Thin films have been deposited by rf magnetron sputtering from a stoichiometric Ta2Zn3O8 ceramic target (3ZnO + 1Ta2O5). Negative ion re-sputtering effects have been observed in the stoichiometric Ta2Zn3O8 target and have been attributed to O ion formation from primarily Ta-O bonds. Zinc deficient thin films were deposited as a result of the preferential re- sputtering of Zn versus Ta. The negative ion re-sputtering effects are exacerbated at higher powers and lower pressure. This observation is correlated to the oxygen ion transport through the dark space and the plasma, which ultimately controls the energy distribution of the oxygen particles that arrive at the substrate. To circumvent the negative ion re-sputtering, a mosaic ZnO-Ta target was sputtered, which resulted in stoichiometric and luminescent thin films.

The electromagnetic behavior of nanoscale layered and particulate structures of FexAl1-xNyO1-y materials have potential applications in medical device technologies. Iron and aluminum have been co-sputtered in an Ar-N-2 ambient to form a combinatorial array of FexAl1-xNyO1-y thin films. Using this approach, we are able to achieve an Fe/(Fe + Al) cation range from similar to 12-60% over a 10 cm long substrate. The deposited films were annealed in vacuum at various temperatures and the films have been characterized by X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, scanning electron microscopy, scanning transmission electron microscopy, and X-ray diffraction. Furthermore, the direct current magnetic properties of the films have been characterized. In this paper, we describe in detail the reactive combinatorial FexAl1-xNyO1-y sputtering approach. The chemical, structural, and morphological properties as a function of Fe/(Fe+Al) content are demonstrated and correlated to the measured dc magnetic properties. (c) 2007 Elsevier B.V. All rights reserved.

The photo- and cathodoluminescence properties of epitaxial lithium-doped zinc gallate thin-film phosphors grown on (100) MgO single crystal substrates using pulsed laser ablation were investigated. The addition of lithium to both undoped and Mn-doped ZnGa2O4 films significantly enhanced the photo- and low-voltage cathodoluminescent intensity. Cathodoluminescent efficiencies for as-deposited undoped and Mn-doped lithium zinc gallate films as high as 0.21 lm/W and 0.29 lm/W, respectively, were achieved for 1 kV and 2.26 μA/cm2. Based on these results, lithium-doped zinc gallate thin-film phosphors appear to be attractive for applications in low-voltage field emission display devices.

Cathodoluminescence emission spectra and photoluminescence (PL) excitation spectra were used to evaluate Eu+3 and Cr+3 as activators for red luminescence in ZnGa2O4. In the ZnGa2O4:Eu materials red emission from Eu+3 and blue intrinsic emission were observed. The blue intrinsic emission increased relative the Eu+3 emission with increasing current density and is attributed to preferential current saturation of the Eu+3 activators. In addition, PL excitation measurements revealed that the inefficient energy transfer from the ZnGa2O4 host to the Eu+3 is due to poor spectral overlap between the ZnGa2O4 emission and the Eu+3 absorption. Cr-doping resulted in a saturated red-color, and no host emission was observed over the entire current density regime investigated. The PL excitation of the ZnGa2O4:Cr revealed good overlap between the ZnGa2O4 host and the Cr+3 absorption. Efficient energy transfer to the Cr+3 activators occurs via multipolar interactions.

Tantalum zinc oxide (TZO) with the chemical formula Ta2Zn3O8 can be generated from the reaction of 3 mol ZnO and 1 mol Ta2O5 at elevated temperatures. This phase has been shown to exhibit blue cathodoluminescence at low electron beam voltages. It has also been realized in thin film form on silicon substrate, making TZO an important material for monolithic field emission display devices. The structure type of TZO has been investigated using powder x-ray diffraction techniques. The unit cell of this phase has been determined and found to be monoclinic. These results allow for indexing of the powder pattern first reported by Kasper in 1967 and correct for a discrepancy in the single-crystal structure lattice constants reported by Waburg and Muller-Buschbaum in 1984.

