Cyclotron Resonance-metal Organic Chemical Vapor Research Articles

Employment of SnO2:F@Ni3Sn2/Ni nanoclusters composites as an anode material for lithium-ion batteries

Surface modification of SnO2:F particles which obtained from a large-scale electron cyclotron resonance-metal organic chemical vapor deposition system was carried out by two consecutive processes: electroless plating processing and annealing. First, Ni film on the SnO2:F and Ni nanoclusters were observed after Ni electroless plating; the film on the SnO2:F was then converted to Ni3Sn2 after annealing at 800 °C under an argon atmosphere. A Ni3Sn2 bimetallic structure formed instead of NiO during the annealing process because of the presence of carbon impurities in SnO2:F. The surface-modified Ni3Sn2-covered SnO2:F with Ni nanoclusters (SnO2:F@Ni3Sn2/Ni-nc) was employed as an anode material for lithium-ion batteries. The inactive Ni in Ni3Sn2 acts as a buffer matrix against the Sn active material during the charge-discharge reactions, enhancing the electrochemical performance. The Ni nanoclusters in SnO2:F@Ni3Sn2/Ni-nc perform dual functions: they not only improve the conductivity as the contacting media, but also increase the initial columbic efficiency by the decomposition of Li2O—an electrochemically irreversible material. An outstanding reversible capacity of 600.69 mA h g−1 and a coulombic efficiency of 99.23% for SnO2:F@Ni3Sn2/Ni-nc were observed at the 350th cycle under 200 mA g−1 in the our experimental range.

Pilot-scale electron cyclotron resonance-metal organic chemical vapor deposition system for the preparation of large-area fluorine-doped SnO2 thin films

The authors report the surface morphology, optical, electrical, thermal and humidity impacts, and electromagnetic interference properties of fluorine-doped tin oxide (SnO2:F or “FTO”) thin films on a flexible polyethylene terephthalate (PET) substrate fabricated by a pilot-scale electron cyclotron resonance–metal organic chemical vapor deposition (PS ECR-MOCVD). The characteristics of large area FTO thin films were compared with a commercially available transparent conductive electrode made of tin-doped indium oxide (ITO), prepared with an identical film and PET thickness of 125 nm and 188 μm, respectively. The results revealed that the as-prepared FTO thin films exhibited comparable performances with the incumbent ITO films, including a high optical transmittance of 97% (substrate-subtracted), low electrical resistivity of about 5 × 10−3 Ω cm, improved electrical and optical performances due to the external thermal and humidity impact, and an excellent shielding effectiveness of electromagnetic interference of nearly 2.3 dB. These excellent performances of the FTO thin films were strongly attributed to the design of the PS ECR-MOCVD, which enabled a uniform plasma environment resulting from a proper mixture of electromagnetic profiles and microwave power.

Electrochemical characteristics of fluorine-doped tin oxide film coated on stainless steel bipolar plates

In order to improve the interfacial contact resistance (ICR) and corrosion resistance of STS316 bipolar plates of PEMFCs, after surface pretreatment at mild plasma condition, the fluorine-doped tin oxides (FTO) thin films were deposited by electron cyclotron resonance-metal organic chemical vapor deposition. The mild plasma pre-treatment of the bipolar plate substrate before its coating with the FTO film has rendered a higher efficiency to the pertinent fuel cell, which can be attributed to a smooth charge transfer at the interface of the plate and the film due the removal of fine impurities on the substrate that could not be done just by washing. The deposition of FTO as a protect layer of fuel cell electrode after mild plasma pre-treatment improved the electrochemical stability. In our experimental range, with the increases in microwave power up to 1000W, both of the corrosion resistance and ICR significantly decreased, however, those values sharply increased above 1100W due to the crack and unstable film formation with the void space. Selecting the optimized value of the microwave power appeared to be the critical process step on the formation of the corrosion-protective layer for bipolar plates.

High thermal performance of SnO2:F thin transparent heaters with scattered metal nanodots.

Facile production and novel transparent heaters consisting of fluorine-doped tin oxide (SnO2:F or FTO) thin films covered with three different scattered metal nanodots (Cr-nd, NiCr-nd and Ni-nd) prepared by plasma-enhanced sputtering system and electron cyclotron resonance-metal organic chemical vapor deposition are investigated. The heaters exhibit excellent optical transmittances of over 85% and superior saturated temperatures of more than 80 °C when a relatively low 12 V DC is supplied. The scattered metal nanodots FTO heaters successfully improve the specific power of bare FTO heater by 21, 15, and 12% for NiCr-nd FTO, Cr-nd FTO, and Ni-nd FTO, respectively. These results reveal that the FTO transparent heaters with scattered metal nanodots are the suitable heating materials that can be applied for various functional devices.

