Elucidating the Surface Reaction Mechanisms During Atomic Layer Deposition of Li_<i>x</i>Al_<i>y</i>Si_<i>z</i>O by in Situ Fourier Transform Infrared Spectroscopy

Reaction mechanisms in the atomic layer deposition (ALD) of Li_<i>x</i>Al_<i>y</i>Si_<i>z</i>O (LASO) using a LiOC­(CH₃)₃/H₂O–Al­(CH₃)₃/H₂O–Si­(OCH₂CH₃)₄/H₂O chemistry were studied via in situ Fourier transform infrared spectroscopy (FTIR) at 225 °C. ALD deposition of Al₂O₃ using an Al­(CH₃)₃/H₂O chemistry and LiOH using a LiOC­(CH₃)₃/H₂O chemistry demonstrated ideal ALD growth. ALD deposition of SiO₂ alone by Si­(OCH₂CH₃)₄/H₂O chemistry was unsuccessful; however, incorporation of the same Si­(OCH₂CH₃)₄/H₂O chemistry in between ALD processes of Al₂O₃ and LiOH resulted in ALD deposition of Li_<i>x</i>Al_<i>y</i>Si_<i>z</i>O. The as-deposited ALD LASO film with a composition of Li_0.40Al_0.32Si_0.28O on a Si(100) substrate was amorphous but crystallized into β-LiAlSiO₄ upon rapid thermal annealing (RTA) at 900 °C under N₂. The ionic conductivity of as-deposited, amorphous ALD Li_0.40Al_0.32Si_0.28O was as high as 1.62 × 10^–6 S/cm at 361 °C with an activation energy of <i>E</i>_a = 0.70 eV