Development of SPM operational in a plasma environmental and its application to the nano-scopic structural study of solid-plasma interface

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In this project, we developed a scanning tunneling microscope/spectroscopy operational under a cold glow plasma environment. The first in-situ observation of plasma-solid surface reaction on a nanometer scale level was succeeded. This was achieved by employing a special scanning funneling microscopy (STM) which can be operated under a plasma environment. This STM system and a radio-frequency (r. f.) (430 MHz) plasma generation system were housed in a vacuum chamber with a rotary pump. The plasma generated in this study was diagnosed that an electron temperature was 4 eV and an electron density was 2 x 10ィイD19ィエD1 cmィイD1-3ィエD1 by a double probe method, respectively. To prevent noise current from the plasma, a probing tip was coated with epoxy grease and insulated glass, and an apex of the probing tip was sharpened by focused ion beam (FIB). The STM had an enough stability and reproducibility to measure a region of 10 μm x 10 μmィイD12ィエD1 for no less than 5 hours under a plasma environment. Using this apparatus, sequential in-situ STM images of highly oriented pyrolytic graphite (HOPG) were obtained under an r. f. low-pressure (1 Torr) air glow plasma. These images show the projection of which the height is 50 nm has been etched by the plasma and disappeared.