published_or_final_version / abstract / toc / Physics / Master / Master of Philosophy

published_or_final_version / abstract / Physics / Doctoral / Doctor of Philosophy

published_or_final_version / Physics / Master / Master of Philosophy

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<p>This master thesis in physics mainly treats Auger spectroscopy of interfaces that has been adhesively bond together with so called controlled delaminating materials (CDM). CDM is a new technology which involves adhesives with the distinctive property that they by the appliance of electricity can be released from a substrate. The reason for using Auger spectroscopy was that it gives a surface sensitive view of the chemical composition of the samples examined and this was believed to give hints of the mechanisms behind loss of adhesion. The samples were so called laminates which is an aluminium foil, CDM adhesive, aluminium foil structure. As expected Auger spectroscopy produced some promising results, especially regarding the breakdown of a certain anion contained into the examined CDM adhesive. This awoke new questions regarding how this anion was decomposed and the idea that it could be due to hydrolysis took form. The by far most important result within this work is that the anion breaks down. This could lead to the formation of hydrofluoric acid if this breakdown in fact is due to hydrolysis and the hydrofluoric acid could then react with the aluminium causing loss of adhesion. This could be the good starting point of a continuing work on CDM.</p>

<p>The properties relevant for electron transfer processes between dye molecules and semiconductor substrates, titanium dioxide (TiO₂) and zinc oxide (ZnO), have been studied by means of photoelectron spectroscopy, PES, near edge X-ray absorption spectroscopy, NEXAFS, and resonant photoemission, RPES.</p><p>For dye-sensitized solar cells, the currently used dyes are ruthenium polypyridine complexes adsorbed to the semiconductor via carboxyl linker groups. A series of such complexes has been investigated, and the most efficient dye so far, cis-bis(4,4'-dicarboxy-2,2'-bipyridine)-bis(isothiocyanato)ruthenium(II), RuL'₂(NCS)₂, was studied in more detail. The results revealed a high content of thiocyanate orbitals in the highest occupied molecular orbital, HOMO, of this complex, which partly explains its efficiency in the solar cell. The thiocyanate ligands were found to be highly influenced by the substrate when the dye is adsorbed onto ZnO, which is not the case for the corresponding TiO₂ system. </p><p>A bridge bonding between TiO₂ and the L' ligand was proposed, where the carboxyl groups are deprotonated and all oxygens interact with surface titanium ions. For ZnO, the results indicate a different bonding geometry, involving protonated carboxyl groups.</p><p>For the display system a dye molecule, which shifts color upon electrochemical treatment, was adsorbed on TiO₂ and studied in its reduced and oxidized states. The major electronic difference between the two states was shown to occur on the nitrogen atom. In addition, a reversible photoreduction process during the measurements was observed.</p>

Graduation date: 1997

The properties relevant for electron transfer processes between dye molecules and semiconductor substrates, titanium dioxide (TiO2) and zinc oxide (ZnO), have been studied by means of photoelectron spectroscopy, PES, near edge X-ray absorption spectroscopy, NEXAFS, and resonant photoemission, RPES. For dye-sensitized solar cells, the currently used dyes are ruthenium polypyridine complexes adsorbed to the semiconductor via carboxyl linker groups. A series of such complexes has been investigated, and the most efficient dye so far, cis-bis(4,4'-dicarboxy-2,2'-bipyridine)-bis(isothiocyanato)ruthenium(II), RuL'2(NCS)2, was studied in more detail. The results revealed a high content of thiocyanate orbitals in the highest occupied molecular orbital, HOMO, of this complex, which partly explains its efficiency in the solar cell. The thiocyanate ligands were found to be highly influenced by the substrate when the dye is adsorbed onto ZnO, which is not the case for the corresponding TiO2 system. A bridge bonding between TiO2 and the L' ligand was proposed, where the carboxyl groups are deprotonated and all oxygens interact with surface titanium ions. For ZnO, the results indicate a different bonding geometry, involving protonated carboxyl groups. For the display system a dye molecule, which shifts color upon electrochemical treatment, was adsorbed on TiO2 and studied in its reduced and oxidized states. The major electronic difference between the two states was shown to occur on the nitrogen atom. In addition, a reversible photoreduction process during the measurements was observed.

This master thesis in physics mainly treats Auger spectroscopy of interfaces that has been adhesively bond together with so called controlled delaminating materials (CDM). CDM is a new technology which involves adhesives with the distinctive property that they by the appliance of electricity can be released from a substrate. The reason for using Auger spectroscopy was that it gives a surface sensitive view of the chemical composition of the samples examined and this was believed to give hints of the mechanisms behind loss of adhesion. The samples were so called laminates which is an aluminium foil, CDM adhesive, aluminium foil structure. As expected Auger spectroscopy produced some promising results, especially regarding the breakdown of a certain anion contained into the examined CDM adhesive. This awoke new questions regarding how this anion was decomposed and the idea that it could be due to hydrolysis took form. The by far most important result within this work is that the anion breaks down. This could lead to the formation of hydrofluoric acid if this breakdown in fact is due to hydrolysis and the hydrofluoric acid could then react with the aluminium causing loss of adhesion. This could be the good starting point of a continuing work on CDM.