Probing Surface Photovoltage Effect Using Photoassisted Secondary Electron Emission

Area of Science:

• Surface Science
• Materials Science
• Nanotechnology

Background:

• Surface and interface properties are vital for modern devices but challenging to study due to bulk signal interference.
• Existing methods often struggle to isolate and analyze surface-specific electronic phenomena.

Purpose of the Study:

• To introduce a novel methodology for probing surface electronic phenomena.
• To investigate surface photovoltage (SPV) effects using a combined scanning electron microscopy (SEM) and pulsed laser approach.
• To enable contactless and bias-free analysis of the topmost material layers.

Main Methods:

• Utilized scanning electron microscopy (SEM) integrated with a pulsed optical laser source.
• Employed a pulsed laser to induce transient surface photovoltage (SPV).
• Monitored changes in secondary electron (SE) yield, modulated by the SPV under primary electron beam illumination.

Main Results:

• Observed distinct SPV-induced secondary electron (SE) yield changes in n-type and p-type semiconductors.
• Analyzed the dependence of SE yield changes on primary electron beam energy, optical fluence, and modulation frequency.
• Revealed detailed photocarrier dynamics influenced by the surface built-in potential.

Conclusions:

• The developed technique offers a fast, contactless, and bias-free method for surface electronic analysis.
• This approach provides high spatial resolution for probing nanoscale surface effects.
• The findings contribute to understanding contrast mechanisms in advanced time-resolved electron microscopy techniques.