Simulation and Experimental Investigation on the Performance of Co-, Bi-, and La-Doped AgSnO₂ Contact Interface Models

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This study investigates the effects of doping on the electrical properties of silver-tin oxide electrical contacts. The authors analyzed the influence of three different doping elements, Co, Bi, and La through simulations and validated these simulations through experimental tests.
The manuscript is well written, highlighting the challenges of AgSnO2 switching electrical contact materials. However, crucial information is missing in the experimental section and certain results/discussions require further explanation or modifications. I recommend the manuscript be accepted to Coatings after the following comments have been addressed.
1. The introduction accurately describes the motivation of the work, as well as briefly summarizes the current state of the art and challenges with silver tin-oxide electrodes. However, it lacks a brief overview of the characterization techniques employed in the work. For example, there is no mention of contact angle measurements, arcing tests, XRD, etc. It is recommended that this information is mentioned in the last paragraph of the introduction.
2. The authors used several acronyms that were not previously defined. For example: ITO, PBE, BFGS, etc.
3. The equations numbers need to be referenced in the main text.
4. Certain sections require further citation for the concepts introduced, for example section 3.3 when introducing the Mulliken population analysis. Another example is in line 342, page 10, where constriction resistance is introduced but there the authors do not provide the relevant citation. Or for example, in line 404 when the authors mention the solubility of oxygen in liquid silver. I recommend the authors go through the manuscript and add citations where appropriate.
5. Check for some typos and syntax errors (e.g., “increaseed” on page 6, line 227, “material electrical contact” page 9, line 305) and proofread to eliminate unnecessarily long sentences, superfluous commas, etc.
6. Sample preparation details are missing in section 4.1. For example, the authors did not mention the sintering process (e.g., hot-isostatic pressing, pressureless sintering, etc.) and sintering parameters such as temperatures, pressures, holding times, etc. Moreover, the manufacturing of the sol-gel is not detailed enough for readers to replicate the methodology.
7. Further experimental details need to be described in section 4.3. From the results, it is led to understand that a droplet of molten silver was deposited on the material’s surface. However, this needs to be mentioned explicitly. Moreover, what was the volume of the droplet? How long was the droplet deposited before the contact angle was measured? Which fitting contour was used to determine the contact angle?
8. The power source symbol in Figure 6 shows an ~, which indicates alternating current. However, in the text it was described that the arc erosion tests were performed using direct current. The symbol shows the + and – symbols for DC power sources, but the ~ may lead to misinterpretations. I recommend removing the ~ from the figure since it does not add any significant information.
9. In the arc erosion tests, how many samples of each type were evaluated? Were the 100,000 cycles conducted once in a single spot? Or where these tests conducted multiple times on different spots and/or sample of the same type? This information is not included in the manuscript; however, it is understood that the electrical tests were conducted only once per sample type. If so, are the results reported statistically relevant? Would inhomogeneities in the doped samples lead to variations in their expected performance?
10. In line 321 (page 10), the authors state that “doping improves the arc erosion resistance of AgSnO2 electrical contact materials.”. However, in this section, the authors were discussing the arc’s energy. Although the authors show that doping with Co and La indeed reduces arc energy and makes the arc more stable, they cannot conclude that this will reduce erosion. This could be hypothesized, but it cannot be stated as fact since erosion rates are not determined.
11. Figures 7 – 10 show arc energy, arc duration, welding force and contact resistance, these parameters are plotted with a continuous line plot. However, the values measured are the points. Therefore, it is incorrect to connect these points by a continuous line, since this indicates a continuous measurement between points. Accordingly, the authors should replace the solid line in Figures 7 – 10 with a dashed line to indicate that the line is there to merely highlight the overall trends, and not a continuous measurement. Moreover, the standard deviation for each of the 100 datapoints plotted should be included in the graphs. In these figures, it is also a bit off-putting that the authors placed the standard deviation above the average value in the inset tables. I recommend placing the average above the standard deviation.
12. When discussing the contact resistance of the samples (page 11, line 350), the authors say, “Doped systems manifested markedly reduced and more stable contact resistance fluctuations.”. This statement is not justified by Figure 10. I recommend rephrasing this sentence. The reduction in contact resistance is not “markedly”, with Co- and La-doped samples showing reductions, but Bi-doped samples showing similar average values as the undoped samples. Moreover, “more stable fluctuations” is an oxymoron, I suggest rephrasing it; maybe saying “show less fluctuations”, for example.
13. The contrast of the white text on the SEM micrographs in Figure 13 is low. I recommend changing the color of the text or adding a background.
14. In the arc erosion tests, the authors are evaluating the break operation (as described in line 456). In their test setup, do the authors also consider the make operation? Or is the current source switched off during making and switched back on before breaking? If so, what is the current stabilization time?
15. The description of the mechanisms behind arc ignition and material transfer (from line 455 to 480) are not the authors’ findings, but rather well-known phenomena already extensively described in the available literature. Therefore, it is out of place in the current section. It would be better suited in the introduction of the manuscript. Contrarily, it is recommended that the authors synthesize the two paragraphs into a few sentences and cite the relevant literature, since the full explanation is not needed in this manuscript.

