Low-cost picoammeter for dielectrics

The research carried on in the field of dielectric nanomaterials requires a large amount of fast and accurate measurements, such as the current/voltage characteristics, which produce currents under the 1nA range. The size of the available devices forces them to be placed outside the measurement setup, allowing a large influence of the electric noise. Supplementary, they are unable to measure during the transient phenomena and expensive (“sourcemeters” available from different producers). This paper presents a more convenient solution (under 500 euros) for fast automatically measuring the characteristics in the range of 10pA to 1000nA. A major advantage of this device is its size (10×6×10cm), allowing it to fit into the shielding enclosure, together with the probe, needle manipulator and microscope. It allows the experimenter to specify the voltage range and the number of measuring points and it automatically provides the resulting data file, without raising neither the uncertainty level (under 10pA), nor the measuring time (down to 0.1 seconds per measuring point). The error is kept low through active guarding, mains synchronization, careful shielding and the use of extremely low bias amplifiers (3fA). The device communicates with the host computer via the galvanic isolated USB interface and does not require separate power supply (USB powered).