Thermal oxidation of oxynitride films as a strategy to achieve (Sr₂Ta₂O₇)_100-x(La₂Ti₂O₇)_x based oxide perovskite films with x = 1.65

L. Le Gendre (1) , C. Le Paven (1) , M. Haydoura (1) , R. Benzerga (1) , Florent Marlec (1) , A. Sharaiha (1) , François Cheviré (2) , Franck Tessier (2) , A. Moréac (3)

1 IETR - Institut d'Électronique et des Technologies du numéRique
2 ISCR - Institut des Sciences Chimiques de Rennes
3 IPR - Institut de Physique de Rennes

This study concerns STLTO compounds of the ferroelectric (Sr 2 Ta 2 O 7) 100-x (La 2 Ti 2 O 7) x solid solution. The purpose is to produce the STLTO composition x = 1.65 as thin films by thermal oxidation of the corresponding oxynitride composition. Indeed, the combination of an STLTO oxide target with a dioxygen-rich reactive atmosphere during the sputtering deposition leads to Sr-deficient oxide thin films, shifting composition and structure from the perovskite to the tetragonal tungsten bronze type. An alternative synthesis pathway is to first deposit, under nitrogen-rich atmosphere, stoichiometric oxynitride films and produce, by thermal annealing under air, the stoichiometric oxide. For low oxidation temperatures ([550-600°C]), samples remain intact and display an oxide character but still contain a significant amount of nitrogen; they could be described as intermediate phases containing nitrogen-nitrogen pairs as demonstrated by Raman. Dielectric characteristics of these original film materials are of interest with a tunability value of 26 % at 30 kV/cm (10 kHz).

Domains: Chemical Sciences; Chemical Sciences; Material chemistry; Physics [physics]

L. Le Gendre, C. Le Paven, M. Haydoura, R. Benzerga, Florent Marlec, et al.. Thermal oxidation of oxynitride films as a strategy to achieve (Sr₂Ta₂O₇)_100-x(La₂Ti₂O₇)_x based oxide perovskite films with x = 1.65. Journal of the European Ceramic Society, 2020, 40 (16), pp.6293-6300. ⟨10.1016/j.jeurceramsoc.2019.12.023⟩. ⟨hal-02421162⟩