Multi-Layered Sol–Gel Spin-Coated CuO Nanofilm Characteristic Enhancement by Sn Doping Concentration

Round 1

Reviewer 1 Report

The present work is devoted to synthesis by sol-gel method of multi-layered thin CuO films doped Sn. Crystal structure, morphology and optical properties of samples was studied by XRD, AFM and UV-Vis spectroscopy techniques. The authors claim that as result of doping multi-layered thin CuO films by Sn ions, the electrical properties  enhancement, such as conductivity, occur.

The work is done at a good scientific level, the methods well described.

Нowever, I have some recommendations and remarks:

1. The text symbols of axis scales of fig. 1 (XRD results) must be  reduced;

2. I recommend to rescale the Tauc plot results;

3. The description of equation 1. duplicates in p. 10 (...... where β is a constant reflecting the degree of disorder of the amorphous solid material, h is Planck constant, Eg is the optical gap (eV), hν is photon energy (eV));

4. To improve the impact of present work in the state of art i recommend to use some techniques (XPS or EDX) to observe the chemical composition and chemical state of samples.

Author Response

Responses: We thank our Reviewer for the useful comments and suggestions. Please see our point-by-point responses below:

1. The text symbols of axis scales of fig. 1 (XRD results) must be  reduced;

Response: Figure 1 has now been revised and edited. The y-axis values have now been reduced. X and y-axes have also bee better edited. I hope that the new Figure 1 is now OK. If any further help is needed, please let us know. We will revise promptly.

2. I recommend to rescale the Tauc plot results;

Response: We cannot get what our Reviewer’s recommendation clearly is. We could not know exactly what to scale.

If scaling refers to the values of E_bg, we surely cannot make any changes.

If scaling up is needed for the Figures, we can do that but the journal will scale down the Figures again, and in such a case there will be new difficulty in resolution.

Therefore, we are leaving the Figures as they are, and we hope our Reviewer will accept that. Else, we will make revisions immediately if our Reviewer insists, if we know what exactly is needed.

3. The description of equation 1. duplicates in p. 10 (...... where β is a constant reflecting the degree of disorder of the amorphous solid material, h is Planck constant, Eg is the optical gap (eV), hν is photon energy (eV));

Response: Thanks to our Reviewer. This has now been revised (please see pages 3 and 10.

4. To improve the impact of present work in the state of art i recommend to use some techniques (XPS or EDX) to observe the chemical composition and chemical state of samples.

Response: Our Reviewer’s recommendation is absolutely relevant. However, we have no such service in our laboratories. If we send the samples to other laboratories now, it will take months before having the XPS or EDS results, keeping in mind that we have only a few days to re-submit our revisions.

Therefore, we appreciate if our Reviewer forgives our lack of resources. We hope we can do that in our future works, but now it will not be possible for us.   

Author Response File: Author Response.docx

Reviewer 2 Report

The presented paper concerns the important topic of transparent conductive oxides (TCOs). The manuscript can be published after minor corrections.

1. The introduction should provide a review of TCO materials. CuO is not the only alternative to ITO, other good TCO condidates for solar cells are proposed in the literature.

2. The XRD patterns presented in Figure 1 have a line at 2θ ~ 48°, which crystalline phase is connected with it?

3. On p. 13 of the manuscript the Authors wrote that at 0% Sn concentration the film conductivity was 'immeasurably low'. However, the Tables 1-2 and the Figures 4-5 show that the 0% Sn samples have only about 5 times lower conductivity in comparison to the maximum of 1.5-2% Sn samples. Either the undoped CuO is not that bad, or the Sn:CuO does not provide a dramatic improvement.

4. The Conclusion part does not describe the significance of the reported work. 

Extensive language editing is required.

Author Response

1. The introduction should provide a review of TCO materials. CuO is not the only alternative to ITO, other good TCO condidates for solar cells are proposed in the literature.

Response: We agree with our Reviewer’s comment, about the TCO having various types such as ITO and FTO, which are normally deposited onto glass, plastics and other substrates. We also agree about using TCOs in solar cells and other applications.

However, in our writing we did not describe CuO as a TCO materials. On Line 2 on the Introduction, we describe CuO as having a high visible absorption coefficient material. This does not apply to TCOs.

Moreover, in our results (and in literature) CuO has low transmittance in the visible region (please, see Figure 3).

On the contrary, we have used ITO/Glass as TCO substrates to deposit CuO (please see Sections 2.1 and 2.2)

We hope that our Response to our Reviewer is acceptable. Otherwise, we will surely respect our Reviewer’s demands should heshe give us a clearer idea what to do.

2. The XRD patterns presented in Figure 1 have a line at 2θ ~ 48°, which crystalline phase is connected with it?

Response: Thanks to our Reviewer. It is now corrected on Page 3 as “The signal at 2θ=48º refers to the (202) reflection in CuO, The signal at 2θ=48º refers to the (202) reflection in CuO (JCPDS:card no. 48-1548) and [29].”. Other references also confirm that but we do not wish to use excessive referencing.

3. On p. 13 of the manuscript the Authors wrote that at 0% Sn concentration the film conductivity was 'immeasurably low'. However, the Tables 1-2 and the Figures 4-5 show that the 0% Sn samples have only about 5 times lower conductivity in comparison to the maximum of 1.5-2% Sn samples. Either the undoped CuO is not that bad, or the Sn:CuO does not provide a dramatic improvement.

Response: We respect our Reviewer comment. That is true. The writing has now been revised as shown on Page 13.

4. The Conclusion part does not describe the significance of the reported work. 

Response: Thanks to our reviewer again. Statements have been added to the Conclusion to highlight the significance of the study.

Extensive language editing is required.

Response: We have carefully revised the manuscript for English language. Please see our revisions on the manuscript.

Author Response File: Author Response.docx