Metalorganic chemical vapor deposition of metal oxides

Ruthenium dioxide, zirconium dioxide and bismuth titanate thin films were deposited on Si, sapphire disks, and Pt/Ti/SiO₂/Si substrates by hot wall metalorganic chemical vapor deposition (MOCVD). Bis(cyclopentadienyl)ruthenium [Ru(C₅H₅)₂], zirconium tetramethylheptanedione [Zr(thd)₄], triphenylbismuth [Bi(C₆H₅)₃], and titanium ethoxide [Ti(C₂H₅O)₄] were used as precursors. MOCVD RuO₂ film structure was dependent on MOCVD process parameters such as bubbler temperature, dilute gas flow rates, deposition temperature, and total pressure. Either pure RuO₂, pure Ru, or a RuO₂ + Ru mixture was obtained under different deposition conditions. As-deposited pure RuO₂ films were specular, crack-free, and adhered well on the substrates. The Auger electron spectroscopy depth profile showed a good composition uniformity across the bulk of the films. The MOCVD RuO₂ thin films exhibited resistivities as low as 60 <i>μ</i>Ω-cm. In addition, the reflectance of RuO₂ in the NIR region showed a metallic character. Zr(thd)₄ was synthesized and the process was optimized. Purity of Zr(thd)₄ was confirmed by melting point determination, carbon and hydrogen elemental analysis and proton nuclear magnetic resonance spectrometer (NMR). The MOCVD ZrO₂ film deposition rates were very small (≤ 1 nm/min) for substrate temperatures below 530°C. The film deposition rates were significantly affected by: (1) source temperature, (2) substrate temperature, and (3) total pressure. As-deposited films are carbon free. Furthermore, only the tetragonal ZrO₂ phase was identified in as-deposited films. The tetragonal phase transformed progressively into the monoclinic phase as the films were subjected to high temperature post-deposition annealing. The optical properties of the ZrO₂ thin films as a function of wavelength, in the range of 200 nm to 2000 nm, were also reported. In addition, a simplified theoretical model which considers only a surface reaction was used to analyze the deposition of ZrO₂ film. The deposition rates can be predicted well for various deposition conditions in the hot wall reactor. The deposition rates of MOCVD Bi₄Ti₃O₁₂ were in the range of 3.9-12.5 nm/min. The Bi/Ti ratio was controlled by precursor temperature, carrier gas flow rate, and deposition temperature. As-deposited films were pure Bi₄Ti₃O₁₂ phase. The films were specular and showed uniform and fine-grain morphology. Optical constants as a function of wavelength were calculated from the film transmission characteristics in the UV-VIS-NIR region. The 550°C annealed film had a spontaneous polarization of 26.5 <i>μ</i>C/cm² and a coercive field of 244.3 kV/cm.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Materials Science and Engineering

Department dc:contributor.department

Materials Science and Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1993

Author dc:creator

• Si, Jie

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Dc Identifier Other

etd-12302008-063204

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/46433