Optical Properties of a-SiC:H Thin Films Deposited by Magnetron Sputtering

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript investigates the optical properties of amorphous silicon carbide (a-SiC:H) thin films deposited by magnetron sputtering. It focuses particularly on the stability of these properties over a 12-year period, which is a novel and interesting point.

The manuscript is generally clear and well-organized. However, there are several areas where clarification, additional explanation, and technical corrections are needed to improve scientific quality, reproducibility, and flow. Figures and tables are informative but could be improved with better labeling and discussion. Some references also need corrections or better integration.

Specific comments

1. Lines 23–77: Good background, but there are minor English errors (e.g., “such us” → “such as” in line 24).
2. Line 23-31. More new supporting references are needed here, otherwise there are doubts about the relevance and novelty of work. This part could be improved by organizing the discussion around key parameters (temperature, pressure, hydrogen content) and their effects.
3. Line 18-19: "Deposited 12 years ago and their optical properties remained stable":
   ➔ Was any degradation at all detected, even minor? Which measuring techniques were used now vs 12 years ago? Was these the same experimental devices?
4. To study various modifications of SiC, other experimental methods, such as Raman, FTIR and Luminescence, are usually very successfully used. Why are they not used? Discuss and explain. 

Huczko, A., Dąbrowska, A., Savchyn, V., Popov, A. I., & Karbovnyk, I. (2009). Silicon carbide nanowires: Synthesis and cathodoluminescence. physica status solidi (b), 246(11‐12), 2806-2808.

Burton, J. C., Sun, L., Pophristic, M., Lukacs, S. J., Long, F. H., Feng, Z. C., & Ferguson, I. T. (1998). Spatial characterization of doped SiC wafers by Raman spectroscopy. Journal of Applied Physics, 84(11), 6268-6273.

5. Lines 80–91: Question: Was the hydrogen content (H/(Si+C)) in the final film measured or estimated?
6. Figure 2. Please indicate explicitly how Eg values were extracted (method for linear fit? software used?). The legitimacy and accuracy of the drawn lines and their belonging to the edge of fundamental absorption, and not to defective levels at the absorption edge, requires a more serious definition. See the latest article by the Editors of “Optical Materials” journal (Elsevier):

Brik, M. G., Srivastava, A. M. (2022). A few common misconceptions in the interpretation of experimental spectroscopic data. Optical Materials, 127, 112276.

7. Table 1. It is unclear if the films labeled A–E correspond exactly to different hydrogen flows or temperatures. Suggestion: Add a note or additional column to clearly show hydrogen content and Ts.
8. Lines 140–168: Solid discussion relating hydrogen incorporation, optical bandgap, and disorder is given. However, the explanation regarding hydrogen content exceeding a "limit" (line 164) needs a quantitative reference or number.
9. Some references (e.g., [6] Mukesh Kumar) look suspicious: journal name "Zas Mat" is unusual. Please double-check this reference.
10. In general, the manuscript is interesting and can be recommended for publication after constructive reflection on the above comments. However, the conclusions must clearly formulate what new data is obtained in this work. And to the conclusions, to make a more clear analysis of the data obtained in comparison with what is already in the literature https://scholar.google.com/scholar?hl=ru&as_sdt=0%2C5&q=%22amorphous+silicon+carbide%22&btnG=

Author Response

Response to Reviewers

We would like to thank the reviewers for the time that took to read our manuscript

and for their constructive comments. Below we present our responses to their

comments.

Reviewer 1

Reviewers' comment:

The manuscript is generally clear and well-organized. However, there are several areas where clarification, additional explanation, and technical corrections are needed to improve scientific quality, reproducibility, and flow. Figures and tables are informative but could be improved with better labeling and discussion. Some references also need corrections or better integration.

Response:

Following the Reviewer suggestion we made the appropriate changes in Figures and References.

