The Authors regret that the Young's Modulus and Hardness measurements were not properly acknowledged and the passage referring to Fig. 8 (page 109) is inaccurate with regard to the measurement method.
As such following together with affiliation to be added as an author (page 105): - “John Kavanagh, Research Centre in Surface Engineering, Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD, UK”.
Also paragraph 6 in Section 3.4 page 109 as follows;
“The same samples were measured using a Hysitron SN5 060-040 triboscope set to 40 nm depth to minimise substrate effects with the reduced Young's modulus and hardness calculated. Fig. 8 shows the corresponding reduced Young's modulus and hardness.” to be replaced with the following;
“A Hysitron triboscope was used to measure the same samples with the applied force chosen to keep indentation depth at approximately 10% of film thickness to minimise substrate contributions. Fig. 8 shows the calculated reduced Young's modulus and hardness.”
In addition Fig. 8 caption, Section 3.4 page 109, “Reduced Young's modulus Er and hardness H calculated from nanoindentations at 500 μm with indentation depth at 10% of film thickness; 4 indentations per measurement” should read “Reduced Young's modulus Er and hardness H calculated from nanoindentations at 500 μN”.
The Authors would like to apologise for any inconvenience caused.