CHAPTER 3
 EXPERIMENTAL PROCEDURE

 3.1 Introduction

 In this chapter, the procedures for fabricating half-stack and full-stack ZnS:REF3

thin film devices will be described. Characterization methods, including electrical and

optical characterization, will also be discussed.

 3.2 Device Fabrication

3.2.1 Substrates

 The substrates are 7059 glass coated with transparent conductor indium tin oxide

(ITO) and insulator aluminum titanium oxide (ATO) deposited using atomic layer

deposition (ALD) by Planar Systems, Inc. Before phosphor layer deposition, the

substrates were cleaned with methanol followed by 6 minute ozone clean.

3.2.2 Phosphor Film Deposition

 The ZnS:REF3 layers (RE=rare earth, ErF3, TmF3 were used in this study) were

deposited by RF magnetron sputtering using independent 2 (5 cm) ZnS and REF3

sources. The ZnS target was bulk polycrystalline ZnS purchased from Morton Thiokol,

Inc., and the REF3 targets were purchased from Target Materials, Inc. The sputtering

system is designed to simultaneously operate 3 RF-sputtering guns which make it

possible to co-sputter elements and compounds from separate targets. In this study, the

concentration of rare earth was controlled by the power and duty cycle of the ZnS:REF3

versus pure ZnS source.