Spacer visibility problem in field emission displays due to surface contamination

Spacer visibility is a critical issue in field emission displays (FEDs). Many reasons can lead to visible spacers, such as charging due to secondary electron emission under electron bombardment. In this paper, we will present results on spacer visibility due to chemical contamination on the spacer surface. We have identified Na contamination as the cause for the white spacer problem observed in the early developing stage of FED. The diffusion of Na from spacers to its adjacent cathode area during field emission operation caused higher field emission current from those field emitters. We believe the higher emission is due to the temporary gettering effect from the Na species, which cleaned the local field emitters. We have also found the existence of Pb on the spacer surface could create the dark spacer problem. To avoid any spacer visibility problem, the spacer surface must be kept clean. Any post clean procedure used to clean the surface should not leave any trace of elements such as Na, or Pb.