Deposition of metal oxide films and nanostructures by methods derived from photochemical metal organic deposition

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(Thesis) Ph.D.
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Author: Zhang, Xin
In this research, methods for the deposition of patterned films and nanostructures were developed from photochemical metal organic deposition (PMOD). Positive lithographic PMOD was demonstrated with films of titanium (IV) di-n-butoxide bis(2-ethylhexanoate) (Ti(OBun)2(eh)2), titanium (IV) diisopropoxide bis(2,4-pentanedionate), and zirconium (IV) di-n-butoxide bis(2,4-pentanedionate). The photochemistry of these complexes in films was studied by FTIR, AES, and XRD. Photo-induced reactivity and polarity changes are believed to affect film solubility in developers. This made it possible to achieve both negative and positive PMOD by simply altering the developers. Electron beam induced metal organic deposition (EMOD) was studied. Feature sizes as small as 12 nm were achieved by negative lithographic EMOD, using Ti(OBun)2(eh)2 and bis(2,2,6,6-tetramethyl-3,5-heptanedionato)(1,5-cyclooctadiene)ruthenium (II), Ru(cod)(tmhd)2. Positive lithographic EMOD was demonstrated for the first time. Two dry lithographic PMOD (and EMOD) methods were developed. In one method, a film formed from tetrakis(trimethylsiloxy)titanium (IV) was used to produce a latent image by masked UV exposure followed by a thermal treatment, which consists of TixSi1-xO2 in the exposed region but TiO2 in the unexposed region. A negative pattern was obtained by etching the latent image with argon plasma. In the other method, a bis(triphenylphosphine) nickel (0) dicarbonyl film was subjected to masked UV exposure followed by a thermal treatment, resulting in a negative pattern. Ru(cod)(tmhd)2 was also tested with this method and feature sizes as small as 20 nm were obtained. The lithographic deposition of films with multiple layers was demonstrated. In this method, a film prepared by sequentially spin coating three solutions of complexes, was subjected to a wet lithographic PMOD process, resulting in a negative pattern with three layers. With this method, bi-layer films with different patterns in each layer were obtained too. The deposition of patterns with nanostructures was demonstrated using immiscible complexes. In this method, solutions containing immiscible zirconium (IV) 2-ethylhexanoate and yttrium (III) nitrate were used for spin coating. By altering the complexes’ ratio and the spinning speed, films with nanostructures of various sizes and densities were obtained. A negative pattern with nanostructures was produced by wet lithographic PMOD from one of the films.
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