Improved Adhesion Strength of Silica Thin Films on Polycarbonate Substrates Without an Interlayer Using Remote Atmospheric-Pressure Chemical Vapor Deposition

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1. (TrMS; C3H10Si) and oxygen (O2) at room temperature. Here subscript should be used. Please check throughourt the manuscript and correct the similar problems.
2. From Table 1, the coatings of without primer show more thicker than that of with primer. It was well-known, the thicker is the coatings, the higher is the internal stress in the coatings. Obvirously, the design is irrational and unscientific. The same thicker of the coatings for the without primer should also be selected.
3. Please explain why the surface of the sample treated by flame has a Si content of over 20% despite the small flow rate of trimethylsilane (TrMS) introduced.
4. “The surface free energy, especially hydrogen and polarity, as shown in Figure 2”. Please explain why the author uses the polar component of surface energy to represent hydrogen?
5. Based on the result of Fig.2, authors said “These results indicate that improving the wettability of a substrate improves the thin-film adhesion.” I don’t understand why the results of the surface energy from can respresent the wettability of the substrate? Because from the description of section 3.2, the surface energy is film-coated samples surface not substrate.
6. I think that Figure 3 lacks the results of a sample. I can not judge which sample is represented by the icon “Baking the silicone” on the Fig.3’s horizontal axis, with or without acrylic primer? The same doubt also appears in Figure 5.
7. “Polymer substrate samples”. What the polymer substrate is?
8. From this sentence “The properties of the silicone-baking-treated samples synthesized with and without acrylic primer were investigated”, which show the silicone-baking-treated have been applied in samples synthesized with and without acrylic primer. But in the Fig.4, only two SEM results, which is incomplete.
9. Error bars are missing in Figure 3 and Figure 5. This indicates that the results lack statistical rigor.
10. In the discussion, the author said the Si content is benefial to adhesion, but no explanation why the Si content will be raised after using the related surface treat. Moreover, adhesion of acrylic primer-treated sample is far higher the silicone-baking-treated sample. So, what is the significance of surface treatment to increase the surface Si content?

Author Response

1.    (TrMS; C3H10Si) and oxygen (O2) at room temperature. Here subscript should be used. Please check throughourt the manuscript and correct the similar problems.
A1. Thank you for pointing that out. We have corrected the areas you mentioned and similar issues.
2.    From Table 1, the coatings of without primer show more thicker than that of with primer. It was well-known, the thicker is the coatings, the higher is the internal stress in the coatings. Obvirously, the design is irrational and unscientific. The same thicker of the coatings for the without primer should also be selected.
A2. There are samples with similar thicknesses that use primer, we will present those results in Table 1.
3.    Please explain why the surface of the sample treated by flame has a Si content of over 20% despite the small flow rate of trimethylsilane (TrMS) introduced.
A3.　 When thin films are deposited using the atmospheric pressure plasma CVD apparatus used in this study, the Si content in the thin film tends to exceed 20%, regardless of whether flame treatment is performed or not. The reason for this is that the gases used for film deposition are mainly argon, oxygen, and trimethylsilane. After each gas is decomposed by the plasma, argon easily returns to a gaseous state, and the organic components produced from the decomposition of trimethylsilane combined with oxygen to become gases in the form of CO or CO2, which are then exhausted. The thin film in a solid state consists mainly of silica components, with O elements that make up SiO2 and C elements that could not be completely removed or decomposed, remaining bonded with Si elements.
4.    “The surface free energy, especially hydrogen and polarity, as shown in Figure 2”. Please explain why the author uses the polar component of surface energy to represent hydrogen?
A4. We calculate the surface free energy using the Owens and Wendt method, which separates the surface free energy into a dispersion component and a component based on hydrogen bonding and dipole interactions. An explanation of this method and references have been added to section 2-3 of this document.
5.    Based on the result of Fig.2, authors said “These results indicate that improving the wettability of a substrate improves the thin-film adhesion.” I don’t understand why the results of the surface energy from can respresent the wettability of the substrate? Because from the description of section 3.2, the surface energy is film-coated samples surface not substrate.
A5.　 The wording was misleading. The surface energy results were measured after surface treatment but before film deposition, so the text has been revised for clarity. Also, the order of Figure 2 and Table 2 has been changed.
6.    I think that Figure 3 lacks the results of a sample. I cannot judge which sample is represented by the icon “Baking the silicone” on the Fig.3’s horizontal axis, with or without acrylic primer? The same doubt also appears in Figure 5.
A6. The wording was misleading, so I will revise the text. In Figures 3 and 5, I want to compare three things: No treatment, acrylic primer, and silicone baking.
7.    “Polymer substrate samples”. What the polymer substrate is?
A7. I've indicated that it's made of polycarbonate.
8.    From this sentence, “The properties of the silicone-baking-treated samples synthesized with and without acrylic primer were investigated”, which show the silicone-baking-treated have been applied in samples synthesized with and without acrylic primer. But in Fig.4, there are only two SEM results, which is incomplete.
A8. Like answer 6, this comparison only compares two methods: Acrylic primer, and silicone baking.
9.    Error bars are missing in Figure 3 and Figure 5. This indicates that the results lack statistical rigor.
A9. For Figure 3, the error bar cannot be displayed because only one measurement was taken. It has been added to Figure 5.
10.    In the discussion, the author said the Si content is benefial to adhesion, but no explanation why the Si content will be raised after using the related surface treat. Moreover, adhesion of acrylic primer-treated sample is far higher the silicone-baking-treated sample. So, what is the significance of surface treatment to increase the surface Si content?
A10. We believe that the fact that increasing the Si content improves adhesion is significant. On the other hand, the reason why the adhesion does not increase as much as with acrylic primer treatment is that, as shown in Figure 4, the shape in which Si is formed on the substrate surface is different, which we suspect is the reason.

