CHAPTER 5
 CONCLUSION

 The effects on RF magnetron sputter deposited ZnS:ErF3 and ZnS:TmF3 alternating

current thin film electroluminescent (ACTFEL) devices of a single (half-stack device)

versus both a top and bottom dielectric layer (full-stack device) has been investigated.

The half-stack device was formed by depositing Al dot contacts directly on the doped

ZnS phosphor film. For full-stack devices, a BaTa206 (BTO) film was first deposited as a

top insulator, followed by deposition of the Al dot contacts. The half-stack device was

found to have lower turn-on voltages (180V vs. 220V for full-stack) in as deposited

ZnS:ErF3 ACTFEL devices. In addition, the half-stack device was also found to increase

the infrared B40 brightness by a factor of 10 over full-stack devices. Both external and

internal conduction charge were shown to increase for half versus full stack devices,

suggesting that this was the origin of the larger brightness. The effects on EL brightness

and spectral distribution of annealing for one hour in nitrogen at 4250C was studied for

ZnS:ErF3 films. Compared to as-deposited films, annealed devices showed improved

infrared intensity by 35% and lower the turn-on voltages by 30V. Again, increased

external conduction and internal charge was the main reason for the improved brightness.

 Similar parameters were tested for ZnS:TmF3 half and full stack devices prepared

in a similar fashion. The trends for both ZnS:TmF3 and ZnS:ErF3 ACTFEL devices were

similar. Half-stack devices exhibit a 40V lower turn-on voltage and a 3.5 times higher

infrared signal versus full stack devices, consistent with larger external conduction and

internal charges in half-stack devices.