Electroplating Cobalt Films on Silicon Nanostructures for Sensing Molecules
Round 1
Reviewer 1 Report
In this paper, the authors electroplated cobalt films on silicon nanostructures for sensing CO and CO2. They found that both Co and Cu are primarily coated on the spike surfaces without changing the morphology of the nanospikes and the nanoscale bridges form connecting the Co coated silicon spikes. This work is interesting and timely, thus, I recommend to publish this paper after minor revision in the following
line 29: cobalt dioxide (CoO) should be cobalt dioxide (CoO2) or cobalt monoxide (CoO)
Authors have already showed the abbreviation of CO2: carbon dioxide (CO2), thus, but it appeared carbon dioxide (CO2) again in line 63
line 141, authors said that Cu could be uniformly coated on Si spikes from SEM results. But I can not obtained this information and no reference was cited here. Please explain how you get this conclusion.
line 174-177, the format is out of whack. Please check
In Figure 7 (b), how authors know where is Pt, where is Co? Any other characterization?
Author Response
Point-by-point responses to the Reviewer 1’s comments and suggestions.
Dear Reviewer,
Thank you very much for your questions. Answering your questions has improved the manuscript. In the following, we answered your questions and improved the manuscript according to your questions. You can also find the revised parts in blue color in the manuscript.
line 29: cobalt dioxide (CoO) should be cobalt dioxide (CoO2) or cobalt monoxide (CoO)
This is cobalt monoxide, we have corrected as shown in blue colored word also in line 29 in the revised manuscript.
Authors have already showed the abbreviation of CO2: carbon dioxide (CO2), thus, but it appeared carbon dioxide (CO2) again in line 63
We have deleted “carbon dioxide” and only use CO2 also in line 63 in the revised manuscript
line 141, authors said that Cu could be uniformly coated on Si spikes from SEM results. But I can not obtained this information and no reference was cited here. Please explain how you get this conclusion.
Image for Cu is Figure 4b in the old manuscript (Figure 2b in the revised manuscript), we have revised as:
(In line 131 of the revised manuscript)
SEM image in Figure 2b showed that Cu could be uniformly coated on Si spikes; however, there is a tendency of forming bridge structures among Co coated Si spikes as shown in Figure 2c.
We have also changed the sentence:
“From SEM images, we observed that the coating of Cu was like a metal sheet covering on the whole wafer; the coating of Co was like a spider web building between spikes and covering the whole wafer.”
into
“We have observed that the Co coating forms a spider-web structure between spikes and covers the whole wafer. This is very different from that of Cu where no unusual structure is found. Hence only the Co coating is studied in this work.”
for better description.
line 174-177, the format is out of whack. Please check
We have fix this.
In Figure 7 (b), how authors know where is Pt, where is Co? Any other characterization?
In the caption the figure (Figure 4 in the present manuscript), we have added the description:
The area with the nanospikes is identified as Si, and its boundary between Co (shown in green color) is recognized with silicon’s dark and cobalt’s gray colors; the subsequent layers were then identified as the coated Co and the coated Pt for FIB milling, the boundary between Co and Pt (shown in orange color) is clearly shown with their uniformity, Co coating is uniform while the Pt is not uniform.
Best regards,
Mengyan Shen, Ph.D., APS Fellow
Professor of Physics,
Department of Physics, and Nanomanufacturing Center
University of Massachusetts, Lowell
One University Avenue, Lowell, MA 01854, U.S.A.
Office: Olney 118, Lab: Olney G16
Phone: 978-934-3756 (office), 978-934-3749 (lab)
Fax: 978-934-3059 (nano center)
Email: [email protected]
Author Response File: 
Author Response.docx
Reviewer 2 Report
My comments related you submitted manuscript are as follows:
1- In general, there are too many figures in this manuscript. Some of them can be merged.
2-In general, the gas sensing results are not good. The responses are too small. Also, gas sensing studies are not completed. For example, selectivity studies are missing, effect of water vapor is missing, long-term stability is missing, repeatability, etc. Thus, I think the author either can complete the gas sensing tests or change the title and direction of their paper.
3- Please test different concentrations of tested gases.
4- Please put digital photo of the fabricated gas sensor and sensing set up.
5- Please compare the current results with previous results.
