Non-parabolic potential dependence of optical second harmonic generation from the Si(111) electrode/electrolyte...

Area of Science:

• Surface science
• Nonlinear optics
• Electrochemistry

Background:

• The Si(111) electrolyte interface is crucial for semiconductor devices.
• Understanding its electronic properties under potential bias is essential.
• Second harmonic generation (SHG) is a surface-sensitive nonlinear optical technique.

Purpose of the Study:

• To investigate the potential-dependent behavior of the Si(111) electrolyte interface using SHG.
• To explore the influence of azimuthal angles and polarization on SHG response.
• To elucidate the interfacial electronic structure changes under applied potential.

Main Methods:

• Potential-dependent second harmonic generation (SHG) measurements.
• Systematic variation of applied external potential from equilibrium to negative potentials.
• Measurements conducted at different azimuthal angles and polarization combinations.

Main Results:

• Linear decrease in SHG intensity with potential bias from equilibrium to flatband potential (Efb) at 30° azimuthal angle.
• Quadratic SHG response beyond Efb, deviating from traditional Mott-Schottky linearity.
• Asymmetric potential dependence suggesting a semiconductor-to-metal transition with electron accumulation.
• Anisotropic contributions shifting the minimum of the potential-dependent SHG curve away from Efb.

Conclusions:

• SHG effectively probes potential-induced electronic structure changes at the Si(111) electrolyte interface.
• The observed asymmetric behavior indicates a significant shift in interfacial properties with applied potential.
• The findings challenge existing models and highlight the importance of interfacial anisotropy.