Reviewer 2 Report

Comments and Suggestions for Authors The article has merits  being  a good schort report  with well described procedures in a good research design. The study want to demonstrate that increasing the silicon content of a substrate  improves thin-film adhesive strength.  In such surface treatment the adhesive strength of the  silicone-baking- sample  is much lower than that of the acrylic primer-treated  sample. The result  presentation with two tables and five figures is very clear one and useful for the application in automotive industry. But the subchapter Discussion seems to be more a conclusion about what was presented in other parts of the articles  The original character in my opinion is  not sustained  in the introduction and is not  claear  what is really new in this article  the subchapter reeferences having only nine  titles and 5 of them being self citations. It is to noted as well that the cited self references are not new . In a time with a very dynamic  technology development  is a need to introduce in a paper very new references.   Recommandations I do suggest the present contribution to be modified according to the followings A In the introduction to sustain original character of the article  ( comparison to self citations) B In the introduction  as well it is necessary to describe  other coating methods in more detail and indicate their advantages and disadvantages compared to the method used in the present article. This part has to be enriched with more new references.   C. In paragraph 3 it is necessary to add the results of other surfacee treatment mentioning what is the benefit of the present procedure C The paragraph 4 Discussion which now is a very schort one and seems to be more a conclusion is is necessary to introduce as well more information about  the procedure used and obtained results giving to the  presnt contribution the aspect  of an article.  The present format is a schort scientific raport D it is necessary the number of self references to be  around 10% of total number of  references 

Comments for author File: Comments.pdf

Author Response

I do suggest the present contribution to be modified according to the followings 
A In the introduction to sustain orinal character (comparison to self citations) 
AA. We have added further content to the introduction that introduces additional citations.

B In the introduction as well it is necessary to describe other coating methods in more detail and 
indicate their advantages and disadvantages compared to the method used in the present article. This 
part has to be enriched with more new references. 
AB. This information (and references) has been added in the revised manuscript.

C. In paragraph 3 it is necessary to add the results of other surfacee treatment mentioning what is the 
benefit of the present procedure
AC. We do not have any results evaluating combinations of other surface treatments with atmospheric pressure plasma-enhanced CVD, and therefore cannot present them.

C The paragraph 4 Discussion which now is a very schort one and seems to be more a conclusion is 
is necessary to introduce as well more information about the procedure used and obtained results 
giving to the presnt contribution the aspect of an article. The present format is a schort scientific 
raport
AC. We have revised the discussion in line with this comment.

D it is necessary the number of self references to be maximum 10% of total references number
AD. Although there are still a relatively high proportion of self-cited papers (5 out of 32, ~15%), we have added more references in the revised manuscript.

Reviewer 3 Report

Comments and Suggestions for Authors

Please see the attached file.

Comments for author File: Comments.pdf

Author Response

Required revisions 
1.    The manuscript refers to “abrasion tests” and a “critical peel load”, but does not provide enough detail on the test setup (geometry, loading rate/conditions, failure criterion, and any standard/protocol). As written, another lab cannot reproduce the measurement or compare it to the literature. 
A1. We have included a statement indicating that the test setup conforms to JIS standards.

2.    The SiO₂ thickness differs substantially between conditions (e.g., ~187 nm untreated; ~223–235 nm for flame-treated; ~57 nm in the primer case). Because thickness/residual stress can strongly affect cracking and apparent adhesion, the study should either control thickness across conditions or explicitly analyze/discuss how thickness may influence the reported adhesion values. 
A2. There are samples with similar thicknesses that use a primer; these results are now presented in Table 1.

3. The tables report “Average” and “Div”, but the number of replicates (n) is not stated, and “Div” is not defined. Please report n clearly, define the statistical metric used, and add error bars where appropriate. 　 
A3. We are using the Standardized Differential (SD) calculation method and have explicitly specified this in the revised manuscript.

4. Table 1 reports an adhesion of 229.4 mN for “With primer”, while the text in the adhesion section states the primer-coated substrate shows a maximum adhesion of 150 mN (Figure 5). These values should be reconciled explicitly (different test conditions/sample sets, or a table/figure/text error). 
A4. The value in Table 1 has been corrected to ensure consistency with Figure 5.

