Homo-epitaxial growth of Lithium Niobate by Pulsed-Laser Deposition
Résumé
Nowadays LiNbO3 single crystals in electro-optics are equivalent to silicon in electronics, and about 70% of radio-frequency (RF) filters, based on acoustic waves (acoustic resonators such as Surface Acoustic Waves (SAW) and Bulk Acoustic Wave (BAW) resonators), are fabricated on these single crystals [1]. LiNbO3-based structures have been mainly obtained by film transfer approaches [2], since obtaining single-phased, stoichiometric, and epitaxial LiNbO3 is challenging by conventional physical and chemical deposition techniques [1]. However, the layers used for devices can be nanometer-level in thickness, which is not always possible with Thin-Film Transfer technics [3]. Homo-epitaxial growth of LiNbO3 thin films by PLD (0 0 1), (1 1 0), and (1 0 0) monocrystalline substrates was demonstrated by L. C. Sauze et al. [4], and the present publication will be the continuation of her work.
In this study, LiNbO3 thin films were homo-epitaxially grown by Pulsed Laser Deposition (PLD). Different substrates' orientations ((0 0 1), (1 1 0), and (1 0 4) crystal orientations) were investigated in an attempt to control the LiNbO3 crystalline orientation. In order to control the film crystallinity and chemical composition, growth parameters, such as substrate temperature, oxygen pressure, and target composition, were studied. The physical and chemical properties of the as-deposited LiNbO3 layers were characterized and correlated to the deposition conditions. The surface morphology of films was investigated by Atomic Force Microscopy (AFM). Structural properties of the layers have been characterized by XRD including High-Resolution X-Ray Diffraction (HRXRD). High-resolution reciprocal space mappings were performed to measure the homo-epitaxial deposited layer quality.
References
[1] A. Bartasyte et al., "Toward High-Quality Epitaxial LiNbO3 and LiTaO3 Thin Films for Acoustic and Optical Applications," Adv. Mater. Interfaces, vol. 4, 2017.
[2] J. Shen et al., "A Low-Loss Wideband SAW Filter with Low Drift Using Multilayered Structure," IEEE Electron Device Letters, vol. 43, no. 8, pp. 1371-1374, 2022.
[3] Z. Ren et al., "Heterogeneous Wafer Bonding Technology and Thin-Film Transfer Technology-Enabling Platform for the Next Generation Applications beyond 5G," Micromachines, vol. 12, no. 8, p. 946, 2021.
[4] L. C. Sauze et al., "Homo-epitaxial growth of LiNbO3 thin films by Pulsed Laser deposition," Journal of Crystal Growth, vol. 601, p. 126950, 2023.