 Specific comments

1. Lines 23–77: Good background, but there are minor English errors(e.g., “such us” → “such as” in line 24).

 

Response:

Now minor English errors have been corrected.

 

2. Line 23-31. More new supporting references are needed here, otherwise there are doubts about the relevance and novelty of work. This part could be improved by organizing the discussion around key parameters(temperature, pressure, hydrogen content) and their effects.

 

Response:

New relevant references have been added in the text (Ref. 7, 8, 11, 20, 21). Also, the text:” Especially, the degree of …. and structural properties [8,9]” has been added to the bottom of page 1 and the top of page 2 of the revised version.

1. Line 18-19: "Deposited 12 years ago and their optical properties remained stable":
   Was any degradation at all detected, even minor? Which measuring techniques were used now vs 12 years ago? Was these the same experimental devices?

Response:

Added the text: “However, it has to be noted that ... true ‘calculation’” as well as the text “… using the same apparatus, as well as the same technique…” lines 128 to 131 of the new version of the paper.

4. To study various modifications of SiC, other experimental methods, such as Raman, FTIR and Luminescence, are usually very successfully used. Why are they not used? Discuss and explain. 

 

Response:

Added the following text: “In the present work, the optical properties of a-SiC:H thin films for different substrate temperatures from 100^oC to 290^oC have been studied and the results are explained with the absorption spectra measurements. These explanations are based on the fact that the films are amorphous SiC alloy thin films and the variation of their properties is attributed to the hydrogen incorporation in the films and not to different structural properties, as it has been found in many other research works [18, 19, 26, 31].” Lines 188 to 193 of the revised version of the paper. 

 

1. Lines 80–91: Question: Was the hydrogen content (H/(Si+C)) in the final film measured or estimated?

Response:

There is no presentation about the hydrogen content (H/(Si+C)) in the a-SiC:H thin films.

 

1. Figure 2. Please indicate explicitly how Eg values were extracted (method for linear fit? software used?). The legitimacy and accuracy of the drawn lines and their belonging to the edge of fundamental absorption, and not to defective levels at the absorption edge, requires a more serious definition. See the latest article by the Editors of “Optical Materials” journal (Elsevier):

Response:

Added the following text: “The optical band gaps have been estimated [25] by applying the absorption spectrum fitting method, using the Tauc model [26]. With this method, no additional information is needed, such as the reflectance spectra. Extrapolating the straight-line portion of the plots shown in Figure 2 to zero  gives the corresponding Eg values [27,28]. OriginLab was used for the fitting. However, it has to be noted that the determination of the band gap from the Tauc plot can be referred to as an ‘estimation’ and not the true ‘calculation’ [25].” Lines 124 to 130 of the revised version of the paper.

 

1. Table 1. It is unclear if the films labeled A–E correspond exactly to different hydrogen flows or temperatures. Suggestion: Add a note or additional column to clearly show hydrogen content and Ts.

 

Response:

Now the table has changed according to Reviewer 1. More specifically, now the table contains the hydrogen flow rate of each sample.

 

1. Lines 140–168: Solid discussion relating hydrogen incorporation, optical bandgap, and disorder is given. However, the explanation regarding hydrogen content exceeding a "limit" (line 164) needs a quantitative reference or number.

 

Response:

Following the reviewer’s suggestion, the text has now been changed to “It can also be noticed that slope B decreases significantly in sample E, where Eg reach the maximum value revealing that the hydrogen incorporation is responsible for this.” (Now lines 210 and 211)

 

1. Some references (e.g., [6] Mukesh Kumar) look suspicious: journal name "Zas Mat" is unusual. Please double-check this reference.

Response:

Following the reviewer’s suggestion, the reference [6] of the previous version of the paper has been corrected to:

Kumar, M. Studies of Structural and Optical Properties of Sputtered SiC Thin Films. Zastita Materijala 2024, 65 (2), 343–349. https://doi.org/10.62638/ZasMat1143.