Coating of spinel LiNi0.5Mn1.5O4 cathodes with SnO2 by an electron cyclotron resonance metal–organic chemical vapor deposition method for high-voltage applications in lithium ion batteries

Tin oxide coating by employing electron cyclotron resonance metal–organic chemical vapor deposition was performed on 5V-class spinel LiNi0.5Mn1.5O4 cathode electrodes prepared by a conventional tape-casting method. The pristine and SnO2-deposited LiNi0.5Mn1.5O4 electrodes were characterized by X-ray diffraction, field-emission electron probe microanalyzer, field-emission scanning electron microscopy, Auger electron spectroscopy, charge–discharge measurements, and electrochemical impedance spectroscopy were evaluated in lithium cells using the fabricated electrodes. The SnO2-deposited LiNi0.5Mn1.5O4 electrodes exhibited better rate capability at room temperature and superior electrochemical performance during the storage test evaluated at 60°C in a fully charged state than the pristine LiNi0.5Mn1.5O4 electrode. Also, surface modification of the LiNi0.5Mn1.5O4 electrode was found by impedance analyses to be effective for suppressing the increase of the charge transfer resistance during the storage test at elevated temperatures.

Double-layer effect on electrothermal properties of transparent heaters

Transparent double-layer heaters that consist of aluminum-doped zinc oxide and fluorine-doped tin oxide films are prepared by electron cyclotron resonance-metal organic chemical vapor deposition and RF-sputtering systems, in sequence. The double-layered transparent conducting oxide film is designed and prepared to achieve both of high conductivity and high-temperature performance. This double-layer structure has lower sheet resistance, due to the grain size increase with respect to the single-layer films. The fluorine-doped tin oxide/aluminum-doped zinc oxide double-layer film shows a sheet resistance as low as 36.7 Ω sq−1, and an optical transmittance of ∼82%, which are suitable properties for low-voltage transparent heaters. Hall measurement results show that the double-layer film has remarkably increased conductivity and decreased resistivity. In addition, the time-versus-temperature profile shows that the performance of the fluorine-doped tin oxide/aluminum-doped zinc oxide double layer is superior to that of the aluminum-doped zinc oxide and fluorine-doped tin oxide single-layer films.

SnO2-coated LiCoO2 cathode material for high-voltage applications in lithium-ion batteries

Abstract In order to improve the electrochemical performances of LiCoO2 cathode in high voltage cycling range (3.0–4.5 V), SnO2 thin film has been deposited on the surface of electrode material by an electron cyclotron resonance-metal organic chemical vapor deposition (ECR-MOCVD). Scanning electron microscopy (SEM) images and X-ray diffraction (XRD) patterns confirm the presence of SnO2 thin layers on the tape-casted electrode composed of nanocrystalline structure with agglomerated grain size ranging from 30 to 40 nm. The electrochemical tests show that the SnO2 coating layer significantly enhances the cycling performance of LiCoO2 cathode material. While the bare LiCoO2 cell does not work after 370 cycles, the surface-modified electrode exhibits the extended performance over 500 cycles with excellent capacity retention. In addition, it is also observed that SnO2 coating material is able to amplify the initial discharge capacity of bare LiCoO2 from 172 to183 mAhg− 1 at 1 C and effectively increase the coulombic efficiency of pristine LiCoO2 cathode. We conclude that these electrochemical improvements are strongly due to the suppression of charge transfer resistance and prevention of side reactions during the charge/discharge process via surface coating of electrodes.

Electrochemical behavior of a laser microstructured fluorine doped tin oxide anode layer with a plasma pretreatment for 3D battery systems

Fluorine-doped tin oxide (FTO) films with a thickness of about 3 micrometers were prepared by electron cyclotron resonance-metal organic chemical vapor deposition (ECR-MOCVD) under 800 W of microwave power, with tetra-methyl tin (TMT) as a tin precursor. The dome-shaped micro-patterned FTO layer was prepared on a copper current collector using a KrF excimer laser micromachining system for application as an anode for 3D lithium-ion batteries. Mild ECR plasma treatment at 600 W was carried out on the surface of the microstructured FTO anode, and the electrochemical characteristics were investigated with regard to the plasma treatment effects. The results show that physical properties such as the smooth and dense surface morphology and reduced surface oxygen functional groups of the plasma-treated samples enhanced the specific capacity, rate capability, and capacity fading. This was probably due to the reduction of side reactions, which may be closely related to the plasma treatment of the microstructured FTO layer. The ECR plasma treatment plays an important role in reducing the charging transfer resistance. In the experimental range studied, a higher specific capacity of 1425 mA h g−1 at a current density of 117 mA g−1 was observed, with capacity fading of 37.8% after 100 cycles for the plasma-treated microstructured FTO anode.

