Tantalum Oxide Thin Films Sputter-Deposited by Oxygen Gas Pulsing

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This scientific research is quite well developed and presented. The theme of metal oxide growth and characterization is a hot topic since the diversity of potential applications. I have no experimental design related questions concerning the manuscript under consideration. All results are obtained within well known technique, while data curation, description and discussion are clearly presented. That is why, I reccomend to accept this article after  minor editting of English listed bellow.

Comments on the Quality of English Language

line 25: semi-conducting => semiconducting

line 62: based on tantalum => Ta-based thin films

line 76: semi-conductors => semiconductors

line 82 => ultimate pressure = > base pressure

line 104: van der Pauw's => van der Pauw

line 399: 500 nm thick tantalum oxide thin films are...(instead of current version)

Figure 1: it is better to use micrometers per hour for Y axes

The caption of Figure 4 should disclaim thatthe scale bar fo all SEM images is 200 nm or something like that

Author Response

Reviewer 1

Quality of English Language

( ) I am not qualified to assess the quality of English in this paper
( ) English very difficult to understand/incomprehensible
( ) Extensive editing of English language required
( ) Moderate editing of English language required
(x) Minor editing of English language required
( ) English language fine. No issues detected

 

	Yes	Can be improved	Must be improved	Not applicable
Does the introduction provide sufficient background and include all relevant references?	(x)	( )	( )	( )
Are all the cited references relevant to the research?	(x)	( )	( )	( )
Is the research design appropriate?	(x)	( )	( )	( )
Are the methods adequately described?	(x)	( )	( )	( )
Are the results clearly presented?	(x)	( )	( )	( )
Are the conclusions supported by the results?	(x)	( )	( )	( )

Comments and Suggestions for Authors

This scientific research is quite well developed and presented. The theme of metal oxide growth and characterization is a hot topic since the diversity of potential applications. I have no experimental design related questions concerning the manuscript under consideration. All results are obtained within well known technique, while data curation, description and discussion are clearly presented. That is why, I reccomend to accept this article after  minor editting of English listed bellow.

 

Comments on the Quality of English Language

line 25: semi-conducting => semiconducting

            Answer: It has been corrected, accordingly.

line 62: based on tantalum => Ta-based thin films

            Answer: It has been corrected, accordingly.

line 76: semi-conductors => semiconductors

            Answer: It has been corrected, accordingly.

line 82 => ultimate pressure = > base pressure

            Answer: It has been corrected, accordingly.

line 104: van der Pauw's => van der Pauw

            Answer: It has been corrected, accordingly.

line 399: 500 nm thick tantalum oxide thin films are...(instead of current version)

            Answer: It has been corrected, accordingly.

Figure 1: it is better to use micrometers per hour for Y axes

Answer: It has been corrected in figure 1 as well as in the graphical abstract, accordingly.

The caption of Figure 4 should disclaim that the scale bar for all SEM images is 200 nm or something like that

            Answer: It has been added in the caption, accordingly.

Reviewer 2 Report

Comments and Suggestions for Authors

1. The cross-section images in Fig. 4 are of low quality. It is hard to believe the brittle behavior for films and the columnar growth of the films.

2. The profile analysis is required as mentioned in Line no. 270.
3. EDX mapping is required for the confirmation of Ta and Oxygen.

4. The corresponding diffraction pattern from the TEM image (FFT) is required to confirm the amorphous nature of the oxide film.

5. The authors need to confirm the bright contrast layer formed between the substrate and TaOx layer.

6. the annotation for the injection time should be used properly throughout the manuscript. It seems to read like "ton" or "ion". 7.

7. Section 3 should be Results and discussion.

8. Why there is a shift of the amorphous humps to lower 2-theta value in the XRD plot?

9. The authors need to compare the TaOx film with other nitride forming hard ceramic film processed by RF Sputtering on the basis of deposition rate and sputtering yield, For example: Refer the paper by Sahu et al. (Structure and properties of Ni1-xTixN thin films processed by reactive magnetron co-sputtering) to make strong discussion in the revised version.  

