Study of High Transmittance of SiO2/Nb2O5 Multilayer Thin Films Deposited by Plasma-Assisted Reactive Magnetron Sputtering
, Jung-Hwan In 1, Seon Hoon Kim 1, Karam Han 1, Dongkook Lim 1, Yun Sik Hwang 2, Kyung Min Lee 2 and Ju Hyeon Choi 1,*Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsIn the manuscript “Study of high transmittance of SiO2/Nb2O5 multilayer thin films deposited by plasma-assisted reactive magnetron sputtering” Kim and co-workers present results of the structural and optical properties of single layer and multilayer thin films of SiO2 and Nb2O5. Such layered structures show favourable properties for use e.g. in aviation industry, where robust green lighting with wavelength in the range 500-500nm is needed. Thus, the topic that the authors investigated is scientifically and technologically appealing, and the results might have practical outcomes. From that point of view, the manuscript might potentially be interesting to a wider audience.
The manuscript appears well structured and easy-to-read. The main findings are interesting and presented in a clear way, while the conclusions are backed up by nice experimental results. There are some minor points (mostly spelling or grammar), as well as some ambiguities in the text that should be resolved to further improve the quality of the paper. However, the overall feeling is positive and I could recommend the manuscript for eventual publication after the raised issues are fixed.
The points that need to be addressed are listed below (as they appear in the text):
- Line 18: “it was found” instead of “it was founded”
- Lines 45-46: “has been used” instead of “has been attracted”
- Line 58: “and X-ray photoelectron spectroscopy” instead of “and an X-ray photon spectroscopy”
- Line 59: “using scanning electron microscopy” instead of “using a scanning electron microscopy”
- Line 60: “by atomic force microscopy” instead of “by an atomic electron microscopy”
- Lines 125-126: “The XRD patterns representing SiO2 and Nb2O5 crystal phases did not appear, indicating that …” instead of “Those XRD patterns are representing SiO2 and Nb2O5 crystal phases did not appear and indicating that…”
- Line 144: “indicating the respective components” instead of “indicating the composed respective components”
- Lines 148 and 155-158: The authors explain why they used the notation SiO2 and write “It is clear that the peaks of Si and O belong to the SiO2 phase.” Similarly, they write “Therefore, the oxidation state of Nb at the SiO2/Nb2O5 multilayer thin film is considered to be +5 oxidation state (Nb2O5) in this work. “ I would disagree on these conclusions. Namely, the XRD results suggest amorphous phases of both silicon oxide and niobium oxide (I deliberately write only “oxides”), so it would not be absolutely correct to label them with the exact chemical formulae, as those would indicate crystal phases rather than amorphous ones. In fact, the XRD and XPS results (lines 144-153) suggest that the ratios are substoichiometric for both silicon and niobium (niobium valence is something between +4 and +5, so between NbO2 and Nb2O5); what is more, event the authors themselves admitted it in the case of silicon (line 317: SiO1.88). Labelling the samples as SiO2 and Nb2O5 is in my opinion oversimplification i.e. it is not scientific. To be scientifically accurate, these materials should be labelled as SiO(2-x) and Nb2O(5-y) throughout the text.
- Figure 2a XPS survey spectrum: The labels for Nb doublet peaks are not in the correct position, as those should be in 200-210eV range, in accordance to figure 2d. By the way, what is the peak at around 150eV, the authors did not comment on that?
-Lines 161-170: From the description of the investigation of optical parameters, it is not quite clear what was measured and compared, i.e. what do 2 values if refractive index for each type of thin film represent? In other words, it is unclear what results the authors are actually comparing? It should be noted that the optical transmittance plot (Fig 3a) was not mentioned nor commented in the text (?).
- Line 195 “one can reduce” instead of “it can reduce”
- Line 215 “without observable interfacial diffusion” instead of “without interfacial diffusion”. Namely, in reality there could likely be some interfacial diffusion going on, but it is below the levels observable by SEM EDX.
