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

We present an improved liquid crystal microthermography technique for the detection of defects in large area field emission cathode arrays. Defects can cause electrical leakage paths, leading to localized heating at the defect location. The thermal gradients at these hot spots can be detected by liquid crystal microthermography, but, the direct placement of the liquid crystal is a two step process. First the liquid crystal is deposited by spin coating the device and the liquid crystal has to be removed from the device after the test. This process, apart from being time consuming, can lead to contamination of the test device. In this article, we present an improved liquid crystal microthermography technique for the detection of hot spots in field emitter arrays. The improvement is obtained by hermetically sealing the liquid crystal material inside a packaged assembly made from a glass support and a thin plastic membrane. We have used the new method for the detection of hot spots in large area field emission cathode arrays. This technique provides accurate detection of hot spot locations caused by leakage currents as low as 100 μA.