Oxygen implantation and diffusion in pure titanium by an rf inductively coupled plasma

The superficial oxidation of pure titanium, 9 mm diameter, 5 mm thick disc samples by implantation and diffusion from inductively coupled plasmas is reported. Such rf plasmas were generated in a 15 l cylindrical Pyrex-like glass chamber containing pure circulating oxygen. A quarter wavelength solenoidal antenna capable of transmitting 500 W at 13.54 MHz was externally wound around the chamber and connected to an rf generator capable of up to 1200 W through an automatic matching network. The oxidation process was carried out for 6 h periods while varying the gas pressure between 1 × 10² and 5 × 10^-1 Pa and the sample bias up to -3000 V DC. It was found that the sample temperature was a function both of the plasma density and the bias voltage. Without bias, the plasma heated the sample up to ∼200 °C, and with maximal bias voltage, the substrate was heated to 680 °C. At the latter temperature, the presence of the rutile phase was particularly evident in X-ray diffraction patterns. According to EDX data, the average oxygen to titanium ratio rose, from ∼0.06 for an untreated reference sample, to a ∼1.7 value for samples treated up to 680 °C.