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ABSTRACT: The electrical, optical, structural and chemical bonding properties of fluorine-doped tin oxide (SnOx:F) films deposited on a plastic substrate prepared by Electron Cyclotron Resonance–Metal Organic Chemical Vapor Deposition
(ECR–MOCVD) were investigated with special attention to the process parameters such as the H2/TMT mole ratio, deposition time and amount of fluorine-doping. The four point probe method, UV visible spectroscopy, scanning
electron microscopy (SEM), transmission electron microscopy (TEM), atomic emission spectroscopy (AES), X-Ray diffraction (XRD)
and X-ray photoelectron spectroscopy (XPS) were employed to characterize the films. Based on our experimental results, the
characteristics of the SnOx:F thin films were significantly affected by the process parameters mentioned above. The amount of fluorine doping was found
to be one of the major parameters affecting the surface resistivity, however its excess doping into SnO2 lead to a sharp increase in the surface resistivity. The average transmittance decreased with increasing film thickness.
The lowest electrical resistivity of 5.0 × 10−3Ω.cm and highest optical transmittance of 90% in the visible wavelength range from 380 to700nm were observed at an H2/TMT mole ratio of 1.25, fluorine-doping amount of 1.3wt.%, and deposition time of 30min. From the XRD analysis, we found
that the SnOx:F films were oriented along the (2 1 1) plane with a tetragonal and polycrystalline structure having the lattice constants,
a = 0.4749 and c = 0.3198nm.
Journal of Electroceramics 04/2012; 23(2):506-511. · 1.19 Impact Factor
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ABSTRACT: Carbon films from fullerene C60 were coated on the surface of lithium metal for the anode of lithium secondary battery. In order to investigate the relationship
between the electrochemical characteristics of the carbon films and deposition technique, three different vacuum techniques
were employed such as RF (radio frequency)—magnetron sputtering of C60, plasma assisted thermal evaporation of C60 and ion beam assisted thermal evaporation of fullerene C60. From the physical and chemical characterization tests, we found that the carbon films produced by those above techniques
mainly consist of sp2/sp3 hybridized amorphous carbons. Electrochemical tests implied that the cyclic performance was enhanced by the fullerene C60 coating on lithium metal anode in comparison to the pure lithium metal one. This enhanced performance is due to the formation
of thin carbon film on the surface of lithium metal anode which plays a role as a passive layer against the side reaction
between lithium metal and the electrolyte.
Journal of Electroceramics 04/2012; 23(2):248-253. · 1.19 Impact Factor
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ABSTRACT: To improve the electrochemical performances of Si thin film anodes for lithium rechargeable batteries, fullerene thin films
are prepared by plasma-assisted evaporation methods to be used as coating materials. Analyses via Raman and X-ray photoelectron
spectroscopy indicate that amorphous polymeric films originated from fullerene are formed on the surface of the silicon thin
film. The electrochemical performance of these fullerene-coated silicon thin film as an anode material for rechargeable lithium
batteries has been investigated by cyclic voltammetry, charge/discharge tests, and electrochemical impedance spectroscopy.
The fullerene-coated Si thin films demonstrated a high specific capacity of above 3,000mAh g−1 as well as good capacity retention for 40 cycles. In comparison with bare silicon anodes, the fullerene-coated silicon thin
film showed superior and stable cycle performance which can be attributed to the fullerene coating layer which enhances the
Li-ion kinetic property at the electrode/electrolyte interface.
Journal of Solid State Electrochemistry 04/2012; 14(1):51-56. · 2.13 Impact Factor
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ABSTRACT: A Fullerene C60 film was introduced as a coating layer for silicon nanowires (Si NWs) by a plasma assisted thermal evaporation technique. The morphology and structural characteristics of the materials were studied by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). SEM observations showed that the shape of the nanowire structure was maintained after the C60 coating and the XPS analysis confirmed the presence of the carbon coating layer. The electrochemical characteristics of C60 coated Si NWs as anode materials were examined by charge-discharge tests and electrochemical impedance measurements. With the C60 film coating, Si NW electrodes exhibited a higher initial coulombic efficiency of 77% and a higher specific capacity of 2020 mA h g(-1) after the 30th cycle at a current density of 100 microA cm(-2) with cut-off voltage between 0-1.5 V. These improved electrochemical characteristics are attributed to the presence of the C60 coating layer which suppresses side reaction with the electrolyte and maintains the structural integrity of the Si NW electrodes during cycle tests.