Comments on the Quality of English Language

The English writing skill need to be improved.

Author Response

Reviewer 2

Quality of English Language

( ) I am not qualified to assess the quality of English in this paper
( ) English very difficult to understand/incomprehensible
( ) Extensive editing of English language required
(x) Moderate editing of English language required
( ) Minor editing of English language required
( ) English language fine. No issues detected

 

	Yes	Can be improved	Must be improved	Not applicable
Does the introduction provide sufficient background and include all relevant references?	( )	( )	(x)	( )
Are all the cited references relevant to the research?	( )	( )	(x)	( )
Is the research design appropriate?	( )	( )	(x)	( )
Are the methods adequately described?	( )	( )	(x)	( )
Are the results clearly presented?	( )	( )	(x)	( )
Are the conclusions supported by the results?	( )	( )	(x)	( )

Comments and Suggestions for Authors

1. The cross-section images in Fig. 4 are of low quality. It is hard to believe the brittle behavior for films and the columnar growth of the films.

            Answer: The authors tried to improve the quality of the SEM pictures in Fig. 4. These observations are the best views we could obtain.

2. The profile analysis is required as mentioned in Line no. 270.

Answer: The profile analysis has been added in the Supplementary Materials, as suggested by the Reviewer.

3. EDX mapping is required for the confirmation of Ta and Oxygen.

Answer: EDX analyses have been added in the Supplementary Materials, as suggested by the Reviewer.

4. The corresponding diffraction pattern from the TEM image (FFT) is required to confirm the amorphous nature of the oxide film.

Answer: Diffraction pattern has been added in the Supplementary Materials, as suggested by the Reviewer.

5. The authors need to confirm the bright contrast layer formed between the substrate and TaO_x layer.

Answer: The bright layer between the substrate and TaO_x film is the amorphous native silicon oxide layer produced on Si wafer. Some comments have been added in the text and in Fig. 5b and 5d.

6. the annotation for the injection time should be used properly throughout the manuscript. It seems to read like "ton" or "ion".

Answer: The oxygen injection time is systematically noted “t_ON” through the whole manuscript. This notation has been carefully checked, as suggested by the Reviewer.

7. Section 3 should be Results and discussion.

            Answer: It was corrected, accordingly.

8. Why there is a shift of the amorphous humps to lower 2-theta value in the XRD plot?

Answer: That’s a very interesting question and we thank the Reviewer for remarking it. These humps have ever been reported and maybe assigned to some sub-nanometric grains assigned to the orthorhombic phase of the tantalum pentoxide compound, as suggested by Vlcek et al., Surf. Coat. Technol., 2013, 236, 550-556 and Ngaruyia et al., Phys. Stat. Sol., 2003, 198, 99-110. Some comments have been added, accordingly.

9. The authors need to compare the TaOx film with other nitride forming hard ceramic film processed by RF Sputtering on the basis of deposition rate and sputtering yield, For example: Refer the paper by Sahu et al. (Structure and properties of Ni1-xTixN thin films processed by reactive magnetron co-sputtering) to make strong discussion in the revised version.  

Answer: Structural properties of TaO_x films have been compared to nitrides and the paper from Sahu et al. has been cited, as suggested by the Reviewer.

Reviewer 3 Report

Comments and Suggestions for Authors

In this article, the authors deposited Tantalum oxide thin films via DC reactive magnetron sputtering where they tuned its chemical compositions through reactive gas pulsing process. Then they conducted a systematic study of its composition, structure, optical and electrical properties. The manuscript is well-written and aligns with the scope of Coatings. Overall it’s a high-quality manuscript but there is still some room for improvement. Please see my comments below

Major comments

1. Abstract includes too many details - the purpose of abstract is to give the readers a concise summary of the research and therefore it’s better to leave out some details (e.g., “The argon mass flow rate is maintained constant whereas that of the oxygen gas is pulsed during the deposition”)

2. Delve into the “whys” more - the authors sometimes only present the observations but do not discuss what led to the phenomena. For example, why does injecting the oxygen with tON injection times of a few seconds significantly increase the deposition rate? By focusing more on the “whys”, the authors could significantly the quality of this manuscript.

