Rf sputtered Na0.5K0.5NbO3 films on oxide substrates as optical waveguiding material
2003 (English)In: Integrated Ferroelectrics, ISSN 1058-4587, Vol. 54, 631-640 p.Article in journal (Refereed) Published
Highly crystalline Na0.5K0.5NbO3 (NKN) thin films of 1-2 mum thickness were deposited by rf-magnetron sputtering of a stoichiometric, ceramic target on single crystal LaAlO3 (001) and Al2O3 (01 (1) under bar2) substrates. X-ray diffraction measurements revealed epitaxial quality of NKN/LaAlO3 film structures, whereas NKN films on sapphire substrates were found to be preferentially c -axis oriented. A prism-coupling technique was used to characterize optical and waveguiding properties. A bright-line spectrum at lambda = 632.8 nm, revealed sharp peaks, corresponding to transverse magnetic (TM) and electric (TE) waveguide propagation modes in NKN/LaAlO3 and NKN/Al2O3 thin films. Using a least mean square fit the refractive index for the films and film thickness were calculated. The extraordinary and ordinary refractive indices were determined to n(e) = 2.207 +/- 0.002 and n(o) = 2.261 +/- 0.002, and n(e) = 2.216 +/- 0.002 and n(o) = 2.247 +/- 0.002 at lambda = 632.8 nm for 2.0 mum thick NKN films on LaAlO3 and Al2O3 , respectively. This corresponds to a birefringence Deltan = n(e) - n(o) = -0.054 +/- 0.003 and Deltan = -0.031 +/- 0.003 in the films, where the larger Deltan for the NKN/LaAlO3 structure can be explained by the superior crystalline quality compared to NKN/Al2O3 . Atomic force microscopy images of the film surfaces revealed rms roughnesses of 2.5 nm and 8.0 nm for 1.0-mum thick NKN/LaAlO3 and NKN/Al2O3 films, respectively. We believe surface scattering is one of the main sources of waveguide losses in the thin films.
Place, publisher, year, edition, pages
2003. Vol. 54, 631-640 p.
Na0.5K0.5NbO3 films, rf-magnetron sputtering, prism coupling, waveguiding, refractive index, knbo3 thin-films, sapphire, light
Other Materials Engineering
IdentifiersURN: urn:nbn:se:kth:diva-23054DOI: 10.1080/10584580390259047ISI: 000187625200013OAI: oai:DiVA.org:kth-23054DiVA: diva2:341752
QC 201005252010-08-102010-08-102010-09-28Bibliographically approved