Journal of Nanoscience and Nanotechnology 04/2012; 12(4):3547-51. · 1.56 Impact Factor
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ABSTRACT: Phosphorus doped C60 (P:C60) thin films were prepared by a radio frequency plasma assisted thermal evaporation technique using C60 powder as a carbon source and a mixture of argon and phosphine (PH3) gas as a dopant precursor. The effects of the plasma power on the structural characteristics of the as-prepared films were then studied using Raman spectroscopy, Auger electron spectroscopy (AES) and X-ray photo-electrons spectroscopy (XPS). XPS and Auger analysis indicated that the films were mainly composed of C and P and that the concentration of P was proportional to the plasma power. The Raman results implied that the doped films contained a more disordered carbon structure than the un-doped samples. The P:C60 films were then used as a coating layer for the Si anodes of lithium ion secondary batteries. The cyclic voltammetry (CV) analysis of the P:C60 coated Si electrodes demonstrated that the P:C60 coating layer might be used to improve the transport of Li-ions at the electrode/electrolyte interface.
Journal of Nanoscience and Nanotechnology 02/2012; 12(2):1658-61. · 1.56 Impact Factor
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ABSTRACT: An alternative indium-free material for transparent conducting oxides of fluorine-doped tin oxide [FTO] thin films deposited on polyethylene terephthalate [PET] was prepared by electron cyclotron resonance - metal organic chemical vapor deposition [ECR-MOCVD]. One of the essential issues regarding metal oxide film deposition is the sheet resistance uniformity of the film. Variations in process parameters, in this case, working and bubbler pressures of ECR-MOCVD, can lead to a change in resistance uniformity. Both the optical transmittance and electrical resistance uniformity of FTO film-coated PET were investigated. The result shows that sheet resistance uniformity and the transmittance of the film are affected significantly by the changes in bubbler pressure but are less influenced by the working pressure of the ECR-MOCVD system.
Nanoscale Research Letters 01/2012; 7:17. · 2.73 Impact Factor
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ABSTRACT: In order to replace the brittle graphite bipolar plates currently used for the PEMFC stack, coated SUS 316 was employed. As a metallic bipolar plate, coated SUS 316 can provide higher mechanical strength, better durability to shocks and vibration, less permeability, improved thermal and bulk electrical conductivity, as well as being thinner and lighter. To enhance the interfacial contact resistance and corrosion resistance of SUS 316, the deposition of GTO:F and ZTO:F composite films was carried out by ECR-MOCVD. The surface morphology of the films consisted of tiny elliptically shaped grains with a thickness of 1 microm. The corrosion current for GTO:F was 0.13 Acm(-2) which was much lower than that of bare SUS 316 (50.16 Acm(-2)). The GTO:F coated film had the smallest corrosion current due to the formation of a tight surface morphology with very few pin-holes. The GTO:F coated film exhibited the highest cell voltage and power density due to its lower ICR values.
Journal of Nanoscience and Nanotechnology 09/2011; 11(9):7999-8003. · 1.56 Impact Factor
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ABSTRACT: Gallium tin oxide composite (GTO) thin films were prepared by electron cyclotron resonance-metal organic chemical vapor deposition (ECR-MOCVD). The organometallics of tetramethlytin and trimethylgallium were used for precursors of gallium and tin, respectively. X-ray diffraction (XRD) characterization indicated that the gallium tin oxide composite thin films show the nanopolycrystalline of tetragonal rutile structure. Hall measurement indicated that the Ga/[O+Sn] mole ratio play an important role to determine the electrical properties of gallium tin composite oxide thin films. n-type conducting film obtained Ga/[O+Sn] mole ratio of 0.05 exhibited the lowest electrical resistivity of 1.21 x 10(-3) ohms cm. In our experimental range, the optimized carrier concentration of 3.71 x 10(18) cm(-3) was prepared at the Ga/[O+Sn] mole ratio of 0.35.
