Content of review 1, reviewed on September 03, 2013

The work is of great interest and the analysis and discussion is original and sound. However, since a single first-pop-in event is analyzed, the authors should comment and clarify on this point. It is reasonable that they do not need now to change completely the text or make new measurements, if not really required. However, wether indeed this is the case for the other measurements done in addition to the one analyzed in the MS, the authors could probably tackle this point by just adding a sentence stating something like that the curve they analyze is typical and representative of most observed cases, and they have detected some (approximate number?) other first pop-in events that were all at similar Pc (typical deviation was +-? percent), and this would eventually affect all subsequent derivations, accordingly.

Here and there, some language mistakes hinder the true meaning of the text. The following additional edits are therefore compulsory as well, before that the MS can be accepted for publication.

1.

line 39: remove 'behaviors'

2.

line 45: remove comma before Er

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3.

line 48: report both values with some more reasonable (ie less pretentious) accuracy (at least one less digit after the comma)

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4.

line 56: remove 'in this study.

5.

lines 61-63: newly added text is not clear in that form. Also, it is probably a wrong justification! Rather replace with the following one: 'Since the first pop-in typically appears at indentation depth below 100 nm, at such a low depth (within the limit of the same size as the diameter of the tip apex) equations 1 and 2 are still a reasonable approximation also for the Berkovich indenter'.

6.

line 63: remove 'Also'

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7.

line 65: replace 'was' with 'are also'.

8.

lines 66-67: remove the sentence 'The results...films'. It's redundant. Furthermore, we are in the Intro here, not in the Conclusion section!

9.

The authors tend again to misuse the Sections structure of the paper: the sentence at lines 71-73 (after preliminary replacing of the initial 'The' with 'In previous work') should rather be moved from the Experimental section to the beginning of Results and discussion.

Also, the new text added at lines 89-93 should be moved as well at a later point, in the discussion.

10.

line 69: remove 'In this work'.

11.

line 70: 'the helicon sputtering system', replace with 'helicon sputtering'. Even if details are elsewhere, still the authors have to write at least the instrument model and manufacturer.

12.

line 81: replace 'are' with 'were'.

13.

lines 105-106: remove 'the origin of'.

14.

legend fig.1 'times the displacement', replace with 'times the sudden incremental displacement at constant load'

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15.

end of line 146: insert newline.

16.

line 162: replace 'obtained' with 'reported'.

17.

line 167: 'shear stress', add 'required'.

18. line 171: remove 'that'.

19.

line 183: remove 'in both cases '.

20.

line 187 and eq.7: add index c to tau.

21.

eq 8: isn't it e^2 instead of e^3? In case, this would give 1.85 r_core and finally r_c=0.8 nm not 2.1

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22. line 193: remove' with the popin event'.

23.

line 195: remove 'might have been'.

24.

legend fig 2: remove 'immediately'.

25.

line 220: remove 'materials'.

26.

lines 220-221: remove 'governed by'.

Source

    © 2013 the Reviewer (CC BY 4.0).