| Summary: | 碩士 === 國立中正大學 === 化學工程所 === 97 === Organic molecules can generate self-assembled monolayers (SAMs) on silicon substrates through silanization. Because of their organization in molecular scale, higher stability, and easier preparation in lab conditions, SAMs are widely used in many applications.
This study explores mixed SAMs composed of organosilanes (octadecyltrichlorosilane, (3-mercaptopropyl) trimethoxysilane, and (3-aminopropryl) trimethoxysilane) with different chemical functionalities. By changing the deposition time, deposition sequence, and concentration of organosilanes, we investigated the composition, surface energy, roughness of resulting mixed SAMs. Finally, Ag-In-S thin films were deposited on top of mixed SAMs.
First, the growth of single-component monolayer was studied. When the concentration is higher, the coverage of the organic molecules increases at the same immersion time. This study uses stepwise deposition methods to generate mixed SAMs surface. If the Si substrates were first immersed in MPS or APS, then in OTS (denoted as MPS-OTS and APS-OTS). X-ray photoelectron spectra show that the ratio of S/Si, N/Si, C/Si are higher than the other system. In addition, the surface energy and roughness increased. When changing the deposition sequence of organosilanes to OTS-MPS and OTS-APS, the OTS molecules adsorbed on surfaces quickly, leading to less MPS or APS growth on silicon. This type of mixed SAMs has lower ratio of S/Si, N/Si, C/Si , surface energy and roughness.
Finally, we try to deposit Ag-In-S thin films on mixed SAMs surfaces. When the precursor concentration [Ag] / [In] = 0.013 M, the as-deposited thin film has the composition of [Ag]:[In]:[S] is 1:4.5:7.2,which is closed to stoichiometrice AgIn5S8, revealed by EDS. We use this precursor solution to grow thin films on various mixed SAM surfaces. SEM images showed that the morphology of AgIn5S8 can be controlled qualitatively by the surface property of the substrate, ie mixed SAMs in this study. No thermal treatment after deposition is required.
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