Detailed comments (in line number)

87: RGPP is already defined in the abstract

115-117: why there are more data points in the middle compared to the two ends?

126-131: what led to the variation in deposition rate?

237-239: could the authors elaborate on what are the extra bright spots in Fig 4a & 4b?

314-316: please include the thickness of the films

323-324: what led to the dramatic change in transmittance when the atomic composition remained largely unchanged?

374: "optically absorbent" = opaque?

385: can the authors include the plot in the manuscript or supplementary information?

Comments on the Quality of English Language

Overall good writing quality.

Author Response

Reviewer 3

Quality of English Language

( ) I am not qualified to assess the quality of English in this paper
( ) English very difficult to understand/incomprehensible
( ) Extensive editing of English language required
( ) Moderate editing of English language required
(x) Minor editing of English language required
( ) English language fine. No issues detected

 

	Yes	Can be improved	Must be improved	Not applicable
Does the introduction provide sufficient background and include all relevant references?	(x)	( )	( )	( )
Are all the cited references relevant to the research?	(x)	( )	( )	( )
Is the research design appropriate?	(x)	( )	( )	( )
Are the methods adequately described?	(x)	( )	( )	( )
Are the results clearly presented?	(x)	( )	( )	( )
Are the conclusions supported by the results?	(x)	( )	( )	( )

Comments and Suggestions for Authors

In this article, the authors deposited Tantalum oxide thin films via DC reactive magnetron sputtering where they tuned its chemical compositions through reactive gas pulsing process. Then they conducted a systematic study of its composition, structure, optical and electrical properties. The manuscript is well-written and aligns with the scope of Coatings. Overall it’s a high-quality manuscript but there is still some room for improvement. Please see my comments below

Major comments

1. Abstract includes too many details - the purpose of abstract is to give the readers a concise summary of the research and therefore it’s better to leave out some details (e.g., “The argon mass flow rate is maintained constant whereas that of the oxygen gas is pulsed during the deposition”)

            Answer: Abstract has been reduced and simplified, as suggested by the Reviewer.

 

1. Delve into the “whys” more - the authors sometimes only present the observations but do not discuss what led to the phenomena. For example, why does injecting the oxygen with t_ON injection times of a few seconds significantly increase the deposition rate? By focusing more on the “whys”, the authors could significantly the quality of this manuscript.

Answer: Some explanations have been given about the evolution of deposition rate as a function of the t_ON injection time in lines 136-149, and some comments have been added about the order of magnitude of a few seconds for pulsing period T and t_ON injection time, as suggested by the Reviewer.

 

Detailed comments (in line number)

87: RGPP is already defined in the abstract

Answer: Abstract has been modified, as suggested by another Reviewer. As a result, RGPP has been defined in the text when it has been firstly defined.

115-117: why there are more data points in the middle compared to the two ends?

Answer: Since deposition rate vs. t_ON injection time exhibits a maximum, several samples have been prepared in this range of t_ON time in order to get a more precise location of the maximum rate.

126-131: what led to the variation in deposition rate?

Answer: Some explanations about variation in the deposition rate have been given in lines 136-149.

237-239: could the authors elaborate on what are the extra bright spots in Fig 4a & 4b?

Answer: Bright spots in SEM observations are mainly due to charge-up effects. The negative charge of the incident electron beam accumulates on the surface of a non-conductive part of the film. This may occur in some samples.

314-316: please include the thickness of the films

Answer: The thickness of the films has been specified in the beginning of the paragraph 3. It has been again specified in 3.2, as suggested by the Reviewer.

323-324: what led to the dramatic change in transmittance when the atomic composition remained largely unchanged?

Answer: Defects and vanishing of the Ta/TaO_x multilayer structure both contribute to the variation of the optical transmittance in the visible range, although oxygen and tantalum concentrations slightly change (i.e., especially for t_ON in-between 5.7-6 s). Some comments have been added in the article, accordingly.

