Peer review of: Spatial defects nanoengineering for bipolar conductivity in MoS2 (2020)


RR2
 REVIEWER COMMENTS
Reviewer #1 (Remarks to the Author):
  The authors have done a good job in clarifying reviewer’s concerns, with significant time spent on
 improving the manuscript. I appreciate the author’s efforts. Particularly, the new STEM results
 provided direct evidence to back up the claims in the manuscript. As it is natural to get n-type
 MoS2, the reviewer has one remaining question regarding the reproducibility and yield of p-type
 MoS2 fabricated in HCl environments by using this method. In other words, how many devices are
 made in this p-type doping experiments and what is the successful rate. In the manuscript (Page 8,
 Line 9), the authors mentioned that tc-SPL p-type doping is more reproducible and stable, but did
 not provide such discussions.
 Reviewer #2 (Remarks to the Author):
 The Authors have strengthened their work with extensive additional experiments and analysis.
 They appear to resolve all issues indicated on the previous submission by me and (up to my
 understanding) the other reviewers.
 One minor point that does not impact the relevance of the paper, but that should be adjusted,
 concerns my comment on the link of the DFT-DOS with the p-type character [from the first report:
 "(2) The link of the DOS of Fig.4a-c with the p-character is not clear. What is the reader expected
 to look at? The fact that some DOS extends from the VB to the Fermi or slightly above? If so, is
 this robust with respect to the broadening scheme taken?"]
 As a matter of fact, the results shown by the Authors in their reply (Fig.R3) suggest that the Fermi
 level is moving downwards in the valence band as broadening increases. Recall that the integral of
 the DOS up to EF should be constant (it must provide the number of electrons in the system), but
 this situation typically arises because of the common computational practice. Indeed, one
 computes the self-consistent density with Methfessel-Paxton smearing (as the Authors do) and,
 given M-P smearing functions are non-positively defined, the Fermi level is computationally fixed
 at about the valence band edge. Taking symmetric and positively defined Gaussian occupations
 brings the Fermi level at about the middle of the gap.
 Plotting the DOS with positively-defined smearing functions is then usual practice, since it removes
 nasty negative regions in the plotted DOS. Here one also uses a smaller broadening than e.g. the
 0.02 Ry used for self-consistency. By looking to the figures, this is also what the Authors do.
 Summarizing, this is all common practice and I don't believe the Authors should provide further
 details in the paper. However, no physical implications should be derived from this numerical issue,
 that is basically irrelevant for all computational purposes, and the text around line 235 "the Fermi
 level of MoS 2 is shifted down to or even below the valence band maximum" should be removed.
 So the information that samples are p-doped only comes from the experiments.
 Reviewer #3 (Remarks to the Author):
 The authors have addressed all the issues raised during the first review round in a satisfactory
 manner. The paper can be published in its present form.