Comparison of LiNbO3flux systems for deposition on RIE-etched LiTaO3substrates

Single-crystal LiNbO 3 films were deposited by liquid phase epitaxy (LPE) onto inductively coupled plasma-assisted reactive ion etched (RIE) LiTaO 3 substrates. The RIE-etched channels were 6 µm wide by 0.9 µm deep. Surface roughness at the bottom of trenches was 100 nm or better with sidewall roughness below detection limits. This study also compares the suitability of the LiBO 2 –LiNbO 3 and the LiVO 3 –LiNbO 3 flux systems. From high-resolution x-ray diffraction and scanning electron microscopy (SEM) data, LiBO 2 –LiNbO 3 was determined to be the superior flux system with respect to diffraction profile widths of the 0 0 12 reflection. Films grown from boron-based flux were observed to have narrower x-ray rocking curve widths than films grown from vanadium-based flux, with typical values of the FWHM of 0.018° and 0.041°, respectively. Boron-based LPE was then used to deposit LiNbO 3 film onto (RIE) LiTaO 3 substrates. SEM imaging and energy dispersive x-ray analysis showed a sharp composition change between film and substrate indicative of a step index change suitable for waveguiding.