Abstract
Abstract Layers of LiNbO3 were grown on sapphire substrates by r.f. diode sputtering using lithium-enriched LiNbO3 as the source material. For substrate temperatures below 200°C the layers formed as an isotropic film with a refractive index in the range 2.00–2.20. Above 500°C there was evidence for crystallinity, and in samples grown above 600°C the two refractive indices reached 2.30±0.02 and 2.20±0.02 as expected for normal crystalline material. Desorbed water vapour in the discharge resulted in the growth of reduced oxide films. Lithium deficiency arising from the growth conditions led to higher refractive indices in all cases. There are clear trends in the conditions needed to generate the LiNbO3 films and optimum conditions were achieved with a 35vol.%O2–65vol.%Ar mixture at power levels which led to deposition of the film at a few angstroms per minute. As an alternative to using a lithium-enriched LiNbO3 r.f. target, niobium metal was reactively sputtered in a d.c. magnetron. When lithium was added to the source the refractive index of the oxide film was reduced below that of the niobium oxides. Thus reactive sputtering of separate metal components may lead to the formation of LiNbO3 films.
Published Version
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