Multilayer foils that react exothermically are a new class of nanostructured materials that can be used to solder or braze components together.  The multilayer foils, called NanoFoil, range in thickness from 20 to 200 microns and they contain hundreds of nanoscale layers that alternate between materials with large heats of mixing, such as Al and Ni. By inserting a free-standing NanoFoil between two solder (or braze) layers and two components, heat generated by the reaction of the foil melts the solder and consequently bonds the components. The joining process can be completed in less than one second, in air, and at room temperature. The use of NanoFoil as a local heat source eliminates the need for furnaces or hot plates, speeds soldering and brazing processes, and dramatically reduces the total heat that is needed. Thus, temperature-sensitive components and metals and ceramics can be joined without thermal damage, over small or large areas.

This presentation will first describe the vacuum deposition of NanoFoil and how one can control the energy, ignition and reactivity of these foils. Next, the use of NanoFoil as a local heat source for joining will be presented, with a particular focus on the bonding of sputtering targets to backing plates.  Predictions and measurements of heat transfer during the reactive joining process will be offered and the strength and uniformity of the resulting bonds will be identified. These true metallic bonds have less than 3% voiding and have enabled substantial increases in sputter rates compared to identical targets bonded with conventional methods, for both metallic and ceramic targets.

CrN coatings were prepared by magnetron sputtering with target-substrate orientations varying between 0° and 90° and N2 flow rates of 43, 40 and 30 sccm. The coatings were deposited on (111) Si wafers at a chamber pressure of 0.2 Pa for 1 hr. Initial results indicate that the target-substrate orientation to the incoming flux of ionized species has a strong influence on the microstructure, phase and preferred orientation of the crystallites in Cr-N coatings. The SEM studies of the film morphology showed a distinct change from coarser, less dense coating to smooth, dense and fine-grained morphology as a function of the changing orientation of the substrate, while the cross-sectional micrographs showed a columnar growth of the crystallites independent of substrate orientation. When the target-substrate angle was varied from 0° to 90°, the average roughness (Ra) decreased from 78 to 23 nm. We report on the details of the microstructural and chemical characterization of the films deposited in this study.

* Currently Program Manager, SBIR/STTR, National Science Foundation, Arlington, VA.

Niobium oxide was sputter-deposited reactively using a rotary magnetron and a new high-density plasma source. Both sources are of interest because of high target utilization with an enlarged plasma beam footprint.

The rotary magnetron in this study has a 125 mm diameter Nb metal target. From the reactive sputter hysteresis, the use of a plasma emission monitor is necessary for the deposition of stoichiometric niobia. Niobia films about 200 nm thick were deposited at oxygen flow rates that produced visibly absorbing to non-absorbing oxides.

A description of the high-density source and sputter configuration has been reported previously.¹ A remotely generated plasma beam of high density is focused onto a 100 mm diameter target. Deposition parameters were established to produce non-absorbing niobium oxide for films of about 350 nm thick.

The quality of the niobium oxide films were studied spectroscopically, ellipsometrically, and with XPS. Coating stress and density were determined. The dispersion curves from this work are compared to those reported in the literature of e-beam² and other magnetron³ deposited niobium oxide films.

This work (UCRL-ABS-224417) was performed under the auspices of the U.S. Dept. of Energy by Univ. of CA, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

¹R. Chow, M.A. Schmidt, A.W. Coombs, J. Anguita, M.J. Thwaites, Niobium Oxide Film Deposition Using a High-Density Plasma Source, SVC 49th Ann. Tech. Conf. Proc., Soc. of Vac. Coaters, 2006.

²O. Arnon, T.J. Chou, Wide band measurement of the refractive index of optical thin films during their deposition, Thin Solid Films, 91, 1982, pg 23-31.

³M.G. Krishna, A.K. Bhattacharya, Processing and size effects on the optical properties of sputtered oxide thin films, Materials Science and Engineering B, 86, 2001, pg 41-47.

Chromium doped carbon coatings produced by closed field unbalanced magnetron sputter ion plating have already demonstrated exceptional wear resistance combined with high load bearing capability^1,2. They have been adopted for use on a wide range of mechanical parts including some in harsh environments such as fuel injection components. The tribological properties of these coatings, and their electrically conducting nature offers further potential for exploitation, but in order to broaden the envelope of application as far as possible it may be necessary to reduce process times and costs further. In particular, the production of thin, high quality carbon films in short times, at very low cost, is of considerable interest for applications such as fuel cells. Faster deposition rates are needed to meet these requirements.

Modifications³ to the design of magnetrons has allowed operation of the magnetrons at much higher power. This has enabled deposition rates to be increased by up to three times. There is also scope to increase rates further. Coatings have been produced at different deposition rates and the tribological properties and film characteristics compared to those for coatings produced with standard magnetrons. High quality coatings were produced at the faster deposition rates and specific wear rates below 5x 10^-17 m³/Nm obtained from pin on disc testing at 80N load (1 to 2 GPa).

¹Stallard, J., Mercs, D., Teer, D.G. , and Shipway, P.H., A Study of the Tribological Behaviour of Three Carbon-Based Coatings, Tested in Air, Water and Oil Environments at High Loads. J Surf. And Coat. Tech., 2004, 177-178: 545-551.

²Field, S.K., Jarratt, M., Teer, D.G.. Tribological Properties of Graphite-Like and Diamond Like Carbon Coatings. J. Trib. Int., 2004, 37 : 949-956.

³Goruppa, A.A., Teer, D.G.; Current and Voltage Characteristics of the Novel High Power Density Magnetron. ICMCTF 2007, to be published.