Study of erosion rate, erosion products, and arc velocity under transverse magnetic field in vacuum.

摘要

The advantages of the cathodic arc-coating method include high energy efficiency, high film deposition rates, and good film-to-substrate adhesion. The principal shortcoming of the arc-coating method is that macroparticles are deposited on the substrate as part of the film. The presence of the macroparticles in the coated film degrades film quality which is particularly severe when the deposition process relies on a reaction to form a compound material as the coating. In this case, the macroparticles contain unreacted metal cores which represent impurities in the coated film. This research attempts to identify methods to eliminate or reduce the formation of macroparticles in the coated film by reaching an understanding of the behavior of macroparticles and the angular distribution of erosion products.; A transverse magnetic field has been applied to control the arc motion. This reduces the cathode erosion rate and also the formation of macroparticles. The angular distributions of erosion products, i.e. metal ions and macroparticles, are measured to determine the optimum position for the specimens to be coated, and to better understand the cathode spot characteristics. The arc velocity is also measured to determine the effect of the transverse magnetic field on the cathode erosion rate.; The variation of the solid angle which the probe represents with respect to the cathode spot when it moves spirally over the cathode surface has been calculated, and it has been shown that the macroscopic measurements can be used to correlate with the microscopic phenomena of the cathode spot.; The cooling of macroparticles during the time of flight from the cathode spot to the substrate has been calculated taking into account evaporation and radiation.; In general, the low melting point materials produce large macroparticles and high melting point materials produce small ones. It is easier to reduce the number of macroparticles coated on the substrate for low melting point materials, such as Al and Cu, by applying a magnetic field than it is for high melting point materials. In other words, using a magnetically steered cathode spot can reduce production of large macroparticles more effectively than that of small ones.