Synthesis and Characterization of a Zirconium (Zr) Thin Film on Si(100) via Pulsed Laser Deposition

Round 1

Reviewer 1 Report

In this study entitled ‘Synthesis and characterization of Zirconium (Zr) thin film on Si(100) by pulsed laser deposition’, Khuzhakulov et al. have systematically investigated the pulsed laser deposition growth of Zr thin film by exploring the effect of laser wavelength, substrate temperature, and laser fluence on the quality of the Zr thin films. The results indicate that the use of long-wave laser and low laser fluence can give rise to low surface roughness. In addition, the optimal growth temperature is found to be 300 ℃, where the highest crystalline quality is achieved. On the whole, this study highlights the potential parameters affecting the quality the PLD-derived Zr thin film. It will hold broad interest to researchers working on coating. However, in the current stage, there are still some critical issues to be addressed. Therefore, a major revision is recommended. The following comments may help.   

1. Some experimental details have been missed, such as the purity of the Zr target, the gas atmosphere during the thin film deposition, the total pulse number, and the rotating rates of the substrate holder and target holder. These details should be provided so that the readers can follow this study more easily.   

2. As for the investigation of temperature on the crystallinity, the current temperature intervals are too large. To find out the optimal growth temperature, it is suggested that the substrate temperatures of 100, 200, 400 ℃ should also be investigated.

3. Following the above comment, the fundamental mechanism for realizing the optimal crystallinity at 300℃ should be discussed in detail to provide an in-depth insight.

4. The parameters in Figure 5 (Page 6) are too blurry and small to read. The font should be larger and clearer. This comment is also applicable to Figure 7 (Page 8).

5. The introduction section can be further enriched to increase credibility and broaden the readers’ horizons. For example, in the sentence of ‘zirconium is widely used in the manufacture of pumps, valves, and heat exchangers’ (Page 1), is there any evidence to be provided? For the sentence of ‘pulsed laser deposition (PLD) technique is considered as highly versatile technique for growing number of thin films…’ (Page 2), the latest supporting references (e.g., Nanomaterials 2023, 13, 1799; Adv. Mater. 2023, 35, 2211562; Tungsten 2023, 10.1007/s42864-023-00235-z) are recommended.

6. Some minor errors. a) Page 1, ‘Al2O3’, the numbers should be subscripted; b) Page 3, ‘LiCoO2’ and ‘BaTiO3’, the numbers should be subscripted; c) Page 4, ‘500C’ should be ‘500℃’; d) Page 7, in the figure caption of Figure 5, ‘AFM data’ should be ‘SEM data’; e) Page 8, in the figure caption of Figure 6, ‘J/cm2’, the number should be superscript. The whole manuscript needs to be carefully checked.  

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

My principal arguments against this manuscript to be accepted in the present forms are as follow:

1) Why authors used Si substrate and Si(100) one in particular to investigate PLD parameters influence on the Zr films growth and related crystal quality? Me-Si systems are of high reactivity and as a result one can expect silicidation at least at the Si/Me interface, especially if one check https://doi.org/10.1016/j.matlet.2014.02.043. Why did not you use any inert substrate especially concerning the fact that Si/Zr films are out of the focus for any reliable application?

2) Demonstrated XRD, AFM and SEM investigations are of low scientific level: it only contains prelminary analysis without any deepness (crystallite size extracted from the Scherrer equation in the case of XRD, RMS roughness value from AFM, elemental composition and particles size distribution from SEM observation etc.).

3) Instead of results discussion, authors simply gave some example for the other investigated substrate/film system produced by the PLD technique after every XRD pattern and SEM images. In addition, it is not truly correct since mentioned articles dealt with compounds, while the manuscript under consideration does with mono-elemental Zr target which simplified the descriptionof the laser-target interaction a lot.

