We have investigated systematically the interaction between Er

3+

ions in ZnS:Er

3+

and ZnS:ErF

3

thin films. In this paper

we will investigated the effect of annealing on the AC electroluminescence (ACEL) of ZnS:ErF

3

thin films.The devices arc ITO-Y

2

O

3

-ZnS:ErF

3

-Al structure.The devices were prepared by sequential depositions of Y

2

O

3

insulating layer

ZnS:ErF

3

emission iaytr and Al electrode onto an indium tin-oxide(lTO) coated glass plate. The deposition of Y

2

O

3

and ZnS:ErF

3

layers were carried out by electron-beam evaporation.The thickness of Y

2

O

3

and ZnS:ErF

3

layers are 300nm and 500nm

respectively. Before Al electrode were evaporated

the samples were annealed in N

2

atmosphere. The annealing conditions were 200℃

300℃

400℃ and 500℃ for two hours

and 2

4

6

8

10 an d12 hours at 500℃

respectively.