enhance the P/E efficiency. In this work, iridium-nanocrystals (Ir-NCs) lying on SiO2/Si3N4 (3-nm/3-nm) tunnel layer stacks have been demonstrated and compared its characteristics with SiO2 (6-nm) as tunnel oxide in the application of nonvolatile memory. Two type of metal-insulator-semiconductor (MIS) capacitor stacks of Al/SiO2/Ir-NCs/Si3N4/SiO2/P-Si/Al and Al/SiO2/Ir-NCs/SiO2/P-Si/Al were analyzed by scanning electron microscope (SEM), high resolution transmission electron microscopy (HRTEM), capacitance-voltage (C-V) measurement, and current-voltage (I-V) measurement, respectively. SEM images showed the mean size of Ir-NCs and density was approximately 5 nm and 1 × 1012 cm-2, respectively. Due to the bi-stacked tunneling layer improving P/E efficiency, significant hysteresis window of 11.6 V have been observed with a sweep voltage of +/- 10 V. The hysteresis window was larger than the single tunneling layer. And then, data storage decay percentage of the bi-stack (SiO2/Si3N4) after 104 sec was only less 5 percentages than the single (SiO2). Furthermore, the endurance of these devices shows excellent characteristics by P/E voltage stressing at +/- 9 V, 100 msec. In summary, Ir-NCs nonvolatile memory with bi-stacked tunneling layer provided high P/E efficiency, sufficient data retention and good device endurance.

References:

[1] J.J. Lee et al : Appl. Phys. Lett. 86 (2005) 103505.

[2] S. S. Yim et al : Appl. Phys. Lett. 89 (2006) 093115.

[3] C. C. Wang et al : Appl. Phys. Lett. 91 (2007) 202110.

[4] Konstantin K. Likharev : Appl. Phys. Lett. 73 (1998) 152137.

[5] T. H. Hou et al : Appl. Phys. Lett. 92 (2008) 153109.

HP-5 Structure and Properties of Nanocrystalline TiN Thin Film Produced by High Power Impulse Magnetron Sputtering: Effect of Ionization Rate
Cheng-Yang Su, Jia-Hong Huang (National Tsing Hua University, Taiwan); Ge-Ping Yu (National Tsing Hua University); Jin-Yu Wu (Institude of Nuclear Energy Research, Taiwan)
Magnetron sputtering has been widely used in surface coating industry; however, there are a few shortcomings that limit the applications on high added-value products. The most significant one may be the low ionization rate (about 5%) that causes poor adhesion and low denseness of the thin film. The newly developed High Power Impulse Magnetron Sputtering (HIPIMS) technique is for overcoming the shortcomings of traditional magnetron sputtering. HIPIMS technique can produce thin film with very high ion to neutral ratio, similar to ion plating method; moreover, the ionization rate can be controlled by adjusting HIPIMS power and frequency. In this study, TiN thin film, 600 nm thick, was deposited on Si wafer by HIPIMS with different power and frequency, and the ionization rate of the target material was monitored. The plasma density was measured by a flat Langmuir Probe. The microstructure, composition, and mechanical properties of the TiN thin film were characterized to understand the effect of ionization rate. The preferred orientation was characterized by X-ray diffraction. Field-Emission Scanning Electron Microscopy was used to observe the microstructure. The composition depth profile was analyzed by Auger electron spectroscopy. Nanoindentation was used to measure the film hardness. The composition of the film was determined by X-ray photoelectron spectroscopy. The packing factor was calculated from the results of Rutherford backscattering spectroscopy. The results showed that the structure and properties of the TiN thin films are quite sensitive to the ionization rate. TiN films presented a dense columnar structure when the target material was highly ionized, which led to excellent mechanical properties. However, under the conditions that the ionization rate was too high, the deposited film had very high residual stress that even caused the spallation of the film. On the other hand, a nearly pure Ti film was obtained at the lower ionization rate.
HP-6 Effects of Seed Layer Precursor Type on the Synthesis of ZnO Nanowires using Chemical Bath Deposition
Wan-Yu Wu (National University of Tainan, Taiwan); Tzu-Ling Chen, Jyh-Ming Ting (National Cheng Kung University, Taiwan)
A two-step process was used to grow aligned ZnO nanowires on the glass substrates. The process involves first the deposition of a ZnO nanocrystal seed layer using spin coating, followed by the growth of aligned ZnO nanowires using chemical bath deposition (CBD). The characteristics of the seed layers were controlled by using different precursors and spinning coating conditions. During the CBD, the bath pH value was varied. T he seed layers and the nanowires obtained were examined using scanning electron microscopy, transmission electron microscopy (TEM). Effects of the seed layer characteristics and the CBD bath pH value on growth and characteristics of obtained ZnO nanowires were then investigated. The obtained ZnO nanowires also show interesting photoluminescence spectra in which near band-edge emission occurs at 380 nm.
HP-7 X-Ray Images Obtained from Cold Cathodes Using Carbon Nanotubes Coated with Gallium-Doped Zinc Oxide Thin Films
Jong-Pil Kim, Young-Rok Noh (Hanyang University, Korea); Kyoung-Chul Jo, Sang-Yeol Lee (KIST, Korea); Hae-Young Choi, Jong-Uk Kim (KERI, Korea); Jin-Seok Park (Hanyang University, Korea)

