Ichimatsu Abiko

ZnS:Mn Thin Film Electroluminescent Devices Having Doubly-Stacked Insulating Layers

ZnS:Mn thin film electroluminescent devices having doubly-stacked insulating layers have been developed. The insulating layer consists of electron-beam evaporated Ta2O5, and rf-magnetron sputtered SiO2 stacked layers. It is concluded that the thick semi-insulating Ta2O5 films (1000 nm) deposited on both sides of the ZnS:Mn active layer act as a carrier injctor for electroluminescence and the thin insulating SiO2 films (80 nm) inserted between the electrodes and Ta2O5 films act as a carrier limiter. The breakdown voltage margin defined by (Vbd-Vth)/Vth was improved from 15% to more than 80% by introducing thick semi-insulating Ta2O5 films.

Preparation of Plasma Chemical Vapor Deposition Silicon Nitride Films from SiH2F2 and NH3 Source Gases

Fluorinated silicon nitride films are prepared by plasma chemical vapor deposition (PCVD) of the difluorosilane (SiH2F2)-ammonia (NH3) system. The films deposited with varied gas-phase composition were characterized by means of infrared spectroscopy (IR) and Auger-electron spectroscopy (AES). It is shown that the deposition rate, refractive index and density of silicon nitride films depend on the SiH2F2-NH3 ratio of the input gases. It is further shown that the stress, resistivity and dielectric breakdown strength do not depended on it. The resistivity and breakdown strength were observed to be as high as 1016 Ωcm and 5 MV/cm, respectively.

Difference in Electroluminescent ZnS:Tb, F Thin Films Prepared by Electron-Beam Evaporation and RF Magnetron Sputtering

To clarify the difference in ZnS:Tb,F films fabricated by electron-beam evaporation (EB) and by rf magnetron sputtering (SP), the doping condition of Tb and F ions was investigated by electron probe micro analysis and secondary ion mass spectroscopy. The F/Tb atomic ratio of 3 and EL spectra for EB films are found to be hardly affected by annealing. As the model for luminescent centers, it is proposed that the Tb and F ions are substituted for Zn and three S ion sites, respectively, with two Zn vacancies for satisfying charge compensation. For the SP films, interstitial F ions are released from ZnS film and Tb-F complex centers are formed by annealing.

Effects of Annealing on ZnS:Tb, F Electroluminescent Thin Films Prepared by rf Magnetron Sputtering

The effects of annealing on sputtered ZnS:Tb, F thin films is investigated by electron probe microanalysis, secondary ion mass spectroscopy and X-ray photoelectron spectroscopy. It is shown that the annealing decreases the F/Tb atomic ratio from 4 to 1, due to the release of F atoms. It is concluded that many of the F ions not contributing to the formation of luminescent centers with Tb ions exist in as-sputtered film and that efficient Tb-F complex centers are formed by annealing at over 400°C. Luminance is enhanced by increasing the Tb-F complex centers and decreasing the hot-electron scattering centers of the F ions.