Effect of oxygen plasma treatment on the electrochemical properties of Prussian blue electrodes for transparent electrochromic devices

The effect of oxygen plasma on the electrochromic characteristics of electrochromic devices that utilize Prussian blue electrodes is investigated. Prussian blue working electrodes were electrodeposited on fluorine-doped tin oxide films that were grown on glass substrates by electron cyclotron resonance-metal organic chemical vapor deposition. An indium tin oxide coated glass was employed as the counter electrode that served as an ion storage layer. The goal of the oxygen plasma treatment is to increase the oxygen functional groups on the surface of the Prussian blue electrode leading to the enhancement of the oxidation reaction and eventually the increase in coloration efficiency. Improvement of electrochromic properties, such as optical density and response time, was also observed following plasma treatment.

Electrochemical characteristics of ZnO patterned column/SnO2 films for anodic electrodes of lithium ion batteries

Micro-patterned ZnO columnar structures on the surface of SnO2 film are prepared by combined photolithography and chemical vapor deposition processes. The ZnO patterned column/SnO2 film was employed as an anode of lithium ion batteries. The film deposition process is carried out by using the electron cyclotron resonance-metal organic chemical vapor deposition system. In order to investigate the relationship between the micro pattern and its electrochemical characteristics, X-ray diffraction, field emission-scanning electron microscopy and X-ray photoelectron spectroscopy are used. Field emission-scanning electron microscopy images revealed that the diameter of columnar ZnO ranges from 3 to 5μm. The highest reversible capacity of the micro-patterned anode exhibited 1725mAhg−1 at a current density of 200mAg−1. Based on our experimental results, ZnO micro-patterning at the interface of the electrode plays an important role in mitigating capacity fading during repetitive cycling.

Comparison of Characteristics of Fluorine Doped Zinc and Gallium Tin Oxide Composite Thin Films Deposited on Stainless Steel 316 Bipolar Plate by Electron Cyclotron Resonance-Metal Organic Chemical Vapor Deposition for Proton Exchange Membrane Fuel Cells

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.

Structural and Electrical Characteristics of Gallium Tin Oxide Thin Films Prepared by Electron Cyclotron Resonance-Metal Organic Chemical Vapor Deposition

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.

Effect of deposition temperature on the formation of the corrosion-protective SnOx:F coating layer on SUS 316 bipolar plates for PEMFC

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.

Preparation of Fluorine Doped Zinc Tin Oxide Coating Layer on SUS 316 Bipolar Plates by ECR-MOCVD for PEMFC

Fluorine-doped zinc tin oxide (ZnSnOx:F) films on SUS316 are prepared by electron cyclotron resonance-metal organic chemical vapor deposition (ECR-MOCVD) in order to achieve the corrosion-resistant and low contact resistance bipolar plates for polymer electrolyte membrane (PEM) fuel cells. The prepared ZnSnOx:F films coated on SUS316 substrate are 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 of the electrochemical experiments are conducted in 1M H2SO4 + 2ppm HF solution at 70oC. The fluorine doping appears to be one of the critical process parameters on the formation of the corrosion-protective layer for PEMFC bipolar plates, as well as affecting the electrical properties of the films.

Electrical and optical properties of fluorine-doped tin oxide (SnOx:F) thin films deposited on PET by using ECR–MOCVD

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 × 10−3 Ω.cm and highest optical transmittance of 90% in the visible wavelength range from 380 to700 nm were observed at an H2/TMT mole ratio of 1.25, fluorine-doping amount of 1.3 wt.%, and deposition time of 30 min. 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 = 0.3198 nm.

Effect of hydrogen content on the ZnO thin films on the surface of polyethylene terephthalate substrate through electron cyclotron resonance-metal organic chemical vapor deposition

Zinc oxide thin films were deposited on polyethylene terephthalate (PET) substrate by the electron cyclotron resonance-metal organic chemical vapor deposition (ECR-MOCVD) method at room temperature with the addition of hydrogen to the reaction gas. Diethyl zinc (DEZn) as the source precursor, O2 as oxidizer and argon as carrier gas were used for the preparation of ZnO film. Scanning electron micrography and X-ray diffraction analyses revealed that the ZnO grains with size of ca. 20 nm had an elliptic cylindrical configuration and were highly c-axis-oriented. The hydrogen content strongly affected the crystallographic structure, electrical property, and composition, as well as the surface roughness of the zinc oxide films. The chemical composition and surface states of the films were further examined by RBS and XPS to find the reason for the different electrical resistivity with variation of H2/Ar ratio. It can be concluded that hydrogen content plays an important role in increasing the Hall mobility, hole concentration, and electron concentration in our experimental range.

