In-situ synthesis of the anhydrous La(hfac)₃ precursor: A viable route to the MOCVD of LaF₃

The anhydrous La(hfac)₃ precursor was obtained in situ by a vapor-solid reaction between hexafluoroacetylactonate (Hhfac) and La₂O₃ powder in the source reservoir of a metal-organic chemical vapor deposition (MOCVD) reactor. Fourier transform infrared spectroscopy (FTIR) in-situ measurements were used to identify the nature of the precursor in the gas phase. Clean LaF₃ films (60-260 nm thick) were deposited on SiO₂/Si substrates in both Ar and Ar/O₂ environments. They were characterized by grazing incidence X-ray diffraction, (GIXRD), X-ray photoelectron spectroscopy (XPS) depth profiles, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis. Very thin (<15 nm) films were also deposited in order to investigate the nucleation and growth processes. Deposited films were found to consist of islands grown on the silicon substrate. The surface coverage depends on the sublimation and substrate temperatures, as well as on the nature of the carrier/reacting gas.