| 摘要 |
PURPOSE:To observe the surface of an insulator, by applying high frequency voltage between a probe and a specimen and adjusting the distance between the probe and the specimen so as to keep the change ratio of the magnitude of the current generated constant. CONSTITUTION:A means (a resistor Rs, a synchronous detection circuit 14) detecting the magnitude of the high frequency current flowing between a probe 10 and a specimen 11, an AC signal source 15 generating an AC signal for cyclically changing the distance between the probe 10 and the specimen 11, a synchronous detection circuit 16 measuring the change ratio of the magnitude of the high frequency current and a feedback circuit 17 sending a control signal to an actuator 12 so as to bring said change ratio to a constant value are provided. When AC is applied to the specimen 11 from an AC power source 13, a tunnel current wherein an electron moves from the leading end of the probe 10 to the level of the surface of the specimen 11 and moves reversely is measured and the current abruptly changes with the minute change of the distance. Therefore the value of the change ratio of the AC current is kept constant while said change ratio is measured by changing the distance between the probe 10 and the specimen 11 to measure the unevenness of the specimen 11.
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