33 research outputs found
Poled Copoly(Vinylidene Fluoride-Trifluoroethylene) as a Host for Guest Nonlinear Optical Molecules
Structural and Optoelectrical Properties of ZnTe Thin Films Prepared by E-Beam Evaporation
Enhanced Field-Emission Properties of Sol–Gel-Derived Nanostructured SnO 2 :F Thin Film for Vacuum Microelectronics
Crystalline phase change and improvement in electro-optical parameters of SnSx thin films by different ambients
Photopyroelectric Spectroscopy (P2ES) of a-Si:H Thin Semiconducting Films on Quartz
Photopyroelectric Spectroscopy has proven to be a sensitive qualitative [1] and quantitative [2] technique for thin film spectroscopic applications. An important feature of this back-surface detection technique, not shared with the more conventional front-surface photothermal detection methods (Photothermal Deflection Spectroscopy, PDS; and Photoacoustic Spectroscopy, PAS) is its ability to measure directly and separately two independent spectrally-varying parameters: the optical absorption coefficient [3] and the nonradiative quantum efficiency. PDS of thin semiconducting films of amorphous hydrogenated Si [4] readily yields information about the product of the optical absorption coefficient, α(λ), and the nonradiative quantum efficiency, η(λ). The standard assumption is, however, that η(λ) is not a sensitive function of the exciting photon energy. This assumption is generally wrong, and nonradiative quantum efficiencies have been found photoacoustically to vary by one order of magnitude [5] across the optical gap in Ge doped As 2 Se 3 chalcogenide glasses. PAS yields amorphous thin film spectra similar to PDS [6]. The working assumption has been that PA spectra are essentially accurate above the optical gap, as η(λ) is expected to be independent of photon energy. Kitamura et al. [5] were able to derive extended η(λ) spectra of (As 2 Se 3 )100-x Ge xglasses upon combining PA spectra with optical absorption coefficient information obtained in an independent spectrophotometric experiment using ordinary polished bulk samples. These authors, however, were not able to guarantee that the glasses and the bulk samples had the same (or even nearly similar) α(λ) spectra.</p
Ba0.8Sr0.2TiO3 films crystallized on glass and platinized substrates by laser-assisted annealing at room temperature
In this work, Ba0.8Sr0.2TiO3 (BST) films were
grown by pulse laser ablation on bare glass and platinized
substrates. The crystalline phase was obtained with the help
of laser-assisted annealing (LAA) at room temperature, in
air environment. By adjusting LAA conditions, like frequency
of the laser and number of shots, we were able to
grow crack-free BST thin films with pure perovskite phase
on bare glass and platinized substrates. The crystalline
layer was found to be the same irrespective of the substrate
used, c.a. 250 nm thick. The electric characteristics of the
amorphous and LAA crystalline BST films deposited on
platinized substrate were further studied and analyzed.
While in amorphous films it was found that the oxygen
defects are responsible for conduction, in LAA films the
amorphous/crystalline interface layer plays an important
role in current leakage.This study has been partially funded by: (i) European COST Actions MP0901-NanoTP and MP0903-Nano-
Alloy; (ii) Portuguese Foundation for Science and Technology through the Strategic Project Pest-C/FIS/UI0607/2011. The authors would also like to thank Engineers Jose´ Santos and José Cunha for technical support at the Thin Film Laboratory. The author J.P.B.S. thanks FCT for the financial support (grant SFRH/BD/44861/2008)