Infrared Optical Properties ofBi4..,NdxTi3Ol2 ThinFilms Prepared bya Chemical Solution Method

Infrared optical properties ofBi4-NdxTi3Ol2 (BNT(x=0,0.25,0.50,0.75)) thin filmshave been investigated using theinfrared spectroscopic ellipsometry inthewavelength rangeof2.5-11.4gm (0.11-0.50eV). Theirrefractive indexdecreased and extinction coefficient increased asthewavelength increased. Both therefractive indexand theextinction coefficient decreased astheconcentration ofNd increased. In addition, the wavelength and Nd concentration dependence oftheabsorption coefficient showedthe similar behavior tothatoftheextinction coefficient. I. INTRODUCTION Ferroelectric thinfilms areverypromising fora wide range ofapplications suchasnonvolatile memories, electro- optic devices, uncooled infrared detectors andfocal plane arrays (IRFPA). Recently, bismuth-based layer-structured compounds, suchasBi4Ti3O12 (BIT) andits doped materials, haveattracted muchattention duetotheir lead-free, high dielectric constants, excellent ferroelectricity , piezoelectric and electro-optic properties. La-substituted BIT,Bi4 xLaxTi3O12 (BLT), isapromising candidate foranalternative material ofPbZrl xTixO3 (PZT), because ofitslarge spontaneous polarization andgoodfatigue endurance. Recently, ithasbeenreported that Nd-substituted BIT,Bi4 xNdxTi3O12 (BNT), showedbetter ferroelectricity thanBLT (1).Up tonow,thestudy ofBITrelated material dealt mainly withtheir electric properties. Several reports onthe optical properties only focused ontheBITfilms andtheBLT films. Inourprevious work,theoptical properties of BNT(x=0.75) thin film inthewavelength range of0.2-1.7tm havebeeninvestigated. However, theinfrared optical properties ofBNT thin films havenotbeenreported yet, to ourknowledge. Study oftheinfrared optical properties of BNTthin films withvarious Ndconcentrations should beof interest foritspotential applications ofintegrated optics devices.