M.Sc Thesis

M.Sc StudentMalkes Elena
SubjectPassivation of III-V Devices by Organic Self-Assembles
Monolayers (SAMs)
DepartmentDepartment of Chemical Engineering
Supervisors PROF. Yaron Paz
PROF. Dan Ritter
Full Thesis textFull thesis text - English Version


This work presents a study of step-by-step formation of SAMs on InP surfaces of different orientations using two methods of SAM formation (molten thiol approach and thiol solution approach). Of major interest were the comparison of SAM films prepared using two different approaches as well as a comparison between films formed on different InP planes. In this study several samples of InP(100), InP(110), InP(111)A and InP(111)B were immersed in molten octadecylthiol (ODT) or in ODT solution for different immersion times in order to get the chemisorbed ODT films. The thiolated films formed on InP samples were investigated by FTIR, contact angle measurements, AFM and XPS. Films prepared in molten thiol on InP(100) and InP(110) had different structure on the semiconductors surfaces. The tilt angle of the film relative to surface normal was higher in films prepared on InP(110) than that in film prepared on InP(100). It was very difficult to get a good quality film from the molten thiol. Generally, films prepared in molten thiol had big 3-D clusters. ODT films prepared using two different approaches (molten thiol and thiol solution 0.1M) on InP(100) consisted both of small thiol islands connected together into various curves-like structures. Thiol islands in films formed in molten thiol had smaller average radii. Films prepared in thiol solution consisted of double-layers (2 or 4) thiol islands, were indicated by specific height of the islands, whereas films prepared in molten thiol had height in the range of the thiol islands height, i.e. 1-6 layers. The tilt angle of the thiol molecules was bigger in films prepared in thiol solution. Thiol films on InP(100) were partial even after 44 hours of immersion, inclined, consisted of small thiol islands, of 2-4 layers in height, connected together and had big roughness. ODT molecules on InP(111)A formed after 24 hours of immersion smooth films consisted of dense thiol domains on the entire surface. On InP(111)B separated thiol dots did not formed a coverage. Thiol films on InP(111)A and on InP(100) were made of chains inclined with nearly the same tilt angles to the surface normal. FTIR results showed that InP(111)A is the best surface orientation for the thiol coverage formation: the absorbance of CH2 as peak was nearly 0.003OD (0.0015OD - on InP(100)). The temperature of the preparing substance had large effect on ODT coverage formation: high temperature (70˚C vs. the “normal” 53˚C) prevents the adsorption of the thiol molecules to the surface.