Synthesis, crystal structure and thermal decomposition of [La_2(CH_3CH_2COO)_6·(H_2O)_3]·3.5H_2O precursor for high-k La_2O_3 thin films deposition

摘要

Lanthanum acetylacetonate La(C_5H_7O_2)_3·xH_2O has been used in the preparation of the precursor solution for the deposition of polycrystalline La_2O_3 thin films on Si(111) single crystalline substrates. The precursor chemistry of the as-prepared coating solution, precursor powder and precursor single crystal have been investigated by Fourier Transformed Infrared Spectroscopy (FTIR), differential thermal analysis coupled with quadrupole mass spectrometry (TG-DTA-QMS) and X-ray diffraction. The FTIR and X-ray diffraction analyses have revealed the complex nature of the coating solution due to the formation of a lanthanum propionate complex. The La_2O_3 thin films deposited by spin coating on Si(111) substrate exhibit good morphological and structural properties. The films heat treated at 800 ℃ crystallize in a hexagonal phase with the lattice parameters a = 3,89 A and c = 6.33 A, while at 900 ℃ the films contain both the hexagonal and cubic La_2O_3 phase.