Lanthanide N,N-dimethylaminodiboranates: Highly volatile precursors for the deposition of lanthanide-containing thin films

New lanthanide CVD precursors of stoichiometry Ln(H3BNMe2BH3)3 have been prepared, where Ln = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu. The ligand is N,N-dimethylaminodiboranate, a new kind of multidentate borohydride. The structures of the Ln(H3BNMe2BH3)3 complexes are highly dependent on the size of the lanthanide ions: the coordination number decreases from Pr (CN = 14) to Sm (CN = 13) to Er (CN = 12) corresponding with the decrease in ionic radii. The Ln(H3BNMe2BH3)3 complexes are highly volatile and sublime at temperatures as low as 65 °C in vacuum. These complexes are useful CVD precursors; for example, Y(H3BNMe2BH3)3 has been used to deposit Y2O3 on silicon at 300 °C by CVD using water as a coreactant.