Highly efficient cathodoluminescent phosphors and screens for mid- and high-voltage field emission displays
Authors: Goldburt E. T. , Bolchouchine V. A. , Levonovitch B. N. , Sochtine N. P. 
Published: July 2002

The commercialization of field emission displays (FEDs) has been delayed despite optimistic promises in the mid 1990’s. Apparently, more time is needed to identify optimum solutions to the complex problems associated with fabrication, assembly, and operation of the displays. One of the reasons for this delay is that a majority of the development effort has been focused on the back plate with the traditional cold cathodes or other emitting matrix structures. As a result, the development of light-emitting anodes, i.e., the front phosphor plate or screen, was based on high-voltage cathode ray tube (CRT) phosphors [L. E. Tannas, Jr., Flat-Panel Displays and CRTs (Van Nostrand Reinhold Company, New York, 1985); V. L. Gerus, Fizicheskiye osnovy ELP (Fizmat Literatura-Nauka, 1993), p. 352]. According to published data, the FED screens are deposited with the photolithography techniques for RGB phosphor screen deposition used in CRTs. In addition, nonoptimized processing is used for aluminizing these standard high-voltage phosphor screens, again using the technology developed for CRTs. This yields a screen luminance of less than 150 cd/m2 and an unsatisfactory RGB luminous screen efficiency of about 1 lm/W at accelerating voltages less than 5 kV. Transfer of known CRT technologies and materials provided some economy of time in the short run to get FED programs started. However, in the case of novel FED device development, the past experience should be examined carefully and used wisely. The FED screens should have significantly better emission and power parameters, as well as maintenance [R. O. Petersen, Inf. Disp. 13, 22 (1997)]. As compared to other novel and traditional flat displays, FED displays, in our opinion, have the following advantages. A high excitation power density from 50 to 250 mW/cm2 can be achieved without activator quenching or device damage. The extremely high concentration of secondary cathodoluminescent excitation, 1022–1024 pairs/cm3 s, does not cause heat and electric breakdowns. High efficiency, over 10%, is standard as compared to low-efficiency and frequently nonradiative one-particle processes in Xe, Kr plasma, or organic semiconductor based displays. An instantaneous pixel pulse luminance of 106–107 cd/m2 allows a variety of addressing schemes of the display including HDTV applications. The phosphor’s luminescent decay times can be adjusted to enable image frequency generation of 50–100 Hz. This eliminates image flicker and RGB temporal defects on the FED screen. Adjustable linear or band emitters can be selected to provide a range of colors to match traditional PAL, SECAM, and NTSC standards, as well as HDTV systems. In this short review, we will present some of our recent results. The work covers new territory in the field of phosphor screen fabrication and maintenance. In particular, we report on the fabrication of highly efficient FED screens. We estimate their light output efficiency as a function of aluminum layer thickness and density, and discuss critical parameters associated with phosphor layer adhesion.