(Please notice that the correction concerned the journal (was Zas Mat now Zastita Materijala)

10. In general, the manuscript is interesting and can be recommended for publication after constructive reflection on the above comments. However, the conclusions must clearly formulate what new data is obtained in this work. And to the conclusions, to make a more clear analysis of the data obtained in comparison with what is already in the literature https://scholar.google.com/scholar?hl=ru&as_sdt=0%2C5&q=%22amorphous+silicon+carbide%22&btnG=

Response:

All necessary changes have been formulated according to the new data in conclusions.

Reviewer 2 Report

Comments and Suggestions for Authors

The authors report a a-SiC:H thin films were prepared using magnetron sputtering technique for different substrate temperatures from 100℃ to 290℃. Their optical properties were studied using the ellipsometry technique. The experimental results show that the optical band gap of the films varies from 2.00 eV to 2.18 eV for the hydrogenated films, whereas Eg is equal to 1.29 eV when the film does not contain hydrogen atoms and for Ts=100℃. The optoelectronic quality of the films seems to be the optimum when Ts=100℃ or Ts=220℃. Additionally, the refractive index exhibits an inverse relationship with E₉ as a function of Tₛ.

Overrall, the topic of the present work is good and present some result interesting but is necessary to add and remarked some major revision:

By example: What is the importance of this work with respect a others work publicated?, What happend after 12 years with the films with respect anothers films, is not clear this experimental part?. Its not clear as is used calculation of the optical band gap energies via Mott and Davis method, because in Figure 2 the regions considered to obtain the band gap are very small, this can be seen in the dotted lines that are being considered.

Results, In this sentence “the slope B of Tauc constant as a function of substrate temperature. It is clear that maximum value of samples B and D reveals that these films present the minimum disorder”, How can you be sure of this with just the slope to obtain the band gap?

This work can be improved with a better writing and greatly improving explains of varios process. It is necessary to carry out more compositional characterizations such as XPS, FTIR, Raman and the most important structural ones such as XRD and HRTEM since the .

 

Besides, the dangling bonds in the amorphous network of a-SiC can be obtained experimentally with more compositional characterizations and in this work it is not explained how they exist and what type they are the dangling bonds.

In the results the Table 1 should be included from the beginning of the results text, as the graphs are presented at the beginning and it is not clear what each sample is. In figure 1, sample D is repeat.

Comments on the Quality of English Language

The authors report a a-SiC:H thin films were prepared using magnetron sputtering technique for different substrate temperatures from 100℃ to 290℃. Their optical properties were studied using the ellipsometry technique. The experimental results show that the optical band gap of the films varies from 2.00 eV to 2.18 eV for the hydrogenated films, whereas Eg is equal to 1.29 eV when the film does not contain hydrogen atoms and for Ts=100℃. The optoelectronic quality of the films seems to be the optimum when Ts=100℃ or Ts=220℃. Additionally, the refractive index exhibits an inverse relationship with E₉ as a function of Tₛ.

Overrall, the topic of the present work is good and present some result interesting but is necessary to add and remarked some major revision:

By example: What is the importance of this work with respect a others work publicated?, What happend after 12 years with the films with respect anothers films, is not clear this experimental part?. Its not clear as is used calculation of the optical band gap energies via Mott and Davis method, because in Figure 2 the regions considered to obtain the band gap are very small, this can be seen in the dotted lines that are being considered.

Results, In this sentence “the slope B of Tauc constant as a function of substrate temperature. It is clear that maximum value of samples B and D reveals that these films present the minimum disorder”, How can you be sure of this with just the slope to obtain the band gap?

This work can be improved with a better writing and greatly improving explains of varios process. It is necessary to carry out more compositional characterizations such as XPS, FTIR, Raman and the most important structural ones such as XRD and HRTEM since the .

 

Besides, the dangling bonds in the amorphous network of a-SiC can be obtained experimentally with more compositional characterizations and in this work it is not explained how they exist and what type they are the dangling bonds.

