Design Method for Stress Reduction of Multilayer Thin Films

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript presents a combined theoretical and experimental approach to reduce residual stress in multilayer thin films by optimizing both mechanical and optical properties. The proposed model is tested on ITO, Ti₂O₃/SiO₂, and Ti₂O₃/SiO₂/HfO₂ film systems, with experimental data supporting the stress predictions in simpler structures. The work is relevant to the design of optical coatings and offers practical insight into film stress control.

Major comments, questions and suggestions:

1. The section introducing the stress database could be improved by clarifying whether the data for Ti₂O₃, SiO₂, and HfO₂ were obtained under consistent deposition conditions and how these values remain valid across different multilayer stacks.

2. The linear relationship between stress and thickness is only tested on ITO films. It would be useful to confirm this trend for the other materials used in the multilayer structures to support the generality of the model.

3. The agreement between calculated and measured stress in the Ti₂O₃/SiO₂ multilayer is promising. However, more discussion is needed on the possible role of interfaces and deposition order on the stress distribution in multilayer systems.

4. The deviation between measured and theoretical stress in the broadband 16-layer structure is significant. A brief explanation of how this could result from layer number, material combinations, or changing film properties during deposition would improve the analysis.

5. The possible variation of refractive index and film density with thickness is mentioned. Including more explanation or a reference to similar findings in literature would help support this argument.

6. The results indicate that stress uniformity is better at the center of the samples. A short comment on how thickness or substrate curvature might influence this distribution would be useful for readers interested in process control.

7. The conclusion notes that the model becomes less accurate for thicker or more complex stacks. Suggestions on how to improve it in such cases, for example by including interfacial stress or more adaptable parameters, would add value.

8. Some figures lack clear legends and visual quality. Improving the resolution and ensuring that all labels are visible would enhance clarity.

9. Tables include values with excessive precision. Rounding to meaningful digits and indicating measurement uncertainty would improve the presentation.

10. A short remark on the long-term stability or repeatability of the films would help assess the method’s usefulness for practical applications.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript presents a novel mathematical model based on Stoney’s formula that accurately predicts and reduces residual stress in multilayer optical thin films.

1. Abstract – contains long, dense sentences, making it hard to follow, and missing the significance of the novel. I recommend rewriting the abstract to improve clarity by breaking up long, dense sentences and better emphasizing the novelty and importance of the work.
2.  The introduction clearly explains the importance of stress in optical thin films and reviews standard methods used to manage it. However, it lacks a comparison of the study's findings with previous research.
3.  The authors introduce important variables, such as σᵢ and qᵢ, in the stress model, but their definitions are not clearly stated in the text. Line 66 - add  E - Young’s modulus.
4. The authors are measuring film stress using the FST5000 film stress meter, which relies on substrate curvature and Stoney’s equation. To validate or correlate your stress measurements, can the authors compare with other complementary techniques that provide independent stress or strain information?

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The manuscript is generally understandable, but the quality of English needs improvement to enhance clarity and readability. Several sentences are long, dense, or awkwardly structured, which may hinder comprehension. I recommend thorough language editing to correct grammar, improve sentence flow, and ensure technical terms are clearly defined.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have addressed all comments, thereby improving the clarity and overall quality of the paper. It may now be suitable for publication in Coatings.

Reviewer 2 Report

Comments and Suggestions for Authors

The paper is of high quality and makes a valuable contribution to the field of optical thin films. It is suitable for publication in Coatings.