IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Vacuum Science & Technology Monday Sessions
       Session VST-MoP

Paper VST-MoP9
Surface Modification of Chamber Material for Standard Vacuum Pressure Measurement

Monday, October 29, 2001, 5:30 pm, Room 134/135

Session: Developments in Vacuum Technology Poster Session
Presenter: M. Tosa, National Institute for Materials Science, Japan
Authors: M. Tosa, National Institute for Materials Science, Japan
M. Goto, National Institute for Materials Science, Japan
A. Kasahara, National Institute for Materials Science, Japan
K. Yoshihara, National Institute for Materials Science, Japan
Correspondent: Click to Email
Main residual gas in a vacuum chamber mainly contains hydrogen molecules in an ultra high vacuum. Reduction of adsorption of hydrogen and other gas molecules is inevitable for standard stable vacuum atmosphere to calibrate standard vacuum pressure g auge. We tried to develop surface modification to reduce adsorption of hydrogen as well as other molecules. Surface modification is developed with surface segregation of hexagonal boron nitride (h-BN) on copper coating film. Copper is excellent in low hyd roge n solution, high thermal conductivity and high vacuum packing but suffers from easy oxidation that becomes large outgassing source. Surface of h-BN is excellent in low gas adsorption but is brittle and preparation of uniform BN layer on the entire sub str ate surface is not easy. Co-sputtering technology using helicon radio frequency wave with a sintered BN disc and a Cu disc deposited mixture of Cu and BN (Cu/B/N) on stainless steel substrates as chamber material. Annealing Cu/B/N film could remove all three main copper spectra peaks with Auger electron spectroscopy, carbon and oxygen peaks largely, then boron and nitrogen peaks increased much higher. Scanning i mage shows perfect uniformity of surface coverage with BN and no element by gas adsorption on the surface after atmospheric exposure. X-ray photoelectron spectroscopy showed @pi@ bond shake-up satellite of boron peak peculiar to h-BN. It is concluded that h-BN segregated uniformly on all the surface of the deposited film. Atomic force microscop e shows that the surface of the segregated h-BN layer has same small value of van der Walls' force as that of a sintered h-BN disc. This concludes that h-BN surface segregation layer on the substrate mixed with BN and copper can weaken surface interaction with gas molecules in a vacuum chamber and can much lower gas adsorption on the surface of the chamber wall for steady standard vacuum atmosphere.