In experiments such as transistor off state current measurement, high resistance material resistivity measurement, electrical characteristics of nanodevices, scanning probe microscopy, etc., when the device size is reduced to the nanometer level or the material is very thin, the leakage current and the measured current themselves are extremely small. At this level, the experimenter needs to struggle with various noises and interferences, including thermal noise, vibration noise, and even charges generated by molecular ionization in the air.

An experiment with such a small current requires a current of less than 100 picoamperes (fA), which is equivalent to 10 ^ {-13} amperes. Conventional multimeters are not useful for measuring currents below 100 fA. Specialized equipment and technology must be used.

1. Electrometer/source measurement unit: This is the core equipment. High precision electrostatic meters or SMUs can measure currents as low as 0.1fA or even lower. They use special "virtual ground" technology and ultra-high feedback resistance (e.g.>10 ^ {14} Ω).

2. Triple coaxial cable: Use a double-layer shielded triple coaxial cable to connect the tested device and the electrostatic meter. The outer shield is grounded, and the inner shield is driven to the same potential as the central conductor (protection technology) to minimize cable leakage current and parasitic capacitance to the greatest extent possible.

3. Shielding and grounding: The entire testing system (including the probe station) must be placed in a good Faraday cage (metal shielding box) to shield against external electromagnetic interference.

4. Environmental control: Controlling humidity is very important because humid air can form conductive paths on insulation surfaces, introducing huge leakage currents. Usually measured in a dry nitrogen environment or vacuum.

5. Vibration isolation: Mechanical vibration can cause slight displacement of cables and connectors, generating frictional electrical noise, which is a significant source of noise in high impedance measurements.

To solve the problem of 100fA current in the palace, a vacuum probe station KT-Z1604T can be used. The carrying platform of this probe station is a 60x60 stainless steel table, which can be heated up to a maximum temperature of 350 ℃. The vacuum chamber design has an air inlet and a vacuum extraction interface. The probe arm is X/Y/Z three-axis movable, and can be precisely adjusted in three directions under vacuum environment. The adjustment range for the X direction is 0-30mm; the adjustment range for the y direction is 0-20mm; and the adjustment range for the z direction is 0-20mm. Users can adjust it according to their needs. When in use, fix the device to be tested on the heating table, then fine tune the probe holder's X/Y/Z direction travel, observe through a microscope, align the probe with the detection point, and then proceed with the test.