Atomistic Simulation of Stresses in Growing Silicon Dioxide Films
Round 1
Reviewer 1 Report
The manuscript presents a theoretical study of stress induced in the deposition of silicon oxide from vapour phase by varying the deposition angle from normal to glancing deposition angle. No experimental data was included to support the results obtained from theoretical calculations, but the manuscript is clear and well written. In my opinion, the topic is interesting enough for Coatings audience and should be published. I suggest a minor revision to shed light on some aspects that are not very clear to me.
The authors often use the citation numbers as a word. E.g. Pag 1, “The effect of the deposition angle … was studied in [5] using …”. I’m not sure about the journal policy about that but by adding the first author name (e.g. The effect of the deposition angle … was studied by Surname [5] using …”) or changing the sentence in another way will make the reading more fluent.
The total number of silicon and oxygen atoms is equal to 180 in vapour phase, with a ratio of 1:2. Is the simulated oxygens in the atomic form and not in the molecular ones? In the real chamber you will have Si vapour atoms and O2 molecules. Could this variation change the results?
The dimensions of the box are equal to 10x30x6 nm. Performing some quick calculations (PV=nRT) I obtained 4 atm but then in the manuscript you say that the pressure is kept constant to 1 atm. Moreover, whether the pressure is 1 or 4 atm, these values seem exaggeratedly high compared to those actually used in vapor deposition systems (generally lower than mbar). Why was this pressure chosen? Don't you think there could be differences in results using lower values?
Pag 3, “The initial velocities of oxygen atoms are directed to the substrate perpendicular to its surface.” Shouldn’t the direction of the oxygen molecules be random since they are not produced from the sputtering?
Pag 5 “Results of the stress calculations agree with the available experimental data”. How these measurements were performed? Do you correlate the stress with the refractive index, it could be an experimental way? Do you have any experimental validation of your results to attach to this work?
Author Response
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Author Response File: 
Author Response.doc
Reviewer 2 Report
The paper uses MD simulation method to deposit silicon dioxide films with different deposited angles. This paper needs to modify before published. The comments are as followings:
- The author should describe how to loading the pressure on the thin film including the direction. From the fig. 2(right area), the deposited thin film with 70o contain very hole within the film. It seems the quality of the film is not well.
- The author said "The simulation results are in the agreement with the experimental data" in the conclusion section. How to identify? It is a wrong presentation.
Author Response
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Author Response File: Author Response.doc
Reviewer 3 Report
This manuscript reports MD simulation results of the stress evolution during the deposition process of silicon dioxide thin films, as well as the dependence of stress on the deposition angles. The simulation method in general clearly presented. However, the novelty of the article is not clear, especially when compared to the authors’ own previous work (ref. 14). My recommendation is a major revision that clearly addresses the following points.
Please point out the major novelty of this work compared to the previous work by the authors and by others. For example, ref. 14 investigated the same material, used the same simulation set up, with the deposition angle being the only new variable in this work as I could see. The introduction and conclusion need to be improved, especially the conclusion, there is a lack of discussion about the impact of the work to the research field. Also, introduction should point out what is new in this work compared to the literature. The author emphasized that simulation results compared well with the experiments. However, it is not clear whether the deposition processes in experiments and in simulations are comparable. For example, on page 2, Section “2 Method”, the calculation of stress dependence is organized as 5 steps. In step 3, “At the initial state of the film growth, the value of Ns is reduced to 100 to study a fast increase of the stress value.” It is not clearly stated why and how could it be compared to experimental process. Also, in second 2, “the vertical dimension of the simulation box is increased by 0.01 nm after each injection step in order to compensate for the growth of film thickness.” Could the author please explain the increase by 0.01 nm can “compensate for the growth of the film thickness”? In the same paragraph, “the initial values of the silicon and oxygen atoms velocities correspond to the deposited atoms kinetic energy E(Si)=10eV and E(O)=0,1 eV.” do you mean “0.1 eV” instead of “0,1 eV”? “Stress” is the major quantity of interest in this work. Could the author explain why only the average stress is studied instead of the stress distribution throughout the thickness? Would it be better to scale the axes with the equal increments in Fig. 3 for all different plots?
Author Response
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Round 2
Reviewer 3 Report
Please double check the spell and format throughout the entire article. F
or example, the second equation of equation (3), "sin" is misspelled as "sn", and it shows up repeatedly in the following context, e.g., in line 209. "4. Conclusion" is shown as ".4. Conclusion", etc.
If all these similar issues are addressed, I'll accept this manuscript for publication.