Comments for author File: Comments.pdf

Author Response

Comments 1: The introduction accurately describes the motivation of the work, as well as briefly summarizes the current state of the art and challenges with silver tin-oxide electrodes. However, it lacks a brief overview of the characterization techniques employed in the work. For example, there is no mention of contact angle measurements, arcing tests, XRD, etc. It is recommended that this information is mentioned in the last paragraph of the introduction.

Response 1: We concur with your perspective and have supplemented the introduction's concluding section with specific experimental methodologies.

Comments 2: The authors used several acronyms that were not previously defined. For example: ITO, PBE, BFGS, etc.

Response 2: The acronyms ITO (Indium Tin Oxide), PBE (Perdew-Burke-Ernzerhof), and BFGS (Broyden–Fletcher–Goldfarb–Shanno) have been explicitly defined within the revised manuscript text.

Comments 3: The equations numbers need to be referenced in the main text.

Response 3: Equation numbers have been duly referenced throughout the revised manuscript.

Comments 4: Certain sections require further citation for the concepts introduced, for example section 3.3 when introducing the Mulliken population analysis. Another example is in line 342, page 10, where constriction resistance is introduced but there the authors do not provide the relevant citation. Or for example, in line 404 when the authors mention the solubility of oxygen in liquid silver. I recommend the authors go through the manuscript and add citations where appropriate.

Response 4: We are grateful for your guidance. Citations supporting the introduction of relevant concepts have been added, such as Reference 24 for Mulliken population analysis.

Comments 5: Check for some typos and syntax errors (e.g., “increaseed” on page 6, line 227, “material electrical contact” page 9, line 305) and proofread to eliminate unnecessarily long sentences, superfluous commas, etc.

Response 5: We appreciate your guidance and have conducted thorough proofreading of the manuscript text.

Comments 6: Sample preparation details are missing in section 4.1. For example, the authors did not mention the sintering process (e.g., hot-isostatic pressing, pressureless sintering, etc.) and sintering parameters such as temperatures, pressures, holding times, etc. Moreover, the manufacturing of the sol-gel is not detailed enough for readers to replicate the methodology.

Response 6: Sintering parameters (temperature, duration, applied pressure, etc.) have been incorporated into the main text (Page 4, Lines 144-145). Details of the sol-gel methodology have been expanded (Page 4, Lines 122-132).

Comments 7: Further experimental details need to be described in section 4.3. From the results, it is led to understand that a droplet of molten silver was deposited on the material’s surface. However, this needs to be mentioned explicitly. Moreover, what was the volume of the droplet? How long was the droplet deposited before the contact angle was measured? Which fitting contour was used to determine the contact angle?

