Though Active Matrix displays used on portable computers produce high quality flat displays, the yield from the manufacturing process is low, and the cost of manufacture significantly higher that the cathode-ray tube. The largest active matrix display in commerical production is only 15 inches, compared to 45 inches for the humble cathode ray.

Now Nalin Kumar and Chenggang Xie in Texas have developed a new method of making a flatter cathode tube display in Patent 5675216.

Their display consists of a layer of conductive material and a layer of amorphic diamond film. The latter functions as a low effective work-function material, deposited over the conductive material to form emission sites. The emission sites each contain at least two sub-regions having differing electron affinities. This is the first patent awarded that uses a amorphic diamond film in a cathode.