TUNA and Conductive AFM use contact mode AFM and a conductive probe. Sensor signal is the electric current between tip and sample for an applied DC bias. In feedback mode, the output signal is the DC bias, adjusted to maintain the electric current setpoint. Current range is from fA (TUNA) to µA (CAFM). Applications include studies of dielectric strength and thickness uniformity in thin films, e.g., for semiconductor and data storage devices, and conductive polymers.