Deposition of Ceramic Materials Using Powder and Precursor Vehicles Via Direct Write Processing
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29 Mat. Res. Soc. Symp. Proc. Vol. 624 ©2000 Materials Research Society
A new, vacuum deposition technique, known as matrix assisted pulsed laser evaporation (MAPLE) has been developed at the Naval Research Laboratory (NRL) for depositing thin, uniform layers of chemoselective polymers [3-5] as well as other organic materials, such as carbohydrates [6]. MAPLE is a variation of the conventional pulsed laser evaporation process with respect to the laser interactions and the spatial dynamics of the thin film growth. The "soft" transfer mechanism associated with the matrix assisted pulsed laser deposition process enables the deposition of complex and fragile organic molecules into thin films without denaturing. Irreversible structural degradation is typically observed with conventional pulsed laser deposition even at low fluences. MAPLE direct write is a new process that combines aspects of the transfer mechanism of matrix assisted pulsed laser evaporation with the direct write resolution of laser induced forward transfer [7]. This enables the transfer of polymer, metallic, ceramic and electronic materials without degradation in performance. MAPLE direct write can be utilized for micromachining, drilling and trimming applications, by simply removing the transfer material support from the laser path, and as such it is both an additive as well as subtractive direct write process. In this paper, we demonstrate the application of the MAPLE direct write process to both thick film powder phosphors and sol gel precursors. EXPERIMENTAL PROCEDURES The thick film phosphor ribbons were fabricated by initially sputtering a thin (100nm) gold film onto a 5cm diameter x 2mm thick quartz wafer. The phosphor powders (ZnSi 20 4 :Mn - green, Y 20 3 :Eu - red, and BaMg 2A160 27 :Eu - blue) were suspended in a glycerin/isopropanol solution with LaNO 3 and Mg 3(NO 3)2 salts and electrophoretically deposited onto the gold coated quartz wafers to form thick dense ribbons. The output from a KrF excimer laser (X = 248 nm, 25 ns pulse) was directed through a variable circular aperture and then through a lOx ultraviolet grade objective lens. By changing the aperture size, beam spots from 10 to 300 microns were generated. The laser fluence (0.100-2.5 J/cm 2) was estimated by averaging the total energy of the incident beam over the irradiated area. All laser transfers were performed at room temperature and atmospheric pressure. Two different solutions were examined for the MAPLE-DW process of sol gel materials: 1) a ZrO2 solution comprised of zirconium acetate + DI-water and 2) a PZT solution comprised of lead acetate trihydrate + titanium isopropoxide + zirconium acetylacetonate + DI-water + acetic acid. For the sol gel materials investigated, a ND:YAG laser (frequency tripled ?, = 355 nm, 5-10 ns pulse) was used with a constant spot size of-40 jim and a fluence of -1 J/cm 2 . Optical absorption measurements showed both solutions are transparent at the laser wavelength of 355 nm, therefore a thin absorbing layer of zirconium metal was used to tran
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