Response 7: As detailed in the revised manuscript: Wettability was assessed using the sessile drop method (DSAHT12 contact angle measuring instrument) on undoped and doped SnO₂ substrates against Ag. A consistent silver droplet mass of 0.3 g was deposited and allowed to settle for 24 hours prior to measurement. To ensure reliability, the wetting angle was measured three times per sample, with the average value reported.

Comments 8: The power source symbol in Figure 6 shows an ~, which indicates alternating current. However, in the text it was described that the arc erosion tests were performed using direct current. The symbol shows the + and – symbols for DC power sources, but the ~ may lead to misinterpretations. I recommend removing the ~ from the figure since it does not add any significant information.

Response 8: Thank you for your valuable observation; the relevant figures have been amended accordingly.

Comments 9: In the arc erosion tests, how many samples of each type were evaluated? Were the 100,000 cycles conducted once in a single spot? Or where these tests conducted multiple times on different spots and/or sample of the same type? This information is not included in the manuscript; however, it is understood that the electrical tests were conducted only once per sample type. If so, are the results reported statistically relevant? Would inhomogeneities in the doped samples lead to variations in their expected performance?

Response 9: To accurately reflect real-world operating conditions (e.g., relay contacts functioning without intervention), the experimental procedure simulated contact movement without external adjustment. Contact surfaces were meticulously aligned (via vertical, horizontal, and lateral positioning) prior to testing to ensure optimal engagement. For statistical robustness, three independent tests were performed per sample type to mitigate variability.

Comments 10: In line 321 (page 10), the authors state that “doping improves the arc erosion resistance of AgSnO2 electrical contact materials.”. However, in this section, the authors were discussing the arc’s energy. Although the authors show that doping with Co and La indeed reduces arc energy and makes the arc more stable, they cannot conclude that this will reduce erosion. This could be hypothesized, but it cannot be stated as fact since erosion rates are not determined.

Response 10: We fully accept your assessment and have modified the relevant statements in the manuscript.

Comments 11: Figures 7 – 10 show arc energy, arc duration, welding force and contact resistance, these parameters are plotted with a continuous line plot. However, the values measured are the points. Therefore, it is incorrect to connect these points by a continuous line, since this indicates a continuous measurement between points. Accordingly, the authors should replace the solid line in Figures 7 – 10 with a dashed line to indicate that the line is there to merely highlight the overall trends, and not a continuous measurement. Moreover, the standard deviation for each of the 100 datapoints plotted should be included in the graphs. In these figures, it is also a bit off-putting that the authors placed the standard deviation above the average value in the inset tables. I recommend placing the average above the standard deviation.

Response 11: We thank you for your constructive feedback. Figures 7-10 (depicting arc energy, arcing time, welding force, and contact resistance) have been re-plotted utilizing dashed lines to signify trend representation, not continuous measurement. Furthermore, the presentation within inset tables has been revised to position the average value above the standard deviation.

Comments 12: When discussing the contact resistance of the samples (page 11, line 350), the authors say, “Doped systems manifested markedly reduced and more stable contact resistance fluctuations.”. This statement is not justified by Figure 10. I recommend rephrasing this sentence. The reduction in contact resistance is not “markedly”, with Co- and La-doped samples showing reductions, but Bi-doped samples showing similar average values as the undoped samples. Moreover, “more stable fluctuations” is an oxymoron, I suggest rephrasing it; maybe saying “show less fluctuations”, for example.

Response 12: In accordance with your suggestion, the pertinent description (e.g., Manuscript Page 12, Line 403) has been rephrased.

Comments 13: The contrast of the white text on the SEM micrographs in Figure 13 is low. I recommend changing the color of the text or adding a background.

Response 13: To enhance clarity, the annotation color on the SEM micrographs (Figure 15) has been changed from white to yellow, improving contrast.

