| 摘要 |
PURPOSE:To hold opposite electrodes or a probe and a sample at an accurate distance by controlling the relative distance so that a tunnel current or electric field radiation current is held constant. CONSTITUTION:When the probe 2 is applied with a voltage Vt (<0) through a current detector 5, an electron 3 flows from the probe 2 to the sample 4. The tunnel current flows when the voltage is low or electric field radiation current flows when it is high. At this time, a current detector 5 outputs a signal corresponding to the electric field radiation current and a difference current detecting current 7 subtracts said signal from a voltage corresponding to a desired current to detect a difference current. The detected difference current is converted by an error position converting circuit 9 into an error quantity of distance. An actuator 1 is driven with this signal through a servo circuit 10 and a high-voltage amplifier 11 so that the error quantity is zero, thereby holding the electrodes or the probe 2 and sample 4 at the accurate distance.
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