Electrical contrast observations and voltage measurements by Kelvin probe force gradient microscopy

Kelvin probe force gradient microscopy is proposed to image and measure local dc voltage variations using the double pass method. The various voltages between sensor and sample induce electrical force gradients that change the resonance of the sensor. Images of the various phase shifts show contrasts, which, as we demonstrate, can be interpreted in terms of local changes in voltage and capacitive coupling. The interest of this method for observation and local voltage measurements is demonstrated and explained.