4) The computated model of the thin films growth looks like an another AFM images serving as just some kind of supporting material for article to appear like complex investigation and appropriate volume (words count). It is nither understandable no comparable with the real AFM data, be cause while the former deals with 3D, the latter does with pseudo-3D (XY scales with color map) and there are no RMS calculations to compare both. 

5) There are many errors in conducting an experiment and results analysis:

- what about native oxide removing from Si substrate prior PLD experiment?

- the unclear nature of the XRF peaks at 2 theta = 31, 41 and 44 degrees (some of the peaks can be attributed to the zirconium silicide formation as mentioned above)

- line 121: [13] reference deals with LIPSS formation e.g. laser-substrate interaction instead of PLD processes, that isinappropriate self-citations by authors

- XRD patterns should contain reference PDF card from any database for Zr crystal

- line 150: what surface prperties?

- line 197: any proofs? It is possible if we asume film densification or atoms re-evaporation at higher substrate temperature. However, authirs did not present any thickness estimation or measurement. Otherwise, this paragraph sounds tenuous.

- line 243: "more crustalline"  - how can you operate with this term without any analysis at least with Scherrer equation performed?

- line 334: [38] reference deals with the model of quantum dots growth and coarsening that is not your case

In summary, the manuscript under considiration can demonstrate some interest for readers after providing deeper analysis during major revision

line 35: poses=> pose

line 61: nanoparticle => nanoparticles

line 67: "depressions" is somewhat confusing for film characterization, consider pits or voids instead

line 96: did you mean ion pump instead?

Captions od Figures 5 and 7 must be corrected with SEM instead of AFM

Author Response

Please see the attachment

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors have well addressed my comments. Now the manuscript is ready for publication. 

Author Response

We thank the reviewer. Our paper is in much better condition due to his/her contributions.

Reviewer 2 Report

Authors ignored the comment "the unclear nature of the XRF peaks at 2 theta = 31, 41 and 44 degrees (some of the peaks can be attributed to the zirconium silicide formation as mentioned above)" Of course, it is just a mispeling and XRD was assumed. That is why, please adressed that comment once again, which rise a serious question about phase purity of the resulted Zr films. That is a crucial issue to be adressed before article acceptance.

lines 133-141: Once again: In addition, it is not truly correct since mentioned articles dealt with compounds, while the manuscript under consideration does with mono-elemental Zr target which simplified the description of the laser-target interaction a lot.  So, it is unnecessary discussion. Phenomenon described resulted from different in melting points, oxidations rates for different elements and congruent vs. non-congruent melting. 

"Our study shows that microstructure and surface properties such as phases of zirconium films can be adjusted with laser fluence and wavelength" - I see no solid evidences about laser parameters on zirconium "phase". Any experiments on a-Zr to b-Zr transition should be added if any. Otherwise, it is just an unusefull information to be deleted.

line 171: "the Zr thin film using 532 nm is shown to be more crystalline as the ratio of height of the peak and its width at half-maximum is larger." The trick is that larger FWHM assumes worse crystallinity. So the current deduction should to be rewritten.

lines 199-201 were added without any comparisson with the current results especially in view of comment provided above concerning some silicide related traces in XRD.

lines 188-198: Once again, this discussion has no meaning concerning results obtained. If you claimed that a possible LIPSS formation on the Zr targer during PLD may affect ablation threshold, please provide any solid proofs. If it will be provided, next, please discuss its influence on the resulted Zr films.

