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  • Angang Song 1,2,3,*,
  • Yiwen Wang 1 and
  • Junhua Hu 2,3
  • et al.

Reviewer 1: Vidya Nand Singh Reviewer 2: Darius Milčius

Round 1

Reviewer 1 Report

Index all the peaks of XRD, some of the peaks are not indexed. Should there be a difference in properties in the samples deposited with 4.5 and 5 sccm flow rates? The fitting of the inset of figure 3 is not appropriate please do it properly. Compare the results with already reported results in the literature on the same material and similar materials. You can use a table of transparency and electrical properties. This will help in showing the importance of this work, please compare.

Author Response

Reply: We thank the reviewer for the supportive comments and for raising excellent points.

We have now indexed all the peaks of XRD in Fig. 1 in the revised version. It is clearly indicated that amorphous films transform into rutile tin dioxide (PDF#41-1445). The thin-film diffraction peaks revealed sharp (110) and minor (101), (200), (211), (220), (002), (310) and (301) orientations. With increasing oxygen flow rate from 4.5 to 5 sccm, the films become more transparent in the visible spectral range. The resistivity of the film decreased with the increasing O2 flow rate until to the critical value around 4.0 sccm of O2 flow rate, then resistivity increased with the further increase of the O2 flow rate beyond 4.5 sccm. We have corrected the fitting of the inset of figure 3 in the revised version.

We thank the reviewer for this suggestion. We compared the transparency and electrical properties of Nb-doped SnO2 thin films prepared by different methods as followes:

 

Resistivity/Ω cm

Transmittance/%

Method

1

6.65 × 10−3

85

Pulsed  laser deposition (PLD)

2

4.3 × 10−3

70

spray pyrolysis

3

1.69 × 10−3

75

spray pyrolysis

4

0.62 × 10−3

70

spray pyrolysis

5

6.453 × 10−4 

82

spray pyrolysis

6

3.7 × 10-3

85

Pulsed  laser deposition (PLD)

7

1.0 × 10-3

79

chemical vapor deposition (MOCVD)
  1. Y. J. Seo, G. W. Kim, C. H. Sung, M. Anwar, C. G. Lee and B. H. Koo, Current Applied Physics, 2011, 11, S310-S313.
  2. V. Gokulakrishnan, S. Parthiban, K. Jeganathan and K. Ramamurthi, Journal of Materials Science, 2011, 46, 5553-5558.
  3. R. Ramarajan, M. Kovendhan, K. Thangaraju and D. P. Joseph, Ceramics International, 2020, 46, 12224-12231.
  4. G. Turgut, E. F. Keskenler, S. Aydın, E. Sönmez, S. Doğan, B. Düzgün and M. Ertuğrul, Superlattices and Microstructures, 2013, 56, 107-116.
  5. R. Ramarajan, Superlattices and Microstructures, 2019, 135, 106274.
  6. A. Y. Suzuki, K. Nose, A. Ueno, M. Kamiko and Y. Mitsuda, Applied Physics Express, 2012, 5, 011103.
  7. He, L.A., Luan, C.N., Wang, D., Le, Y., Ma, J., 2020. Preparation and Characterization of High Mobility Nb-Doped SnO2 Transparent Conducting Films. MSF 993, 869–875.

Reviewer 2 Report

The manuscript presents original and technologically valuable results on remote plasma sputtering deposition of niobium doped SnO2 transparent conductive oxides on glass substrates. Following question/suggestion could improve quality of the work:

1.      Nb-doped SnO2 films are a rather popular subject. Would be useful to clarify the precise novelty and added value of the presented manuscript.

2.      What was the motivation to use remote plasma sputtering deposition?

3.      What was the deposition rate for different sccm (or deposition time)?

4.      Which Raman equipment was used for analysis?

5.      Would be useful to present not only EDS mapping but also % of Nb in the films.

6.      Which sample (sccm) was used for Figure 2?

7.      Is the thickness of all samples similar?

8.      Are received results comparable with the other author's results?

9.      Water splitting was not tested in this work and the sentence “…Nb:SnO2 films can be employed as low-temperature transparent and conductive protective layers for solar water splitting…”. Sounds too speculative.

 

1.   English language should be checked, for example, Line 67: „mBar“should be changed to „mbar“.

Author Response

  1. Nb-doped SnO2 films are a rather popular subject. Would be useful to clarify the precise novelty and added value of the presented manuscript.

