Yttrium silicate activated with Ce3+, (Y1−xCex)2SiO5, has been found to be an efficient phosphor that can potentially be used as the blue-emitting component in field emission flat panel displays. This highly refractory powder can be synthesized by combustion synthesis, a low cost technique used to fabricate multicomponent oxide powders in a single step process. The effect of activator concentration and post-synthesis annealing was examined on the fluorescent properties. The powders were found to be monoclinic space group P21/c in the as-synthesized state, and transformed to monoclinic space group C2/c after annealing. The maximum luminous emission intensity was reached after a one hour anneal at 1350°C for x=0.0075, with the peak Ce3+ emission wavelength between 420 and 450 nm. When co-doped with Gd3+, no increase in the emission intensity was observed.

A low cost and efficient method of doping pure zinc oxide powders for luminescence applications is presented. The powders have been obtained from pure, non-luminescent ZnO by thermally induced doping under a nitrogen flux and in the presence of ZnS powders. Structural characterization has been carried out by X-ray diffraction analysis (XRD), while luminescence properties have been studied with both a spectrofluorimeter and microraman spectrometer. Emission spectra have shown an increase of the luminescence with treatment temperature. The XRD patterns of all samples showed, along with reflections of the hexagonal phase of ZnO, other reflections ascribed to the hexagonal phase of ZnS. Upon further annealing in air at 800°C, the ZnS reflections disappear even though the luminescence still persists with a comparable intensity. Luminescence is ascribed to ZnO reduction due to the interaction of S with ZnO. It has also been observed that excitation with a He-Ne laser beam (λ=633 nm) with a high specific power (5×10−3 W·µm−2) yielded blue-green luminescence in spite of excitation below the band-to-band absorption threshold.

The origin of the electronic fine structure in thin-film SrS:Cu has been interpreted in terms of the several possible perturbations including spin-obit coupling, the Jahn-Teller effect and low symmetry splittings. Photoluminescence excitation measurements showed that the peak position of the excitation bands were independent of temperature suggesting that the electronic fine structure in our system was not due to the Jahn-Teller effect. Selective excitation measurements revealed that no peak shift occurs with changing excitation wavelength, indicating that Cu+ pairs or aggregates and Cu+-defect coupled centers were not existent in our system. Finally, several models were proposed for off-center displacements of Cu in SrS, since a rigorous treatment of these displacements is difficult. Both the tetragonal and trigonal distortion models for a <111> displacement yielded reasonable distortions parameters of 0. 16Å and 0.11Å, respectively. However, crystal field analysis showed that a <110> displacement was more likely since the energy level splitting scheme more closely resembled the observed data.

This work was focused on the MOCVD of the cerium-doped strontium sulfide (SrS:Ce) phosphor for use in thin film electroluminescent displays (TFELs). Following previous research on a small scale reactor, a feasibility scale-up using a commercially available reactor enlarged the size of the deposition area to a 4” diameter wafer or a 2” by 2” glass slide. Films were deposited from the reaction of Sr(thd)2, Ce(thd)4, and H2S at 450 °C and 5 torr. This system employed a liquid delivery system for the accurate and repeatable delivery of the metal organic reagents. The deposition from this reactor was shown to be crystalline-as-deposited SrS with a (200) orientation, possibly a result of the thin nature of the coating and the involvement of (200) grains in the initial nucleation process. The wafers showed good uniformity, but had some thickness variation near the outer radius of the wafer resulting from the addition of H2S from the outside edge. There were eighteen total deposition experiments, of which nine were characterized for EL performance. The highest brightness observed was 5 fL. The samples were exceedingly thin as a result of the fifteen fold increase in the surface area between the deposition reactors. Increasing the sample thickness to 7,000 Å or higher will dramatically increase the brightness of the emission.

High quality luminescent thin films of strontium sulfide (SrS) doped with rare earths have been grown using Pulsed Laser Deposition (PLD). SrS films ranging in thicknesses from 0.05 to 2 µm. were deposited on MgO (001) and glass substrates. Deposition parameters such as growth temperature and H2S background gas pressure were varied and their effect on the structure, morphology and luminescence of the films was evaluated. The PLD grown films all showed texture and were highly oriented when deposited on MgO substrates as determined by their XRD spectra. Optical microscopy, SEM and AFM analysis were used to study the films' surface morphology. The thermally and optically stimulated luminescence properties of these films were evaluated as well. The data indicates that these materials may be useful for optical data storage applications.

