טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentYaron Nechemja
SubjectSPM Studies of Self-Assembled Monolayers Adsorption
on Silicon Dioxide and Titanium Dioxide
DepartmentDepartment of Chemical Engineering
Supervisor Professor Yaron Paz
Full Thesis textFull thesis text - English Version


Abstract

Octadecyltrichlorosilane (OTS) is a common model for the study of self assembled monolayers (SAMs). It chemisorbs on oxides and other surfaces. Chemisorption of OTS was studied on different types of substrates including silicon, alternating stripes of silicon and gold, TiO2, and alternating stripes of TiO2 and gold. The substrates were prepared using microelectronic technology and the chemisorption took place under laboratory conditions. FTIR and SPM were used to study the samples. It was found that pretreatment in oxygen and argon plasma prior to chemisorption has a detrimental effect on the ratio of the concentrations of chemisorbed OTS on titania with stripes and titania without stripes. In contrast, pretreatment with a UV-Ozone cleaner was found to have a beneficial effect on the ratio. SPM study of the kinetics of the growth of OTS monolayers on silicon has confirmed that the growth proceeds via island formation. Measurements of samples containing alternating stripes of silicon and gold have shown that chemisorption was not affected by the distance from the gold stripes and that it was similar to chemisorption on bulk silicon. A comparison of the surface of TiO2 in three different sample types was made using SPM. The sample types included clean TiO2, alternating stripes of TiO2/Au and alternating stripes of TiO2/Au that were held in OTS solution following the removal of the OTS SAM in a UV-Ozone cleaner. The results showed that all surfaces were similar and that the processes that the titania underwent did not have a major effect on its surface. Analysis of acoustic alternating current (AAC) mode SPM measurements made in dry conditions of TiO2 samples held in an OTS solution for different times showed that under the studied chemisorption conditions OTS monolayer grows through adsorption of molecules on the boundaries between crystallites, island formation, the filling of the valleys between the crystallites and the completion of a full monolayer. Magnetic alternating current (MAC) mode SPM measurements made under humid conditions of samples containing alternating stripes of TiO2/Au revealed different structures at different distances from the gold stripes for different times. AAC mode SPM measurements made in humid conditions of other TiO2/Au samples showed an OTS coverage which was lower near the gold stripes and higher away from the gold stripes, in contrast to the situation with silica/gold stripes.