Electroluminescence of ZnS Lumocen Devices Containing Rare-Earth and Transition-Metal Fluorides

Abstract

ZnS LUMOCEN (luminescence from molecular centers) films typically 2000-Å thick doped with rare-earth and transition-metal fluorides have been fabricated by vacuum coevaporation. Details of the fabrication techniques are presented for the 12 fluorides studied: PrF3, NdF3, SmF3, EuF3, TbF3, DyF3, HoF3, ErF3, TmF3, YbF3, CrF3, and MnF2. Concentration dependence of the brightness has been investigated for the ZnS/TbF3 device, the maximum occurring at 1.8 at.% Tb. Studies of brightness as a function of input power indicate that the ZnS/TbF3 device is the brightest with 50 foot-lamberts readily obtained. The power efficiency for ZnS:TbF3 is about 10−4. Emission spectra of the devices have been measured from 0.35 to 1.1 μ and related to known energy level schemes where possible. The intensity distributions of the spectra generally differ from those obtained by doping ZnS with the bare ions; the ZnS:CrF3 device yields a spectrum radically different from any Cr3+ luminescence previously investigated.

Line Spectrum Emission of Eu-Activated ZnS

“…Furthermore, taking into account the broadening due to the low resolution of the spectral apparatus used in our measurements (the spectral band width of the monochromator is about 0.017 eV), it is reasonable to assume that line emission of trivalent Eu-centres takes place. The peak positions and relative band intensities differ partly from those presented in [9], The strongest line in our spectrum (E = 2.27 eV) is almost absent in [9] and the 2.10 eV (592 nm) line is much stronger than the band at 587.5 nm registered by those authors. Instead of the most intensive band in [1] at 611 nm we obtain only a deformation of the emission curve.…”

“…It is also reported that Eu-doped ZnS does not exhibit lumines cence [6][7][8], Line emission of Eu3 + has been estab lished only in the electroluminescence spectrum of ZnS: Eu-layers obtained by coevaporation of ZnS and EuF3, i.e. using F" as coactivator [9]. Our investiga tions show that ZnS:Eu phosphors with 4f-4f-emi> sion may be prepared without introduction of F~ or other coactivators.…”

Cathodoluminescent and Photoluminescent Properties of Al2O3 Powders Doped with Eu

“…3, where the spectrum for Eu-doped powders with 10% of Eu, annealed at 900 C, is shown. spectrum presents peaks centered at 540, 592.5, 615, 652.5, and 700 nm that are associated with interlevel transitions for the electronic energy levels of Eu 3+ ions, in particular to those corresponding to transitions from 5 D 1 to 7 F 1 , and from 5 D 0 to 7 F 1 , 7 F 2 , 7 F 3 , and 7 F 4 , respectively [13,14]. The strongest emission corresponds to the 615 nm red line associated with the 5 D 0 to 7 F 2 transition of the Eu 3+ ion.…”

“…5, presenting also the characteristic peaks that are associated with transitions between the levels 5 D 1 to 7 F 1 (545 nm), and from 5 D 0 to 7 F 1 , 7 F 2 , 7 F 3 , and 7 F 4 (590, 615, 650, and 700 nm, respectively) [13,14] of the Eu 3+ ion. Besides these peaks, there is a broad emission centered at 475 nm that is associated with instrumental artifice coming from the spectrofluorometer.…”

New organosols of ZnS and HgS in N,N-dimethylformamide and dimethyl sulfoxide. Use in the preparation of semiconductive polymer-metal sulfide composite films

“…Poly(acrylonitrile)-ZnS or-HgS composite films prepared from organosols are semiconductive, and the electrical conductivity of the film increases by a factor of 102-103 on exposure to moisture or alcohol vapour. Poly(acrylonitrile)-fl-HgS composite films, prepared from heated jg-HgS, show electrical conductivity of a range ofl0-i-10 -2 S cm -1 and a large electron mobility.Key words: Organosol, zinc sulfide,__mercury sulfide, semi-conductor, polymer composite.Zinc sulfide [1][2][3][4][5] and mercury sulfide [6][7][8] show interesting physical and electrical properties such as semiconductivity, luminescence, and photoconductivity. However, their utilization has been somewhat restricted due to difficulties in molding them and to their low solubilities.…”