Effects of Heteroaromatic Thiol Additives on Co Electrodeposition by Surface Adsorption
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsIn this manuscript, the inhibitory effect of heteroaromatic thiol additives on Co Electrodeposition has been investigated. As a result, the 2-mercaptobenzimidazole(MBI) shown the strongest inhibitory effect because of the adsorption of the thiol group, the pyridine-like nitrogen in the heterocycle, and the benzene ring. This manuscript can be accept for publication with minor revisions.
- In the introduction,the importance of cobalt electrodeposition in semiconductor technology, especially in comparison with copper interconnect materials, should be further emphasized to highlight the innovation and practical application value of the research.
- In the materials and methods section, author should give more details about the electrochemical experimental conditionsto enable other researchers to replicate the experiments, such as the pH of the electrolyte, temperature control, etc.,
- The positions of functional groups (e.g., thiol and sulfonic acid groups) should be labeled on Figure 2 to visually demonstrate how differences in electron density influence adsorption sites.
- In Figure 3, the more detailed explanation of the CV curves should be provided, particularly the mechanism of how different additives affect the starting potentials.
- There are minor formatting issues in the article, such as inconsistencies in figure numbering and citations; a careful proofread should beadvised in the revised-vision.
Comments for author File: 
Comments.pdf
The English could be improved to more clearly express the research.
Author Response
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Author Response File: Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe submitted manuscript is devoted to the influence of the thiol additives on the electrodeposition of cobalt. The importance of this subject could be explained by the possible application of the cobalt films as interconnectors in electronic industry to substitute copper. I am sure this subject is interesting for wide audience because its importance in many different fields. The manuscript is nicely written and contains both computer simulations and the experimental investigations. The quality of English is rather high. In my opinion, this manuscript could be accepted for publication. However, I have the following questions to the authors?
- What about thermal stability of the deposited films?
- does the electric conductivity of Co films depend on the type of the thiol additive?
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe inaccuracies found, recommendation and reviewer’s questions are listed below:
line 131 – commas and spaces are missed
line 200 – extra dot
line 211 - but
The necessity of using boric acid as a component of the working solution and Au/Ti/Si as the working electrode should be briefly discussed and explained (from the point of view of practical application in semiconductor technology) for better understanding by the readers. The manufacturing process of the working electrode or the supplier, if it was purchased commercially, should be disclosed.
The blank experiments should be carried out. CVs and LSVs in solution without Co(II) should be added to Figure 3 or as a separate figure.
The design of the reference electrode should be specified. Was it Ag/AgCl immersed in a separated chloride solution? This may be important in terms of potential drift in thiol-containing solutions.
According to the obtained CV data, only MBI additives (Fig. 3c) resulted in a significant decrease in the electrodeposited mass. The area of ​​the reverse anodic oxidation (corresponding to the dissolution of the Co film) is noticeably lower than in the case without additives. Whereas for MBO (Fig. 3d) there is an increase in the area of ​​the anodic peak, indicating an increase in the electrodeposited mass despite the negative shift of the initial potential. The chronopotentiometric data (Fig. 4c) can also be interpreted as a catalytic effect for Co deposition (for 50 ppm MBO). The authors should discuss this point.
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
Comments and Suggestions for AuthorsThe manuscript entitled “Effects of Heteroaromatic Thiol Additives on Co Electrodeposition by Surface Adsorption” describes the changes in the process of electrodeposition of cobalt by the addition of adsorbent molecules. This manuscript might be suitable for publication as long as major clarifications are made.
- For me, the interest in adsorbing molecules is still not clear. Authors describe in the Introduction section that the interest is in improving the quality of the deposits, aiming application as interconnection material for semiconductors. Nevertheless, most of the discussion is based in the inhibition caused by the presence of the additives. Why is this inhibition of the deposition process important? Also, resistivity of the additives-containing cobalt is higher, is not this something to be avoided for this kind of application?
- The used model to understand the potential adsorbability properties of the molecules considers that cobalt is electrically neutral (lines 336-337). In the end, they observed discrepancies between the model and the electrodeposition process. Why did not the authors perform the model taking consideration a negatively charged material?
- Section 2.1: What is the pH of the electrolytic solutions?
- Cyclic voltammetry: did the authors also do CV for the pure additives to know their behaviour? Is there a possibility that the molecules are also been reduced together with cobalt? How could this affect the purity, composition and structure in the bulk of the material?
- Figure 5: the Figures are not in the same magnification.
- Lines 228-230: Authors discuss their results using grain boundaries and crystal grain. This is not what is seen from the SEM images. From those SEM images, one can see the morphology of the surfaces and the features present on it. Grain boundaries and crystal grain sizes and/or formats can be revealed only after an etching process.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors have replied the reviewer's comments. The quality of manuscript has been improved. As the last suggestion:
Supplementary information (such as the results of blank experiments) should be mentioned in manuscript.
Author Response
Comment 1: Supplementary information (such as the results of blank experiments) should be mentioned in manuscript.
Response 1: We greatly appreciate the reviewer’s comment. The information of the blank experiments has been added to the manuscript.
The following sentences were added to clarify:
The cyclic voltammetry experiments were conducted in the solution with additives and without cobalt ions. The results are shown in the figure S1. No reaction peak was observed on the CV curve of the additives without cobalt, indicating that the additives are relatively stable in the system. These dates have been inserted into the supporting information.
Reviewer 4 Report
Comments and Suggestions for AuthorsThe authors clarified my questions and improved the quality of the manuscript. It can now be considered for publication.
Author Response
Comment 1: The authors clarified my questions and improved the quality of the manuscript. It can now be considered for publication.
Response 1: We greatly appreciate the reviewer’s comment.
