Yu DING, Ruggero MICHELETTO¹, Hiroaki HANADA², Toshihiko NAGAMURA², Satoshi OKAZAKI and Koji OTSUKA

Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan ¹Department of Electronic Science, Graduate School of Engineering, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan²Unisoku Co., Ltd., 2-4-3 Kasugano, Hirakata, Osaka 573-0131, Japan

(Received June 28, 2002; Accepted August 15, 2002)

This work describes a groundbreaking process that provides a direct highly localized measurement of the atomic mass on surfaces at room temperature. Employing an original system that joins a scanning tunneling microscopy (STM) device and a time of flight (TOF) mass analyzer, we could previously ionize surface atoms by the combination of an optical laser pulse and an electric pulse at the STM tip. Desorbed ions from a localized area were accelerated and detected by a TOF chamber. We will demonstrate in this paper that high localization and mass discrimination can be obtained even without the aid of an electric pulse from the tip. We reduced the angle of incidence of the laser beam to zero (laser beam parallel to the sample surface). In this condition we were able to demonstrate for the first time ionic desorption at a confinement level of the order of 5–10 nm, an order of magnitude better than previous configurations.

Key words: TOF, STM, near field, mass spectrometer, ionization, laser, surface analysis, surface characterization