Chemically Modified Thin Organic Films Supported on Chemomechanically Polished Inorganic Substrates

[摘要] In this work an investigation of chemomechanical polishing of silica and silicon has been conducted, in order to produce ultrasmooth surfaces (roughness ≤ 1 nm) rapidly and to understand the mechanisms of the chemical processes involved. A comparison of fluoride-based reagents (alkaline colloidal silica sol modified by the addition of potassium hydrogen difluoride and a reagent described in the patent literature (69), comprised of an aqueous suspension of hydrochloric acid, potassium hydrogen difluoride, cerium(IV) oxide and sucrose) with conventional polishing reagents (an aqueous suspension of cerium(IV) oxide and alkaline colloidal silica sol) was made. Fluoride based reagents have been used successfully for the polishing of silica glass and the work developed further and amplified with model studies using fluorine-18 as a radiotracer. Identification of surface and bulk species by FT-IR spectroscopy (diffuse reflectance, photoacoustic, attenuated total reflection and transmission) and FT-IR microspectroscopy coupled with silicon-29 MAS-NMR, SEM and powder XRD techniques has been accomplished. Similar strategies were employed for polishing of silicon. Surface roughness measurements were conducted using a Nomarski light microscope and Talystep stylus profiler, allied with laser interferometry. Work conducted in this part of the study has enabled the positive identification of a reaction intermediate {the passivating layer) formed during the chemomechanical polishing of silica for the first time. By employing highly polished silica and silicon wafers the production of ordered organic films derived from polycyclic aromatic hydrocarbons was achieved by high vacuum sublimation techniques. The compounds chosen in this study were anthracene, tetracene, pentacene, perylene, ovalene, fluoranthene, rubrene, decacyclene, violanthrone, coronene tetracarboxylic acid, coronene tetracarboxylic dianhydride, peryiene tetracarboxylic dianhydride, bis(ethylenedithio) tetrathiafiilvalene, pyrene, chrysene and polymeric fluoro-bridged aluminium(III) phthalocyanine. Chemical modification of the fihns has been achieved by formation of electron donor: acceptor complexes with the volatile high oxidation state main group and transition metal halides arsenic pentafluoride, molybdenum and tungsten hexafluorides and the solid organic electron-acceptor species tetracyano-p-quinodimethane. Films were characterised by UV-vis-NIR and FT-IR spectroscopy. The Quartz Crystal microbalance technique was employed to investigate the oxidative doping of polymeric fluoro-bridged aluminium(III) phthalocyanine, to determine both reaction stoichiometry and mechanism. By comparison of the unmodified organic films with their derived donor: acceptor complexes, films could be placed into one of three categories; those which exhibited both electronic and physical perturbations, those which exhibited physical perturbations only and those for which the electronic spectra were dominated by interference patterns. In all cases there was no conclusive evidence in the electronic spectra for the formation of radical cations derived from donor polycyclic aromatic hydrocarbons.

[发布机构] University:University of Glasgow

[关键词] Inorganic chemistry, Organic chemistry