Comments 14: In the arc erosion tests, the authors are evaluating the break operation (as described in line 456). In their test setup, do the authors also consider the make operation? Or is the current source switched off during making and switched back on before breaking? If so, what is the current stabilization time?

Response 14: The electrical contact experiments encompassed both contact closing (make) and opening (break) operations. Each complete make-break cycle was counted as a single operation, with testing conducted for a total of 100,000 cycles. Throughout the experimental procedure, the power source remained continuously enabled.

Comments 15: The description of the mechanisms behind arc ignition and material transfer (from line 455 to 480) are not the authors’ findings, but rather well-known phenomena already extensively described in the available literature. Therefore, it is out of place in the current section. It would be better suited in the introduction of the manuscript. Contrarily, it is recommended that the authors synthesize the two paragraphs into a few sentences and cite the relevant literature, since the full explanation is not needed in this manuscript.

Response 15:  We agree with your viewpoint and have consequently removed the indicated passages.

 

 

Reviewer 2 Report

Comments and Suggestions for Authors

The similarity index reported for this manuscript raises significant concerns. In particular, the 8% similarity from a single source is unacceptably high, especially for a high-impact journal like Coatings. The overall similarity of 21% also exceeds typical expectations for original research articles. Such a high degree of overlap with a single source suggests potential issues with originality or insufficient paraphrasing. The authors are strongly encouraged to revise the manuscript to reduce these similarities, particularly by ensuring proper rephrasing and citation of previously published material.

A direct structural comparison between the theoretically constructed AgSnO₂ interface model and the experimental samples (e.g., at atomic resolution using TEM, HR-TEM, or STEM) has not been performed. The validity of the model has been supported solely by XRD analysis.

The rationale behind the selection of the DFT parameters used (e.g., the PBE functional, GGA, BFGS algorithm) has not been elaborated. Why was the PBE functional chosen? Why were more accurate hybrid functionals (e.g., HSE06) not considered?

The statement “Lattice mismatch was reduced to below 10%” is made, yet there is no explanation of how this was achieved (e.g., to what extent the supercell was expanded, whether any strain was applied). Moreover, even a 10% mismatch is still considered relatively high.

Is the doping ratio the same for each element (Co, Bi, La)? The statement “Ag:SnO₂-X = 85.5%:14.5%” is given, but the exact proportion of X is not specified. What percentage does X alone correspond to? This information is missing.

The interface models shown in Figure 1 lack essential visual details—there is no indication of atom types, crystallographic orientations, or bonding configurations. The figure is missing necessary annotations and descriptive elements.

The current manuscript lacks a clearly defined "Results and Discussion" section, which is a critical component in standard scientific writing. The separate presentation of "Simulation Analysis" and "Experimental Investigation" under different main sections is not optimal. These two should be integrated and reorganized under a unified "Results and Discussion" section. This will improve the manuscript's coherence and allow the authors to effectively compare simulation outcomes with experimental validation. A suggested structure would include subsections such as "Simulation Results," "Experimental Results," and "Comparative Discussion."

The content of Section 4.1 does not belong under a "Results" section. It solely describes the sample preparation process and includes no data, analysis, or discussion of outcomes. Therefore, this subsection should be relocated under the "Methods" section, for example, as a subsection titled "Sample Preparation." The current structure may mislead readers into expecting experimental findings, which are not presented here.

The presented XRD patterns lack any peak indexing (e.g., 2θ values, (hkl) planes). It is unclear which peaks correspond to which phases, making it difficult to interpret the results accurately.

Quantitative analyses such as peak shifts, full width at half maximum (FWHM), and crystallite size have not been provided. However, such parameters are expected to change upon doping and should have been discussed.

There is no direct correlation established between the simulated structures and the XRD results. This is a significant shortcoming, as such a connection is crucial for validating the theoretical predictions.

Although surface roughness directly influences the contact angle, no profilometry or AFM data has been provided. Instead, assumptions have been made without experimental support.

