Room-Temperature Synthesis of Titanium Nitride Using Metastable Nitrogen
Round 1
Reviewer 1 Report
In this work TiN was synthesized on titanium surface assisted by a commercial direct analysis in real time (DART) source. The generated TiN layer was demonstrated to produce surface enhanced infrared absorption (SEIRA). However, there are key points were missing in the content so the content seems not complete.
(1) The characterizations of the TiN coatings were less to support the experimental results.
(2) Belongings of the peaks were not identified on the spectra images.
(3) Comparison of the SEIRA effect between the original and TiN-coated layer should be studied to illustrate coating advantage.
Author Response
Thank you for your time and thoughtful comments. This has clearly improved this paper. I have changed the manuscript to address each of your points listed below.
- The characterizations of the TiN coatings were less to support the experimental results.
Response 1: The results section was expanded to provide a better interpretation of the infrared and Raman spectra.
- Belongings of the peaks were not identified on the spectra images.
Response 2: The peaks in all of the figures 2 and 3 were more clearly identified, and labeled and interpreted.
- Comparison of the SEIRA effect between the original and TiN-coated layer should be studied to illustrate coating advantage.
Response 3: The SEIRA results in figure 4 was modified to include a comparison the analyte coated bare metal, TiN coated samples, along with a reference spectrum of the analyte sample.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Dear Mark S. Anderson,
the paper is interesting and suitable for Coatings journal. It contains very interesting data on phonon and plasmon resonance energies in the coating but it requires serious improvements.
First of all, it is not correct to compare surface nitriding of titanium with application of TiN coatings: PVD or CVD are forming TiN layer on any substrate while your technology could form nitride layer only on the surface of Ti alloys. This technology is most close to nitriding of steel parts so it is necessary to characterise the thickness of TiN layer and transition layer(s) between the nitride and Ti by SEM + EDX or Auger methods.
After this characterisation, it is necessary also to provide information about analytical depths of IR diffuse reflectance, Raman and SEIRA methods to make sure that spectra are related to the nitride layer.
The Discussion section should be expanded taking into account new information about surface structure and composition and it should be clearly separated for Conclusions section.
The Introduction should be corrected taking into account my first comment, probably by putting more attention to surface saturation of metals. There are also two points to edit in this section:
Line 21 "the upcoming Mars 2020 spacecraft mission": Mars 2020 mission is already on Mars, it cannot be "upcoming". The collected samples will be returned to Earth by future Mars Sample Return Mission. I suppose that this sentence should be corrected.
Lines 38-39 "To produce TiN surfaces, metal surface nitriding processes 38 generally use high temperatures (>500°C) for a long duration (20 to 80 hours).": Of course one can use such extremely small deposition rates but typically PVD film is growing at 3-6 mkm per hour.
I suppose that this paper cannot be published in its current form and it should be reconsidered for publication after major revision.
Author Response
Thank you for your time and thoughtful comments. This has clearly improved this paper. I have changed the manuscript and responded to each of your points listed below.
- First of all, it is not correct to compare surface nitriding of titanium with application of TiN coatings: PVD or CVD are forming TiN layer on any substrate while your technology could form nitride layer only on the surface of Ti alloys. This technology is most close to nitriding of steel parts so it is necessary to characterize the thickness of TiN layer and transition layer(s) between the nitride and Ti by SEM + EDX or Auger methods.
Response 1: The introduction and discussion sections more clearly distinguish this method from PVD or CVD coatings. The results section was changed to provide a better interpretation of the infrared and Raman spectra. The conclusion section now states: “The TiN film formation on the titanium metal was confirmed by both infrared reflectance spectroscopy and Raman spectroscopy. Indirect confirmation of the presence of TiN is the gold color and demonstration that the TiN film supports surface plasmon resonance needed for SEIRA”. The thickness was discussed and estimated in the updated discussion section.
- After this characterization, it is necessary also to provide information about analytical depths of IR diffuse reflectance, Raman and SEIRA methods to make sure that spectra are related to the nitride layer.
Response 2: The text was made clearer in the methods section that this was a total reflectance measurement, not strictly a diffuse reflectance measurement. The thickness was discussed and estimated in the discussion section.
The Discussion section should be expanded taking into account new information about surface structure and composition and it should be clearly separated for Conclusions
Response 3: The Discussion section was rewritten and expanded and a distinct conclusions section was added.
- The Introduction should be corrected taking into account my first comment, probably by putting more attention to surface saturation of metals. There are also two points to edit in this section:
Line 21 "the upcoming Mars 2020 spacecraft mission": Mars 2020 mission is already on Mars, it cannot be "upcoming". The collected samples will be returned to Earth by future Mars Sample Return Mission. I suppose that this sentence should be corrected.
Lines 38-39 "To produce TiN surfaces, metal surface nitriding processes 38 generally use high temperatures (>500°C) for a long duration (20 to 80 hours).": Of course one can use such extremely small deposition rates but typically PVD film is growing at 3-6 mkm per hour.
Response: The introduction was modified and newer references were added. Line 21 was corrected. Lines 38-39 was removed.
Author Response File: Author Response.pdf
Reviewer 3 Report
Some brief quantitative results are required in abstract
The state of art was treated very superficial ! Please revise it and create a better introduction.
Line 57-65 from introduction can be moved in methods.
How did you have controlled “The temperature was controlled to 30” ?please provide details
Please keep consistent font size for all figures, as now they differ very much !
Figure 3 is poor interpreted – not clear interpreted each peak ! The same apply for figure 4
There is required a conclusion !
Some recent references are required as most of them now are out of date !
Author Response
Thank you for your time and thoughtful comments. This has clearly improved this paper. I have changed the manuscript to address each of your points listed below.
