Influence of Defects and Heteroatoms on the Chemical Properties of Supported Graphene Layers

Round 1

Reviewer 1 Report

This manuscript can be accepted without revision.

Major concerns in the field have been discussed sufficiently.

Author Response

We thank the referee for his/her positive evaluation of our review paper.

Reviewer 2 Report

This is a very well researched and presented review paper which could be useful to researchers entering the field or researchers looking for an up-to-date overview of the state of the art. As a review this is very useful and worth publishing.

Author Response

We thank the referee for his/her very positive evaluation of our review paper.

Reviewer 3 Report

The paper reviews the influence of defects of graphene on its chemical properties. The topic is very interesting and can contribute to a wide research community. However, there are some weak points. Please address the following comments.

 

1. The writing is not very well because there are some repetition and typos, and important points are not clear. Please reconsider the structure of the paper and use a professional English language service including a substantial editing.
2. Please explain the definition of “Stone-Wales (SW) defect” briefly.
3. The conclusion in each section and the relation between them are not clear.
4. What is the main message of the review paper? In the conclusion section, the authors claim that “We find that there is a general agreement that the presence of defects enhances the reactivity of graphene, making it interesting from the sensoristic and catalytic point of view.” However, it is common knowledge. Please clarify the specific conclusion, which is unique to this review paper.
5. Please add more applications. For example, gas and chemical sensors using defects in graphene.

Author Response

We thank the reviewer for considering the topic of our review as very interesting. A point to point answer is given below.

1. We thank the Referee for his/her comment. Following his/her suggestion, we extensively revised the English grammar and syntax.

2. We added the definition of Stone-Wales in the caption of Figure 1. An example of Stone-Wales defect is shown in Figure 1b.

3. The relationship among the different sections of the manuscript is detailed in the last paragraph of the introduction, which we improved with respect to the previous version. We do not think that adding conclusions to each section would increase the readability of the manuscript but it would be a partial repetition of the general conclusions.

4. We have extensively revised and expanded the conclusions of the review paper.

   An entire paragraph has been added to clarify the relationship between the adsorption energy of gas molecules at graphene and its possible use as a sensor.

   We concluded indeed that the higher adsorption energy  attainable at defects or heteroatoms implies that the equilibrium coverage attainable at a given temperature is higher and thus increases the sensitivity.

   We underlined in the final part that the amount of defects or dopants cannot however be increased at will, since their density significantly affects the mobility of the carriers, thus limiting the performance of the sensor. 

5.  

    We have expanded the last section significantly by adding an example of the use of defected or B-doped graphene to enhance the sensitivity of FET based sensors to NH₃ and NO₂. New Figure 12 and Table I and new refs 59-61 have been added.

Reviewer 4 Report

This short review presents a valuable synthesis of theoretical concepts and experimental findings about defects in graphene. There is no doubt that it should be published, in spite that the review of experimental techniques is not very extensive.

Authors write that ion bombardment is widely available tool to produce defects in a singe layer of graphene. However, damage produced inside of underneath substrate may play an important role. In the case of generation of graphene defects being on SiO₂ after He and N implantation reported damage of radius about 1.5nm [G.Gawlik et al, Applied Science -Basel 9, 514 (2019)]. That exceeds the radius of point defects such as graphene vacancy, and directly indicate that damage inside substrate play an important role. I think that this issue should be more extensively discussed.

The other point is that the size of lettering on some figures is too small. For example, on Fig 10  (left panel) it is hardly  possible to read the presented information.

Author Response

“This short review presents a valuable synthesis of theoretical concepts and experimental findings about defects in graphene. There is no doubt that it should be published, in spite that the review of experimental techniques is not very extensive. Authors write that ion bombardment is widely available tool to produce defects in a singe layer of graphene. However, damage produced inside of underneath substrate may play an important role. In the case of generation of graphene defects being on SiO after He and N implantation reported damage of radius about 1.5nm [G.Gawlik et al, Applied Science -Basel 9, 514 (2019)]. That exceeds the radius of point defects such as graphene vacancy, and directly indicate that damage inside substrate play an important role. I think that this issue should be more extensively discussed.”

We thank the referee for his/her positive evaluation of our review paper.

The paper by Gawlik et al. (Applied Sciences Basel 9, 544 (2019) reports indeed that He and N implantation causes a damage inside the substrate and estimates the radius of the damaged area to be approximately 1.5 and 1.34 nm, respectively. However in that experiment implantation was performed at an energy of 100 KeV while in the experiments reported in our review the energy is about tree order of magnitude lower. This kind of experiments was out of our focus, since we preferentially reported  on point-defects produced by mild sputtering. Under these conditions, the damage to the substrate is negligible and the main properties of the graphene layer are largerly preserved. To make the text clearer we added the citation to the paper by Gawlik et al. (new ref. 18) and a sentence on page 5 addressing this issue.

“The other point is that the size of lettering on some figures is too small. For example, on Fig 10 (left panel) it is hardly possible to read the presented information.”

We agree with the Referee that some labels were pretty small. Since Figures are taken from previously published paper, we cannot edit and modify them. However, we rearranged Figures 9 and 10 in order to make the panels larger and hence more readable. We have also modified the caption of Figure 10 adding the description of the different contributions to the photoemission lines.

Round 2

Reviewer 3 Report

Thank you for your response. The authors addressed well with my comments.