High field characteristics of thin-film metal electrodes

Abstract

In order to investigate prebreakdown and breakdown characteristics of micrometric vacuum gaps relevant to field emission displays, a specially designed thin film electrode structure, easy to fabricate, was developed to closely simulate electrode gaps in field emission displays (FEDs). An extra-low light detection three-dimensional-imaging system using an intensified charge-coupled device camera was used to diagnose and record the different prebreakdown phases and the breakdown between planar metal film electrodes. Experimental results showed that the prebreakdown activity occurred mostly along the edge of the smaller diameter electrode and obeyed Fowler–Nordheim behavior. Breakdown of the gap at relatively larger gap distances (750 μm) caused damage to the thin-film electrodes; there was no significant damage for small gap distances (250 μm). The extent of electrode damage strongly depended on the film deposition temperature and was believed to be caused by the high-energy electron bombardment. The hold-off voltage of thin-film vacuum gaps was relatively high (>18.0 kV for a Ni/Cr 750 μm gap) which could be improved significantly by direct current glow discharge treatment. The insulation capability of such a vacuum gap was mainly limited by the edge effect and the thin-film quality. The high field characteristics of micrometric thin-film gaps, relevant to FEDs, are reported for the first time in the literature. These results can be used to define the theoretical limits to which actual gaps can be stressed in vacuum microelectronic devices and provide a basis for the design of the phosphor anode and the gate edges of the FEAs.