Europium-activated yttrium oxide (Eu:Y2O3) phosphor films have been grown in-situ on (100) bare silicon and diamond-coated silicon substrates using a pulsed laser deposition technique. Diamond-coated silicon substrates were prepared by hot filament chemical vapor deposition on (100) silicon wafer. Measurements of photoluminescence and cathodoluminescence properties of Eu:Y2O3 films showed that the films grown on diamond-coated silicon substrates are brighter than the films grown on bare silicon substrates. The improved brightness of the Eu:Y2O3 films on diamond-coated silicon substrates is attributed to reduced internal reflection and enhanced scattering of incident beam with lattice. These effects are primarily brought about by the presence of a rough diamond buffer layer between the phosphor film and substrate. Oxygen environment during deposition is necessary for better crystallinity but excess oxygenation of the Eu:Y2O3 films during cooling degrades the brightness of the films.

Bulk samples of transparent conducting oxides (TCOs) in the Zn-In-Sn and Ga-In-Sn oxide systems were prepared by solid state processing. Phase relations and physical properties were determined and the results compared to similar measurements on thin film materials.

Investigation of the properties of indium zinc oxide (IZO) thin films sputter-deposited on LCD-grade glass substrate showed that the resistivity of an IZO film decreases markedly as the substrate temperature is increased from room-temperature to 120°C. This phenomenon can be attributed to the growth of In-Zn intermetallic compounds in the amorphous region as a result of annealing. The compound growth was observed by plan-view transmission electron microscopy.

Although the transmittance and resistivity of IZO are inferior to those of indium-tin oxide, these disadvantages do not present any difficulties in the practical use of IZO for designing TFT-LCDs. Since IZO is an amorphous material, we propose a five-mask process with this characteristic.

Among the issues associated with the fabrication of polysilicon thin film transistor (TFT) active matrix displays is the contact resistance between indium tin oxide (ITO) pixel electrodes and the aluminum data lines. We have investigated the use of Co and Ni for use as barrier layers between the Al and ITO in order to provide good ohmic contacts. For comparison, a titanium barrier layer has also been used and measured. A thin, 10 nm Co layer sufficed to provide good ohmic contacts in an ITO-Co-Al stack, while a thicker layer was required in the case of Ni in order to form a similar good ohmic contact. The contacts have been characterized using resistance measurements in conjunction with X-ray photo-electron spectroscopy (XPS) and X-ray diffraction (XRD) in order to correlate the electrical results with the physical metallurgy of the contacts.

The effects of adding a third transition metal element, Co, Cu, Zr, or Ta, to Al-Nd (or Gd) alloy thin films were studied in order to investigate the changes in the film's microstructure and resistivity, and also their tendency to form hillocks or whiskers at high temperatures. The addition of Zr (or Ta), which has repulsive interactions with both Nd and Gd, to the Al-RE binary alloy films causes an increase of residual resistivity and enhances the formation of hillocks or whiskers at high temperatures. On the other hand, the addition of Cu or Co, which has attractive interactions with both Nd and Gd, results in a resistivity of less than 6 µωcm (depending on the content of added elements). Addition of either of these elements largely suppresses the growth of thermal defects after annealing at over 350 °C. The above results were explained by employing a theory of grain boundary segregation based on a chemical interaction between constituent elements of an alloy.

The effects of using an extra layer of nickel, cobalt or titanium with Al-1%Cu films were examined with regard to hillock formation. The density and sizes of hillocks in these double layer metallization structures were characterized using scanning electron microscopy (SEM) and interfacial reactions between the transition metal layer and Al-l%Cu were examined using glancing angle x-ray diffraction (GA-XRD). Resistivities of the double layer films were characterized using conventional 4-point probe measurements. Hillock formation was totally suppressed when Ni and Co was used as the transition metal, while Ti did not eliminate hillocks. Hillock formation and resistivities are explained on the basis of interfacial reactions.