Epitaxial ZnGa 2 O 4 and Sr 2 CeO 4 thin-film phosphors were successfully grown on (100) MgO, YSZ, and SrTiO 3 single crystal substrates using pulsed laser ablation. Cathodoluminescence efficiency was remarkably enhanced by adding lithium in the ZnGa 2 O 4 and ZnGa 2 O 4 :Mn for both blue and green light emitting thin-film phosphors. The highest efficiencies, in this experiment, were 0.35 and 0.29 lm/W at 1kV for as-deposited blue and green zinc gallate phosphor films, respectively. In case of Sr 2 CeO 4 films, the highest luminescence was 0.14 lm/W at 1kV and 0.26 A/m 2 for films annealed at 1000°C in air.

Orthorhombic epitaxial Sr2CeO4 thin-film phosphors were grown on (100) SrTiO3 and yttria-stabilized-zirconia (YSZ) single crystal substrates with epitaxial relationships of (100) [010]Sr2CeO4//(100)[010]SrTiO3 and (100)[010]Sr2CeO4//(100)[011]YSZ, respectively. As-deposited films exhibit a broadband photoluminescence (PL) emission, peaking at about 477–481 nm with a maximum cathodoluminescence (CL) intensity at about 465 nm. Enhanced PL intensity was observed for the films deposited on (100) YSZ and SrTiO3 substrates as compared to deposits on c-plane sapphire substrates, correlating with improved intragranular crystallinity and reducing defects via epitaxy. Postannealing in air significantly enhanced both of the PL and CL intensities. Luminous efficiency of 0.14 lm/W at 1 kV and 22 μA/cm2 was observed for a 2-μm-thick film annealed at 1000 °C in air.

This paper describes the development of a low voltage thin film phosphor material by an alliance between the Rochester Institute of Technology, Advanced Vision Technology Inc., a Rochester based small company and the National Science Foundation (NSF) through the NSF's small business technology transfer (STTR) program. The overall goal of the Phase I program was to develop tantalum zinc oxide (TZO), a novel low voltage blue phosphor that can be deposited in thin film form and integrated with semiconductor device fabrication for flat panel display applications. A lower temperature process for depositing TZO thin films was achieved by rf sputtering from a ZnO-Ta mosaic target. A thorough investigation of the intrinsic blue luminescence showed that the mechanism responsible for luminescence in TZO is metal-to-ligand (Ta 5d/sup 0/-O 2p/sup 6/) radiative transition. Saturated red and green colors were obtained by doping the TZO host lattice with Mn. An exhaustive study of processing parameters, such as annealing, etching, and subsequent deposition processes was done. Successful integration of the TZO phosphor using standard IC processing was realized in working field emission devices.

Blue luminescence from Ta2Zn3O8 and green luminescence from Mn doped Ta2Zn3O8 has been observed under low voltage cathodoluminescent excitation. In this article, the luminescence mechanisms of Ta2Zn3O8 and Mn doped Ta2Zn3O8 are discussed in detail. The results suggest that the intrinsic blue luminescence of Ta2Zn3O8 results from a metal-to-ligand transition, whereas the green luminescence of Mn doped Ta2Zn3O8 results from the Mn 4T1–6A1 transition. The suppression of the blue intrinsic luminescence in Mn doped Ta2Zn3O8 suggests that efficient energy transfer from the host material to the Mn occurs. This energy transfer phenomenon is also discussed by comparing the photoluminescence excitation spectra of both thin film materials. Finally, the relative efficiency versus voltage and current density is demonstrated and discussed pertaining to field emission device operation.

Abstract— Blue cathodoluminescence (CL) with a spectral peak at 400 nm is reported in tantalum‐incorporated ZnO thin films at low voltages. The CL is visible at 10 V at a current density of 10 μA/cm2. The CL chromaticity coordinates are found to be x = 0.160, y = 0.075. The films have been prepared by depositing a thin tantalum film on rf‐magnetron‐sputtered and annealed ZnO films, followed by another annealing step. The films also exhibit strong photoluminescence, peaking at 383 nm (3.2 eV). The x‐ray‐diffraction analysis shows the presence of a Ta2Zn3O8 phase in these films, which is believed to be responsible for the observed luminescence.