5. Only polycarbonate (2 mm) is studied. Either narrow the title/claims accordingly or include at least one additional polymer substrate to justify “polymer substrates” in general. 
A5. The revised title now clearly specifies the use of polycarbonate substrates.

Recommended revisions 　　
6. Reporting adhesion only in mN is hard to interpret without normalization (e.g., per width/contact area) or a clearer link to common peel/fracture metrics and application requirements. 
A6. As indicated in Answer 1, it is now stated that the method conforms to JIS standards.

7. The “silicone baking” mechanism is plausible, but the interface chemistry remains somewhat inferential. Additional interface-sensitive evidence (e.g., high-resolution XPS analysis, depth profiling, complementary chemistry/roughness measurements) would strengthen the mechanistic argument. 
A7. Thank you for your valuable suggestion. However, we were unable to perform the recommended measurements within the scope of this study. We hope to confirm the mechanism through future work.

8. Please define “silicone-containing gas” more clearly (identity/composition) and clarify whether any surface residues or conditioning/cleaning steps are expected.
A8. We have clarified in the revised manuscript that the silicon-containing gas used is trimethylsilane.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

1. About comment 4, I think this explain or description in revised manuscript is not enough. Why think the polar component to represent hydrogen even a Ref.[33] was provided. The authors must give detailed calculate formula to shown in the manuscript. The research workload of this manuscript itself seems relatively inadequate.

2. Why only flame treated samples were considered in doing contact angle measurement? But in this manuscript, the author said that “The surface-treated substrates were evaluated by contact angle measurements”.  I also question what is the significance of contact angle measurement for a substrate with only one type of surface treatment?

3. XPS full spectra and high resolution spectra need to be provided.

4. The authors said that abrasion tests were performed to measure the critical peel load. But I have not seen any description about the abrasion tests and how to obtain the adhesion load results? No curves, no images. The results is not credible.

5. To my comment 10, the explanation is unacceptable.

Author Response

Comment 1: About comment 4, I think this explain or description in revised manuscript is not enough. Why think the polar component to represent hydrogen even a Ref.[33] was provided. The authors must give detailed calculate formula to shown in the manuscript. The research workload of this manuscript itself seems relatively inadequate.
Response 1: I have added the calculation formulas and references to the main text.
Comment 4
　4. “The surface free energy, especially hydrogen and polarity, as shown in Figure 2”. Please explain why the author uses the polar component of surface energy to represent hydrogen?
A4. We calculate the surface free energy using the Owens and Wendt method, which separates the surface free energy into a dispersion component and a component based on hydrogen bonding and dipole interactions. An explanation of this method and references have been added to section 2-3 of this document.

Comment 2: Why only flame treated samples were considered in doing contact angle measurement? But in this manuscript, the author said that “The surface-treated substrates were evaluated by contact angle measurements”.  I also question what is the significance of contact angle measurement for a substrate with only one type of surface treatment?
Response 2: The results for the silicon-baked samples are also shown in Fig. 4.

Comment 3: XPS full spectra and high resolution spectra need to be provided.
Response 3: Figures 5 and 6 have been added.

Comment 4: The authors said that abrasion tests were performed to measure the critical peel load. But I have not seen any description about the abrasion tests and how to obtain the adhesion load results? No curves, no images. The results is not credible.
Response 4: We have added a detailed explanation of the abrasion test and provided an example in Fig. 2.

Comment 5: To my comment 10, the explanation is unacceptable.
Response 5: The effects of silicon baking were discussed again in the discussion section, including the surface free energy results added to Fig. 4.
10. In the discussion, the author said the Si content is benefial to adhesion, but no explanation why the Si content will be raised after using the related surface treat. Moreover, adhesion of acrylic primer-treated sample is far higher the silicone-baking-treated sample. So, what is the significance of surface treatment to increase the surface Si content?
 A10. We believe that the fact that increasing the Si content improves adhesion is significant. On the other hand, the reason why the adhesion does not increase as much as with acrylic primer treatment is that, as shown in Figure 4, the shape in which Si is formed on the substrate surface is different, which we suspect is the reason.

Reviewer 2 Report

Comments and Suggestions for Authors

Second review 4197354

The authors significantly improved their paper introducing more references ( from nine to thirty four the majority still being not very new ) and more discussion. The article still has the aspect of a technical report and not other experiments were made according to my recommendations but I have to noticed that is a good piece of work now in a better form which deseves publication as it is

Author Response

Comment 1: The authors significantly improved their paper introducing more references ( from nine to thirty four the majority still being not very new ) and more discussion. The article still has the aspect of a technical report and not other experiments were made according to my recommendations but I have to noticed that is a good piece of work now in a better form which deseves publication as it is

Response 1: We sincerely thank the reviewer for the positive evaluation of our revised manuscript.

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have accepted all my suggestions , and now the manuscript is ready for publication.

Author Response

Comment 1: The authors have accepted all my suggestions , and now the manuscript is ready for publication.

Response 1: We sincerely thank the reviewer for the positive evaluation of our revised manuscript.