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Thick films of lithium niobate (LiNbO[sub 3]) have been epitaxially grown on sapphire substrates by multistep radio-frequency magnetron sputtering. We have investigated the optical properties of the deposited layers by the m-line spectroscopy technique. The relationship between the film-substrate interface, the surface morphology of the LiNbO[sub 3] layer, and the optical measurements has been carefully established. Since this optical technique is sensitive to material defects, a detectable degradation of the optical data is observed when the microstructure of the LiNbO[sub 3] film changes. In particular, the angular width of the excited optical guided modes (Δθ) varies with the film thickness. This agrees perfectly with the evolution of the surface roughness as a function of the film thickness. We report a surface roughness r[sub ms] of 2 nm corresponding to an angular width Δθ of 0.1° for the TE[sub 0] mode. The accuracy and the sensitivity of this technique can be advantageously compared to the classical tool of atomic force microscopy. [ABSTRACT FROM AUTHOR]

We present the results of investigations of lithium niobate (LiNbO[sub 3]) films grown on (0001) sapphire substrate by radio-frequency magnetron sputtering. With the aim of producing thick films we have developed a multistep process. To assess the structural quality of our films, we performed x-ray diffraction, transmission electron microscopy, and atomic force microscopy of the films. The results revealed that the epitaxial structure is verified on sapphire whatever the film thickness. Based on our studies we concluded that the proposed multistep process leads to a good controlled epitaxy of thick LiNbO[sub 3] samples on sapphire. Using the prism coupling technique we have characterized the optical properties of the deposited layers. The ordinary (n[sub o]) and extraordinary (n[sub e]) refractive indices are, respectively, 2.289±0.001 and 2.206±0.001 at 632.8 nm, and waveguide losses of 1.2 dB/cm have been demonstrated. In addition, we have qualified the film properties between each growth step and between the substrate to layer interface, directly from the measured optical data. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Thick films of lithium niobate are epitaxially grown on sapphire substrates by multistep radio frequency magnetron sputtering. Results indicate that the angular width of the excited optical guided modes varies with the film thickness.

The results of investigations of lithium niobate (LiNbO3) films grown on (0001) sapphire substrate by radio-frequency magnetron sputtering are presented. The film properties between each growth step and between the substrate to layer interface, directly from the measured optical data are qualified.

Surface acoustic wave (SAW) technology based on lithium niobate/diamond/silicon multilayered structures has been investigated due to the large demand of frequency filters for communication systems, particularly for cellular phones. Thick LiNbO[sub 3] layers (∼1 µm) with a good morphology, i.e., surface roughness lower than 10 nm have been grown at 490 °C on diamond-coated silicon substrates by multistep rfmagnetron sputtering. A SAW devices operating at 300 MHz was designed and fabricated in order to validate the proposed structure; in particular, our main objective was to verify the high velocity in the layered structure. Preliminary filter responses were very promising: the SAW velocity was estimated to 8200 m/s and the coupling factor was K²∼0.93%. The film growth, the technology, and the electrical measurements are described in this letter. [ABSTRACT FROM AUTHOR]