Effect of Underlayer on Coalescence of Silver Islands Grown Byfiltered Cathodic Arc Deposition

For low-emissivity application on window glass, coalescenceof thin film silver islands is crucial for high transmittance in thevisible andhigh reflectance in the infrared. It is well known that theenergy of ions arriving at the substrate (kinetics) as wells as the typeof underlayer (thermodynamics) affect the nucleation and growth mode.Little is known about coalescence of silver islands synthesized byenergetic condensation, e.g., by filtered cathodic vacuum arc deposition.In this work, the effect of the underlayer on nucleation and growth ofsilver films deposited by filtered cathodic vacuum arc was investigatedby transmission electron microscopy (TEM) and atomic force microscopy(AFM). The results are compared with data obtained on magnetron sputteredfilms. It was found that uncoated and titanium-oxide-coated glass requiremore silver to achieve the same low value of sheet resistance than silveron zinc-oxide-coated glass. This can be associated with the energy ofinteraction between surface and silver atoms. Silver films made bycathodic arc deposition show an earlier onset of island coalescence andformation of short links. It was found that silver islands in energeticdeposition exhibit a reduced aspect ratio compared to evaporation andsputtering. A nominal 0.1 nm niobium underlayer increases the nucleationdensity and promotes coalescence of silver islands, however, a 0.2 nmlayer did not show these features, indicating the need for furtherstudies

Microstructure and thermal conductivities of suspension vacuum plasma sprayed YSZ coatings

To increase the efficiency of gas turbine, the turbine inlet temperature should increase. As the turbine inlet temperature increases, the heat load of thermal barrier coating increases. Suspension plasma spraying(SPS) was developed to enhance the performance of thermal barrier coating. Suspension allows nano-sized powders to be injected into the plasma flame, which has advantage of forming a variety of microstructures. However, there is a disadvantage of SPS that cannot be completely transmitted the enthalpy of plasma flame due to evaporation of solvent in the suspension, which causes decrement of coating formation rate. In this study, disadvantages of the suspension atmospheric plasma spraying(SAPS) can be solved by forming YSZ coatings through suspension vacuum plasma spraying(SVPS). The length of plasma flame in vacuum condition becomes longer, powders can stay longer inside the plasma flame. A variety of microstructured YSZ coatings were formed by SPVS at various spraying conditions. Microstructure of SVPS YSZ coatings were analyzed by SEM. Thermal conductivity of SVPS YSZ coatings were analyzed by laser flash method. Coating formation rate showe

A physics-based model of temperature-exposure-dependent interfacial fracture toughness of thermal barrier coatings

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Ion energy distribution functions of vacuum arc plasmas Ion energy distribution functions of vacuum arc plasmas

Abstract The velocity distribution function of vacuum arc ions can be measured by a time-of-flight technique similar to a method originally proposed by Yushkov. The measuring principle makes use of the welljustified assumption that the ion drift velocity from the cathode spot region to a collector is approximately constant. It is shown that the negative time derivative of the collector current is directly proportional to the ion distribution function provided that the time-averaged source intensity (i.e., emission of ions from cathode spots) is constant until the arc is rapidly switched off. In the experiment, arc termination took about 700 ns, which is much faster than the decay of the ion current measured at the collector placed in more than 2 meters distance from the cathode. The experimental distribution functions for most cathode materials show one large peak with a tail and one or more small peaks at higher ion velocities. The distribution functions for some other materials exhibit several peaks. No conclusive answer can be given about the nature of these peaks. Arguments are presented that the peaks are not caused by different charge states or plasma contamination but rather due to insufficiently averaged source fluctuations and/or acceleration by plasma instabilties. a Author to whom correspondence should be addressed; electronic mail: [email protected]

Effect of underlayer on coalescence of silver islands grown by filtered cathodic arc deposition Effect of underlayer on coalescence of silver islands grown by filtered cathodic arc deposition

