AVS 45th International Symposium
    Thin Films Division Thursday Sessions
       Session TF-ThA

Paper TF-ThA8
Thickness-Dependence of Infrared Reflection-Absorption Spectra from Thin Film of Anatase-type TiO@sub2@ Grown on Polished MgO(001) Substrate by Ar-ion Beam Sputtering

Thursday, November 5, 1998, 4:20 pm, Room 310

Session: Ex-situ Characterization of Thin Films
Presenter: K. Maki, Yokohama City University, Japan
Authors: D. Osabe, Yokohama City University, Japan
T. Uchitani, Yokohama City University, Japan
K. Maki, Yokohama City University, Japan
Correspondent: Click to Email
The structure of thin film of TiO@sub2@ grown on air-cleaved surface of MgO(001) by Ar-ion beam sputtering on a Ti target is controlled by adjusting the partial pressure of O@sub2@ vapour (P@subO@) flowing near the substrate, which has previously been published in J.Vac.Sci.& Technol., A, 15, 2485(1997). In the present study we will show that the preferred oriented anatase-type thin film of TiO@sub2@ with its c-axis parallel to the surface is grown on polished MgO(001) substrate held at 550 °C in P@subO@ = 1.1 x 10@super-2@ Pa. The polished substrate was used for studying optical property after X-rays diffraction. The diffraction peak height from the (200) lattice plane of the anatase TiO@sub 2@ film increases sigmoidally with increasing its thickness, d, below 20 nm, and linearly with d above 20 nm. The relationship between infrared reflection-absorption peak height near at 510 cm@super-1@ and d also shows the similar one between the diffraction peak height and d. Some discussion is given how to determine the dielectric function, @epsilon@, as a function of the angular frequency, @omega@, from the infrared reflection-absorption(IR-RAS). @epsilon@(@omega@) is determined by comparing the measured IR-RAS with the calculated one which is performed by evaluating from the Fresnel coefficient for the anisotropic materials on isotropic substrate by adopting the Lorentz model for the dielectric constant. After determining the dielectric function, the ratio of @omega@ for exciting of the longitudinal optical phonon, @omega@@subL@, to the transverse one, @omega@@subT@, that is, so called Lyddane-Sachs-Teller relation, is determined, which equals to the square root of @epsilon@(0)/@epsilon@. For this aim IR-RAS at 100 @<=@ @omega@ @<=@ 1000 cm@super-1@ is required which is shown for rutile-type single crystal of TiO@sub2@. However, IR-RAS at 400 @<=@ @omega@ @<=@ 1000 cm@super-1@ in the present study will be available for judging whether epitaxially-grown thin film is prepared or not and will show that the dielectric property of crystalline regions in thin films of TiO@sub2@ at d > 20 nm are similar to the bulk single crystal.