Chemistry of silicon-containing compounds and molecular approaches to materials for silicon-based microelectronics. Preparation of metal silyl complexes, studies of reactions between alkylidenes and silanes, and deposition of titanium oxide thin films

This dissertation describes studies of the chemistry of silicon-containing compounds and molecular approaches to silicon-based microelectronic materials. The preparation of new silyl dianions and transition metal silyl complexes, studies of the mechanism of reactions between alkylidenes and silanes, and fabrication of TiO₂ thin films on Si as microelectronic gate materials are presented.; Chapter 1 provides a brief overview of the field of early transition metal silyl chemistry, experimental techniques used in the research, and a summary of research conducted in each subsequent chapter. Chapter 2 describes the synthesis and characterization of new silyl dianions of the type [K(18-crown-6)] ₂[(Me₃Si)₂Si-(CH₂)_n-Si(SiMe ₃)₂] (n = 1, 4; 2, 5; 3, 6). These represent some of the few known disilyl dianions. Crystal structures of the starting materials to 5 and 6, (Me₃Si)₃Si-(CH₂)_n-Si(SiMe ₃)₃, (n = 2, 2; 3, 3) were determined by X-ray diffraction studies. The preparation and characterization of novel Zr and Zn silyl complexes from the reactions of 5 with (Me ₂N)₃ZrCl and ZnCl₂, respectively, are presented in Chapter 3. Both complexes are anionic with K(18-crown-6)+ counterions. {lcub}(Me₂N)₃Zr[η2-(Me ₃Si)₂Si(CH₂)₂Si(SiMe₃) ₂]{rcub}− (7) consists of a five-coordinate Zr center. [K(18-crown-6)]₂{lcub}[η2-(Me₃Si) ₂Si(CH₂)₂Si(SiMe₃)₂]Zn ₂[μ-(Me₃Si)₂Si(CH₂)₂-Si(SiMe ₃)₂]{rcub} (8) is the first trisilyl Zn complex. 8 is a dimer with each Zn metal center coordinated by a chelating and a bridging disilyl ligand. Chapter 4 presents new mechanistic insights into the reactions of a Ta alkylidene complex (Me₃SiCH₂) ₃Ta(PMe₃)[=CHSiMe₃] (9) with H ₂SiMePh. Such reactions yielded new silyl-substituted alkylidene complexes. Experiments conducted in the presence of 20-fold PMe₃ were 19 times slower than those conducted with no added phosphine. Mass spectral analysis of the gaseous products from the reaction conducted in the presence of H ₂ suggested hydrogen scrambling. Finally, Chapter 5 discusses the preparation and characterization of TiO₂ thin films on Si from the reaction of Ti(NMe₂)₄ with O₂ by chemical vapor deposition. These films were characterized by X-ray photoelectron spectroscopy, powder X-ray diffraction, infrared spectroscopy, ellipsometry and scanning electron microscopy, and found to be amorphous before annealing but crystalline anatase after annealing at 600°C for 1 h in air. Importantly, these analyses suggested that the films were C-free and contained no TiN or TiO_xN_y species.