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Pulsed laser deposition of KNbO3 thin films

M.J.Martin, J.E.Alfonso, J.Mendiola, and C.Zaldo
Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Cantoblanco, 28049 Madrid, Spain

D.S.Gill and R.W.Eason
Department of Physics and Optoelectronics Research Centre, University of Southampton

P.J.Chandler
School of Mathematical and Physical Sciences, University of Sussex, Brighton BN1 9QH, UK

Abstract

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) α-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.


Journal of Materials Research (1997) Vol.12(10) pp.2699-2706

doi: 10.1557/JMR.1997.0359

Southampton ePrint id: 77920

 

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Copyright University of Southampton 2006