Metastability Phenomena in VO₂ Thin Films

Round 1

Reviewer 1 Report

I have read the manuscript “Metastability phenomena in VO2 thin films” by Gioacchiano et al. with interest. It reports the experimental observations of permanent change is resistivity in both insulating and metallic states of VO₂ thin film with/after application of strong magnetic field. The results are very intriguing, and potentially very useful for control of the VO₂ electrical properties. The authors explain this variation by magnetic field affecting the local microstructure and the balance between the various VO₂ states. However, I cannot recommend the manuscript for publication in its current form, since more information must be provided to both understand the result and propose a plausible explanation.

First, not sufficient information is provided about the experimental arrangements. Figure 1 (that presents the main results of the paper) is very hard to understand with many closely overlapping lines. Also, the authors mention something about the wait time and cycle time making a difference, but do not provide any details. I have very hard time making sense of the evolution of the hysteresis cycles as the magnetic field increases – for example, there is no difference between the cycles measured for 5T and 15T, then there is sudden overall increase in resistivity for B=30T with no change for magnetic field shifting to 20T, and then further increase when B=0 again. At the same time it is hard to see if there are any changes in the shape of the hysteresis cycle for different magnetic field. It has been shown in many publications that this shape is sensitive to the microstructure of VO₂ film and internal stresses, so its analysis would provide a useful supporting information regarding claimed changes.

It is also not discussed if the observed change in overall resistivity is permanent. The authors use the term “metastable” in the title – does that mean the sample eventually returns in its original state? What happens if the sample undergoes a repeated exposure to the strong magnetic field? Similarly, for the non-repeating hysteresis loop, shown in Fig. 2, it would be very interesting to see what happens after a repeated looping of the temperature.

Then, there is a question of generality. The presented data are for one particular sample, so it is hard to say if this is a common behavior, or something special about the particular sample. I cannot get rid of the thought that similar behavior would have been observed if some small mechanical damage to the contacts would have happened at strong magnetic field, increasing the implied film resistance, but not due to any long-term effect on VO₂ film. I trust that the authors have verified that, but I would like to see more evidence of structural changes they imply (maybe some additional sample structure characterization?)

Also, I would suggest the authors to ask an English native speaker to proof read the manuscript, I often had hard time understanding the sentences without reading them a few times.

Author Response

Dear Referee,

all comments, suggestions and criticisms have been clarified and introduced in blue color in the ‘marked copy of the revised manuscript’. Abstract and conclusion were reviewed and added some references.

The answers to the questions are in the additional PDF files upload 

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript, entitled to “metastability phenomena in VO2 thin films" by Bianconi et al., reported on the possible metastability of VO2 by thermal stain and magnetic field. In this paper, the authors have shown the interesting metastable phase in VO2. However, the English must be improved to deliver the importance of their finding to readers. Moreover, the figures needs to be clear because the information in the figure is very limited. In my opinion, I would not accept this paper in the present form. Here is my suggestion to improve the manuscript.

English needs to be proofread. In some sentence, I cannot understand the meaning.

The authors need to add more information on the legend of Fig. 1.

The authors need to add more reference on the recent study on the chemical and physical local perturbation in VO2 thin films along with ref. 2. Suggested references are “1. Nature Phys. 9, 661 (2013), 2. Nature Mater. 15, 1113 (2016)”

Author Response

Dear Referee,

all comments, suggestions and criticisms have been clarified and introduced in blue color in the ‘marked copy of the revised manuscript’. Abstract and conclusion were reviewed and added some references.

The answers to the questions are in the additional PDF files upload

Author Response File: Author Response.pdf

Reviewer 3 Report

please see the document file

Comments for author File: Comments.pdf

Author Response

Dear Referee,

all comments, suggestions and criticisms have been clarified and introduced in blue color in the ‘marked copy of the revised manuscript’. Abstract and conclusion were reviewed and added some references.

The answers to the questions are in the additional PDF files upload

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I think the revised version of the manuscript is significantly improved. I recommend its publication in the present form. One small correction: line 95 should refer to Fig. 3B, not 2B.

Author Response

I changed the words' Fig. 2B 'in' FIG. 3B 'in line 95

Reviewer 2 Report

The paper was quite improved. I would like to recommend the acceptance of this paper.

Author Response

Thanks to of the positive opinion after the corrections introduced in the article

Reviewer 3 Report

Author Response

All typos have been corrected and the changes are highlighted in yellow