In the results the Table 1 should be included from the beginning of the results text, as the graphs are presented at the beginning and it is not clear what each sample is. In figure 1, sample D is repeat.

Please revise all document in your redaction and spelling carefully.

In agreement with the corrections realized, it is necessary improvement the discussion and conclusions.

Author Response

Response to Reviewers

We would like to thank the reviewers for the time that took to read our manuscript

and for their constructive comments. Below we present our responses to their

comments.

Reviewer 2

Reviewers' comment:

Overrall, the topic of the present work is good and present some result interesting but is necessary to add and remarked some major revision:

1. By example: What is the importance of this work with respect a others work publicated?, What happend after 12 years with the films with respect anothers films, is not clear this experimental part?. Its not clear as is used calculation of the optical band gap energies via Mott and Davis method, because in Figure 2 the regions considered to obtain the band gap are very small, this can be seen in the dotted lines that are being considered.

Response:

The samples were fabricated 12 years ago and have retained the same optical properties as they exhibit today.

“During this period, the samples were stored under laboratory conditions, at room temperature and at ambient pressure typical for coastal regions, i.e., approximately 1 atm” (Text has been included in lines 172-174 of the revised version)

The following text has been added to the revised version: “The optical bandgap energies (Eg) were determined from the regions of the plot as specified in the relevant literature. [22]” (Lines 116-117)

 

2. Results, In this sentence “the slope B of Tauc constant as a function of substrate temperature. It is clear that maximum value of samples B and D reveals that these films present the minimum disorder”, How can you be sure of this with just the slope to obtain the band gap?

 

Response:

The following part has been added to the revised version (Lines 159 to 162):

“Taking into account the relationship  … which induces an increase in internal stress.”

 

3. This work can be improved with a better writing and greatly improving explains of varios process. It is necessary to carry out more compositional characterizations such as XPS, FTIR, Raman and the most important structural ones such as XRD and HRTEM since the .

Response:

The present study investigates the optical properties of hydrogenated amorphous silicon carbide (a-SiC:H) thin films, and the results of the optical analysis are presented. Further investigation of other properties, such as structural characteristics, is under consideration for future work. 

 

4. Besides, the dangling bonds in the amorphous network of a-SiC can be obtained experimentally with more compositional characterizations and in this work it is not explained how they exist and what type they are the dangling bonds.

Response:

The following text has been added to the revised version of the paper between Lines 216 and 220: “Dangling bonds in a-SiC:H arise from structural disorder and incomplete hydrogen passivation, mostly as Si₃≡• and C₃≡• defects [23]. They critically influence electronic and optical properties, making their control essential for applications in solar cells, sensors, and thin-film transistors.”

5. In the results the Table 1 should be included from the beginning of the results text, as the graphs are presented at the beginning and it is not clear what each sample is. In figure 1, sample D is repeat.

 

Response:

Table 1 has been transported to the beginning of the results text, as suggested, and the repeated “D” has been corrected. Now this sample is renamed to “Sample E”.

6. Please revise all document in your redaction and spelling carefully.

Response:

Grammar and spelling errors have been corrected.

 

7. In agreement with the corrections realized, it is necessary improvement the discussion and conclusions.

Response:

All necessary changes have been formulated according to new data in conclusions.

 

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript titled "Optical properties of a-SiC:H thin films deposited by magnetron sputtering" addresses an interesting and highly relevant research topic within the scope of this journal. Studying optical properties and their long-term stability in thin films is essential for both fundamental science and practical technological applications. However, several critical concerns need substantial revision and supplementary data before acceptance can be recommended. In its present form, the manuscript has important deficiencies regarding experimental completeness, clarity, and scientific robustness.

