AVS 45th International Symposium
    Surface Science Division Thursday Sessions
       Session SS-ThP

Paper SS-ThP21
Field Desorption of Gallium from Liquid Metal Ion Source Studied by Back Scattered Electron Scanning Electron Microscopy

Thursday, November 5, 1998, 5:30 pm, Room Hall A

Session: Surface Science Division Poster Session
Presenter: H. Kimata, ERATO, Japan Science and Tech. Corp.
Authors: H. Kimata, ERATO, Japan Science and Tech. Corp.
Y. Kondo, ERATO, Japan Science and Tech. Corp.
K. Takayanagi, Tokyo Institute of Technology, Japan
Correspondent: Click to Email
Field desorption of gallium metal from a home-made liquid metal ion source (LMIS) was studied in a scanning electron microscope (SEM). The LMIS has a needle and a reservoir filled with the liquid gallium and a filament. The needle apex is electrochemically sharpened, and the temperature of the LMIS was controlled. We found that the back scattered electron scanning electron microscopy (BSE-SEM) can give images of the needle apex during operation, the emission current being monitored simultaneously. The Taylor-cone and the change of the cone angle depending on the extraction voltage was observed by BSE-SEM. In case that the needle was grooved enough to supply liquid gallium towards the apex,@footnote 1@ the emission current vs. extraction voltage relations were found to fit well with the previous experimental results and theoretical predictions qualitatively. Rarely, the emission did not occur at the apex but the side of the needle, when the supply was limited by poor grooving on the needle. The critical voltage Vc was found to decrease linearly as the temperature T of the ion source increased from 200 to 450(°C). The Vc vs. T relations were analyzed to estimate temperature dependence of the surface tension of the liquid gallium, using the tip radius measured in SEM. The surface tension change like (0.8) - (3x10@super -4@)T, in accordance with the value given in a literature, (0.721) - (1.0x10@super -4@)T. Thus, BSE-SEM is useful to study the dynamics of LMIS. The present techniques are applied for testing a commercial LMIS because of large sample space in a SEM. @FootnoteText@ @footnote 1@A. Wagner and T. M. Hall, J. Vac. Sci. Technol. 16, 1871 (1980).