X-ray tubes using cold cathodes as electron source attract great attention in a wide range of applications, especially in x-ray radiography such as diagnostic medical imaging and embedded-type radiation brachytherapy, because they have a lot of advantages, including possibility of miniaturization, fast response, low power consumption, and low fabrication cost, over the x-ray systems using conventional thermionic cathodes. Carbon nanotubes (CNTs) have been considered to be one of the most promising materials for point-type cold electron sources due to their mechanical and chemical stability as well as superior electron emission properties. In order to achieve high resolution x-ray images, CNT-based emitters must have a large current capacity and, at the same time, ensure a stable prolonged-operation of current emission. Furthermore, x-ray images may strongly depend on the emission performance of CNT-based electron sources. Recently, coating of CNTs’ surface with wide bandgap materials has been attempted to obtain a stable and uniform emission current from CNT-emitters. However, this manner may cause the increase of turn-on voltage for electron emission and also the decrease of tunnelling probability.

In this study, we present x-ray imaging data obtained from cold cathodes using gallium-doped zinc oxide (GZO) coated CNT-emitters. Multi-walled CNTs were directly grown on conical-type (250 μm in diameter) metal-tip substrates at 700°C by inductively coupled plasma-chemical vapor deposition (ICP-CVD). GZO films were deposited on the grown CNTs at room temperature using a pulsed laser deposition (PLD) technique. Field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) were used to monitor the variation in morphologies and microstructures of CNTs before and after GZO-coating. Energy-dispersive x-ray spectroscopy (EDX) was used to extract the relative atomic content in GZO films. Effects of GZO-coating on the electron-emission performances of fabricated CNT-emitters were examined by characterizing turn-on fields for electron-mission, maximum emission currents, and field enhancement factors. The CNT-emitters with a triode in structure were installed in the x-ray tube which was composed of gate-electrode meshes and electrostatic lens inside. The x-ray tube was housed in a vacuum chamber pumped down to 3×10-7 Torr. X-rays radiated from the anode (Cu) was extracted passing through a beryllium (Be) window where the specimen was in contact with. The relationship between the electron-emission performance of GZO-coated CNT-emitters and the x-ray imaging data was also elucidated.

HP-8 Fabrication and Photo-Sensing Properties of Sb-Doped SnO2 Nanowire Sensors
Po-Sheng Lee (National Tsing Hua University, Taiwan)

Recently, one dimensional (1-D) tin oxide nanostructures, including nanowires, nanorods and nanobelts, have attracted considerable attention because of their application in constructing nanoscale devices. In order to enhance and modulate the various properties, SnO2 nanostructures are frequently doped with appreciate elements, such as indium (In) and antimony (Sb). In this present work, Sb-doped SnO2 nanowires were synthesized on an Al2O3 substrate using a thermal evaporation. It is found that both the diameter and Sb concentration of the nanowires increases with increasing growth time (0.5-4 hr). The morphology and microstructure of Sb-doped SnO2 nanowires were characterized by a field emission scanning electron microscope (FESEM) and a transmission electron microscope (TEM). The composition and chemical bonding nature were investigated by x-ray photoelectron spectroscopy (XPS). The photo-sensing measurements were carried out using a volt-amperometric technique, which shows that both the reaction and response time of the nanowires decrease with increasing growth time.

