An improved method for detecting hot spots in field emission cathode arrays

We present an improved liquid crystal microthermography technique for the d etection of defects in large area field emission cathode arrays. Defects ca n cause electrical leakage paths, leading to localized heating at the defec t location. The thermal gradients at these hot spots can be detected by liq uid crystal microthermography, but, the direct placement of the liquid crys tal is a two step process. First the liquid crystal is deposited by spin co ating the device and the liquid crystal has to be removed from the device a fter the test. This process, apart from being time consuming, can lead to c ontamination of the test device. In this article, we present an improved li quid crystal microthermography technique for the detection of hot spots in field emitter arrays. The improvement is obtained by hermetically sealing t he liquid crystal material inside a packaged assembly made from a glass sup port and a thin plastic membrane. We have used the new method for the detec tion of hot spots in large area field emission cathode arrays. This techniq ue provides accurate detection of hot spot locations caused by leakage curr ents as low as 100 mu A. (C) 1999 American Institute of Physics. [S0034- 67 48(99)04110-6].