Synthesis, microstructure, and electronic band structure properties of nanocrystalline neodymium-doped bismuth titanate ferroelectric films fabricated by the sol-gel method

摘要

Bi_(4-x)Nd_xTi_3O_(12) (BNT) films with different Nd contents (from 0 to 1 with 0.25 intervals) are prepared by the sol-gel process. The Nd substitution effects on the preferred orientation, surface morphology, phonon modes, emission bands, andelectronic band structures of the BNT films are investigated by microscopy, Raman scattering, photoluminescence, and spectroscopic ellipsometry (SE) at room temperature. X-ray diffraction indicates that the films are polycrystalline with the pure perovskite phase. Ten Raman active modes and one silicon substrate mode can be observed. The A_1 _g[Bi] at about 59cm~(-1) is unchanged whereas the B_1 g and A_1 g[Ti] phonon modes shift towards higher frequencies. Photoluminescence shows that the intensities of the two peaks increase with Nd concentration except the Bi_3NdTi_3O_(12) film, due to the smallest grain size and oxygen vacancy defects. Good optical functions of the BNT films are achieved due to the SE suggesting potential applications in ferroelectric-based optoelectronic devices.