酸素を添加した超臨界流体二酸化炭素による超高真空装置用アルミニウム表面の汚染除去 [in Japanese] Surface Cleaning on Aluminum for Ultrahigh Vacuum Using Supercritical Fluid CO_2 with O_2 [in Japanese]
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Supercritical fluid (SCF) CO<SUB>2</SUB> has been employed for cleaning of organic contamination on the surface. However, the cleaning rate was 2% at 25 MPa in SCFCO<SUB>2</SUB> alone. Oxygen (O<SUB>2</SUB>) was added to base SCFCO<SUB>2</SUB> to improve the rate by utilizing oxidizing effect. Aluminum sample is φ5 × t1. After a sample was cleaned in the fluid with 02, the surface was analyzed using x-ray photoelectron spectroscopy (XPS). Assuming that C1s peak in XPS spectra represents organic contamination, the contamination rate is defined as the ratio of area of C1s peak and summation of the area of C1s, O1s, and Al2p peaks. The cleaning rate at 55°C for 30 minute cleaning was 25% at 2030 MPa in SCFCO<SUB>2</SUB>with O<SUB>2</SUB> of 1.5 MPa. The cleaning at the constant ratio of O<SUB>2</SUB> pressure against SCFCO<SUB>2</SUB> pressure showed that cleaning rate is approximately proportional to the oxygen molecule number. The addition of oxygen is primarily effective on cleaning of the organic contamination, where base SCFCO<SUB>2</SUB> showed secondary effect on cleaning.
Shinku 45(4), 372-376, 2002-04-20
The Vacuum Society of Japan