374: "optically absorbent" = opaque?

            Answer: It has been corrected, accordingly.

385: can the authors include the plot in the manuscript or supplementary information?

            Answer: Supplementary Materials have been added, as suggested by the Reviewer.

Reviewer 4 Report

Comments and Suggestions for Authors

coatings-2692213

Tantalum oxide thin films sputter-deposited by oxygen gas pulsing

 

This study provides a detailed description of a research study involving the deposition of tantalum oxide thin films using DC reactive magnetron sputtering and the use of a Reactive Gas Pulsing Process (RGPP) to control the chemical composition of these films. Here are some comments and insights regarding the content of the review:

 

1.      The paper provides a clear and concise overview of the experimental setup and the main findings. However, it would be helpful to define some technical terms and acronyms such as "RGPP" and "tON" early in the text for better understanding.

2.      The systematic change in the tON injection time is a key aspect of the study. The paper successfully communicates how this parameter influences the chemical composition and structure of the deposited films, which is essential for the reader to understand the research objectives.

3.      This paper effectively conveys how the films' chemical composition evolves as tON injection time increases. It provides a clear understanding of the transition from metallic tantalum to over-stoichiometric Ta2O5 material, highlighting the importance of this parameter.

4.      Mention of the crystallographic analysis through X-ray diffraction is valuable. It describes how the films' structure changes with varying tON injection times, from a body-centered cubic structure to an amorphous state.

5.      The review emphasizes the importance of tON injection time as a key parameter in controlling the properties of the tantalum oxide films. However, it might be beneficial to explain why this parameter is significant and its implications in practical applications.

6.      This paper effectively describes the changes in optical and electrical properties of the films, such as their transmittance and electrical conductivity, as a function of oxygen concentration. This information provides a comprehensive view of the film's behavior. These references should be studied and included in the revision.

https://doi.org/10.3390/coatings12121831

https://doi.org/10.3139/120.111060

 

7.      Including specific data points or graphs that illustrate the changes in chemical composition, crystallographic structure, and optical/electrical properties as a function of tON injection time could enhance the paper's clarity.

8.      This paper could benefit from a brief summary or discussion of the implications of the findings and how they may be relevant in practical applications or future research.

 

 

In summary, the technical review provides a well-structured and informative description of the experimental process and its results. It effectively communicates the impact of tON injection time on the properties of tantalum oxide films. To enhance its completeness, it could provide more context and implications of the findings.

Comments on the Quality of English Language

The linguistic level and the mechanics of English writing are not appropriate for publication. There are few grammatical and typing errors in the manuscript, so please check and revise. The way of writing is not clear and it is difficult for the readers to understand. The paper should be rewritten and proofread again thoroughly. Extensive editing of English language is required. 

Author Response

Reviewer 4

Quality of English Language

( ) I am not qualified to assess the quality of English in this paper
( ) English very difficult to understand/incomprehensible
(x) Extensive editing of English language required
( ) Moderate editing of English language required
( ) Minor editing of English language required
( ) English language fine. No issues detected

 

	Yes	Can be improved	Must be improved	Not applicable
Does the introduction provide sufficient background and include all relevant references?	( )	(x)	( )	( )
Are all the cited references relevant to the research?	( )	(x)	( )	( )
Is the research design appropriate?	( )	(x)	( )	( )
Are the methods adequately described?	( )	(x)	( )	( )
Are the results clearly presented?	( )	(x)	( )	( )
Are the conclusions supported by the results?	( )	(x)	( )	( )

Comments and Suggestions for Authors

coatings-2692213

Tantalum oxide thin films sputter-deposited by oxygen gas pulsing

 This study provides a detailed description of a research study involving the deposition of tantalum oxide thin films using DC reactive magnetron sputtering and the use of a Reactive Gas Pulsing Process (RGPP) to control the chemical composition of these films. Here are some comments and insights regarding the content of the review:

 

1. The paper provides a clear and concise overview of the experimental setup and the main findings. However, it would be helpful to define some technical terms and acronyms such as "RGPP" and "tON" early in the text for better understanding.

