The appearance of discharge near the cathode surface in a vacuum-arc-deposition apparatus is observed when the pressure is increased gradually from 0.1 to 100Pa, with applied voltage held at DC 1, 180V. The result shows that the glow discharge appears at pressures above 1Pa, and then changes to arc discharge. This phenomenon is explained by the glow-to-arc transition mechanism due to the increase of the discharge current.
Arc transition probability is measured as a function of pressure (0.01-100Pa) with constant applied voltages of 590 and 1, 180V, the cathode materials being Al, Ti, and C, and the introducing gases being Ar and N₂. The result shows that (1) the arc transition occurs at higher pressure and with higher applied voltage. (2) The transition with Al cathode occurs at lower pressure than with Ti cathode. (3) The transition N₂ gas occurs at lower pressure than in Ar gas.
The influence of cathode material in Ar gas on the arc transition probability is qualitatively interpreted by comparing the melting points of the materials. The influence in N₂ gas is qualitatively interpreted by examining whether a compound grows on cathode surface or not, and whether the compound is electrically conductive or not.