Formation of Micro- and Nano-Trenches on Epitaxial Graphene

Round 1

Reviewer 1 Report

Comments: This manuscript reports on graphene cutting using metal particles. The graphene was cut under ultra-high vacuum using Ag and In particles, and analyzed. It is short and well written paper, however some minor modifications are needed.

1.     In line 17, ‘particles.’, the sentence is not completed.

2.     In line 58, ‘ultra-high vacuum’ should be expressed in Torr (unit).

3.     In line 64, Field scanning electron microscopy

4.     It is recommended to add SEM images of Ag and In layer before annealing. What is the thickness of Ag and In before and after annealing?

5.     In line 146 and 147, ‘Most of the trenches are highly orientated and well-paralleling, and the trenches are stable even exposed under atmosphere for many days.’ It is advisable to add evidence that the trenches are stable after a few days. ( OM, SEM images, etc. after several days)

6.     In Figure 4, please indicate where the EDS analysis was performed.

7.     In Fig 4d, there are peaks at the same positions in A2 and B2 (about 1550, 1700 cm-1). Please describe each peak. Also, the graphene peak appears clearly in A2, not negligible.

Author Response

1. In line 17, ‘particles.’, the sentence is not completed.

Response: The sentence in line 17-19 has been rewritten for better understanding.

2. In line 58, ‘ultra-high vacuum’ should be expressed in Torr (unit).

Response: The unit of ultra-high vacuum has been added in line 62.

3. In line 64, Field scanning electron microscopy

Response: The statements in line 67-69 has been revised.

4. It is recommended to add SEM images of Ag and In layer before annealing. What is the thickness of Ag and In before and after annealing?

Response: This is a good question. Actually, we did not focus on the change of surface morphology as well as the thickness of Ag and In layer before and after annealing. But, only through the annealing, the trenches can be induced.

5. In line 146 and 147, ‘Most of the trenches are highly orientated and well-paralleling, and the trenches are stable even exposed under atmosphere for many days.’ It is advisable to add evidence that the trenches are stable after a few days. ( OM, SEM images, etc. after several days).

Response: Actually, the sample shown in Fig. 3(a) has been exposed under atmosphere for more than 10 days. It is stable and can be observed by OM. Fig. 3(b) shows the corresponding Raman mapping of the sample. The corresponding statements are added in line 149-152.

6. In Figure 4, please indicate where the EDS analysis was performed.

Response: Thanks for the question. The performed place of the EDS analysis has been marked. The statements has been added in line 161-164 and line 176-178.

7. In Fig 4d, there are peaks at the same positions in A2 and B2 (about 1550, 1700 cm-1). Please describe each peak. Also, the graphene peak appears clearly in A2, not negligible.

Response: The peaks located at 1550 and 1700 cm-1 in A2 and B2 are related to the SiC substrate. The graphene peaks in A2 spectrum are much weaker than that in B2 spectrum, which means the influence of indium atoms to graphene layer. The statements has been added in line 179-185. 

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper describes directional etching of graphene layers by Ag and In particles under vacuum conditions.
 
In the abstract on line 17, the word "particles" appears without a full sentence. This should be corrected. Overall, the paper would benefit from proof-reading to correct the use of English (eg misspelling of "iron" as "ion" in line 32).
 
The acronym "DLC" (presumably Diamond-Like Carbon) should be defined the first time it is used.  
 
In figure 4, the EDS results shown as insets are very small and lack x-axis scales (which would be necessary to verify that the peaks shown correspond to Ag or In); it might be useful to show the graphs in more detail, e.g. as supplementary material.
 
Also in figure 4, part d, the Raman spectra shown do not differ strongly between the undamaged graphene (B2) and the trench (A2). I would disagree with the statement that "Raman peaks of EG is hardly detected inside trench [sic]" as the 1590/cm and 2700/cm peaks are visible in the A2 spectrum (although they are weaker in the A2 spectrum than in the B2). In addition, the 1350/cm peak is not clearly visible in either the A2 or B2 spectrum - if it is present, it is close to the noise threshold. The authors should comment on this and clarify their discussion of the spectra shown. It might be of interest to include spectra recorded well away from the etched region and/or on the graphene film before etching, to allow comparison between the etched and pristine material.

Author Response

In the abstract on line 17, the word "particles" appears without a full sentence. This should be corrected. Overall, the paper would benefit from proof-reading to correct the use of English (eg misspelling of "iron" as "ion" in line 32).

The acronym "DLC" (presumably Diamond-Like Carbon) should be defined the first time it is used.

Response: Thanks for the question. The sentence in line 17-19 has been revised for better understanding. The word “ion” in line 34 has been revised to “iron”. The full name of diamond-like carbon has been added in line 171.

In figure 4, the EDS results shown as insets are very small and lack x-axis scales (which would be necessary to verify that the peaks shown correspond to Ag or In); it might be useful to show the graphs in more detail, e.g. as supplementary material.

Response: Fig. 4 has been rearranged, and the EDS results with x-axis scale has been added. The peaks in Fig. 4(a) and 4(c) correspond to Ag and In. The statements has been added in line 161-164 and line 176-178.

Also in figure 4, part d, the Raman spectra shown do not differ strongly between the undamaged graphene (B2) and the trench (A2). I would disagree with the statement that "Raman peaks of EG is hardly detected inside trench [sic]" as the 1590/cm and 2700/cm peaks are visible in the A2 spectrum (although they are weaker in the A2 spectrum than in the B2). In addition, the 1350/cm peak is not clearly visible in either the A2 or B2 spectrum - if it is present, it is close to the noise threshold. The authors should comment on this and clarify their discussion of the spectra shown. It might be of interest to include spectra recorded well away from the etched region and/or on the graphene film before etching, to allow comparison between the etched and pristine material.

Response: This is a good question. The statements of “Raman peaks of EG is hardly detected inside trench [sic]” in line 179-185 has been revised. The Raman spectra of A2 and B2 do not differ strongly between each other. The peaks located at 1550 and 1700 cm-1 in A2 and B2 are related to the SiC substrate. Different from Ag particles, there is no enhanced intensity observed in In/SiC system due to special metals for SERS detection. So that, the graphene peaks are weak, and the 1350 cm-1 peak is very close to the noise threshold, it is not clearly visible in either A2 and B2 spectrum. But, the graphene peaks in A2 spectrum is much weaker than that in B2 one, which also indicates the damage influence of sliding In particles to EG sheets. Actually, for Ag particles on EG, the spectra recorded well away from the etched region will be enhanced, as displayed by B1 in Fig. 4(b). For In particles on EG, the spectra is similar to pristine EG on SiC, as displayed by B2 in Fig. 4(d). 

Author Response File: Author Response.pdf