Hazime Shimizu1, Naoyuki Koyama2, Yoichi Ishida3, Masatoshi Ono1 and Ryuichi Kudo1
1Electrotechnical Laboratory, Ibaraki
Compositional changes of the surface and near-surface layers in Cu/Ni alloys during Ar ion bombardment (3 keV) at temperature from room to 873 K was studied by means of micro-probe Auger spectroscopy (μ-AES), X-ray micro analysis (XMA) and scanning electron microscopy (SEM). After sputtering at room temperature the surface was enriched with nickel by the selective sputtering of copper. The sputtering yield ratio of Cu/Ni was 1.9±0.1 over a wide range of the alloy composition. The yield ratio agreed with the value calculated from the yields of pure metals. With the increase in the specimen temperature further enrichment in nickel occurred at high argon ion densities. The apparent sputtering yield ratio changed from 0.3 to 8.5 during sputtering the 40 at% Ni alloy at 873 K under the ion beam current density from 4×10-4 A/m2 to 4×10-1 A/m2.
The nickel enrichment occurred mainly by the irradiation enhanced diffusion of copper to the surface of the specimen and the selective sputtering of copper during argon ion bombardment. The enhanced diffusion of copper at 873 K resulted in the formation of a copper depletion zone 400∼500 nm in thickness at 873 K for the ion beam current density of 4×10-1 A/m2. The depletion zone was of the order of 1 μm along the grain boundary. SEM observation revealed a large difference in the topographical features of each grain surface both at room temperature and elevated temperatures.
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