Abstract
The present work is focused on the structural and electronic properties of thermally and photochemically grafted alkene molecules. The semiconductor substrates used in this work are the group IV-semiconductors silicon, diamond, and silicon carbide. On silicon, functionalization via the commonly known hydrosilylation reaction was performed. During thermal treatment in vacuum-distilled 1-octadecene, the alkene molecules covalently added to the substrate via Si-C bond formation, resulting in self-assembled organic monolayers. The reaction resulted in smooth and homogeneous alkyl-terminated surfaces. Static water contact angles were determined to be 113 . Photoelectron spectroscopy was performed and showed no evidence of surface oxidation. The high packing of the organic layers is indicated by the asymmetric methylene vibrational mode, which has been redshifted by -4 cm{sup -1} with respect to the liquid alkene mode position. The average molecular tilt-angle of the alkyl-molecules, relative to the surface normal, has been identified to be 34 . The transport properties have been determined to be dominated by tunneling processes. On diamond, first results on the thermal functionalization of hydrogen- and oxygen-terminated surfaces are demonstrated. Thermal functionalization with octadecene showed high selectivity, while hydrogenated diamond surfaces were found to be inert to the thermally induced reaction with alkenes. In contrast,
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Citation Formats
Hoeb, Marco Andreas.
Functionalization of group IV semiconductors; Funktionalisierung von Gruppe IV-Halbleitern.
Germany: N. p.,
2011.
Web.
Hoeb, Marco Andreas.
Functionalization of group IV semiconductors; Funktionalisierung von Gruppe IV-Halbleitern.
Germany.
Hoeb, Marco Andreas.
2011.
"Functionalization of group IV semiconductors; Funktionalisierung von Gruppe IV-Halbleitern."
Germany.
@misc{etde_21488676,
title = {Functionalization of group IV semiconductors; Funktionalisierung von Gruppe IV-Halbleitern}
author = {Hoeb, Marco Andreas}
abstractNote = {The present work is focused on the structural and electronic properties of thermally and photochemically grafted alkene molecules. The semiconductor substrates used in this work are the group IV-semiconductors silicon, diamond, and silicon carbide. On silicon, functionalization via the commonly known hydrosilylation reaction was performed. During thermal treatment in vacuum-distilled 1-octadecene, the alkene molecules covalently added to the substrate via Si-C bond formation, resulting in self-assembled organic monolayers. The reaction resulted in smooth and homogeneous alkyl-terminated surfaces. Static water contact angles were determined to be 113 . Photoelectron spectroscopy was performed and showed no evidence of surface oxidation. The high packing of the organic layers is indicated by the asymmetric methylene vibrational mode, which has been redshifted by -4 cm{sup -1} with respect to the liquid alkene mode position. The average molecular tilt-angle of the alkyl-molecules, relative to the surface normal, has been identified to be 34 . The transport properties have been determined to be dominated by tunneling processes. On diamond, first results on the thermal functionalization of hydrogen- and oxygen-terminated surfaces are demonstrated. Thermal functionalization with octadecene showed high selectivity, while hydrogenated diamond surfaces were found to be inert to the thermally induced reaction with alkenes. In contrast, alkene molecules were successfully grafted to oxygen-terminated sites via covalent C-O-C bonds. Reaction temperatures as high as 160 C were necessary to initiate the functionalization process.Wetting experiments on the alkyl-modified surfaces revealed contact angle values of 103 . The high quality of the monolayers on oxygenated surfaces was confirmed by IR-spectroscopy. In addition, polarized IR-measurements indicated a tilt angle of 23 . On silicon carbide, thermal and UV-induced alkoxylation were studied. Hydrofluoric acid treatment effectively removed the surface oxide but, in contrast to silicon, resulted in primarily hydroxyl-terminated surfaces. Organic modification with octadecene produced smooth octadecyl layers, which are shown to form covalent bonds over oxygen bridges to the substrate. Wetting measurements revealed contact angles of up to 106 , indicative of ordered monolayers. Complementary FTIR-studies provided evidence that thermal functionalization proceeds via a Markownikow-addition, causing a