Luminescence improvement of SrS:Ce thin films by rapid thermal annealing: Evidence of energy-transfer model for SrS:Ce electroluminescent devices

Abstract

SrS:Ce thin films and electroluminescent (EL) devices have been deposited on Si substrate using the rf magnetron reactive sputtering method and subsequently submitted to various thermal treatments. The effects of rapid thermal annealing (RTA) on the properties of SrS:Ce thin films and EL devices have been investigated and compared with results obtained using a conventional furnace. Subsequently, the higher temperature of RTA treatment not only remarkably improves the crystallization of SrS phosphor film in the (200) plane but also reduces oxygen interdiffusion problems and enhances both the interface states (Eit) as well as bulk trap (Ebt) densities. These effects all are important factors in yielding brighter electroluminescence. Furthermore, a physical band model based on energy-transfer concept is proposed to elucidate the electroluminescent mechanism of SrS:Ce EL devices. All evidence reveals that the efficient luminous center formed by the Ce atom associated with the Ebt bulk trap is the basis of this energy-transfer model in SrS:Ce EL devices.