Pulsed laser deposition of KNbO₃ thin films

• Main Authors: Martin, M.J (Author), Alfonso, J.E (Author), Mendiola, J. (Author), Zaldo, C. (Author), Gill, D.S (Author), Eason, R.W (Author), Chandler, P.J (Author)
• Format: Article
• Language: English
• Published: 1997-10.
• Subjects: Article
• Online Access: Get fulltext

 The laser ablation of stationary KNbO₃ single crystal targets induces a Nb enrichment of the target surface. In rotated targets this effect is observed only in those areas irradiated with low laser fluence. The composition of the plasma formed close to the target surface is congruent with the target composition; however, at further distances K-deficient films are formed due to the preferential backscattering of K in the plasma. This loss may be compensated for by using K-rich ceramic targets. Best results so far have been obtained with [K]/[Nb] = 2.85 target composition, and crystalline KNbO₃ films are formed when heating the substrates to 650 °C. Films formed on (100)MgO single crystals are usually single phase and oriented with the (110) film plane parallel to the (100) substrate surface. (100)NbO may coexist with KNbO₃ on (100)MgO. At substrate temperatures higher than 650 °C, niobium diffuses into MgO forming Mg₄Nb₂O₉ and NbO, leading to K evaporation from the film. Films formed on (001) alpha-Al₂O₃ (sapphire) show the coexistence of (111), (110), and (001) orientations of KNbO₃, and the presence of NbO₂ is also observed. KNbO3 films deposited on (001)LiNbO₃ crystallize with the (111) plane of the film parallel to the substrate surface. For the latter two substrates the Nb diffusion into the substrate is lower than in MgO and consequently the K concentration retained in the film is comparatively larger.