Spontaneous Grafting of OH-Terminated Molecules on Si−H Surfaces via Si–O–C Covalent Bonding

Abstract

The surface functionalization of oxide-free hydrogen-terminated silicon (Si−H) enables predictably tuning its electronic properties, by incorporating tailored functionality for applications such as photovoltaics, biosensing and molecular electronics devices. Most of the available chemical functionalization approaches require an external radical initiator, such as UV light, heat or chemical reagents. Here, we report forming organic monolayers on Si–H surfaces using molecules comprising terminal alcohol (–OH) groups. Self-assembled monolayer (SAM) formation is spontaneous, requires no external stimuli–and yields Si–O–C covalently bound monolayers. The SAMs were characterized by X-ray photoelectron spectroscopy (XPS) to determine the chemical bonding, by X-ray reflectometry (XRR) to determine the monolayers thicknesses on the surface and by atomic force microscopy (AFM) to probe surface topography and surface roughness. The redox activity and the electrochemical properties of the SAMs were studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The availability and the ease of incorporating OH groups in organic molecules, makes this spontaneous grafting as a reliable method to attach molecules to Si surfaces in applications ranging from sensing to molecular electronics where incorporating radical initiator setups is not accessible.

Impermeable Graphene Oxide Protects Silicon from Oxidation

“…A freshly prepared SiH surface has been recently shown to form direct SiO bonding with OH-containing molecules and GO x . − ,,, Covalent attachment of GO x on the surface of SiH was achieved by immersing freshly prepared SiH in a deoxygenated GO x suspension for 24 h. The reaction involves direct SiO covalent bonding via OH groups in GO x reacting with freshly prepared SiH surfaces. The method requires no additives or catalysis, and it is based on simply incubating a SiH surface in GO x suspension solution.…”

“…We recently reported a method of spontaneously attaching GO x to the Si–H surface by direct Si–O covalent bonding . Si–O covalent bonding has also been previously reported for attaching a range of molecules to the Si surface. − In this article, we test the suitability of a thin layer of GO x in protecting Si–H from oxidation as a function of time. This is related to the recently reported impermeability of GO x to gases and molecules. , In addition, we test whether the protective GO x layer can be used as a bifunctional interface that not only protects the underneath semiconductor Si from oxidation but also is capable of connecting molecules from the distal end.…”

Optimized Technologies for Cointegration of MOS Transistor and Glucose Oxidase Enzyme on a Si-Wafer

“…The results were also confirmed by the SEM characterization, where agglomerations and film inhomogeneities were acceptable in the enzymatic membrane with GA + NA crosslinking agents (Figure 11). In future experiments, the enzyme immobilization can be further improved by direct binding on the electrode surface by covalent Si-S or Si-O covalent chemistry [25][26][27]. In this way, the intermediate nanostructured layer can be completely eliminated, keeping the receptor membrane as close as possible to the silicon surface.…”

“…In our experiments the reaction occurs in normal conditions at p = 1 atm, T = 20 °C. The potential variations at the reference electrode modulate In future experiments, the enzyme immobilization can be further improved by direct binding on the electrode surface by covalent Si-S or Si-O covalent chemistry [25][26][27]. In this way, the intermediate nanostructured layer can be completely eliminated, keeping the receptor membrane as close as possible to the silicon surface.…”

“…In future experiments, the enzyme immobilization can be further improved by direct binding on the electrode surface by covalent Si–S or Si–O covalent chemistry [ 25 , 26 , 27 ]. In this way, the intermediate nanostructured layer can be completely eliminated, keeping the receptor membrane as close as possible to the silicon surface.…”