- Line 230: Can you please explain the unusual notation for sputtering power “8/1kW and 6/0kW”? Perhaps it should write 8.1 kW and 6.0kW?
- Line 247: Can you please define the acronym in “AR coating”?
- Line 253: similarly, can you please define the acronyms ED and IS upon the first usage? I guess these represent the manufacturers Edmund and Isuzu (first mention in line 107)?
- Lines 265-266: “no significant interfacial diffusion was observed” instead of “no inter diffusion was found”
- Line 269, Figure 7: “deposited by sputtering” instead of “deposited by Sputter”
- Line 316: “it was found” instead of “it was founded”
- Lines 320-321: “and transmittance of 96.14% in the range of 500 nm to 550 nm with a flat top surface and square bandwidth.” instead of “and transmittance in the range of 500 nm to 550 nm with a flat top surface and square bandwidth shown over 96.14%.”
Comments on the Quality of English Language
Minor editing of English language, as mentioned in the report
Author Response
We would like to thanks for taking the time and effort necessary to review the manuscript. We sincerely appreciate all valuable comments and suggestions, which helped us to improve the quality of the manuscript.
"Please see the attachment."
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsIn this paper, the authors have prepared SiO2/Nb2O5 multilayer thin films deposited by plasma-assisted reactive magnetron sputtering. The paper presents an interesting material, regarding both fundamentals and applications. The authors explicitly described the preparation of samples, what is important and positive.
The basic characteristics of the material are well presented. However, there is one problem that needs to be addressed. The tests were carried out on three types of glass substrates (B33, D263 and D270, Schott AG). Why was it decided to choose such substrates? Please present their characteristics and indicate the differences.
I recommend to accept the manuscript for publication in its current form. However, additional information about the substrates should be included.
Author Response
We would like to thanks for taking the time and effort necessary to review the manuscript. We sincerely appreciate all valuable comments and suggestions, which helped us to improve the quality of the manuscript. "Please see the attachment."
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe paper "Study of high transmittance of SiO2/Nb2O5 multilayer thin films deposited by plasma-assisted reactive magnetron sputtering" reports experimental studies of the SiO2/Nb2O5 films. The basic experimental propositions are widely recognized in the scientific community and are beyond doubt. The authors use the well-known method of deposition of films, hence the presented results should be reliable.
The title of the article reflects its content. The abstract is concise and presents the main theses of the work. The structure of the paper is concise and the scientific level is high.
There are however some misprints in the text that should be corrected, e.g.
1. In the section “2.1. Fabrication”. Need to be added in text layer thicknesses (d(SiO2)=?, d(Nb2O5)=?) and method of their determinations.
2. In the section “2.1. Fabrication”. What temperature of the substrate was used?
3. In the section “2.1. Fabrication”. In text (lines 87-88) and table 1: “Deposition Rate”. Need to be added in text figures with time dependence of thicknesses films. This dependence can approve the value of the deposition rate.
4. In the section “3. Results and Discussion”, lines 119-120: How obtained coefficients of thermal expansion?
5. In the section “3. Results and Discussion”, Fig. 3: authors studied the transmission spectra and refractive index of the SiO2 and Nb2O5 films. However, the characterization of these layers is absent. Need to add XRD, SEM and EDAX (if chance) for these layers.
6. In the section “3. Results and Discussion”: How taken into accounts diffusion between layers?
7. In the section “3. Results and Discussion”, Fig. 3 and 7: From Fig. 3: maximum transparency is near 93 %, but from Fig. 7 is 95 %. What is the nature of increasing transparency with change in SiO2 films on the SiO2/Nb2O5 films?
In summary - I recommend this article for publication in the “Applied sciences” after a major revision.
Author Response
We would like to thanks for taking the time and effort necessary to review the manuscript. We sincerely appreciate all valuable comments and suggestions, which helped us to improve the quality of the manuscript. "Please see the attachment."
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors answered all questions. The article shows a high level of research. I will recommend the publication of this article in the Applied Sciences.
