Scanning tunneling microscope tip current excited by modulated X-rays

Kouichi Tsuji, Toshihiko Nagamura, Kazuaki Wagatsuma

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


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.

Original languageEnglish
Pages (from-to)2028-2032
Number of pages5
JournalJapanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers
Issue number4 SUPPL. A
Publication statusPublished - 1998 Apr
Externally publishedYes


  • Electron emission
  • Modulation frequency
  • Scanning tunneling microscope
  • X-ray excited current
  • X-ray irradiation

ASJC Scopus subject areas

  • Engineering(all)
  • Physics and Astronomy(all)


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