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Dabirian A.,Ecole Polytechnique Federale de Lausanne | Kuzminykh Y.,Ecole Polytechnique Federale de Lausanne | Afra B.,Ecole Polytechnique Federale de Lausanne | Harada S.,Ecole Polytechnique Federale de Lausanne | And 7 more authors.
Electrochemical and Solid-State Letters | Year: 2010

Combinatorial high vacuum chemical vapor deposition (HV-CVD) of mixed HfO2 - Nb2 O5 thin films has been demonstrated to yield amorphous layers at substrate temperatures where individually deposited pure HfO2 and Nb2 O5 films are polycrystalline. Spectroscopic ellipsometry of the films shows that adding HfO2 to Nb2 O5 improves the transparency of the films while still maintaining a high refractive index. Atomic force microscopy measurements show that the root-mean-square surface roughness of the films is about 1.2 nm. © 2010 The Electrochemical Society. Source


Dabirian A.,Ecole Polytechnique Federale de Lausanne | Kuzminykh Y.,Ecole Polytechnique Federale de Lausanne | Kuzminykh Y.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Sandu S.C.,Ecole Polytechnique Federale de Lausanne | And 8 more authors.
Crystal Growth and Design | Year: 2011

Combinatorial high-vacuum chemical vapor deposition (HV-CVD) was used to identify the conditions required to obtain hafnium-doped lithium niobate thin films on sapphire {001} substrates. Niobium tetraethoxydimethylaminoethoxide (Nb(OEt)4(dmae)), lithium tert-butoxide (Li(OBut)), and hafnium tert-butoxide (Hf(OBut)4) were used as precursors. X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that a single phase of textured {001} Hf-doped lithium niobate film was obtained under certain precursor flux conditions. The lithium content ([Li]/([Li] + [Nb])) of the textured film was estimated using Raman spectroscopy to be about 49 mol %. The presence of hafnium inside the films was confirmed by X-ray photoelectron spectroscopy (XPS) measurements, and the hafnium content of the textured film ([Hf]/([Hf] + [Nb])) was estimated to be about 3 mol %. XPS data confirmed that Hf and Nb, respectively, are in the +4 and +5 oxidation states inside the film. The film consists of nearly parallel {001} hafnium-doped lithium niobate columns with different in-plane orientations. © 2010 American Chemical Society. Source


Dabirian A.,Ecole Polytechnique Federale de Lausanne | Dabirian A.,Technical University of Delft | Harada S.,Ecole Polytechnique Federale de Lausanne | Kuzminykh Y.,Ecole Polytechnique Federale de Lausanne | And 9 more authors.
Journal of the Electrochemical Society | Year: 2011

A combinatorial chemical beam epitaxy technique was used to optimize deposition of {001} lithium niobate thin films on {001} sapphire substrates. Lithium tert-butoxide [Li (O But)] and niobium tetra-ethoxy di-methyl-amino-ethoxide [Nb(OEt)4(dmae)] were used as precursors. The highest quality films obtained exhibited rocking curve full-width at half-maximum values of about 0.03° and lithium contents { [Li]/[((Li)) + (Nb)] } larger than 48 (mol %) estimated by Raman spectroscopy. High-resolution transmission electron microscopy observations revealed that the lithium niobate film consists of a buffer layer (thickness <8 nm) with a high density of defects above which the epitaxial lithium niobate film was obtained. © 2010 The Electrochemical Society. Source

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