HP-9 Indium Layer Through Different Process in High-Quality CuInSe2 Film for Solar Cell
Tsung-Wei Chang, Wen-Hsi Lee, Guan-Sian Lyu (National Cheng Kung University, Taiwan)

Different process of fabricated Indium layers was by Thermal Evaporation, Sputter, and electrodeposited to make high-quality CuInSe2. The great method was found in this work. First, the precursor layer of copper was sputtered onto the Mo-coated glass. The same thickness of indium layer through different process was deposited on the precursor layer of copper. Then, the layer of selenium was electrodeposited on the indium layers, and annealed by rapid thermal processing (RTP). The method of rapid thermal processing reduces selenium dissipation. We deposit CIS respectively to control ratio, and to fabricate the superior structural properties of these selenized films were also clearly reflected by X-ray diffraction. Field-Emission-Scanning electron microscopy indicates that the ordered copper indium diselenide thin-film are entirely filled and the structure of the molybdenum thin-film. X-ray diffraction result shows that the copper indium diselenide thin-films are crystalline and have the highly preferential orientation. Energy dispersive spectrometer analysis observation shows the composition atomic ratio of copper indium diselenide. Mobility of the CIS film was indicated by Hall Measurement.

HP-10 Reactive High Power Impulse Magnetron Sputtering of Titanium Oxide Thin Films
Martynas Audronis (Gencoa Ltd.); Victor Bellido-Gonzalez (Gencoa Ltd); Peter Korgul, Allan Matthews (The University of Sheffield, United Kingdom)

Many of the technologically important metal oxide thin films (e.g. Al2O3, TiO2, etc.) are sputter deposited from metal targets in a reactive gas atmosphere, usually argon and oxygen, i.e. using reactive magnetron sputtering to ensure industrially relevant coating deposition rates. High Power Impulse Magnetron Sputtering (HIPIMS) is known to provide a highly ionised flux of sputtered material and is thought to provide enhanced coating structure-property relationship control (through self-species plasma/ion assistance), as compared to DC or mid-frequency AC/pulse-DC magnetron sputtering. It is therefore desirable to use HIPIMS in a reactive deposition mode in order to apply its advantages in metal oxide thin film fabrication.

This paper reports on the deposition process and structural and compositional properties of titanium dioxide thin films produced by reactive HIPIMS. A new plasma emission monitoring based reactive sputtering process control system (developed specifically to aid stable and reproducible reactive HIPIMS processes) was used for coating deposition. Coating morphology and structure were investigated by field emission gun scanning electron microscopy, atomic force microscopy and X-ray diffraction. Coating chemical composition was investigated by electron probe micro-analysis and glow discharge optical emission spectroscopy, while their mechanical (hardness and elastic modulus) properties were investigated by nano-indentation testing. Processing parameters are correlated to the film properties.

HP-11 Forming CuInSe2 Using Two-Step Electrodeposition of CuSeχ and InSeχ Layers
Shao-Yu Hu, Ying-Xian Su, Wen-Hsi Lee (National Cheng Kung University, Taiwan); Shih-Chieh Cheng, Ying-Lang Wang (National Chia-Yi University, Taiwan)

One-step electrodeposition is the most well-known technique to form CuInSe2 (CIS) for solar cell applications. However, the composition of CIS films is hard to control in a ternary solution. In this study, the deposition potential and electrolyte concentration were confined in a narrow range to control the atom proportion of CIS films. Two-step electrodeposition of CuSeχ and InSeχ precursors provide another route to form CIS film, which was able to control the deposition amount of copper (Cu) and indium (In) without considering the huge variation of their reduction potentials. For CuSeχ deposition, the reduction potential of Cu is smaller than that of selenium (Se) such that the deposition amount of Cu is more than that of Se at the same electrolyte concentration. Increasing the deposition potential and the concentration of SeO2 raised the percentage of Se. Higher electrolyte concentration also led to a smooth and dense CuSeχ film. The sheet resistance of CuSeχ film decreased and the micro-structure became smoother after thermal annealing. The existence of CuSe leads to easier formation of InSe and low-resistance CuSeχ films could decrease the terminal effect to improve the uniformity of subsequently InSeχ electrodeposition. The deposition potential ranged from –0.8V to –0.9V. The content of In would be too low when the deposition potential was under –0.8V, and when the potential was larger than –0.9V, electrolysis occurred and produced mass SeO2 film on the surface. The ratio of Cu/In was verified by energy dispersive spectrometer (EDS) and easily controlled by electrodeposition coulomb in each step. After two-step electrodeposition, rapid thermal annealing was employed to form CuInSe2. The treatment was carried out at 550℃ for 70S. The formation of CuInSe2 was verified by X-ray diffraction.

