Electrical and Optical Properties of Laser-Induced Structural Modifications in PbSe Films
Round 1
Reviewer 1 Report
The paper is based on the electrical and optical properties study of laser irradiated PbSe thin films and characterized with the techniques like SEM, Reflectance and electrical measurements. The authors have corelated the observed parameters with each other, however, still there are some more discussions are required for the same. There are some major points needs to be addressed with the suggested references. So, my recommendation is Major Revision of the manuscript.
Comments:
1. The advantage of laser irradiation on chalcogenide thin films for changing its different properties needs to be discussed in Introduction.
Refer-https://doi.org/10.1016/j.jallcom.2010.06.035, Laser Physics 25 (3), 036001 (2015), RSC Advances 11 (26), 16015-16025 (2021), Applied Physics A 126 (1), 1-8 (2020)
2. Why laser irradiation is preferred than thermal annealing for the optical and electrical changes is to be focused. Refer-Optics and Laser Technology 140, 107036 (2021), AIP Advances 9, 095065(2019), Journal of Alloys and Compounds 915, 167000 (2022)
3. What is the logic to choose the laser laser intensity of 76 W/cm2?
4. Whether the authors calculated the temperature rise near the irradiated spot? Refer Journal of Non-Crystalline Solids 355 (37-42), 1943-1946 (2009), Phys. Rev. B 62(22) (2000) R14601
5. “Light areas in the image correspond to the crystalline phase,” To confirm this, XRD data is necessary.
6. Why the reflectance decreased for laser irradiated film is to be given?
7. Why the data in Fig.4 b inset untreated absorption data is very noisy, while the laser irradiated data is smooth?
8. The bandgap fitting in Fig.6 for the untreated film is not correct as it is not fitting the linear portions, but only few points.
9. The bandgap values should be given with error bars. Which equation is used to calculate the bandgap?
10. The authors have mentioned about extinction coefficient, refractive index, but not given the data.
11. The formed cracks in the film is good for application point of view or not?
Comments for author File: 
Comments.pdf
Author Response
We thank the reviewers for a thorough review of the manuscript, as well as for the comments and suggestions provided, which made it possible to qualitatively improve the text of the work and make the material presented more accessible to the general reader!
Reply to review #1:
- The advantage of laser irradiation on chalcogenide thin films for changing its different properties needs to be discussed in Introduction.
Refer-https://doi.org/10.1016/j.jallcom.2010.06.035, Laser Physics 25 (3), 036001 (2015), RSC Advances 11 (26), 16015-16025 (2021), Applied Physics A 126 (1), 1-8 (2020)
Answer: We agree with the reviewer's remark and are grateful for the links to similar studies. We have added the following piece of text to the introduction.
«The authors [16] present a study of photoinduced changes occurring during laser irradiation. Such modifications are one of the simple and environmentally friendly methods that make it possible to control morphological and optical changes in the studied films with minimal surface damage.»
- Why laser irradiation is preferred than thermal annealing for the optical and electrical changes is to be focused. Refer-Optics and Laser Technology 140, 107036 (2021), AIP Advances 9, 095065(2019), Journal of Alloys and Compounds 915, 167000 (2022)
Answer: We agree with the reviewer's remark and are grateful for the links to similar studies. We have added the following piece of text to the introduction.
« In addition to the laser modification method ease use to change the optical и electrical characteristics, the method also leads to bond breaking and rearrangements within the material structure [16]. This leads to a modification of the amorphous material localized structures, which leads to changes in such optical properties, such as transmittance, absorption and extinction coefficient, refractive index and optical band gap [16-17].»
- What is the logic to choose the laser laser intensity of 76 W/cm2?
Answer: We agree with the reviewer's remark so we have corrected these data in accordance with the data in Table 2, where 22-33,6 kW/cm2 correspond to the photodarkening mode.
- Whether the authors calculated the temperature rise near the irradiated spot? Refer Journal of Non-Crystalline Solids 355 (37-42), 1943-1946 (2009), Phys. Rev. B 62(22) (2000) R14601
Answer: The authors didn’t calculate the temperature rise near the irradiated spot. In our next articles, we will calculate the temperature rise and present the results.
- “Light areas in the image correspond to the crystalline phase,” To confirm this, XRD data is necessary.