Adhesion characteristics of copper thin film deposited on PET substrate by electron cyclotron resonance–metal organic chemical vapor deposition

The adhesion characteristics of Cu/C:H films on the pretreated PET (polyethylene terephthalate) substrate prepared by ECR–MOCVD with a periodic DC bias system were investigated in the aspect of surface energy, surface morphology, roughness, and adhesion force. For a chromo-sulfuric acid pretreatment, the surface roughness of PET substrate was increased up to a maximum value at 60 min of acid-soaking time, followed by a gradual decrease for longer acid-soaking times. The changes of surface energy by various pretreatment methods (such as Ar-ion implantation, O 2 plasma, chromo-sulfuric acid, and sandblasting) barely affected on the adhesion force because the pretreated PET was changed into hydrophobic surface through ECR-plasma polymerization of hfac (1,1,1,5,5,5-hexafluoro-2,4-pentandione) ligand of copper precursor. The acid pretreatment followed by ECR-deposition was confirmed as an effective method for the good adhesion of copper thin film on PET substrate at room temperature. The adhesion force of deposited metallic films primarily depended on the surface roughness of the pretreated substrate, and there was no strong correlation between the surface energy of the pretreated PET and the adhesion force of deposited Cu/C:H films.

Characteristics of Fluorine-Doped Tin Oxide Thin Films on Poly Ethylene Terephthalate (PET) Substrate

Fluorine-doped tin oxide (FTO) films on PET (Polyethylene Terephthalate) substrate were prepared by the electron cyclotron resonance-metal organic chemical vapor deposition (ECRMOCVD) under an Ar-O2-H2 atmosphere. The used tin and fluorine precursor are TMT (tetramethyltin) and sulfur hexafluoride (SF6), respectively. The hydrogen content plays an important role to control the optical and electrical characteristics of the films. The HF etching effect was clearly observed with increase of H2/TMT mole ratio, on the other hand the hydro-carbon deposition increased with decrease of H2/TMT mole ratio. Therefore the optimum H2 content can be determined by the counter balance effect between HF etching and hydro-carbon deposition. The obtained optimum SnO2: F thin films exhibited over 90 % of optical transmittance at wavelength range from 380 to 780 nm and c.a. 6×10-3 ohm ·cm of electrical resistivity at 1.25 H2/TMT mole ratio.

The effect of direct current bias on the characteristics of Cu/C:H composite thin films on poly ethylene terephthalate film prepared by electron cyclotron resonance–metal organic chemical vapor deposition

Cu/C:H composite films were prepared on poly ethylene terephthalate (PET) substrate at room temperature by the electron cyclotron resonance–metal organic chemical vapor deposition (ECR-MOCVD) coupled with a negative direct current (DC) bias system. The negative DC bias voltage applied around the substrate strongly affected the crystallographic structure and composition as well as the surface roughness of the copper films. The surface resistivity of films decrease sharply as the bias voltage increase up to about 5 μΩ-cm below which the resistivity remains almost constant in the range of − 900 to − 1700 V. Thus, the bias voltage appeared to be a critical deposition parameter for preparing copper films with low resistivity. With interfacial studies of Cu-PET, copper atoms are embedded into the polymer substrate during the growth process. Therefore, Cu/C:H composite films on PET with good interfacial properties could be prepared by ECR-MOCVD coupled with a (−)DC bias system.

Effects of Pretreatments of PET Substrate on the Adhesion of Copper Films Prepared by a Room Temperature ECR-MOCVD Method

Effects of various pretreatments on the adhesion of copper-coated polymer films were investigated. Copper-coated polymer films were prepared by an electron cyclotron resonance-metal organic chemical vapor deposition (ECR-MOCVD) coupled with a DC bias system at room temperature. PET(polyethylene terephthalate) film was employed as a substrate material and it was pretreated by industrially feasible methods such as chromic acid, sand-blasting, oxygen plasma and ion-implantation treatment. Surface characterization of the copper-coated polymer film was carried out by AFM(Atomic Force Microscopy) and FESEM(Field Emission Scanning Electron Microscopy). Surface energy was calculated by based on the value of the contact angle measured. The adhesion of copper/PET films was determined by a pull-off test according to ASTM D-5179. It was found that suitable pretreatment of the PET substrate was required for obtaining good adhesion property between copper films and the substrate. In this study the highest adhesion was observed in sand-blasting, and then followed by those of acid and oxygen plasma treatment. However, the effect of surface energy was insignificant in our experimental range. This is probably due to compensating the difference in surface energy from various pretreatments by exposing substrate to ECR plasma for 5 min or longer at the early stage of the copper deposition. Therefore, it can be concluded that surface roughness of the polymer substrate plays an important role to determine the adhesion of copper-coated polymer for the deposition of copper by ECR-MOCVD.