HP-13 Gas Sensing Properties of SnO2 Nanostructured Films by Electrophoretic Deposition
Sheng-Chang Wang, Ming-Ren Chen (Southern Taiwan University, Taiwan); Ray-Kuang Chiang (Far East University, Taiwan, ROC); Chien-Yie Tsay, Chung-Kwei Lin (Feng Chia University, Taiwan)

In this study, the nanosized SnO2 powder was synthesized by a novel thermal decomposition method and electrophoretic deposited on a patterned Al2O3 substrate for the gas sensing property measurement. The phases and microstructure of the powders were characterized by the XRD, SEM, TEM and BET. Tin oleate complex and 1-octadecanol were used as the precursors, which were thermally decomposed and assembled as octahedron hollow or solid Sn6O4 (OH)4 agglomerate powder at the temperature of 200oC in N2 atmosphere. After heat treatment at 700oC for 1h in air, the powder was transformed to crystalline SnO2 nanoparticle in a size of 50 nm. The SnO2 electrodes with promising gas sensing properties were prepared by electrophoretic deposition using an isopropyl alcohol colloid. The nitrogen-adsorption and desorption isotherms and the relatively gas sensing properties of CO gas were characterized and discussed in details.

HP-15 Parameters Influencing the Deposition Rate During High-Power Impulse Magnetron Sputtering
Stephanos Konstantinidis, Maria Palmucci, Adil Balhamri, Jean-Pierre Dauchot, Michel Hecq, Rony Snyders (Université de Mons, Belgium)

High-Power Impulse Magnetron Sputtering (HiPIMS) is a plasma-based thin film growth technique. Short (several µs) high-power (several kW/cm²) pulses are delivered to the plasma allowing a high ionization degree of the sputtered metal atoms. As a consequence, ion bombardment assists film growth. However, it is commonly found that the deposition rate is lower in HiPIMS than in conventional dc magnetron sputtering (dcMS) processes. This would indicate a different plasma-surface interaction mechanism during HiPIMS.

In our study, plasma composition was characterized by Time-Resolved Optical Emission Spectroscopy (TR-OES) and the amount of material deposited was determined by X-Ray Fluorescence (XRF). HiPIMS and dcMS discharges were operated with a titanium target in argon or neon with a working pressure set to 5 or 10 mTorr.

TR-OES analysis shows a decrease of the argon signal at the end of the pulse ; apparently indicating the rarefaction of the argon gas during the pulse. In contrast, neon signal only presents a weak saturation for long pulses. TR-OES results would suggest that gas heating (induced by the sputtering wind) and the gas rarefaction thereof has a smaller amplitude during HiPIMS in neon. On the other hand, Ti+ signal strongly increases during the pulse in both cases, demonstrating the high ionization rate of the sputtered material. Strong argon rarefaction and the increased number of metal ions would allow the sputtering process to evolve from argon-sputtering to metal-sputtering i.e. self-sputtering. In the case of titanium, self-sputtering is less efficient than argon sputtering. This could be an explanation to the decrease of the deposition rate, as observed by XRF. In neon, the gas rarefaction would be less pronounced and metal ions would contribute to the sputtering process to a smaller extent. The reduction of the deposition rate in neon, as compared to the dcMS discharge, is therefore less pronounced than in argon.