Author Response
Point-by-point responses to the Reviewer 2’s comments and suggestions.
Dear Reviewer,
Thank you very much for your questions. Answering you and other reviewer questions has improved the manuscript. In the following, we answered your questions and improved the manuscript according to your questions. You can also find the revised parts in blue color in the manuscript.
1- In general, there are too many figures in this manuscript. Some of them can be merged.
We have merged some figures:
The original Figure 1, Figure 2 and Figure 3 have merged to Figure 1 in the present manuscript,
The original Figure 5 and Figure 6 have merged to Figure 3 in the present manuscript.
The original Figure 8 and Figure 9 have merged to Figure 5 in the present manuscript.
The total figure number has decreased to 10 from 15 in the present manuscript.
2-In general, the gas sensing results are not good. The responses are too small. Also, gas sensing studies are not completed. For example, selectivity studies are missing, effect of water vapor is missing, long-term stability is missing, repeatability, etc. Thus, I think the author either can complete the gas sensing tests or change the title and direction of their paper.
We agree, the sensing studies for CO and CO2 are not completed. We have changed the title from
“Electroplated cobalt films on silicon nanostructures for sensing carbon dioxide and carbon monoxide”
to
“Electroplating cobalt films on silicon nanostructures for sensing molecules such as carbon dioxide and carbon monoxide”
to reflect that the sensing study is not complete and need further study as described in the end of the discuss section of the old manuscript “Further detailed studies are necessary to know the sensitivity, selectivity, response and recovery time, detection limit, stability, and light irradiation conditions for the CoO gas sensor.”
3- Please test different concentrations of tested gases.
We will address this in a complete sensing study with a lock-in technique in the future.
4- Please put digital photo of the fabricated gas sensor and sensing set up.
We have added the digital photos to the Supplementary Materials because the photos are too busy to describe them clearly for reader.
5- Please compare the current results with previous results.
As far as we know, in previous publications, there are not such results that light illumination activates CO2 sensing with semiconductors. The illumination plays an important role in collecting very weak signals of low concentration gases with a lock-in technique in the future.
In the conclusion section to clarify this, we added a sentence
“As far as we know, in previous publications, there are not such results that light illumination greatly increase the CO2 sensing signals with semiconductors although there are similar results for CO [22, 24].”
We added reference 24 for comparing previous results. References 24 and 25 in the old manuscript has moved to the Supplementary Materials as references s1 and s2.
Best regards,
Mengyan Shen, Ph.D., APS Fellow
Professor of Physics,
Department of Physics, and Nanomanufacturing Center
University of Massachusetts, Lowell
One University Avenue, Lowell, MA 01854, U.S.A.
Office: Olney 118, Lab: Olney G16
Phone: 978-934-3756 (office), 978-934-3749 (lab)
Fax: 978-934-3059 (nano center)
Email: [email protected]
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
Based on your revised version, I think it still need modification in term of gas sensing properties and measurement. Also in title it is not common to write "such as".
I think it is better to focus on other properties rather than gas sensing properties. The as obtained results are so poor.
Author Response
Dear Reviewer,
Thank you very much for your great comments. According to the spirit of the comments, we has improved the manuscript.
Based on your revised version, I think it still need modification in term of gas sensing properties and measurement. Also in title it is not common to write "such as".
I think it is better to focus on other properties rather than gas sensing properties. The as obtained results are so poor.
- We have deleted “such as …..” in the title (please see the changes with the tracking tool in the revised manuscript).
- We have changed the word “sensor” into “sample” for the electroplated cobalt structure in the whole manuscript (please see the changes with the tracking tool).
- The tiles for sections 3.1 to 3.4 (and S4) and the abstract have also correspondingly changed to better focus on the property for the sample, and the property is useful for making a gas sensor (please see the changes with the tracking tool).
Thank you for considerations and time.
Best regards,
Mengyan
Mengyan Shen, Ph.D., APS Fellow
Professor of Physics,
Department of Physics, and Nanomanufacturing Center
University of Massachusetts, Lowell
One University Avenue, Lowell, MA 01854, U.S.A.
Office: Olney 118, Lab: Olney G16
Phone: 978-934-3756 (office), 978-934-3749 (lab)
Fax: 978-934-3059 (nano center)
Email: [email protected]
