kelvin probe

**Kelvin Probe** is a **non-contact technique that measures the work function (or surface potential) by detecting the contact potential difference (CPD)** — a vibrating reference electrode generates an AC signal proportional to the work function difference between the probe and sample. **How Does the Kelvin Probe Work?** - **Vibrating Capacitor**: The probe tip vibrates above the sample surface, creating a time-varying capacitance. - **AC Signal**: The work function difference drives an AC current: $i(t) = Deltaphi cdot dC/dt$. - **Nulling**: Apply a DC bias to null the AC signal — the nulling voltage equals the CPD. - **Scanning**: Move the probe across the surface to map the work function variation. **Why It Matters** - **Non-Contact**: Measures work function without touching or damaging the surface. - **Absolute**: Provides absolute work function if the probe work function is calibrated. - **Contamination Sensitivity**: Detects sub-monolayer surface contamination through work function changes. **Kelvin Probe** is **the non-contact work function meter** — measuring surface potential through the vibrating capacitor effect.