We have observed cathodoluminescence (CL) at low voltages (<50 V) with a peak at /spl sim/410 nm from tantalum zinc oxide, Ta/sub 2/Zn/sub 3/O/sub 8/, (TZO). The thin films were prepared by reacting Ta with ZnO on silicon and silicon dioxide substrates at elevated temperatures (1200/spl deg/C) using rapid thermal annealing. Subsequently, the bulk phase was synthesized from the powder raw materials, ZnO and Ta/sub 2/O/sub 5/ using ceramic techniques. The resulting material shows similar CL characteristics. No charging was observed during the CL measurements, indicating a conducting nature of the material. It is observed that TZO exhibits better blue both in thin film and bulk form, as compared to conventional ZnS:Ag, a blue CRT phosphor and zinc gallate, another low voltage blue phosphor.

It is still not known whether elliptical galaxies are oblate, prolate or triaxial. The prototype ‘prolate’ galaxy NGC2685 has a rapid observed stellar rotation rate around the projected minor axis. We show here that a steady figure, exactly prolate model can have no such rotation, and that a nearly prolate model fails by a factor of 7. We suggest that the galaxy is oblate and that the gas disk is the wreck of a dwarf companion.

view Abstract Citations (25) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Galactic mass loss - A mild evolutionary correction to the angular size test Richstone, D. O. ; Potter, M. D. Abstract Galactic mass loss due to gas production by an evolving stellar population and removal due to supernovae or some other energy source can alter the size of a galaxy over a long time through the adiabatic invariants of the orbits. Numerical and analytic results show that if the mass profile changes homologously, the scale size of the galaxy does also. Under conventional assumptions about galaxy age and initial mass function, this bloating is smaller than the differences between open and flat cosmologies at z = 0.5. If, however, some elliptical galaxies maintain star formation until recent epochs and then lose a (correspondingly) larger fraction of their mass, the effect may be important. It may also be important in decreasing the size of cD galaxies as a result of gas accretion. Publication: The Astrophysical Journal Pub Date: March 1982 DOI: 10.1086/159752 Bibcode: 1982ApJ...254..451R Keywords: Galactic Evolution; Galactic Mass; Mass Distribution; Mass To Light Ratios; Sizing (Shaping); Stellar Mass Ejection; Angular Distribution; Cosmology; Elliptical Galaxies; Outgassing; Stellar Evolution; Astrophysics full text sources ADS |

We have observed cathodoluminescence (CL) at low voltages (-60 V) with a peak at - 410 nm from tantalum zinc oxide, TazZn3Q8., (TZQ). The thin films were prepared by reacting Ta with ZnO on silicon and silicon dioxide substrates at elevated temperatures (1200 C) using rapid thermal annealing. Subsequently, this phase was synthesized from the powder raw materials, ZnQ and Ta& using ceramic techniques. The resulting material shows similar CL characteristics. No charging was observed during the GL measurements, indicating a conducting nature of the material. It is observed that TZO exhibits better blue both in thin film and bulk form, as compared to conventional ZnS:Ag, a blue CRT phosphor and zinc gallate, another low voltage blue phosphor. and coulombic degradation. Most of the known phosphors are sulfide or oxide based In FEDs, sulfides have been reported to outgas or undergo electron stimulated decomposition, which causes emitter contamination. For many years, Zn:ZnO has been the material of choice for producing blue-green emission in vacuum fluorescent displays (VFDs). Some of the phosphors that have shown promise are Eu doped yttrium oxide for red, and zinc gallate for blue. Extensive efforts are being done to develop a saturated blue phosphor material with chromaticity co-ordinated x<0.2 and y<O.O8. In this paper we report blue cathodoluminescence from thin tantalum zinc oxide prepared in thin film as well in bulk form.