Nanopotentiometry: Local potential measurements in complementary metal-oxide-semiconductor transistors using atomic force 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.

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Crystallised and amorphous phase change materials were imaged using two electric force microscopy systems: surface potential microscopy and electric field gradient microscopy. These first experiments permit to detect and observe information recorded in phase change layer with a scanning probe technique in a non contact mode and with an easy sample preparation. The topography can be separated from the electrical information. The lateral resolution is promising to be better than few ten nanometers.