1. The authors emphasize that these films were initially deposited 12 years ago, yet the manuscript lacks critical original measurements from that time. To support the claim that optical properties (such as optical band gap, refractive index, and absorption spectra) remain stable, the authors must explicitly include the original data from 12 years prior. Without direct comparative evidence, conclusions regarding long-term stability are not scientifically robust.
2. The current analysis relies solely on optical characterization techniques, specifically ellipsometry and transmittance spectra. While valuable, these methods alone do not provide sufficient insights into potential structural or compositional changes that could affect optical stability. Morphological analysis using scanning electron microscopy (SEM) along with Energy Dispersive Spectroscopy (EDS) or Transmission Electron Microscopy (TEM) is essential. This will clarify whether the films' microstructure and chemical composition remained unchanged or evolved over the 12-year period.
3. The manuscript lacks detailed information regarding how the samples have been stored over the past 12 years. Factors such as ambient temperature, humidity, light exposure, and atmospheric conditions significantly influence thin-film stability.
4. Currently, the manuscript only includes data from a limited number of substrate temperatures (100°C, 140°C, 220°C, and 290°C). The limited data points make the reported trends in optical bandgap and refractive index appear overly simplified. Additional experiments at intermediate substrate temperatures or varying hydrogen flow rates are crucial for a more comprehensive understanding of how process parameters influence optical properties.

Author Response

Response to Reviewers

We would like to thank the reviewers for the time that took to read our manuscript

and for their constructive comments. Below we present our responses to their

comments.

Reviewer 3

Reviewers' comment:

 

Specific comments

1. The authors emphasize that these films were initially deposited 12 years ago, yet the manuscript lacks critical original measurements from that time. To support the claim that optical properties (such as optical band gap, refractive index, and absorption spectra) remain stable, the authors must explicitly include the original data from 12 years prior. Without direct comparative evidence, conclusions regarding long-term stability are not scientifically robust.

 

Response:

The samples were fabricated 12 years ago, and their optical properties have remained stable over time.

Values measured 12 years ago have been added to Figure 3.

2. The current analysis relies solely on optical characterization techniques, specifically ellipsometry and transmittance spectra. While valuable, these methods alone do not provide sufficient insights into potential structural or compositional changes that could affect optical stability. Morphological analysis using scanning electron microscopy (SEM) along with Energy Dispersive Spectroscopy (EDS) or Transmission Electron Microscopy (TEM) is essential. This will clarify whether the films' microstructure and chemical composition remained unchanged or evolved over the 12-year period.

 

Response:

The present study investigates the optical properties of hydrogenated amorphous silicon carbide (a-SiC:H) thin films, and the results of the optical analysis are presented. Further investigation of other properties, such as structural characteristics, is under consideration for future work. 

 

3. The manuscript lacks detailed information regarding how the samples have been stored over the past 12 years. Factors such as ambient temperature, humidity, light exposure, and atmospheric conditions significantly influence thin-film stability.

 

Response:

During this period, the samples were stored under laboratory conditions, at room temperature and at ambient pressure typical for coastal regions, i.e., approximately 1 atm. (Text has been added to the revised manuscript as well, lines 172 to 174)

 

4. Currently, the manuscript only includes data from a limited number of substrate temperatures (100°C, 140°C, 220°C, and 290°C). The limited data points make the reported trends in optical bandgap and refractive index appear overly simplified. Additional experiments at intermediate substrate temperatures or varying hydrogen flow rates are crucial for a more comprehensive understanding of how process parameters influence optical properties.

 

Response:

As for the intermediate values, they do not add significant value to the study—for instance, noting that for Ts = 180 °C, Eg = 2.07 eV, n=2.81 and B=399 offers little additional insight. However, this sample has now been included in Table 1 as “Sample D”, as well as in both Figures 3 and 4.

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

After  quite successful revision, this manuscript can be recommended for publication.

Reviewer 2 Report

Comments and Suggestions for Authors

The authors made all my suggestions.

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have effectively addressed all previous comments. The manuscript is now improved in terms of clarity, accuracy, and completeness. Thus, I recommend acceptance of this revised manuscript.