Modification of silicon by self-assembled monolayers for application in nano-electronics and biology release_nphg54fbtzgk5a6367ovexxfxu

Abstract

Fourier Transform Infrared Spectroscopy (FTIR) is employed to investigate surface and interface properties of several self-assembled monolayers (SAMs) systems on silicon and applications in optimizing attachment of biomolecules and Atomic Layer Deposition (ALD) of high-k metal oxides are explored. The SAM systems include silane-based SAMs on SiO2 and alkene-based SAMs (with different terminal groups) on H-terminated Si (111).Modification of SiO2 by silane-based SAMs is presented first with emphasis on SAM/SiO2 interfacial characteristics. Spectral changes in the longitudinal-optical (LO) phonon mode of the SiO2 substrate after modification with silane-based SAMs suggest the formation of a dense cross-linked SAM chemically attached to the SiO2 substrate through Sisubstrate-O-Si bonds. A novel method is developed to prepare -NH2 terminated surface for optimized biomolecules surface attachment using (3-Aminopropyl) triethoxysilane (APTES) and hydrogen-terminated Si (111). It is demonstrated that APTES can form more stable siloxane layers on hydrogen-terminated Si (111) without extra pre-hydration or pre-oxidization of surface required by conventional silane-based methods. The formation, structure and stability of alkene-based SAMs thermally grafted on H- terminated silicon (111) via Si-C bond (Si-C SAMs) has been investigated by infrared spectroscopy. The SAM with reactive terminal group (-COOH) shows higher thermal stability than SAM with -CH3 termination. The decomposition of alkyl chains at high temperature is through β-hydride elimination with cleavage of Si-C bond. The alkene-based SAMs are further used as model systems to study reaction and nucleation processes in ALD. The ALD of aluminum oxide on SAM-functionalized silicon with various terminal groups (-CH3, - NH2, -COOH and -OH) was systematically investigated using in situ FTIR. The results show that all Si-C bound SAMs with different terminal groups efficiently eliminate the formation of unwanted interfacial silicon oxide during ALD growth. The result [...]
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