Phosphor thermography is a laser-induced fluorescence method utilized for the temperature sensing of rotating components within inhospitable environments. Results presented here show that thin film coatings for thermographic sensors have a much higher durability than conventional thick film coatings. Room-temperature measurements demonstrate that the intensity of the luminescent emission from thin films is equivalent to that from thick films. Lifetime measurements carried out at C show that thin films survived for up to ten hours, whereas thick film samples survived for less than one. More importantly, post-run measurements of thin films indicate little degradation in the intensity of the fluorescent signal. This illustrates the capability of thin film sensors for remote temperature sensing.
Thin films of ZnS:Mn (800 nm) have been deposited by rf magnetron sputtering onto 100 mm diam n-type single-crystal (100) Si wafers. Specifically for use as active layers in thin film electroluminescent devices, the films need a postdeposition annealing treatment to enhance their luminescent properties. Inherent to the later process step are structural modifications of the phosphor layer which form the basis of this study. Both pulsed laser and thermal postannealing techniques have been investigated. Reported are the induced crystalline and surface morphology modifications via x-ray diffraction and atomic force microscopy analysis. As-grown and thermally treated films were cubic in nature and no significant grain growth or reorientation occurred while heating up to 700 °C. Pulsed (∼ 20 ns duration) KrF laser treated samples were annealed at power densities from 10.76 to 24.27 MW/cm2 under 10.34 bar of argon pressure. Beam quality and diagnostics were emphasized during laser irradiation with particular attention brought to energy and pulse duration measurements. It has been demonstrated that at the power densities used, a gradual phase transition from cubic to hexagonal is occurring while the average crystallite size remains constant. Surface analysis highlights concomitance between the phase transition and the smoothening of the irradiated surface. A one dimensional thermal model of the pulsed laser annealing process shows that a surface temperature for crystalline ZnS equating to the transition temperature should be reached at 17 MW/cm2, significantly below the numerically evaluated melting threshold of 30.5 MW/cm2. Combining experimental and theoretical results, it is concluded that the phase transition occurs in the solid state.
Thin films of BaTiO 3 have been deposited by RF magnetron sputtering onto 100 mm diameter n-type single-crystal Si wafers. Full deposition and post-deposition variables have been investigated with respect to their effect on the dielectric constant and refractive index of the thin films. Specifically for use as insulators for thin film electroluminescent (TFEL) devices, the films need to exhibit a high dielectric constant and a low refractive index. The optimum fabrication route was determined to be deposition at 200 • C in a 30% O 2 in Ar atmosphere at 7 mTorr with a post-deposition anneal at 700 • C for 1 h. Demonstrated here is that films exhibiting suitable characteristics, namely, ε r = 26 and n = 2.1, for use in TFEL devices can be fabricated using RF magnetron sputter deposition.
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