HP-17 Fabrication of AlN Nanowires for Optical-Sensing Properties
Ting Yu Lu (National Tsing Hua University, Taiwan)
Recently, research on the growth and properties of low-dimensional nanomaterials has attracted increasing attention because of their application in constructing nanoscale devices. In order to enhance and modulate the various properties, nanostructures have been doped with appreciate elements frequently. In this study, Zn-doped AlN nanowires were synthesized on the Si substrates using the thermal chemical vapor deposition method. It is found that both the diameters and Zinc concentration of the nanowires increase with increasing growth time (1-4 hrs). The microstructure of Zn-doped AlN nanowires were characterized by field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The composition and chemical bonding energy were investigated by x-ray photoelectron spectroscopy (XPS). The optical properties of AlN nanowires were analysed by Raman spectroscopy and cathodoluminescence(CL). The optical-sensing measurements were carried out by using a volt-amperometric technique, which shows that both the reaction and response time of the nanowires decrease with increasing growth time.
HP-18 High Density of SiC Nanoparticle Formation from Three-Layer Si/C/Si on Si (100) Using Rapid Thermal Annealing
Chen-Kuei Chung, T.Y. Chen, Chun-Wen Lai, C.C. Peng, Bo-Hsiung Wu (National Cheng Kung University, Taiwan)
The density of nanoparticle SiC (np-SiC) film formed by conventional furnace annealing (FA) of Si/C/Si multilayers at 900 °C is about 108 cm-2. In this paper, rapid thermal annealing (RTA) were used to investigate the formation of high density of np-SiC film from thermal reaction of Si/C/Si multilayers on Si(100) substrates deposited by ultra-high-vacuum ion beam sputtering. Two kinds of Si/C/Si multilayer thickness, namely 10/100/10 nm and 10/100/50 nm, were designed to study the annealing and thickness effect on the reaction of np-SiC formation by RTA. The evolution of microstructure and reaction between C and Si was examined by grazing incidence X-ray diffraction (GIXRD) for phase identification, high resolution field emission scanning electron microscope (HR-FESEM) for surface morphology and the depth profile of Auger electron spectroscopy (AES) for interdiffusion behavior. The density of np-SiC on surface formed by RTA at 750 °C than was about 1010 cm-2 which is two orders higher than that by FA at 900 °C . Efficient thermal energy is the diving force for the crystalline np-SiC formation through interdiffusion between C and Si. The lower formation temperature of np-SiC by RTA may be attributed to RTA enhanced SiC nucleation and crystallization behavior at high heating rate. The annealing method also influences the particle size . Smaller particle size less than 100 nm can be obtained by RTA. The particle size, distribution and density are concerned with the bottom layer thickness.
HP-19 Roughness-Enhanced Thermal-Responsive Surfaces by Surface Initiated Polymerization of Polymer on Ordered ZnO Pore-Array Films
Chi-Jung Chang, En-Hong Kuo (Feng Chia University, Taiwan)
Reversible switching of the wettability on a thermal-responsive surface can be achieved by changing the temperature. ZnO pore-array films consisting of growth-hindered vertically-aligned ZnO nanorods were fabricated by the process including microsphere lithography and hydrothermal procedures. Then, a self-assembly 3-amionpropyltriethoxysilane monolayer formed on the pore-array surface, followed by the graft polymerization of poly(N-isopropylacrylamide) (PNIPAm) on the surface. The microstructure of the ZnO pore-array films, silane monolayer and grafted PNIPAm were characterized by contact angle, XPS and AFM measurements. The surface can exhibit hydrophilicity at low temperature. At higher temperatures, the compact and collapsed conformation of PNIPAm chains induced by intramolecular hydrogen bonding in PNIPAm chains leads to low surface free energy and large water contact angle. The nanostructures on the ordered ZnO pore-array surfaces contribute to an increase in the air/water interface. It leads to the enhanced hydrophobicity of PNIPAm films on rough substrates at high temperatures. It results in stimuli-responsive wettability switching by the combination of the change in surface chemistry and surface roughness.
HP-20 Thermal Conductivity and Morphology of Silver-Filled Multi-Walled Carbon Nanotubes and Polyimide Nanocomposite Films
Mei-Hui Tsai, Dong-Sen Chen (National Chin-Yi University of Technology, Taiwan); Chi-Jung Chang (Feng Chia University, China); Jui-Ming Yeh (Center for Nanotechnology at CYCU and R&D Center for Membrane Technology, Taiwan); Jyh-Wei Lee (Mingchi University of Technology, Taiwan)
Polyimide (PI)/Silver-filled multi-wall carbon nanotubes (Ag-MWNTs) hybrid film with high thermal conductance could be applied to electronic circuitry and flexible circuits and buried film capacitors. Silver-filled multi-wall carbon nanotubes (Ag-MWNTs) are successfully incorporated into a polyimide (PI) matrix using a highly efficient and simple methodology. The intercalation of Ag within MWNTs is performed using capillary action prior to adding Ag-MWNTs into PI matrix. In this study, MWNTs are considered as nano-module and also can facilitate the distribution of Ag particle within PI. The morphology and structure of Ag-MWNTs/PI hybrid film is analyzed with a field emission scanning electron microscope (FE-SEM), high-resolution transmission electron microscope (HR-TEM) and X-ray diffraction (XRD). The existence of Ag is also verified with the energy-dispersive X-ray (EDS) spectrum. Furthermore, the thermal conductivity of hybrid film is discussed in relation to the content of Ag-MWNTs incorporated.
HP-22 Corrosion Behaviour in Artificial Seawater of Thermal Sprayed WC-Co Based Coatings on Mild Steel
Smail Brioua, Kamel Belmokre (LCTS, Université de Skikda, Algérie, France); Vincent Debout (Bodycote, CRDA, France); Patrick Jacquot (Bodycote, France); Egle Conforto, Juan Creus (Université de la Rochelle, France)

