Scanning voltage microscopy

A conductive probe, usually only a few nanometers wide at the tip, is placed in full contact with an operational electronic or optoelectronic sample.

By connecting the probe to a high-impedance voltmeter and rastering over the sample's surface, a map of the electric potential can be acquired.

[3] For example, the potential profile across the quantum well structure of a diode laser can be mapped and analyzed; such a profile could indicate the electron and hole distributions where light is generated and could lead to improved laser designs.

A lock-in amplifier aids noise reduction by filtering through only the amplitude oscillations that match the probe's vibration frequency.

Applications include imaging defect sites in carbon nanotubes and doping profiles in nanowires.