Contact angle values should be presented as mean ± standard deviation; however, only single values are reported. Additionally, the number of measurements (n=?) is not specified.

The relationship between the contact angle and properties such as contact resistance or oxidation behavior has not been discussed. This connection is important and should have been addressed to better understand the material's surface characteristics.

The reason why Co doping results in lower ECR has been superficially attributed to "arc stability," without providing any supporting physical or chemical evidence. This explanation lacks depth and should be substantiated with relevant data or analysis.

No direct correlation has been established between the bond stability or surface energies derived from DFT calculations and the experimental ECR data. This is a critical gap, as such a connection could significantly strengthen the interpretation of the results.

A significant omission in the manuscript is the lack of quantitative data on material loss during the arc erosion tests. While electrical contact resistance (ECR) is presented, there is no measurement of mass loss, volume loss, or surface degradation depth after 100,000 switching cycles.

The Conclusions section merely summarizes the previous parts; however, it lacks a discussion on the significance, impact, and broader relevance of the results. A deeper interpretation and contextualization of the findings are needed.

Author Response

Comments 1: A direct structural comparison between the theoretically constructed AgSnO₂ interface model and the experimental samples (e.g., at atomic resolution using TEM, HR-TEM, or STEM) has not been performed. The validity of the model has been supported solely by XRD analysis.

Response 1: We sincerely appreciate this valuable observation. As referenced in Ref. 16, the Ag(111) and SnO₂(100) surfaces exhibit the lowest binding energy, providing the foundation for our interface model. Computational results demonstrate a positive work of separation, indicating stable interface formation. Our simulations predict enhanced electrical contact performance in doped materials, which has been experimentally corroborated. XRD analysis confirms dopant incorporation via substitution within the SnO₂ lattice without secondary phase formation, supporting the validity of our substitutional doping model.

Comments 2: The rationale behind the selection of the DFT parameters used (e.g., the PBE functional, GGA, BFGS algorithm) has not been elaborated. Why was the PBE functional chosen? Why were more accurate hybrid functionals (e.g., HSE06) not considered?

Response 2: We are grateful for your insightful query. Following established methodology in Ref. 19, the PBE functional was selected for its validated balance between computational efficiency and accuracy for systems of this scale. While hybrid functionals like HSE06 offer enhanced precision, their significant computational demands rendered them impractical for our large-scale interface models containing substantial atomic counts.

Comments 3: The statement “Lattice mismatch was reduced to below 10%” is made, yet there is no explanation of how this was achieved (e.g., to what extent the supercell was expanded, whether any strain was applied). Moreover, even a 10% mismatch is still considered relatively high.

Response 3: In the revised manuscript (Page 3, Lines 93-96), we have added the parameters for supercell expansion. No stress was applied in the simulations.

Comments 4: Is the doping ratio the same for each element (Co, Bi, La)? The statement “Ag:SnO₂-X = 85.5%:14.5%” is given, but the exact proportion of X is not specified. What percentage does X alone correspond to? This information is missing.

Response 4: We appreciate your attention to detail. The doping ratios are explicitly presented in Table 2, which provides both atomic and mass percentages for each component. The table clearly specifies the precise proportion of dopant (X) within the AgSnO₂-X system for each dopant type.

Comments 5: The interface models shown in Figure 1 lack essential visual details—there is no indication of atom types, crystallographic orientations, or bonding configurations. The figure is missing necessary annotations and descriptive elements.

Response 5: We fully agree with your suggestion. The simulation model has been redrawn as shown in Figure 1.

Comments 6: The current manuscript lacks a clearly defined "Results and Discussion" section, which is a critical component in standard scientific writing. The separate presentation of "Simulation Analysis" and "Experimental Investigation" under different main sections is not optimal. These two should be integrated and reorganized under a unified "Results and Discussion" section. This will improve the manuscript's coherence and allow the authors to effectively compare simulation outcomes with experimental validation. A suggested structure would include subsections such as "Simulation Results," "Experimental Results," and "Comparative Discussion.

