An investigation into the growth of magnesium niobium oxide and lead magnesium niobate by liquid-injection MOCVD using a magnesium-niobium alkoxide precursor

The double metal alkoxide Mg[Nb(OEt)6]2(2EtOH) has been in investigated as a single-source precursor for the deposition of magnesium niobium oxide and lead magnesium niobate by liquid-injection MOCVD. The presence of Pb(thd)2 (thd=2,2,6,6-tetramethylheptane-3,5-dionate) has been shown to significantly influence the deposition chemistry of the Mg/Nb alkoxide precursor. In the absence of Pb(thd)2 and at low substrate temperatures (˜425 °C) the Mg : Nb ratio in the oxide film grown from Mg[Nb(OEt)6]2(2EtOH) is close to 1 : 2. At higher substrate temperatures (600 °C) the films are magnesium deficient, indicating partial decomposition of Mg[Nb(OEt)6]2(2EtOH). However, in the presence of Pb(thd)2, films grown from Mg[Nb(OEt)6]2(2EtOH) at low temperature (425 – 500 °C) contain no detectable Mg, whilst the 1 : 2 Mg : Nb ratio, required for Pb(Mg0.33Nb0.66)O3, is now obtained at higher substrate temperatures (600°C). This is attributed to the formation of a thermally-stable Mg β-diketonate species via a gas-phase ligand exchange reaction between Pb(thd)2 and Mg[Nb(OEt)6]2(2EtOH).