Authors did not adress the comment "The  model of the thin films growth looks like an another AFM images serving as just some kind of supporting material for article to appear like complex investigation and appropriate volume (words count). It is neither understandable no comparable with the real AFM data, be cause while the former deals with 3D, the latter does with pseudo-3D (XY scales with color map) and there are no RMS calculations to compare both." - Provide RMS values for both experimental and theoretical relief and compare it before judging.

lines 6-9: please, provide Country in affilations

line 10: delete "_" underscore symbol

line 14: distinct patterns and peaks were revealed with XRD alone, be cause neither AFM no SEM did not deal with any peaks

line 30: any references?

line 37: EUV should be first written as Extreme Ultraviolet (EUV)

line 53: a highly - as a highly

line 53: for growing number of thin film applications => for thin films growning in different applications

line 67: "The deposited Zr thin films had exceedingly smooth 67 surfaces and high specular reflectivity." Any reference? Do you mean [13]? If so, it does not contain any thoughts on specular reflectivity 

line 68: "depressions" again

lines 68-69: "Additionally, some depressions were formed in the film when they were exposed to a deuterium atmosphere." - Provide reference concerning deuterium atmosphere influence. Once again, [13] did not deal with this phenomena.

line 89 calims 10-7 Torr pumping, while line 99 does with 10-8 Torr. Please, provide the correct base pressure of the vacuum chamber

line 91: "cross-sectional thickness" is incorrect term

line 88: is KDP a Potassium dideuterium phosphate? provide abbreviation explanation 

line 105: "as the phase" - what phase?

lines 131-132: "and when fluence is just below the threshold laser induced periodic surface structures can be formed [18-21]." => and when fluence is just below the threshold for laser induced periodic surface structures to be formed

Author Response

Authors ignored the comment "the unclear nature of the XRF peaks at 2 theta = 31, 41 and 44 degrees (some of the peaks can be attributed to the zirconium silicide formation as mentioned above)" Of course, it is just a mispeling and XRD was assumed. That is why, please adressed that comment once again, which rise a serious question about phase purity of the resulted Zr films. That is a crucial issue to be adressed before article acceptance.

We thank reviewer for noticing undefined peaks which are now defined. The first peak belongs to SiO2 and other peaks are considered as zirconium silicide which are only observed at 500 C. this is also in agreement with the previous observation. This discussion is now added into our text and figures are updated.

lines 133-141: Once again: In addition, it is not truly correct since mentioned articles dealt with compounds, while the manuscript under consideration does with mono-elemental Zr target which simplified the description of the laser-target interaction a lot.  So, it is unnecessary discussion. Phenomenon described resulted from different in melting points, oxidations rates for different elements and congruent vs. non-congruent melting. 

We believe that this is an important discussion to show the different mechanism in play at different conditions.

"Our study shows that microstructure and surface properties such as phases of zirconium films can be adjusted with laser fluence and wavelength" - I see no solid evidences about laser parameters on zirconium "phase". Any experiments on a-Zr to b-Zr transition should be added if any. Otherwise, it is just an unusefull information to be deleted.

The reviewer correctly point out the misuse of word phase which is replaced by crystalline structure.

line 171: "the Zr thin film using 532 nm is shown to be more crystalline as the ratio of height of the peak and its width at half-maximum is larger." The trick is that larger FWHM assumes worse crystallinity. So the current deduction should to be rewritten.

This sentence is rewritten.

lines 199-201 were added without any comparisson with the current results especially in view of comment provided above concerning some silicide related traces in XRD.

lines 188-198: Once again, this discussion has no meaning concerning results obtained. If you claimed that a possible LIPSS formation on the Zr targer during PLD may affect ablation threshold, please provide any solid proofs. If it will be provided, next, please discuss its influence on the resulted Zr films.

This discussion is added to show the different process that may occur depending on the laser fluence. It is well known that when laser fluences is just below ablation threshold and with correct polarization, periodic surface structures can be observed.

Authors did not adress the comment "The  model of the thin films growth looks like an another AFM images serving as just some kind of supporting material for article to appear like complex investigation and appropriate volume (words count). It is neither understandable no comparable with the real AFM data, be cause while the former deals with 3D, the latter does with pseudo-3D (XY scales with color map) and there are no RMS calculations to compare both." - Provide RMS values for both experimental and theoretical relief and compare it before judging.

We have provided line scan for both experimental and theoretical values. We believe this issue is resolved now.

Author Response File: Author Response.docx