Answer: RGPP and t_ON have been defined in the text when they appeared for the first time, as suggested by the Reviewer.

 

2. The systematic change in the t_ON injection time is a key aspect of the study. The paper successfully communicates how this parameter influences the chemical composition and structure of the deposited films, which is essential for the reader to understand the research objectives.

Answer: We thank the Reviewer for this comment. No changes are required.

 

3. This paper effectively conveys how the films' chemical composition evolves as t_ON injection time increases. It provides a clear understanding of the transition from metallic tantalum to over-stoichiometric Ta₂O₅ material, highlighting the importance of this parameter.

Answer: We thank the Reviewer for this comment. No changes are required.

 

4. Mention of the crystallographic analysis through X-ray diffraction is valuable. It describes how the films' structure changes with varying t_ON injection times, from a body-centered cubic structure to an amorphous state.

Answer: We thank the Reviewer for this comment. No changes are required.

 

5. The review emphasizes the importance of t_ON injection time as a key parameter in controlling the properties of the tantalum oxide films. However, it might be beneficial to explain why this parameter is significant and its implications in practical applications.

Answer: Since tantalum oxide thin films are sputter-deposited by reactive sputtering and due to nonlinear phenomena of the reactive process (hysteresis of some deposition parameters), the Reactive Gas Pulsing Process has been developed to cope with these instabilities. It has been shown in former reports that the injection time of the reactive gas is the key parameter for many metal oxide and nitride systems (to see Martin et al., Surf. Coat. Technol., 2007, 142-144, 615-620). Assuming a constant pulsing period, t_ON appears as a single parameter to control the reactive sputtering and tune thin films properties by means of an easy approach. The latter is very useful for practical applications and industrial processes. Some comments have been added, accordingly.

 

6. This paper effectively describes the changes in optical and electrical properties of the films, such as their transmittance and electrical conductivity, as a function of oxygen concentration. This information provides a comprehensive view of the film's behavior. These references should be studied and included in the revision.

https://doi.org/10.3390/coatings12121831

https://doi.org/10.3139/120.111060

 

Answer: These references have been studied and compared to our results. Some comments have been added in the article and these references have been cited, as suggested by the Reviewer (N.B. The reference https://doi.org/10.3390/coatings12121831 was cited in the first version of the article).

 

7. Including specific data points or graphs that illustrate the changes in chemical composition, crystallographic structure, and optical/electrical properties as a function of t_ON injection time could enhance the paper's clarity.

Answer: As suggested by the Reviewer, all film properties (deposition rate in Fig. 1, composition in Fig. 2, crystallographic structure in Fig. 3, optical transmittance in the visible range in Fig. 6 and electrical conductivity in Fig. 7) have been systematically investigated as a function of the t_ON injection time.

 

8. This paper could benefit from a brief summary or discussion of the implications of the findings and how they may be relevant in practical applications or future research.

Answer: Some comments have been added in the conclusion, as suggested by the Reviewer.

 

In summary, the technical review provides a well-structured and informative description of the experimental process and its results. It effectively communicates the impact of t_ON injection time on the properties of tantalum oxide films. To enhance its completeness, it could provide more context and implications of the findings.

Answer: Some comments have been added in the conclusion, as suggested by the Reviewer.

 

Comments on the Quality of English Language

The linguistic level and the mechanics of English writing are not appropriate for publication. There are few grammatical and typing errors in the manuscript, so please check and revise. The way of writing is not clear and it is difficult for the readers to understand. The paper should be rewritten and proofread again thoroughly. Extensive editing of English language is required. 

Answer: English has been checked and a final reading has been performed by a native English speaker, as suggested by the Reviewer.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

In the revised version, the manuscript is ready for acceptance.

Comments on the Quality of English Language

Good.

Reviewer 4 Report

Comments and Suggestions for Authors

I have gone through the manuscript completely and satisfied with the revision. As such, I will recommend this paper for publication in its present form.