The role of surface microstructure in the sputtering of graphite
- Nuclear Engineering Department, The Pennsylvania State University, University Park, Pennsylvania 16802 (USA)
- Sandia National Laboratories, Albuquerque, New Mexico 87185 (USA)
Extensive exposure to tokamak plasmas may result in significant alterations to the surface microstructure of graphite plasma-facing components. A change in microstructure from a commercial isotropic graphite to an amorphous carbon film may produce a significant change in the total sputtering yield and the level of plasma contamination. To investigate this sensitivity to surface microstructure, sputtering experiments on a variety of graphites with various surface structures were performed using the ion--surface interaction system (ISIS).{sup 1} ISIS is a computerized ion beam sputtering system equipped with twin quartz crystal microbalances capable of simultaneously monitoring both sputtering and redeposition of the beam target material. ISIS was used to obtain sputtering data on two orientations of pyrolytic graphite at seven energies between 100 eV and 10 keV. Helium bombardment perpendicular to the prism plane produced yields 2 to 7 times higher than on the basal plane. Proton bombardment perpendicular to the prism plane produced yields 45% higher than those on the basal plane. Amorphous graphite films produced from Poco AXF-5Q and Union Carbide ATJ graphites using an argon radio-frequency (rf) plasma discharge were also irradiated. Sputtering yields on the amorphous films were as much as 50% to an order of magnitude higher than those measured on commercial bulk samples. Pre and post-irradiation scanning electron microscopy of selected targets was performed to monitor surface microstructure. A structural mechanism responsible for the magnitude of physical sputtering is suggested, and an effective surface binding energy is introduced to quantify this structural dependence.
- OSTI ID:
- 5558164
- Journal Information:
- Journal of Vacuum Science and Technology, A (Vacuum, Surfaces and Films); (USA), Vol. 9:3; ISSN 0734-2101
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GRAPHITE
MICROSTRUCTURE
SPUTTERING
AMORPHOUS STATE
CRYSTALS
FILMS
HELIUM
ION BEAMS
PLASMA
PROTONS
SCANNING ELECTRON MICROSCOPY
SURFACES
BARYONS
BEAMS
CARBON
CRYSTAL STRUCTURE
ELECTRON MICROSCOPY
ELEMENTAL MINERALS
ELEMENTARY PARTICLES
ELEMENTS
FERMIONS
FLUIDS
GASES
HADRONS
MICROSCOPY
MINERALS
NONMETALS
NUCLEONS
RARE GASES
360603* - Materials- Properties