Effects of Ar ion irradiation in an ICP discharge on the titanium surface topology

Abstract

VT1-0 (Russian equivalent of Grade 2) titanium surfaces were modified under argon ion bombardment from the low-pressure inductively coupled plasma (ICP). The ion processing allowed us to prepare various types of structures on titanium with controlled characteristic dimensions at nano- and miscroscale (from tens of nm to 3 µm). The hillock, porous, conical, wall/cell structures as well as their combinations have been obtained. The topology type and the characteristic dimensions of surface features depend on the current density js, Ar ion energy Ei, irradiation fluence Φ (or processing time t), and the sample temperature T during the treatment. The microstructures appear on the surface provided the titanium sample is irradiated at temperatures below 900 °C. The sample temperature was determined by both the average current density (jsav from 0.2 to 20 mA/cm2) and the ion energy (Ei from 150 to 1500 eV). A certain fluence is required for uniform surface coverage with microstructures. We suppose that the titanium surface texturing is a result of a complex interplay of the following mechanisms: sputtering, re-sputtering (shadowing), crystal lattice transformation, accumulation and annihilation of defects, and hypothetically, argon retention.