Response 6: We are deeply grateful for this structural recommendation. The manuscript has been reorganized per your guidance: Section 2 now integrates "Simulation Modeling and Material Preparation Methods", Section 3 combines "Analysis of Simulation and Experimental Results", followed by Section 4: "Conclusions"

Comments 7: The content of Section 4.1 does not belong under a "Results" section. It solely describes the sample preparation process and includes no data, analysis, or discussion of outcomes. Therefore, this subsection should be relocated under the "Methods" section, for example, as a subsection titled "Sample Preparation." The current structure may mislead readers into expecting experimental findings, which are not presented here.

Response 7: We sincerely thank you for this organizational insight. The sample preparation content has been relocated to Section 2.2 ("Sample Preparation") within the Methods section to ensure proper contextual placement.

Comments 8: The presented XRD patterns lack any peak indexing (e.g., 2θ values, (hkl) planes). It is unclear which peaks correspond to which phases, making it difficult to interpret the results accurately.

Response 8: Thank you for this valuable suggestion.Page 9, Lines 292-295 add XRD data: diffraction peak angles corresponding to specific phases.

Comments 9：Quantitative analyses such as peak shifts, full width at half maximum (FWHM), and crystallite size have not been provided. However, such parameters are expected to change upon doping and should have been discussed.

Response 9: We acknowledge this important consideration.Page 9, Lines 303-315 add crystallite size calculations. Results are shown in Table 6.

Comments 10：There is no direct correlation established between the simulated structures and the XRD results. This is a significant shortcoming, as such a connection is crucial for validating the theoretical predictions.

Response 10: Lattice distortion induced by doping. This corresponds to the change in lattice constant caused by the difference in atomic radius of dopant atoms in the simulation. Dopant elements entered the SnO₂ unit cell in the form of atomic substitution, verifying the accuracy of the atomic substitution doping model constructed in the simulation.

Comments 11：Although surface roughness directly influences the contact angle, no profilometry or AFM data has been provided. Instead, assumptions have been made without experimental support.

Response 11: We appreciate your emphasis on experimental validation. Section 3.2.5 now includes quantitative surface roughness characterization using profilometry data, with key parameters (Ssk, Sz, Smr1, Vmp) presented in Table 7 to substantiate our analysis.

Comments 12：Contact angle values should be presented as mean ± standard deviation; however, only single values are reported. Additionally, the number of measurements (n=?) is not specified.

Response 12: Thank you for highlighting this reporting standard. Contact angles represent mean values calculated from triplicate measurements per sample (left/right side averaging). 

Comments 13：The relationship between the contact angle and properties such as contact resistance or oxidation behavior has not been discussed. This connection is important and should have been addressed to better understand the material's surface characteristics.

Response 13: We are grateful for this conceptual connection. As detailed (Page 10, Lines 335-340), enhanced wettability reduces interfacial tension and SnO₂ enrichment, thereby increasing effective contact area and reducing contact resistance. Improved dispersion also elevates melt pool viscosity, significantly enhancing arc erosion resistance.

Comments 14：The reason why Co doping results in lower ECR has been superficially attributed to "arc stability," without providing any supporting physical or chemical evidence. This explanation lacks depth and should be substantiated with relevant data or analysis.

Response 14: We appreciate your request for mechanistic depth. The revised text (Page 12, Lines 405-408) elaborates that Co doping reduces contact resistance through synergistic effects: increased carrier concentration, optimized lattice/interface bonding, and grain refinement.

Comments 15：No direct correlation has been established between the bond stability or surface energies derived from DFT calculations and the experimental ECR data. This is a critical gap, as such a connection could significantly strengthen the interpretation of the results.