- Some brief quantitative results are required in abstract
Response 1: Quantitative information on the enhancement factor was added to the abstract.
- The state of art was treated very superficial ! Please revise it and create a better introduction.
Response 2: The introduction was lengthened and newer references were added.
- Line 57-65 from introduction can be moved in methods.
Response 3: This was changed
4. How did you have controlled “The temperature was controlled to 30” ?please provide details.
Response 4: The methods section was changed to explain the temperature control is part of the commercial DART source (explicit in figure 1).
5. Please keep consistent font size for all figures, as now they differ very much!
Response 5: This was changed the font of the template was followed.
- Figure 3 is poor interpreted – not clear interpreted each peak ! The same for figure 4
Response 6: Figures 2-4 were changed, and the peaks more clearly labeled.
- There is required a conclusion!
Response 7: A conclusion was added.
- Some recent references are required as most of them now are out of date !
Response 8: Newer references were added throughout.
Author Response File: Author Response.pdf
Reviewer 4 Report
This work by Mark S. Anderson reports on room temperature synthesis of titanium nitride (TiN) under ambient pressures by exposing titanium metal to a stream of metastable nitrogen gas produced by a commercial direct analysis in real time (DART) source. The work contains novel results and may be suitable for publication in the Coatings given the following corrections are made.
1. Even though the manuscript is well-written, there are some oxymoron expressions. For example, in page 1, line 20-21, it says “An example of a recent application of TiN coatings is for the upcoming Mars 2020 spacecraft mission.” This should be corrected.
2. Some claims in the Results section need to be supported by data/result. For example, in page 3, line 91, the author claims “After reacting with MSN, the surface had the characteristic gold color of TiN”. However, there is no data either in results section or as supplementary material provided to assure the claim. Moreover, a little is said about the modes related to second-order scattering that are labeled in Figure 3. Furthermore, the author should say something about the active sites of the TiN where the SERS and SEIRA measurements were collected.
3. The author should cite the following relevant literature on plasmonic materials and enhanced spectroscopy:
a. Materials 2021, 14(22), 7095; doi: https://doi.org/10.3390/ma14227095
b. ACS Nano 2021, 15, 4, 6038–6060; doi: https://doi.org/10.1021/acsnano.0c10945
Author Response
Thank you for your time and thoughtful comments that have improved this paper. I have changed the manuscript to address each of your points listed below
- Even though the manuscript is well-written, there are some oxymoron expressions. For example, in page 1, line 20-21, it says “An example of a recent application of TiN coatings is for the upcoming Mars 2020 spacecraft mission.” This should be corrected.
Response 1: This was corrected.
- Some claims in the Results section need to be supported by data/result. For example, in page 3, line 91, the author claims “After reacting with MSN, the surface had the characteristic gold color of TiN”. However, there is no data either in results section or as supplementary material provided to assure the claim. Moreover, a little is said about the modes related to second-order scattering that are labeled in Figure 3. Furthermore, the author should say something about the active sites of the TiN where the SERS and SEIRA measurements were collected.
Response 2: The results section was changed to provide a better interpretation of the infrared and Raman spectra. The conclusion section now states: “The TiN film formation on the titanium metal was confirmed by both infrared reflectance spectroscopy and Raman spectroscopy. Indirect confirmation of the presence of TiN is the gold color and demonstration that the TiN film supports surface plasmon resonance needed for SEIRA.”
- The author should cite the following relevant literature on plasmonic materials and enhanced spectroscopy:
- Materials 2021, 14(22), 7095; doi: https://doi.org/10.3390/ma14227095
- ACS Nano 2021, 15, 4, 6038–6060; doi: https://doi.org/10.1021/acsnano.0c10945
Response: These excellent references were added.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments to the R1:
In this modified version the author added proper content and images to improve the article quality.
(1) In the abstract, how to get a 100-fold signed enhancement?
(2) Since the optical property is one important potential application of this material, what is in the testing data or characterization measurement about this performance?
(3) Figure 4, how to assure the casting layer of DiNP on Titanium as 1nm using the current technology? What is the characterization evidence?
Author Response
Thank you for your useful comments and making this a much-improved paper. The manuscript has been revised to meet the reviewer’s comments below. This has also been reviewed and corrected by an independent editor for grammar and typographical errors.
Reviewer 1
In this modified version the author added proper content and images to improve the article quality.
(1) In the abstract, how to get a 100-fold signed enhancement?
In the revised text, this now described in more detail in the results section (line 104)
“The enhancement factor is calculated from the ratio of the signal strength of the SEIRA and the signal to noise of the unenhanced film.”
(2) Since the optical property is one important potential application of this material, what is in the testing data or characterization measurement about this performance?
The testing is based on the presence of the TiN and the SEIRS spectrum (line 100).
(3) Figure 4, how to assure the casting layer of DiNP on Titanium as 1nm using the current technology? What is the characterization evidence?
In the revised text this is addressed in more detail (line74-77) and also in the reference [25]:
The SEIRA test analyte was diisononyl phthalate (Aldrich). This was cast as a thin film using the ‘‘drop-drying method’’ from a dilute methanol solution that is deposited with a micro-syringe. The drop-drying method has been previously shown to produce a uniform thin film, provided the solvent wets the substrate without beading [25].
Reviewer 3 Report
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Author Response
Thank you for your useful comments and making this a much-improved paper.
The manuscript has been revised. This corrected grammar and typographical errors based on your comments and from an independent editor.
Reviewer 4 Report
The author has addressed all my concerns so that I recommend this manuscript to be published in the Coatings journal.
Author Response
Thank you for your review. As noted "The author has addressed all my concerns (reviewer 4) so that I recommend this manuscript to be published in the Coatings journal."
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
