Fluorinated aminoalkoxide and ketoiminate indium complexes as MOCVD precursors for In₂O₃ thin film deposition

The syntheses of two distinctive types of indium complex derived from trimethylindium (InMe₃) are reported. The first kind has a generalized structural formula [InMe₂(amak)]₂, where (amak)H is an abbreviation for a series of chelating amino alcohol ligands HOC(CF₃)₂CH₂NHR, R = (CH₂) ₂OMe (1), Me (2), and Bu^t (3), as well as HOC-(CF ₃)₂CH₂NMe₂ (4); while the second type of complex is illustrated by [InMe₂(keim)] (5), for which (keim)H is a tridentate ketoimine ligand of structural formula O=C(CF ₃)CH₂C(CF₃)=NCH₂CH ₂NMe₂. The solid-state structures of 2 and 5 were determined using single crystal X-ray diffraction studies. For the aminoalkoxide complexes 2-4, the existence of dimeric In₂O ₂ core structures in the solid state has been established with the amino fragment located trans to the alkoxide ligands, in a molecular arrangement which is in contrast to the distorted, trigonal bipyramidal geometry observed for the ketoiminate complex 5. Moreover, VT NMR studies of 2 revealed a rapid dimer-to-monomer equilibration and simultaneous rupture of the N→In dative interaction, affording two interconvertible isomers related by having the N-Me substituents in either trans or cis dispositions. For complexes 2 and 5, deposition of In₂O₃ thin films was successfully conducted at temperatures 400-500 °C, using O₂ as the carrier gas to induce indium oxide deposition and to suppress carbon impurity present in the thin film. Scanning electron micrographs (SEMs) revealed the surface morphologies. The atomic composition of these films was examined by both X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering (RBS) methods, while X-ray diffraction studies (XRD) confirmed the formation of a preferred orientation along the (222) planes.