Characterization of the mechanical and thermal interface of copper films on carbon substrates modified by boron based interlayers

The manipulation of mechanical and thermal interfaces is essential for the design of modern composites. Amongst these are copper carbon composites which can exhibit excellent heat conductivities if the Cu/C interface is affected by a suitable interlayer to minimize the Thermal Contact Resistance (TCR) and to maximize the adhesion strength between Cu and C.In this paper we report on the effect of boron based interlayers on wetting, mechanical adhesion and on the TCR of Cu coatings deposited on glassy carbon substrates by magnetron sputtering. The interlayers were 5?nm thick and consisted of pure B and B with additions of the carbide forming metals Mo, Ti and Cr in the range of 5?at.% relative to B. The interlayers were deposited by RF magnetron sputtering from either a pure B target or from a composite target. The interlayer composition was checked by Auger Electron Spectroscopy and found to be homogenous within the whole film.The system C-substrate/interlayer/Cu coating was characterized in as deposited samples and samples heat treated for 30?min at 800?°C under High Vacuum (HV), which mimics typical hot pressing parameters during composite formation. Material transport during heat treatment was investigated by Secondary Ion Mass Spectroscopy (SIMS). The de-wetting and hole formation in the Cu coating upon heat treatment were studied by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The adhesion of the Cu coating was evaluated by mechanical pull-off testing. The TCR was assessed by infrared photothermal radiometry (PTR). A correlation between the adhesion strength and the value of the TCR which was measured by PTR was determined for as deposited as well as for heat treated samples.     

Photothermal Evidence of Laterally Inhomogeneous Interfacial Thermal Resistance in Copper-Coated Carbon Samples

In this study, the heat transport in copper?Ccarbon flat model systems was studied by frequency-dependent photothermal radiometry (PTR). The samples consist of Cu films of about 1???m thickness deposited by magnetron sputtering on vitreous carbon (Sigradur). Particular interest was devoted to the influence of interface defects on the interfacial thermal conductance (or resistance) of the CuC systems. The PTR data were analyzed in the frame of a heat diffusion equation for one- and three-dimensional heat transport. By comparing PTR signals from as-prepared and from heat-treated samples, the lateral inhomogeneities of the interfacial thermal conductance could be quantified. The measured phase differences were analyzed in the scope of a model where a small part of the surface area has a different interfacial thermal conductance than the major part of the surface.     

Simultaneous Measurement of Local Magnetic and Thermal Parameters by Thermal Wave Scanning Microscopy

To characterize magnetic materials on nanoscales, a new technique has been developed which is based on the combination of two scanning thermal near-field techniques: the thermally modulated ferromagnetic resonance induced by the probe of a scanning thermal wave microscope and the detection of the 3?? signal from the same thermal probe. The simultaneous detection of the thermally modulated microwave absorption and of the 3?? response of the nanoprobe offers a means to control the thermal contact between probe and sample during scans across the sample. In this contribution, the experimental setup is described and results of measurements conducted on Fe-based structures deposited on a MgO substrate are presented.     

Sputter deposition of thin films on different substrate materials analyzed by means of modulated IR radiometry

Modulated IR radiometry, which is usually applied to sputter-deposited thin films and coatings, to determine the thermal transport properties of the thin films, is applied in this work to analyze the effects of different substrate materials and the effects of the interface coating-substrate on the resulting multi-layer system. For this purpose, a small number of ZrN films of different thickness were deposited on different substrate materials (stainless steel, Si, and glass) and were analyzed with the help of modulated IR radiometry, using heating modulation frequencies in the range from 1 Hz to 100 kHz, allowing depth-resolved thermal measurement from the sub-micron range to the millimeter range. The effects of pre-treatment of the substrates and of the interface between thin films and substrate were also analyzed. Compositional and structural properties of the thin films were obtained by RBS, XRD, and SEM.Preliminary results on the effects of substrates of limited thickness and three-dimensional heat transport, at the transition from coatings of good thermal transport properties to substrates of low thermal transport properties, are reported. A biasing effect related to the deposition process was also identified.     

Synthesis of Na0.5Bi0.5TiO3 anisotropic particles with grain orientation by conversion of Na0.5Bi4.5Ti4O15 crystals

Abstract

A novel method for synthesizing Na_0.5Bi_0.5TiO₃ (BNT) anisotropic particles with grain orientation is reported. Anisotropically shaped particles of BNT were prepared by conversion of Na_0.5Bi_4.5Ti₄O₁₅ (NBT15) single crystals. Platelet NBT15 was produced by molten-salt synthesis. They were converted to BNT by second molten-salt synthesis at 800—1200 ?C. NBT15 single-crystal platelets were transformed into platelet particles of polycrystalline BNT. The reaction is topotaxial, those recrystallized BNT were oriented with (h 0 0) plane parallel to the platelet. The use of converted BNT particles as seed was confirmed by performing templated grain growth (TGG) of BNT with 5% grain-oriented, anisotropic particles of BNT.     

Characterization of the mechanical and thermal interface of copper films on carbon substrates modified by boron based interlayers

The manipulation of mechanical and thermal interfaces is essential for the design of modern composites. Amongst these are copper carbon composites which can exhibit excellent heat conductivities if the Cu/C interface is affected by a suitable interlayer to minimize the Thermal Contact Resistance (TCR) and to maximize the adhesion strength between Cu and C.In this paper we report on the effect of boron based interlayers on wetting, mechanical adhesion and on the TCR of Cu coatings deposited on glassy carbon substrates by magnetron sputtering. The interlayers were 5 nm thick and consisted of pure B and B with additions of the carbide forming metals Mo, Ti and Cr in the range of 5 at.% relative to B. The interlayers were deposited by RF magnetron sputtering from either a pure B target or from a composite target. The interlayer composition was checked by Auger Electron Spectroscopy and found to be homogenous within the whole film.The system C-substrate/interlayer/Cu coating was characterized in as deposited samples and samples heat treated for 30 min at 800 °C under High Vacuum (HV), which mimics typical hot pressing parameters during composite formation. Material transport during heat treatment was investigated by Secondary Ion Mass Spectroscopy (SIMS). The de-wetting and hole formation in the Cu coating upon heat treatment were studied by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The adhesion of the Cu coating was evaluated by mechanical pull-off testing. The TCR was assessed by infrared photothermal radiometry (PTR). A correlation between the adhesion strength and the value of the TCR which was measured by PTR was determined for as deposited as well as for heat treated samples.     

Synthesis of Na0.5Bi0.5TiO3 anisotropic particles with grain orientation by conversion of Na0.5Bi4.5Ti4O15 crystals

A novel method for synthesizing Na_0.5Bi_0.5TiO₃ (BNT) anisotropic particles with grain orientation is reported. Anisotropically shaped particles of BNT were prepared by conversion of Na_0.5Bi_4.5Ti₄O₁₅ (NBT15) single crystals. Platelet NBT15 was produced by molten-salt synthesis. They were converted to BNT by second molten-salt synthesis at 800–1200 °C. NBT15 single-crystal platelets were transformed into platelet particles of polycrystalline BNT. The reaction is topotaxial, those recrystallized BNT were oriented with (h 0 0) plane parallel to the platelet. The use of converted BNT particles as seed was confirmed by performing templated grain growth (TGG) of BNT with 5% grain-oriented, anisotropic particles of BNT.