high degree of structural disorder in the organic layers. This was deduced from the asymmetric methylene vibrational mode position, which was blueshifted to {nu}{sub as}=2927 cm{sup -1} with respect to the liquid alkene mode position. In comparison, the UV-induced functionalization process is dominated by anti-Markownikow- addition reactions associated with a higher molecular density on the surface ({nu}{sub s}=2926 cm{sup -1}). From polarization dependent IR-measurements the average tilt angles between the molecules and the surface normal were calculated to be 23 on the Si-terminated surface and nearly 0 on the C-terminated surface, irrespective of the functionalization method. Electron transport across the organic interface was shown to give rectifying behavior, which can be explained by thermionic emission of electrons through the space charge region formed by the SiC/organic monolayer/Hg junction. (orig.)}
place = {Germany}
year = {2011}
month = {Jan}
}
title = {Functionalization of group IV semiconductors; Funktionalisierung von Gruppe IV-Halbleitern}
author = {Hoeb, Marco Andreas}
abstractNote = {The present work is focused on the structural and electronic properties of thermally and photochemically grafted alkene molecules. The semiconductor substrates used in this work are the group IV-semiconductors silicon, diamond, and silicon carbide. On silicon, functionalization via the commonly known hydrosilylation reaction was performed. During thermal treatment in vacuum-distilled 1-octadecene, the alkene molecules covalently added to the substrate via Si-C bond formation, resulting in self-assembled organic monolayers. The reaction resulted in smooth and homogeneous alkyl-terminated surfaces. Static water contact angles were determined to be 113 . Photoelectron spectroscopy was performed and showed no evidence of surface oxidation. The high packing of the organic layers is indicated by the asymmetric methylene vibrational mode, which has been redshifted by -4 cm{sup -1} with respect to the liquid alkene mode position. The average molecular tilt-angle of the alkyl-molecules, relative to the surface normal, has been identified to be 34 . The transport properties have been determined to be dominated by tunneling processes. On diamond, first results on the thermal functionalization of hydrogen- and oxygen-terminated surfaces are demonstrated. Thermal functionalization with octadecene showed high selectivity, while hydrogenated diamond surfaces were found to be inert to the thermally induced reaction with alkenes. In contrast, alkene molecules were successfully grafted to oxygen-terminated sites via covalent C-O-C bonds. Reaction temperatures as high as 160 C were necessary to initiate the functionalization process.Wetting experiments on the alkyl-modified surfaces revealed contact angle values of 103 . The high quality of the monolayers on oxygenated surfaces was confirmed by IR-spectroscopy. In addition, polarized IR-measurements indicated a tilt angle of 23 . On silicon carbide, thermal and UV-induced alkoxylation were studied. Hydrofluoric acid treatment effectively removed the surface oxide but, in contrast to silicon, resulted in primarily hydroxyl-terminated surfaces. Organic modification with octadecene produced smooth octadecyl layers, which are shown to form covalent bonds over oxygen bridges to the substrate. Wetting measurements revealed contact angles of up to 106 , indicative of ordered monolayers. Complementary FTIR-studies provided evidence that thermal functionalization proceeds via a Markownikow-addition, causing a high degree of structural disorder in the organic layers. This was deduced from the asymmetric methylene vibrational mode position, which was blueshifted to {nu}{sub as}=2927 cm{sup -1} with respect to the liquid alkene mode position. In comparison, the UV-induced functionalization process is dominated by anti-Markownikow- addition reactions associated with a higher molecular density on the surface ({nu}{sub s}=2926 cm{sup -1}). From polarization dependent IR-measurements the average tilt angles between the molecules and the surface normal were calculated to be 23 on the Si-terminated surface and nearly 0 on the C-terminated surface, irrespective of the functionalization method. Electron transport across the organic interface was shown to give rectifying behavior, which can be explained by thermionic emission of electrons through the space charge region formed by the SiC/organic monolayer/Hg junction. (orig.)}
place = {Germany}
year = {2011}
month = {Jan}
}