The corrosion behavior in artificial seawater of different HP-HVOF cermet coatings applied on low alloyed steel was studied. 5 conditions, associated to modifications of the composition of the powder or deposition parameters were evaluated. The degradation mechanisms were studied during extended immersion tests using conventional electrochemical measurement and electrochemical impedance spectroscopy.

The extended immersion tests reveal that these thermal sprayed coatings present a cathodic behavior compared to steel. During the first hours of immersion, the electrolyte infiltrates the defects of the coatings, which then result to the local degradation of the substrate accelerated by the galvanic coupling with the cermet coating. Optical observations and Raman and FTIR analyses reveal the formation of calcium carbonates like aragonite on the cermet surface, very close to the appearance of local anodic sites. The cross-sectioned view reveal the infiltration of the corrosive solution, and the depth penetration of the degradation of steel substrate probably due to the acidification of the anodic sites.

HP-23 A Study of the Influence of Pulse Length and Duty Factor on Hafnium Films Deposited with High Power Impulse Magnetron Sputtering
Amber Reed, Matthew Lange (Air Force Research Laboratory / Universal Technology Corporation); John Jones (Air Force Research Laboratory); Jianjun Hu (UDRI / Air Force Research Laboratory); Andrey Voevodin (Air Force Research Laboratory)
Different pulse widths at constant duty factors were examined to develop an understanding of the relationship between pulse width and deposition rate during high power impulse magnetron sputtering. Specifically, the effect of target heating at long (>100 ms) pulse durations was investigated. In one study, hafnium films were grown on silicon substrates at constant duty factors. The deposition rate was essentially constant for pulse durations of 50 and 100 μs, but doubled at a pulse width of 200 μs. The structure of these films was studied using x-ray diffraction. The XRD measurements of the hafnium films grown with shorter pulse lengths exhibited a preferential growth in the (002) plane, while films grown with longer pulse lengths had a random polycrystalline structure. SEM and TEM were used to examine the surface features, grains and density of the films. Unusual features throughout the cross-sections of films processed at higher pulse widths were observed. It is believed that thermal effects during deposition could be responsible for these differences in film structure, and was investigated by mass spectrometry measurements of ionized and neutral plasma species at different pulse widths.
HP-24 Self-Organized Nanodots of SiOx Deposited by Atmospheric Pressure Plasma Enhanced Chemical Vapour Deposition
Gregory Arnoult, Thierry Belmonte, Gérard Henrion (Ecole des Mines de Nancy, France)

Deposition of patterned nanostructures by atmospheric pressure plasma enhanced chemical vapour deposition (PECVD) is today of fundamental importance in material science research. A breakthrough has recently been done by using micro-plasmas [1]. These results combine the benefits of a plasma environment together with the advantages of self-organization. Observation of self-organization phenomena under plasma conditions is still limited, and even less is known about self-organization promoted by atmospheric microplasmas.

Recently, we have developed a small-scale remote plasma at atmospheric pressure based on a resonant microwave cavity. By controlling the hydrodynamics of the gas, we have shown that it is possible to extract through a tinny hole in the cavity a straight beam of active species (~500 µm in radius) over a length of 10 cm . By mixing this beam of atoms with a flux of HDMSO, we could grow SiOx coatings on stainless steel substrates. Deposition rate is about 80 nm/s.

