A Tunnel Current Spectrometer

摘要

An instrument intended for measuring small nonlinearities of the volt-ampere characteristics of metal-semiconductor-metal tunneling junctions at helium temperatures is described. The spectrometer contains a controlled scan unit and four 24-bit channels for measuring the current, the real and imaginary components of the first derivative of the volt-ampere characteristic (the conductivity), and the second derivate. The derivatives sensitivity of the spectrometer is 10~(-6), and the dynamic range in measuring the current is 116 dB. Physically, the spectrometer is a single unit with an interface to the computer USB port.