Modification of titanium and titanium dioxide surfaces by ion implantation: combined XPS and DFT study

TL;DR

This study combines XPS measurements and DFT calculations to analyze how ion implantation modifies titanium surfaces, revealing defect formation, surface composition changes, and implications for biocompatibility.

Contribution

It provides a detailed combined experimental and theoretical analysis of ion implantation effects on titanium surfaces, highlighting the importance of implantation sequence and defect formation.

Findings

Double implantation affects surface composition significantly.

Formation energies indicate specific substitution mechanisms.

Implanted ions enhance biocompatibility for hydroxyapatite formation.

Abstract

The results of XPS measurements (core levels and valence bands) of P+, Ca+, P+Ca+ and Ca+P+ ion implanted (E=30 keV, D=1x1017 cm-2) commercially pure titanium (cp-Ti) and first-principles density functional theory (DFT) calculations demonstrates formation of various structural defects in titanium dioxide films formed on the surface of implanted materials. We have found that for double implantation (Ti:P+,Ca+ and Ti:Ca+,P+) the outermost surface layer formed mainly by Ca and P, respectively, i.e. the implantation sequence is very important. The DFT calculations show that under P+ and Ca+P+ ion implantation the formation energies for both cation (P-Ti) and anion (P-O) substitutions are comparable which can induce the creation of [PO4]3- and Ti-P species. For Ca+ and P+Ca+-ion implantation the calculated formation energies correspond to Ca2+-Ti4+ cation substitution. This conclusion is in agreement with XPS Ca 2p and Ti 2p core levels and valence band measurements and DFT calculations of electronic structure of related compounds. The conversion of implanted ions to Ca2+ and [PO4]3- species provides a good biocompatibility of cp-Ti for further formation of hydroxyapatite.