Structural and optical properties of BaTiO3 thin films prepared by radio-frequency magnetron sputtering at various substrate temperatures.
Thin films of BaTiO3 were prepd. by radiofrequency magnetron sputtering at substrate temps. from 450 to 750 Deg and analyzed by x-ray diffraction, optical transmittance and Raman spectroscopy. The packing d. of the films relative to the cryst. d. increases from 0.75 at 450 Deg to .apprx.1 at 750 Deg. At a substrate temp. of 450 Deg, the film is nano-cryst. (5 to 20 nm) with big lattice expansion, large band gap and pronounced hexagonal Raman lines. This film is homogeneous in the thickness direction. Films prepd. at higher temps. exhibit perovskite peaks in the Raman spectrum and an optical band gap of 3.38 eV. At 600 Deg, the film exhibits a pronounced two-phase growth with a porous nucleation layer of initial packing d. of 0.78, a preferred (100)-orientation of the grains and min. micro-strain. At 750 Deg, the films are again homogeneous in the thickness direction, have nearly cryst. packing d. and preferably (110)-oriented grains.
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