Low‐energy implantation and sputtering of TiO2 by nitrogen and argon and the electrochemical reoxidation

Abstract In this paper we report the investigation of the implantation and radiation damage during sputter profiles of 30 nm TiO 2 layers on Ti with 3 keV N 2 + . The profiles are analysed by normal and angle‐resolved XPS measurements. Supplementary electrochemical reoxidants are performed, handling the sample without any contact to air during the whole process. Additional information is obtained by comparison with 4 keV Ar + and 3 keV air sputter profiles. At the beginning of a 3 keV N 2 + sputter profile some TiO 2 at the surface is converted to TiN x O y , which is only partially oxidizable by repassivation. A portion of the implanted nitrogen exists as molecular N 2 . After higher sputter dosed the composition changes drastically. Preferential sputtering reduces the oxygen concentration to an extent to allow TiN x O 1− x and TiN formation. The TiN x O y changes its composition since it is now fully reoxidizable, as are all compounds with a Ti oxidation state of less than 4 +. N 2 reacts with TiN x O 1− x by recoil excitation and no longer exists. The occurrence of TiO, Ti 2 O 3 and Ti 3 N 4 is unlikely, but possible in small concentrations. The products of all electrochemical repassivations are TiO 2 and N 2 . Angle‐resolved XPS measurements show Ar‐ and N 2 ‐attenuated surface layers. During Ar and air implantation these layers remain constant owing to an equilibrium between outgassing and implantation of new sputter gas. After nitrogen implantation the N 2 ‐attenuated layers are constant in the beginning and increase when the N 2 begins to react with TiN x O 1− x until the N 2 totally disappears. An addition of oxygen to the sputter gas can decrease the surface roughening effect, which is often found after prolonged sputtering, XPS binding energies show that Ar and N 2 gas do not occur in gas bubbbbles.