Response 15: Low interfacial energy means stronger interfacial bonding ability and better wettability. Strong interfacial bonding facilitates the formation of a continuous and uniform metal film, reducing local current concentration. This helps current distribute evenly throughout the contact area, reducing arc erosion. Good wettability allows more SnO₂ particles to uniformly disperse into the Ag melt pool under arc action, forming a stable AgSnO₂ alloy, thereby lowering electrical contact resistance and improving arc performance.

Comments 16：A significant omission in the manuscript is the lack of quantitative data on material loss during the arc erosion tests. While electrical contact resistance (ECR) is presented, there is no measurement of mass loss, volume loss, or surface degradation depth after 100,000 switching cycles.

Response 16: We thank you for this critical observation. Section 3.2.4 now includes quantitative mass loss measurements for both cathode and anode after 100,000 operations, with total mass loss data enabling comprehensive erosion analysis.

Comments 17：The Conclusions section merely summarizes the previous parts; however, it lacks a discussion on the significance, impact, and broader relevance of the results. A deeper interpretation and contextualization of the findings are needed.

Response 17: We deeply appreciate your guidance on contextualization. The conclusions now emphasize the methodology's significance in enabling resource-efficient development of environmentally sustainable AgSnO₂ contacts, with potential to enhance reliability in complex low-voltage applications while addressing critical engineering requirements.

Reviewer 3 Report

Comments and Suggestions for Authors   The article "Simulation and Experimental Investigation on the Performance of Co, Bi, and La Doped AgSnO₂ Contact Interface Models" addresses contemporary issues and is well-prepared. It is worth further consideration. The literature review is comprehensive, covering a wide range of years, including the most recent publications. However, before publication, the article should be supplemented with additional information. My suggestions are below:

• The abstract should include the numerical values obtained from the research. This should be completed.
• Table 2 and Figure 2 are insufficiently described in the text.
• Where does the data in Table 4 come from?
• It is not enough to write: "The preparation process for the electrical contact samples is depicted in Figure 3"—this process should also be described in the text.
• What exactly do the authors mean by "operation times" in the description of the x-axis in Figures 7-10?
• What units are used for "bar" in Figure 12?

Author Response

Comments 1:The abstract should include the numerical values obtained from the research. This should be completed.

Response 1: As per your suggestion, we have added specific data from the research to the abstract, as seen on page 1, line 26.

Comments 2: Table 2 and Figure 2 are insufficiently described in the text.

Response 2: We have provided detailed descriptions of some data in the table on page 5, lines 177-179. Additionally, we have included detailed descriptions of the DOS diagrams on page 6, lines 206, 213, and 221, and on page 7, line 234.

Comments 3: Where does the data in Table 4 come from?

Response 3: The data in the table are bond overlap population parameters, which are the results of simulation calculations. The table presents the maximum and minimum values, as well as the overall average, from the statistical calculations. The larger the absolute value, the stronger the bonding ability and the more stable the chemical bonds formed.

Comments 4: It is not enough to write: "The preparation process for the electrical contact samples is depicted in Figure 3"—this process should also be described in the text.

Response 4: In the revised manuscript, Section 2.2 (Sample Preparation) now includes detailed steps of the sol-gel process (page 4, lines 124-134) and specific parameters used in sample preparation (page 4, lines 142-146).

Comments 5: What exactly do the authors mean by "operation times" in the description of the x-axis in Figures 7-10?

Response 5: The electrical contact experiments encompassed both contact closing (make) and opening (break) operations. Each complete make-break cycle was counted as a single operation, with testing conducted for a total of 100,000 cycles.

Comments 6: What units are used for "bar" in Figure 12?

Response 6: Figure 12（Figure 14 in the revised manuscript）does not contain 'bar' units. The four right-side diagrams represent height distribution profiles.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors modified their manuscript according to the suggestions. I recommend the article be accepted for publication.

Reviewer 2 Report

Comments and Suggestions for Authors

The authors made revisions satisfactorily.

Reviewer 3 Report

Comments and Suggestions for Authors

After improvement the paper is ready to be published