Under specific conditions, self-organized nanodots are obtained. Their diameter is close to 200 nm. Depending on time, these particles get assembled into threads, separated one from another by an almost constant distance, and reminding a Volmer-Weber nucleation step followed by coarsening.

In this work, we describe the influence of the main experimental parameters on the synthesis of these patterned structures. Image analysis is essentially used to determine the distributions in size and distance of the nanostructures. A specific analysis of thermal fluxes is also carried out to try to determine the influence of the temperature gradients on the growth. Results are based on simulations of rotational spectra of the OH (306.4nm—A2Σ+ ; v = 0–X2Π ; v’ = 0) transition and infra-red camera measurements.

[1] D. Mariotti, V. Švrček and D.-G. Kim, Appl. Phys. Lett. 91, 183111 (2007)

HP-25 Effect of Interlayers on Field Emission Characteristics of Ink-Jet Printed CNT Emitter
Daehoon Song (Korea University, Korea); Kyung-Il Lee, Sung-Hyun Kim, Jong-Hoon Han (KETI, Korea); Ho-Gyu Yoon (Korea University, Korea); Churlseung Lee (Korea Electronics Technology Institute, Korea)
Recently, field emission emitters made by carbon nanotubes (CNTs) and ink-jet method have been extensively studied due to their low cost, little limitation of size and a high resolution. In this process, an interlayer was inevitable which improved adhesion between CNTs and a substrate. In this study, the identity of the interlayer was investigated for field emission characteristic of the ink-jet printed CNT emission device. In order to discern the role of the interlayer, we prepared two series of samples. One was an Indium layer with thickness of 200nm deposited by thermal evaporator, the other was a Chromium layer with thickness of 200nm deposited by magnetron sputter system. The ITO coated glass substrate was printed by ink-jet using 0.5wt% and 5~6cps MWNTs ink. The patterned substrate was thermally annealed using the RTA system for the physical bonding between MWNTs and substrate. After annealing, we executed an activation using the rolling method. We observed the field emission characteristics using the field emission system and analyzed the samples by FE-SEM, AFM, AES. Although In interlayer had the lower turn-on electric field (1.5 V/um) than that of Cr layer, but Cr interlayer showed more stable and reproducible emission properties under repeated measurements. Furthermore, the life time of Cr interlayer was longer than that of In layer. We could conclude that the generated surface oxide layer of Cr interlayer played a role of regulating the destruction by an abnormal arcing phenomenon.
HP-27 Improved Adhesion of Polymethylsilsesquioxane Hard Coatings on Polymer Substrates
Yu-Chih Kao, Franklin Chau-Nan Hong (National Cheng Kung University, Taiwan)

Polymethylsilsesquioxane (PMSQ) is well-known abrasion-resistant coating material as protective coatings for the relatively soft resin, which is particularly desirable in the hard coatings of optically transparent materials such as plastic window glazing, anti-abrasion coating of mobile phone or portable display screens, etc. as well as other applications like oxidation barrier of metal. However, PMSQ films exhibited poor adhesion to polymer substrates. In this study, PMSQ coatings on PMMA, PC, PC/ABS alloy substrates were studied by grafting the substrate with trimethyl ethoxysilane (TMES) after surface functional treatments with oxygen plasma or chromic acid. The polymer surfaces after various surface treatments were also characterized by contact angle measurements and ATR-FTIR in order to optimize the treatment time. The improvement of adhesion and hardness was examined respectively by cross cut test and pencil hardness test.

PMMA substrate treated with oxygen plasma followed by TMES grafting was found to show great improvement of adhesion between PMMA and PMSQ with the significant decrease of the peeling area percentage from ~100% to <1%. PC or PC/ABS substrate showed better adhesion after the chromic acid oxidation treatment than those after oxygen plasma treatment. The peeling area percentages for both PC and PC/ABS alloy with chromic acid oxidation treatment followed by TMES grafting were 50% and <1%, respectively. The hardness of PMSQ-coated polymer substrate was greatly affected by the original hardness of polymer substrate by pencil test. The same results were also observed for the diamond-like-carbon (DLC) coated polymer substrates. The hardness of polymer substrates coated with PMSQ film was significantly improved by two to three levels (e.g. <2B to 1H for PC, 4H to 7H for PMMA) whether surface treated or not.
Time Period ThP Sessions | Topic H Sessions | Time Periods | Topics | ICMCTF2010 Schedule