Synthesis of Wrinkled MoS₂ Thin Films Using a Two-Step Method Consisting of Magnetron Sputtering and Sulfurization in a Confined Space

Round 1

Reviewer 1 Report

The authors investigated a new synthesis method of MoS2 thin films using sputtering and sulphurisation.

The method is clearly described, and the samples were characterised in detail.

I can accept most conclusions, but not all. This approach reduces the S quantity during sulfurization due to the confined space, which is a big advantage. The authors also argue that magnetron sputtering has a lower energy footprint due to its lower operational temperatures compared to CVD processes, but they had to use thermal treatment performed at 800 °C for 45 minutes, which consumes more energy than a typical CVD experiment. The wording should be changed.

The MoS2 samples are full of defects, the combination of sputtering and sulphurisation can not produce high quality films like the CVD. But these samples may be useful in applications where high surface area is needed or defects may act as catalyst. Consequently, these samples may be useful in several applications.

Figure 9. AFM Image of the sulfurized MoS2 sample. AFM images contain 3D information; therefore, a colour scale should be included.

Author Response

Dear Reviewer,

We appreciate your time and attention to give useful suggestions for improving our work. Below are our answers to your comments.

Please see the attachment.

Best regards,

Alin Velea

Author Response File: Author Response.pdf

Reviewer 2 Report

The article entitled as “Synthesis of Wrinkled MoS2 Thin Films using a Two-step Method” presents a more sustainable approach to create MoS2 thin films. The presented study could make an important contribution to the existing state of the art. The article has been carefully reviewed related to content, novelty, and scientific soundness. Based on this evaluation, the article could be published in MDPI Sustainability if authors are able to address the following major concerns and questions. 

General comments:

1.     While the overall title reads interesting and draws attention to the overall article, maybe it would be better to name the fabrication approach instead to remaiing too general with “Two-step Method”. 

2.     The abstract should be carefully reviewed and revised from the language. This holds true for the entire article.  

3.     The abstract seems to focus on the methodological part. Please present a better balanced abstract with motivation/intro, novelty statement, some methodological details, main conclusions and outlook.

4.     The entire manuscript should be revised regarding the used English. Although the overall readability is ok, there are many minor inconsistencies. 

5.     Please revise the captions for clarity and completeness. 

6.     Special care should be dedicated towards the design and selection of figures and sub-figures regarding readability, clarity, scientific soundness, and completeness. Please refer to more specific comments in the following sections.

7.     The selected keywords appear to be appropriate and fine. 

Introduction: 

1.     While the first paragraph of the introduction reads fine and interesting. Authors could extend the use of MoS2 towards tribology, since it is one of the only 2D nanomaterials, which is already commercially used as lubricant additive. This is particularly remarkable and also will underline the need for new, more efficient and more sustainable synthetic routes. 

2.     The following sentence is a repetition “The unique structure of layered materials, 46 including MoS2, offers advantages in energy storage applications due to their high surface 47 area-to-volume ratio and observable characteristics within a few atomic layers [15, 16].” Please avoid. 

3.     Related to magnetron sputtering, the existing state of the art falls very short. Magnetron sputtering has been used for a long time to create well designed MoS2 films with potential doping for property tuning. In this regard, authors are advised to check the existing literature related to doped MoS2 films from the Chinese Academy of Science. 

4.     The introduction reads incomplete and the existing state of the art is not well developed. 

5.     Therefore, authors fail to present an appropriate novelty statement and the last paragraph reads rather weak. 

Experimental section:

1.     Have you used any intermediate adhesion layer?

2.     How did you select the temperature and times for the post-treatment?

3.     Experimental details related to XRD, Raman spectroscopy and XPS are highly incomplete. Please extend the presented description. 

Results and discussion: 

-       Related to Figure 2, please work with a) and b). 

-       Please revise the following sentence “In Figure 3, are presented the X-ray diffraction diagrams”. Many examples like that can be found.

-       The XRD diffractograms are rather noisy and their quality limited. Please revise and improve. 

-       The Raman analysis looks better, but it should be extended towards higher Raman shifts. Some more guidance for the detailed Raman analysis can be found in: 

-       Solid lubrication performance of sandwich Ti3C2Tx-MoS2 composite coatings

-       Moreover, Raman analysis needs appropriate referencing for peak assignment. 

-       It would be appropriate to compare the following section “3.2. Sulfurized thin films 190 “ with the previous resutls. In the current versión, the artilce reads rather repetitive. 

-       Figure 6 must be revised and improved. Please apply appropriate baseline correction for the XRD data. 

-       Figure 8 and Figure 9 do not contribute much. What is the overall purpose?

-       The XPS analysis reads like an add-on. 

-       Partially, the characterization techniques are disconnected. Moreover, the overall purpose of the study is missing. What is the overall application? What are the improved properties of the new synthesis approach. Apart from a sustainable way to produce these films, what is the overall benefit?

-       The manuscript clearly lacks some application-related research to really show the benefit of the new approach. 

-       For appropriate thin film characterization, authors may refer to the following state of the art papers published by Marian et al.: 

-- Evaluation of DLC, MoS2, and Ti3C2Tx thin films for triboelectric nanogenerators

Please see above. 

Author Response

Dear Reviewer,

Thank you sincerely for your thorough review and constructive feedback. The entire manuscript was reorganized, figures were redrawn and new references were added. Below are our responses, incorporating you suggested changes.

Please see the attachment.

Best regards,

Alin Velea

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Thank you very much for revising the manuscript. 

Authros have done a great job and implemented all my suggestions as well as addressed all my concerns. 

The quality has notably improved and therefore the article is recommended for publication in the current version. 

Thank you. 

Fine to proceed.