Fabrication and cathodoluminescent properties of the ZnO–Cu,Ga and ZnS–Cu,Ga film phosphors V. S. Khomchenko V. E. Rodionov V. P. Papusha G. S. Pekar P. M. Lytvyn Yu. A. Tzyrkunov T. G. Kryshtab Abstract — A novel technique for cathodoluminescent screen fabrication using a new method of film phosphor doping has been developed. The crystalline structure and morphology of the films were investigated. Cathodoluminescence spectra were measured at different excitation levels and tempera- tures (300 and 77 K). The luminance is 200 cd/m 2 for ZnS:Cu,Ga and 1100 cd/m 2 for ZnO:Cu,Ga films at a temperature of 300 K and 3700 cd/m 2 for ZnO:Cu,Ga film at a temperature of 77 K. The films show more saturated green color than commercial phosphors. Keywords — Zinc sulfide, cathodoluminescence film, phosphor, surface properties, zinc oxide catho- doluminescence. 1 Introduction Film phosphors are known to have higher contrast and reso- lution than powder phosphors. 1 However, a limitation of cathodoluminescent (CL) films is lower brightness as com- pared with that of powder screens. As a result, the film phos- phors cannot compete with powder phosphors for emissive display applications, and further improvement in the film parameters is required. ZnS and ZnO were selected as host materials because the powder ZnS and ZnO phosphors show high efficiency and fast decay time. Thus, we intended to fabricate ZnS and ZnO film phosphors with better CL parameters compared with similar powder screens. In this work, a new film-phosphor technology is pro- posed for the fabrication of film screens with high bright- ness and better color coordinates, making them promising. The structural characteristics of ZnS:Cu,Ga and ZnO:Cu,Ga films depending on fabrication conditions as well as CL properties of these samples at the temperatures of 300 and 77 K were investigated. 2 Experimental details Sputtering, chemical-vapor deposition, or annealing of ZnS phosphor films in air has been commonly used for ZnO thin- film growth. We have prepared such films by electron-beam evaporation (EBE) of ZnS:Cu target on a single-crystal sap- phire substrate with further post-treatment. The peculiarity of this post-treatment technique is the Ga doping, which takes place simultaneously with the annealing of phosphor films. The substrate temperature during the deposition process was about 150-200°C and the film thickness was 9 μm. The concentration of Cu in a target varied from 0.06 to 0.12 wt.%. The parameters of the film phosphors were significantly modified by the application of special non-vac- uum high-temperature treatment at temperatures of about 700–800°C in a suitable atmosphere. The annealing atmos- phere contained sulfur for ZnS:Cu film preparation and oxygen for ZnO:Cu film preparation. The annealing atmos- phere was prepared by decomposition of a sulfur-containing or oxygen-containing compound for each type of film, respectively. For Cu charge compensation, the films were doped with Ga from the Ga melt during film annealing. 2 It is the first time that such a method was used for CL films. The Al layer with a thickness of 0.1 μm was evaporated directly onto a phosphor film after annealing. CL characteristics were measured in the demountable cathode-ray tube with a variable beam current from 0 to 500 μA. The phosphor screen samples were excited by an electron beam at the accelerating voltage of 50 kV over the 2.8 × 2.1 cm 2 area scanned. The standard television raster was formed on the screen (at 15.625-kHz horizontal and 50-Hz vertical scanning frequencies). The calculated effec- tive ionization depth of electrons was 4.15 μm for ZnS film and 2.85 μm for ZnO film at an accelerating voltage of 50 kV. A phosphor film thickness of 9 μm creates favorable condi- tions for the transfer of effective energy from the exciting electron beam to the phosphor and provides excitation of the film’s deep uniform regions, which are situated far from both the film surface and the substrate surface. The crystal- line structure and morphology of films were investigated by the X-ray diffraction (XRD) technique (Cu K α line) and atomic-force microscopy (AFM). 3 Results and discussion Polycrystalline ZnS in a target had a wurtzite crystal struc- ture before EBE. After EBE, only a sphalerite type of ZnS Revised version of a paper presented at the Tenth SID Advanced Display Technologies Symposium (ADT ‘01) held September 18-21, 2001, in Minsk, Republic of Belarus. V. S. Khomchenko, V. E. Rodionov, V. P. Papusha, G. S. Pekar, and P. M. Lytvyn are with the Institute of Semiconductor Physics (ISP), NAS of Ukraine, 45 Pr. Nauky, 03028 Kyiv, Ukraine; telephone +38-(044)-2657351, fax -2656187, e-mail: vsk@isp.kiev.ua. Yu A. Tzyrkunov is with the Special Technological and Design Office of ISP, Kyiv, Ukraine. T. G. Kryshtab is with the Department of Materials Sciences, ESFM-IPN, Mexico.  Copyright 2003 Society for Information Display 1071-0922/03/1101-0021$1.00 Journal of the SID 11/1, 2003 21