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ABSTRACT: The optical properties of InGaZnO (IGZO) films grown through the sol-gel process as a function of sintering time were investigated with spectroscopic ellipsometry (SE). The IGZO precursor sol was prepared by mixing In nitrate, Ga nitrate, and Zn acetate at a molar ratio of In:Ga:Zn = 3:1:1. The solution was deposited on a SiO2/Si substrate via spin coating. Sintering was performed at 400 degrees C for 1-15 h in an ambient atmosphere. The optical properties were measured over the range 1.12-6.52 eV via variable angle SE, at room temperature. The angle of incidence was varied from 50 to 70 degrees in 5 degree steps. To extract the pure optical properties of IGZO, multilayer-structure calculation with Tauc-Lorentz dispersion relation for IGZO was performed. The changes in the dielectric function of the IGZO films with varying sintering time were observed. The resultant optical properties can be related to the concentration of oxygen vacancies in the material, which can be controlled by the sintering time.
Journal of Nanoscience and Nanotechnology 07/2012; 12(7):5804-7. · 1.56 Impact Factor
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ABSTRACT: We report results on a study of the formation of polycrystalline Si by thermally annealing amorphous Si films. The crystallization of amorphous Si is of increasing interest not only from a basic-physics point of view but also for its wide application in the semiconductor device area. The amorphous Si was deposited on a glass substrate coated with buffer layers and a small amount of Ni to stimulate crystallization. The process was followed with a spatial resolution of 3 microm using an imaging ellipsometer. Imaging ellipsometry constructs sample images from the differences in dielectric functions in different regions. In particular, we can easily detect the polycrystalline Si domains in an amorphous matrix. Results are shown as three-dimensional plots. These are then analyzed to show that the interfaces between domains are not abrupt, and that crystallization within the polycrystalline Si regions is not complete. The fundamental crystallization mechanism is the radial expansion of Ni-seeded needles, forming macroscopic disk-like domains.
Journal of Nanoscience and Nanotechnology 07/2011; 11(7):6198-202. · 1.56 Impact Factor
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ABSTRACT: Mn-doped Bi4Ti3O12(B4T3) thin films grown at 400 degrees C on a Pt/Ti/SiO2/Si substrate through pulsed laser deposition (PLD) were analyzed via spectroscopic ellipsometry (SE). The PLD targets were produced through the conventional solid-state sintering method, and the film samples were annealed at 600 degrees C. The SE spectra of B4T3 films were measured using a rotating analyzer type ellipsometer within the 1.12 to 6.52 eV energy range, with the various incidence angles. The optical properties of the B4T3 films with increasing Mn-mol concentration were extracted using a multilayer model for the whole structure and the Tauc-Lorentz (TL) dispersion relation for the B4T3 film layer. The analysis results clearly showed that the significant changes in optical properties of B4T3 films are caused by thermal annealing procedure and the Mn-mol concentrations. X-ray diffraction (XRD) measurement was also performed to confirm the results of SE analysis.
Journal of Nanoscience and Nanotechnology 01/2011; 11(1):884-8. · 1.56 Impact Factor
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ABSTRACT: Mn-doped Bi4Ti3O12(B4T3) thin films grown at 400 °C on a Pt/Ti/SiO2/Si substrate through pulsed laser deposition (PLD) were analyzed via spectroscopic ellipsometry (SE). The PLD targets were produced through the conventional solid-state sintering method, and the film samples were annealed at 600 °C. The SE spectra of B4T3 films were measured using a rotating analyzer type ellipsometer within the 1.12 to 6.52 eV energy range, with the various incidence angles. The optical properties of the B4T3 films with increasing Mn-mol concentration were extracted using a multilayer model for the whole structure and the Tauc-Lorentz (TL) dispersion relation for the B4T3 film layer. The analysis results clearly showed that the significant changes in optical properties of B4T3 films are caused by thermal annealing procedure and the Mn-mol concentrations. X-ray diffraction (XRD) measurement was also performed to confirm the results of SE analysis.
Journal of Nanoscience and Nanotechnology 12/2010; 11(1):884-888. · 1.56 Impact Factor
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ABSTRACT: We report on the dynamics of bio molecules and a high polymer in a water environment by using imaging ellipsometry (IE). The morphology of collapsed films of arachidic acid (AA) and poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) Langmuir monolayers in a liquid solution is investigated. The IE images clearly show that the multilayer domains and thickness of the collapsed region change sensitively depending on Langmuir compression. Also, the adsorption of bovine serum albumin is observed by using total internal reflection resonance IE (TIRIE), which has the advantage of IE and surface plasmon resonance. We believe that IE is a powerful technique for analysis and applications of bio materials.
Advances in Natural Sciences: Nanoscience and Nanotechnology. 12/2010; 1(4):045003.
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ABSTRACT: In situ imaging ellipsometry is employed to monitor the morphology of collapsed films of fatty acid Langmuir monolayers on pure water and on CaCl2 solution. The ellipsometry images reveal the existence of multilayer domains in the collapsed region, and analysis of the images yields the thicknesses of these domains. The multilayer films formed on water are mainly trilayers, while those on CaCl2 solution are mainly bilayers. The structure of the collapsed films also changes sensitively depending on the history of compression of the molecular layer.
Langmuir 08/2009; 25(16):9262-9. · 4.19 Impact Factor