Reply: We thank the reviewer for the supportive comments and for raising excellent points. We have clarified this in the introduction in the revised version:

“Recently, niobium-doped SnO2 system were explored as an alternative material for ITO and FTO electrodes. The Nb-doped SnO2 thin films are still not commercialized due to lack of exhaustive exploration of its electrical and optical properties by researchers.”

  1. What was the motivation to use remote plasma sputtering deposition?

Reply: We thank the reviewer for this insightful question. Indeed, a novel method was used to prepare the transparent conductive oxide films, a remote plasma source deposition system (HiTUS). In addition to high film quality and good reproducibility, its advantages with respect to magnetron sputtering, also includes rapid sputtering deposition rate and low deposition temperature, which will offer an essential technical basis in defects controlling in wide range and properties optimization. It would be highly desirable that such a low-cost coating route could be applied to fabricate high quality TNO with improved transparent conductivity, thus helping to address the diminishing indium problem with a potential low-cost alternative transparent electrode material for large area photonic applications.

  1. What was the deposition rate for different sccm (or deposition time)?

Reply: We thank the reviewer for this insightful question. Indeed, the thickness of the films was measured by a surface profilometer (Dektak-XT). It was determined that the film had an average thickness of around ∼240 for the deposition time of 10 minutes.

  1. Which Raman equipment was used for analysis?

Reply: We thank the reviewer for this insightful question. The short-range structure and vibration modes were analyzed by Raman spectroscopy (HORIBA Scientific LabRAM HR Evolution) with a laser excitation wavelength of 325 nm (spot size: ∼1 um in diameter). We have clarified the Raman measurement in the Experimental Section in the revised version.

“The short-range structure and vibration modes were analyzed by Raman spectroscopy (HORIBA Scientific LabRAM HR Evolution) with a laser excitation wavelength of 325 nm (spot size: ∼1 um in diameter).”

  1. Would be useful to present not only EDS mapping but also % of Nb in the films.

Reply: We thank the reviewer for this suggestion. Indeed, EDS mapping not only revealed that Nb, Sn and O were homogeneously distributed in the whole film, but also indicated a 5% of Nb in the thin film taken as an average from three measured areas on four different samples.

  1. Which sample (sccm) was used for Figure 2?

Reply: We thank the reviewer for this insightful question. Nb:SnO2 thin film sample deposited at 4.0 sccm of oxygen flow rate. We have added the following sentence to the Fig. 2 caption:

Nb:SnO2 thin films deposited at 4.0 sccm of oxygen flow rate.

  1. Is the thickness of all samples similar?

Reply: We thank the reviewer for this insightful question. There is no big difference in the thickness of all samples.

  1. Are received results comparable with the other author's results?

Reply: We thank the reviewer for this insightful question. Indeed, the result is in good agreement with the report of Dr. Bon Heun Koo et al. They deposited Nb-doped SnO2 thin films on glass substrate by pulsed laser deposition. An electrical resistivity 6.65 × 10−3 Ω cm with an average optical transmittance in visible range (400–800 nm) of 85%, and an optical band gap of 4.27 eV was observed in their work. [Current Applied Physics 11 (2011) S310-313 ]

  1. Water splitting was not tested in this work and the sentence “…Nb:SnO2 films can be employed as low-temperature transparent and conductive protective layers for solar water splitting…”. Sounds too speculative.

Reply:  We thank the reviewer for this suggestion. We have changed the sentence to “Due to its superior chemical stability, such Nb:SnO2 films are intended for applications as transparent and conductive protection layers for metal oxide semiconducting photoelectrodes for solar water splitting”. We have also carefully proof-read the manuscript again. We have made some changes and additions in the revised version, which we hope improves our manuscript further.

  1. English language should be checked, for example, Line 67: „mBar“should be changed to „mbar“.

Reply: We thank the reviewer for pointing out this formatting error, which we have now corrected. We have also carefully proof-read the manuscript again.

Round 2

Reviewer 1 Report

can be accepted from my side

Author Response

We are very grateful to the reviewer for this positive and supportive comments. We have also carefully proof-read our manuscript again. We have made some changes and additions in the revised version, which we hope improves our manuscript further.

Reviewer 2 Report

The manuscript was improved in accordance with most of the review comments. 

Author Response

We thank the reviewer for the positive and supportive comments. We have carefully proof-read the manuscript again. We have made some changes and additions in the revised version, which we hope improves our manuscript further.