Scanning Tunneling Microscope Tip Current Excited by Modulated X-Rays

概要

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We measured the current passing between a sample and a scanning tunneling microscope (STM) tip under conditions of X-ray irradiation. As shown in our previous reports, this STM tip current originated from electron emission on the sample surface. For high precision STM tip current measurement, we applied an X-ray modulation technique using an X-ray chopper and a lock-in amplifier. X-rays modulated by the X-ray chopper irradiated the sample surface of the STM, and the STM tip current was detected using the lock-in amplifier. The largest and most stable output from the lock-in amplifier was obtained under the experimental conditions of low modulation frequency (∼ 10 Hz), strong X-ray intensity, and high STM bias voltage. Compared with measuring the STM tip current directly without the modulation technique, the precision of this measurement is threefold better.
社団法人応用物理学会の論文
1998-04-15