Journal of Nanoscience and Nanotechnology 08/2011; 11(8):7234-7. · 1.56 Impact Factor
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ABSTRACT: A nano carbon coating layer was prepared by the thermal evaporation of fullerene C60 on the surface of lithium metal anodes for rechargeable lithium batteries. The morphology and structure of the carbon layer was firstly investigated by Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The effects of the nano-carbon coating layer on the electrochemical performance of the lithium electrode were then examined by charge-discharge tests and impedance spectroscopy. Raman spectra of carbon coating layer showed two main peaks (D and G peaks), indicating the amorphous structure of the film. A honey comb-like structure of carbon film was observed by TEM photographs, providing a transport path for the transport of lithium ions at the electrode/electrolyte interface. The carbon coated lithium electrodes exhibited a higher initial coulombic efficiency (91%) and higher specific capacity retention (88%) after the 30th cycle at 0.2 C-rate between 3.4 and 4.5 V. Impedance measurements showed that the charge transfer resistance was significantly reduced after cycle tests for the carbon coated electrodes, revealing that the more stable solid electrolyte (SEI) layer was established on their surface. Based on the experimental results, it suggested that the presence of the nano-carbon coating layer might suppress the dendritic growth on the surface of lithium metal electrodes, as confirmed by the observation of SEM images after cycle tests.
Journal of Nanoscience and Nanotechnology 07/2011; 11(7):6569-74. · 1.56 Impact Factor
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ABSTRACT: Fluorescent-labeled magnetic nanoparticles were explored as a biomedical agent for selective magnetic separation. By adjusting the loading volume of citrate-stabilized magnetites during a sol-gel reaction with silicon alkoxide, magnetites were simultaneously embedded into both the surface and inside the silica matrix, consequently leading to magnetic nanoparticles with different doping levels of magnetites. For endowing them with multifunctional tools in biomedical fields, magnetic nanoparticles were further encapsulated with silica thin layer labeled with fluorescent organic dyes (such as Alexa Fluor 488 and 594). Fluorescent-magnetic nanoparticles with different magnetism successfully displayed the differential separation of fluorescence spectra under an external magnetic field.
Journal of Nanoscience and Nanotechnology 05/2011; 11(5):4551-6. · 1.56 Impact Factor
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ABSTRACT: Fluorine-doped tin oxide (SnOx:F) films on SUS 316 were prepared as a function of substrate temperature using electron cyclotron resonance-metal organic chemical vapor deposition (ECR-MOCVD) in order to achieve corrosion-resistant and low contact resistance bipolar plates for polymer electrolyte membrane fuel cells (PEMFCs). The SnOx:F films coated on SUS 316 substrate in the heating range from 200 to 500 °C were characterized by x-ray diffraction (XRD), Auger electron microscopy (AES) and field emission-scanning electron microscopy (FE-SEM). To simulate the aggressive PEMFC environment, all electrochemical experiments were conducted in 1 M H2SO4+2 ppm HF solution at 70 °C. With increases in the heat treatment temperature from 300 to 500 °C, it was shown that both corrosion resistance and interfacial contact resistance (ICR) substantially increase. The AES data revealed that the amount of fluorine decreases with increasing temperature in our experimental range. The deposition temperature appears to be one of the critical process parameters on the formation of the corrosion-protective layer for PEMFC bipolar plates. It is probably caused by microstructural evolution before/after potentiodynamic corrosion tests under the PEMFC environment.
