Formation of Fine Holes by Sputter Etching of Ti-15V-3Cr-3Al-3Sn Alloy and Commercially Pure Titanium

Argon ion sputter etching was applied to a Ti-15V-3Cr-3Al-3Sn alloy (15-3 alloy) specimen placed on a SUS304 stainless steel cathode disk and commercially pure titanium (pure Ti) specimens placed on a vanadium (V, tantalum (Ta), niobium (Nb), molybdenum (Mo), tungsten (NV) disk, respectively. The sputter etching of the 15-3 alloy on the SUS304 disk and pure Ti specimen on the V or Ta disks formed fine dense holes with diameters smaller than 500 nm at a sputter power of 250 W for 0.9-3.6 ks. On the other hand, the sputter etching of the pure Ti specimen on the Nb, Mo, or W disks formed fine column- or ridge-shaped protrusions with sizes smaller than 1 mu m. Because EDX analyses showed a certain amount of V, Ta, Nb. Mo, or W on the pure Ti specimens, we consider that the formation of fine holes or protrusions were due to particles from each cathode disk dissolving into the Ti matrix to form two fine regions with different composition and sputter rate; i.e., the holes were formed by preferential sputtering of Ti atoms in the regions with small V or Ta composition. For the 15-3 alloy, the formation of fine holes seemed to be caused by the preferential sputtering of Ti atoms in the regions with smaller V.