Reduced thermal decomposition of OH-free LiNbO₃ substrates even in a dry gas atmosphere

Abstract

A thermal diffusion process of Ti into a LiNbO 3 substrate for optical waveguides has generally been carried out under a wet gas atmosphere in order to prevent undesirable Li outdiffusion. In this work, such thermal decomposition was confirmed to be significantly suppressed for an OH-free LiNbO 3 substrate, even after a dry atmosphere annealing. No extra x-ray diffraction peak for LiNb 3 O 8 was detected from the OH-free substrate after 10 h of annealing at 1000 ± C in a dry O 2 . Furthermore, the surface morphology of this sample, and as well an unannealed one, were smooth. In a conventional LiNbO 3 substrate containing many OH ions, subjected to a similar dry annealing, the presence of the LiNb 3 O 8 phase and a surface coarsening were observed.

Atomic force and scanning electron microscopic observations of surface and domain structures of BaTiO3 films and bulk crystals

“…18 NanoScope IIIa has a high magnification (ϫ800) monitor system for optical detection of the cantilever position. The TMAFM method is very useful to observe small differences in the height by dry etching due to thermal decomposition 19 during annealing in a vacuum chamber for 5 to 6 hours down to room temperature and/or due to oxygen radical during growth 18 without damage of film surfaces. One group of the films was prepared at a slow deposition rate ͑about 0.01 nm/s͒ 20 showing a full-width at half-maximum ͑FWHM͒ of the rocking curve for the 002 reflection of 0.02°t o 0.03°, called an ''LD series.''…”

О повышении объемной концентрации водорода в нелегированных кристаллах LiNbO-=SUB=-3-=/SUB=- конгруэнтного состава

“…Отметим, что ни в одной из работ [7,11,[20][21][22] не приводится значение парциального давления P H 2 O паров H 2 O в атмосфере, в которой происходил отжиг кристалла. Однако этот параметр, несомненно, должен влиять на результаты термохимической обработки, так как отжиг НЛ в чистых парах H 2 O или D 2 O уже при 773 K приводит к сильному восстановительному эффекту и резкому увеличению оптической плотности НЛ в видимом диапазоне [23,24], но не влияет на значение c H [11].…”