Patterning of Lithium Niobate Thin Films Derived from Aqueous Solution

Abstract

The micropatterning of lithium niobate (LiNbO 3 ) thin films was conducted by applying a photolithographic technique to an aqueous precursor solution that was derived from a double alkoxide. The neutralization process of the alkaline lithium niobium hydroxide solution was essential to avoid the dissolution of the aluminum masking pattern on the sapphire substrate. The acetic acid was a suitable neutralizer to form the stoichiometric and transparent gel film. The gel film that was prepared from a neutralized precursor solution at pH 6.4 gave high-quality crystalline LiNbO 3 films after heat treatment at 500°C.

Characterization of Lithium Niobate Thin Films Derived from Aqueous Solution

“…The values in Table IV are lower compared to those of crystalline LN films reported so far. 16,18 The data in Table IV are determined by assuming all the film-absorption coefficients to be zero, because an assumed absorption coefficient factor strongly affects the refractive index when the refractive index of the film is calculated by ⌿ and ⌬ in the ellipsometry measurement. Therefore, to determine the absolute refractive index via ellipsometry, caution must be taken in assuming the value of the absorption coefficient factor.…”

“…The finepatterned LN thin-film waveguide could be successfully fabricated on sapphire (001) substrates via heat treatment at 500°C, using a neutralized aqueous precursor solution. 18 In addition, the LN films that have been prepared from the neutralized solution at a temperature of 500°C show stoichiometry, homogeneity, and preferred orientation as well.…”

“…L ITHIUM NIOBATE (LiNbO 3 , LN) single crystal is an excellent material for electro-optic and nonlinear optic devices, such as optical waveguides, surface acoustic wave devices, holographic memory, etc. Recently, several processing methods of LN thin films have been reported through sputtering, 1 pulsed laser deposition, 2-4 chemical vapor deposition, 5 liquid-phase epitaxy (LPE), 6,7 and sol-gel methods [8][9][10][11][12][13][14][15][16][17][18] since the development of high-quality LN thin films has been receiving great attention for the miniaturization and integration of the optical waveguide device.…”

“…Figure 1 shows the preparation procedure for LN films. [16][17][18] Lithium ethoxides (99.9%) and niobium ethoxides (99.9%) (Kojundo Chemical Lab Co., Saitama, Japan) were dissolved in absolute ethanol in a 1:1 molar ratio to form double alkoxide ethanol solution, and the solution was refluxed for 20 h under a dry nitrogen atmosphere. The double alkoxide was completely hydrolyzed with 7.5 equiv.…”

Photoreaction of Titanium‐Based Metal‐organic Compounds for Ceramic Fine Patterning

“…T HE patterning of ceramic thin films has attracted great interest for the production of functional microdevices. 1,2 Photoprocessing, which is known as photolithography, is a method that is as promising as microcontact printing (-CP) using self-assembled monolayers (SAMs). 1,3 The photoreaction of ceramic precursors has been studied for the preparation of ceramics and organic-inorganic hybrid materials as in the low-temperature processing of optical devices using metal-organic compounds modified with photocurable organic ligands.…”