Thin ZnS:Cu,Ga and ZnO:Cu,Ga film phosphors

A new technique for electro- and cathodoluminescent screen fabrication with the application of a new method of doping ZnS:Cu and ZnO:Cu thin film phosphors is proposed. Thin films of ZnS:Cu were grown by electron-beam evaporation (EBE) from a ZnS:Cu target on substrates heated to 150-200°C, and the Cu concentration in the target was varied from 0.06 to 0.25 wt.%. BaTiO₃ and sapphire single crystal substrates were used. The film thickness varied from 0.6 to 9 μm. Parameters of ZnS:Cu films grown by EBE were modified by the use of non-vacuum annealing at 700-1000°C in S₂-rich or O₂-rich atmosphere both with and without Ga co-doping. The measurement of electroluminescent (EL) and cathodoluminescent (CL) parameters, as well as X-ray diffraction (XRD) techniques and atomic force microscopy (AFM) were used for this research. The EL ZnS:Cu,Ga blue color emission film with a luminance of 30 cd/m² and green (yellow) color emission film with a luminance of 800 cd/m² were obtained. Devices with such films have a threshold voltage of 10 V. The CL luminance was 200 cd/m² for ZnS:Cu,Ga and 1100 cd/m² for ZnO:Cu,Ga films at 300 K and 3700 cd/m² for ZnO:Cu,Ga films at 77 K. The films show a deeper green color than commercial phosphors. Clarification that gallium co-doping affects the luminance, since Ga influences on recrystallization process, has been carried out.