Solid-state photochemistry of thin films: Metal organic deposition from mesomorphous and amorphous films of inorganic complexes

This thesis pertains to the study of thin films of inorganic complexes as precursor materials for optical lithography. The approach we have taken is based on metal precursors that can be coated like a photoresist and imaged by direct photolysis. With this goal in mind, the photochemistry of inorganic complexes of rhenium, gold and silicon was studied.; One of the key elements in the photochemical deposition of materials from thin films was that the thin film had to be amorphous. This amorphous state allows the diffusion of the organic photo-fragments from the deposited film. To extend our work in the area of inorganic thin films and test this idea, we chose to study materials like liquid crystalline inorganic complexes, which have order together with fluidity. Therefore, the solid state photochemistry of mesomorphous thin films of tetrakis(μ-carboxylato)dirhenium(III)dichlorides of general formula Re₂(O₂C_nH_2n−1 )₄Cl₂ (n = 3–8) was studied. This study demonstrated that liquid crystalline thin films are feasible starting materials for the photoresist free lithography of rhenium oxide. This result challenges the previous belief that only amorphous thin films could be used in PMOD chemistry and can be generalized to any other metallomesogen materials. The photochemical reaction was found to involve the decarboxylation of the carboxylate ligand.; The solid state photodecomposition of R₃PAuX, with R = CH ₂CH₃ or phenyl; and X = NO₃, O₂CCH ₃ or O₂CCH(OH)CH₃ was studied. Metallic thin films of gold were deposited by photochemical reaction on silicon and glass substrates. The photochemical reaction produced colloidal gold clusters that could be thermally annealed to form metallic gold. The photodeposition of gold films by this method was shown to be compatible with current lithographic technology.; Silicon dioxide thin films were deposited by the direct photolysis of thin films of bis(2,4-pentadiono)diacetatosilicon(IV) and bis(2,6-tetramethyl-3,5-heptadiono)diacetato silicon (IV). Spin coating of chloroform solutions of these precursors produced amorphous thin films that contained less water than films prepared by sol-gel. Although both precursors were thermally sensitive, their thermal decomposition rate is significantly slower than their photodecomposition rate. The formation of high purity SiO₂ thin films proved to be compatible with current lithography methods.; In our study, an alternative approach to the deposition of nanostructured thin films was also attempted with successful results. Nanoparticles have attracted much attention due to their size dependent physical and chemical properties. The handling and deposition of nanoparticles have been the biggest challenges for this technology. We demonstrate the fabrication of nanostructured thin films, in which the nanoparticle is deposited in an oxide matrix. By direct photolysis of manganese 2-ethylhexanoate thin films containing CdS nanoparticles, nanostructured thin films were produced at room temperature. Upon photolysis, the precursor thin film decomposed to produce a carbon-free manganese oxide thin film, with the CdS nanoparticles retained inside the film.