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Non-parabolic potential dependence of optical second harmonic generation from the Si(111) electrode/electrolyte interface
摘要： We performed potential dependent second harmonic generation (SHG) measurements on the Si(111) electrolyte interface at different azimuthal angles and for different polarization combinations. When the external potential was biased from the equilibrium potential to the flatband potential (Efb), the SHG intensity decreased linearly with the potential when the azimuthal angle was oriented at 301. This linearity extends well beyond the linear region of the Mott–Schottky plot as measured traditionally by capacitance measurements. When the external potential was scanned from Efb toward more negative potentials, the response of SHG intensity showed quadratic behavior and can be described by the parabolic model. The non-parabolic potential dependence cannot be explained with the parabolic model proposed from previous literature. Such asymmetric behavior only implied that the interfacial structure of the Si(111) electrode changes from semiconductor to metal with the applied electric potential biased negatively, i.e. with accumulation of electrons in the surface region. The anisotropic contribution from the Si(111) electrode can also significantly affect the SHG response as seen where the minimum of the potential dependent SHG curve shifts away from Efb.
关键词： potential dependence,Si(111) electrode,electrolyte interface,non-parabolic behavior,second harmonic generation
更新于2025-09-23 15:19:57
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Surface-Specific Spectroscopy of Water at a Potentiostatically Controlled Supported Graphene Monolayer
摘要： Knowledge of the structure of interfacial water molecules at electrified solid materials is the first step toward a better understanding of important processes at such surfaces, in, e.g., electrochemistry, atmospheric chemistry, and membrane biophysics. As graphene is an interesting material with multiple potential applications such as in transistors or sensors, we specifically investigate the graphene-water interface. We use sum-frequency generation spectroscopy to investigate the pH- and potential-dependence of the interfacial water structure in contact with a chemical vapor deposited (CVD)-grown graphene surface. Our results show that the SFG signal from the interfacial water molecules at the graphene layer is dominated by the underlying substrate and that there are water molecules between the graphene and the (hydrophilic) supporting substrate.
关键词： pH-dependence,interfacial water structure,graphene-water interface,sum-frequency generation spectroscopy,potential-dependence
更新于2025-09-11 14:15:04