In this paper, to clarify the thermal effect of the bridge for long lifetime contacts, the effects of heat conductivity on bridge break at different material contact pairs were discussed experimentally. To examine the relationship between the bridge and material, the electrode materials of the anode and the cathode were chosen as the same and the different material pairs in this experiment. Ag, AgPd60 and Pd were chosen as the electrode materials, because Ag, AgPd60 and Pd had the different thermal diffusivity. Firstly, the voltage waveforms in the bridge with different material pair were compared to the voltage waveform with the same material pair case. Secondary, the effects of heat conductivity on the break of bridge were discussed. In the results, the bridge voltage waveform depends on the electrode material at anode side. The length of the bridge at bridge break depends on the heat conductivity of the electrode material at anode side. This study provides the basic considerations on the thermal condition of the bridge break.

Electron field emission from polycrystalline diamond films has been investigated. Electron emission was measured locally at randomly chosen point on a diamond film fabricated by a microwave plasma chemical deposition method. In the original film, there were some points with a large emission current where flaws were found after the measurements, some points with a small and stable emission current without any flaw, and the other points with no emission. At the point of no emission, the film was electrically broken down by applying a high voltage. After the intentional breaking down, a small and stable emission always appeared there with no flaw. The maximum emission current extracted from an emission site was usually 1µA with no structural flaw found after the measurements. By using a simple model of emission site consisting of a core conductor embedded in insulator, the limitation of emission current is estimated from heating by the current and heat transfer to the insulator.