STRUCTURAL AND ELECTROLUMINESCENT CHARACTERISTICS OF SPUTTERED SRS-CETHIN-FILMS BY RAPID THERMAL-PROCESS

Thin film electroluminescent (EL) structure of Y-2,O-3,/SrS:Ce/BaTiO3, has been deposited by rf-magnetron reactive sputtering and subsequent ly submitted to various thermal treatments. The effects of rapid therm al process (RTP) on the structural and EL characteristics of SrS:Ce th in films have been investigated, and compared with the results obtaine d by the conventional furnace. After the post-deposition annealing, th e SrS film has the tendency to recrystallize preferentially in the (20 0) plane. The higher RTP temperature also results in the larger grain size of SrS. Auger measurements show that the RTP method can overcome the nonstoichiometry and interdiffusion problems encountered in the fu rnace-treated sample. It was found that the EL peaks gradually recover ed to the band transitions of Ce3+ ions (475 and 530 nm) in the SrS cr ystal field as the RTP temperature increased from 650 to 850 degrees C . The threshold voltage can be further reduced to 150 V and the bright ness increases eight times as much as the optimum furnace-treated devi ce. The improvements in EL performance are due to the facts that the R TP can enhance the crystallinity of SrS, alleviate oxygen-induced defe ct centers from interdiffusion, activate Ce3+ ions in phosphor, and yi eld a blue shift in emission colors. (C) 1997 Elsevier Science S.A.