Physica Scripta 05/2010; 2010(T139):014020. · 1.20 Impact Factor
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01/2007: pages 949-952;
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ABSTRACT: By performing a plasma evaporation technique, fullerene C60 was used as a coating material onto a silicon thin film anode for lithium secondary batteries. The effect of the plasma power (20 W, 100 W and 200 W) in the plasma coating process on the structural and electrochemical properties of the fullerene C60-coated silicon anode was then studied by means of Raman spectroscopy, Fourier transform infra red (FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and charge/discharge tests. The Raman and FTIR analysis showed that the polymeric phase of fullerene C60 was formed during the deposition operation and that the fullerene monomers were polymerized to a greater extent at a high plasma power operation (200 W). Furthermore, the fullerene C60-coated silicon electrode obtained at a plasma power of 200 W exhibited excellent electrochemical performance with a specific capacity of more than 2000 mAh g−1. The stable polymeric phase of fullerene C60 was found to be the main factor enhancing the electrochemical performance of the fullerene-coated silicon anode.
Materials Chemistry and Physics. 113(1):249-254.
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ABSTRACT: Silicon composite of nano-capsule type is newly applied as an active anode material for lithium ion batteries. TiO2-encapsulated silicon powders were synthesized by a sol-gel reaction with titanium ethoxide. Silicon nanoparticles were successfully embedded into porous titanium oxide capsules that played as a buffer layer against drastic volume changes of silicon during the charge-discharge cycling, consequently leading to the retardation of the capacity fading of intrinsic silicon materials. The electrochemical and structural properties of silicon nanocomposites with different surface areas of encapsulating TiO2 layer were characterized by X-ray diffraction(XRD), nitrogen gas adsorption analysis by the Brunauer-Emmett-Teller(BET) equation, transmission electron microscopy(TEM), and galvanostatic charge-discharge experiments.
Transactions of Nonferrous Metals Society of China 19(4):1023-1026. · 0.75 Impact Factor
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ABSTRACT: In this work, boron doped fullerene (B:C60) films were prepared by the radio frequency plasma assisted thermal evaporation technique for use as a coating material for the silicon thin film anode in lithium secondary batteries. Raman and XPS analyses revealed that the boron atoms were well inserted into the fullerene film lattices. The effect of the B:C60 film on the electrochemical characteristics of the silicon thin film was studied by charge–discharge tests, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The B:C60 coated silicon film exhibited a high reversible capacity of more than 1200 mAh g−1 when cycled 50 times between 0 and 2 V at a current density of 1200 μA cm−2 (1.5 C). The film also showed good rate capacity at different current densities and a more improved coulombic efficiency of 87.7% in the first cycle in comparison with that of the C60 coated film electrode.Research highlights▶ Boron doped C60 film is prepared by plasma assisted thermal evaporation technique. ▶ B:C60 film is used as a coating material for Si film anodes of lithium secondary batteries. ▶ The B:C60 coated Si anode exhibits a high reversible capacity of 1200 mAh g−1 after 50 cycles. ▶ The electronic conductivity and diffusion coefficients of Li-ion on the Si/electrolyte interface are increased due to the boron doping.
Synthetic Metals 161:158-165. · 1.83 Impact Factor
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ABSTRACT: Different surface coverage of nanosized Au on the TiO2 matrix was simply fabricated in an ultrasound-driven cell by adjusting the loading volume of gold precursor. Non-annealed Au–TiO2 composites with low surface coverage of nanosized Au exhibited a significantly enhanced photocatalytic activity in comparison to pristine TiO2. However, a further increase of nanosized Au loading consequently led to a decrease of photocatalytic efficiency of Au-deposited TiO2, probably due to the reduction of available surface area for organic pollutant adsorption and light absorption. The X-ray photoelectron spectroscopy (XPS) analysis of Au-deposited TiO2 indicated the coexistence of metallic Auo and non-metallic Au species that might play a role as an electron scavenger. The reduction of photoluminescence (PL) intensity also indicated the efficient separation of electrons and holes even in Au–TiO2 composites without heat treatment.
Journal of Crystal Growth 311(3):508-511. · 1.73 Impact Factor