Abstract For low-emissivity application on window glass, coalescence of thin film silver islands is crucial for high transmittance in the visible and high reflectance in the infrared. It is well known that the energy of ions arriving at the substrate (kinetics) as wells as the type of underlayer (thermodynamics) affect the nucleation and growth mode. Little is known about coalescence of silver islands synthesized by energetic condensation, e.g. by filtered cathodic vacuum arc deposition. In this work, the effect of the underlayer on nucleation and growth of silver films deposited by filtered cathodic vacuum arc was investigated by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The results are compared with data obtained on magnetron sputtered films. It was found that uncoated and titanium-oxide-coated glass require more silver to achieve the same low value of sheet resistance than silver on zinc-oxide-coated glass. This can be associated with the energy of interaction between surface and silver atoms. Silver films made by cathodic arc deposition show an earlier onset of island coalescence and formation of short links. It was found that silver islands in energetic deposition exhibit a reduced aspect ratio compared to evaporation and sputtering. A nominal 0.1 nm niobium underlayer increases the nucleation density and promotes coalescence of silver islands, however, a 0.2 nm layer did not show these features, indicating the need for further studies.

Ion energy distribution functions of vacuum arc plasmas

The velocity distribution function of vacuum arc ions can be measured by a time-of-flight technique similar to a method originally proposed by Yushkov. The measuring principle makes use of the well-justified assumption that the ion drift velocity from the cathode spot region to a collector is approximately constant. It is shown that the negative time derivative of the collector current is directly proportional to the ion distribution function provided that the time-averaged source intensity (i.e., emission of ions from cathode spots) is constant until the arc is rapidly switched off. In the experiment, arc termination took about 700 ns, which is much faster than the decay of the ion current measured at the collector placed in more than 2 meters distance from the cathode. The experimental distribution functions for most cathode materials show one large peak with a tail and one or more small peaks at higher ion velocities. The distribution functions for some other materials exhibit several peaks. No conclusive answer can be given about the nature of these peaks. Arguments are presented that the peaks are not caused by different charge states or plasma contamination but rather due to insufficiently averaged source fluctuations and/or acceleration by plasma instabilities

Bias and self-bias of magnetic macroparticle filters for cathodic arc plasmas

Curved magnetic filters are often used for the removal of macroparticles from cathodic arc plasmas. This study addresses the need to further reduce losses and improving plasma throughput. The central figure of merit is the system coefficient Kappa defined as filtered ion current normalized by the plasma-producing arc current. The coefficient Kappa is investigated as a function of DC and pulsed magnetic field operation, magnetic field strength, external electric bias, and arc amplitude. It increases with positive filter bias but saturates at about 15 V for relatively low magnetic field (~10 mT), whereas stronger magnetic fields lead to higher Kappa with saturation at about 25 V. Further increase of positive bias reduces Kappa. These findings are true for both pulsed and DC filters. Bias of pulsed filters has been realized using the voltage drop across a self-bias resistor, eliminating the need for a separate bias circuit. Almost 100 A of filtered copper ions have been obtained in pulsed mode, corresponding to Kappa approximately equal to 0.04. The results are interpreted by a simplified potential trough model

Bias and self-bias of magnetic macroparticle filters for cathodic arc plasmas

Curved magnetic filters are often used for the removal of macroparticles from cathodic arc plasmas. This study addresses the need to further reduce losses and improving plasma throughput. The central figure of merit is the system coefficient Kappa defined as filtered ion current normalized by the plasma-producing arc current. The coefficient Kappa is investigated as a function of DC and pulsed magnetic field operation, magnetic field strength, external electric bias, and arc amplitude. It increases with positive filter bias but saturates at about 15 V for relatively low magnetic field (~10 mT), whereas stronger magnetic fields lead to higher Kappa with saturation at about 25 V. Further increase of positive bias reduces Kappa. These findings are true for both pulsed and DC filters. Bias of pulsed filters has been realized using the voltage drop across a self-bias resistor, eliminating the need for a separate bias circuit. Almost 100 A of filtered copper ions have been obtained in pulsed mode, corresponding to Kappa approximately equal to 0.04. The results are interpreted by a simplified potential trough model

Coalescence of Nanometer Silver Islands on Oxides Grown by Filtered Cathodic Arc Depostion

This report talks about Coalescence of Nanometer Silver Islands on Oxides Grown by Filtered Cathodic Arc Depostio