Answer: We agree with the reviewer's remark that the XRD data is necessary to confirm this. In our next articles, we will make the XRD data measurements and present the results. Therefore, in this article we will exclude the following line: “Light areas in the image correspond to the crystalline phase”
- Why the reflectance decreased for laser irradiated film is to be given?
Answer: Lead selenide films are not transparent in the visible range, so the change in reflection will characterize the change in the absorption capacity of the films. Thus, a decrease in reflection after laser modification indicates an increase in absorption, which was the goal of the study. As a result of layer exposure, the structure of the material changed and became optically denser. Also optical methods for monitoring the laser modification of films will allow contactless and real-time monitoring of all changes.
- Why the data in Fig.4 b inset untreated absorption data is very noisy, while the laser irradiated data is smooth?
Answer: We agree with the reviewer's remark so we have added smoothed untreated absorption data for the Fig.4 b.
- The bandgap fitting in Fig.6 for the untreated film is not correct as it is not fitting the linear portions, but only few points.
Answer: We agree with the reviewer's remark so the bandgap fitting has been changed in Fig.6.
- The bandgap values should be given with error bars. Which equation is used to calculate the bandgap?
Answer: We agree with the reviewer's remark so error bars and equation has been added.
«The PbSe film optical band gap was determined under various processing conditions by the expression: (αhν)2 = B2 (hν-Eg), where hν is photon energy, B is the Tauc parameter, Eg is the band gap [16].»
- The authors have mentioned about extinction coefficient, refractive index, but not given the data.
Answer: We have given data on the extinction coefficient, refractive index and absorption coefficient in Fig.5.
- The formed cracks in the film is good for application point of view or not?
Answer: The resulting cracks in the film have a bad effect on the electrical characteristics, so we strive to minimize them and look for optimal conditions for laser modification.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript by Sergeev et al presents the structural modification of PbSe films and their electrical and optical characterization. The study looks good however, there are a few changes that are suggested:
1. The title can be modified as to make it more clear to readers: Electrical and Optical properties of laser-induced structural modifications in PbSe films.
2. The author should explain in the experimental section, whether the laser was raster scanned or line scanned and whether the laser was scanned at the same spot more than once or not.
3. The scanning rate of 950micron/s is too much and the laser spot is 20 microns so the SEM images show only a part of the etched sample. The exposure time is of the order of few micro seconds. Since there is no shutter involved so please explain in detail how the microsecond exposure time was achieved.
4. Table 1 shows the current after laser irradiation, remain same as 140 nA at both the applied voltage of 4 V and 0.6V even though the resistance is increased 6 times to 1200 ohm please explain it.
Author Response
We thank the reviewers for a thorough review of the manuscript, as well as for the comments and suggestions provided, which made it possible to qualitatively improve the text of the work and make the material presented more accessible to the general reader!
Reply to review #2:
The manuscript by Sergeev et al presents the structural modification of PbSe films and their electrical and optical characterization. The study looks good however, there are a few changes that are suggested:
- The title can be modified as to make it more clear to readers: Electrical and Optical properties of laser-induced structural modifications in PbSe films.
Answer: We agree with the reviewer's remark that the title has been changed.
- The author should explain in the experimental section, whether the laser was raster scanned or line scanned and whether the laser was scanned at the same spot more than once or not.
Answer: We agree with the reviewer's remark. The information would be added to the experimental section: “Laser was line scanned not more than once.”
- The scanning rate of 950micron/s is too much and the laser spot is 20 microns so the SEM images show only a part of the etched sample. The exposure time is of the order of few micro seconds. Since there is no shutter involved so, please explain in detail how the microsecond exposure time was achieved.
Answer: Thanks for the clarification. The time is considered to be ?= ??, where d is the laser spot diameter, where ? is the scanning speed. Such a short time is achieved at the expense of a small spot. The laser spot diameter was equal to 10 μm.
We also correct this part of text on page 3: “The radiation incident power on the film in the laser exposure mode was 76 W/cm2 with a spot diameter about 10 μm. The radiation intensity profile in the spot cross section was a beam with a flat top. The film structure was modified at a laser spot scanning rate of 950 μm/s.”
- Table 1 shows the current after laser irradiation, remain same as 140 nA at both the applied voltage of 4 V and 0.6V even though the resistance is increased 6 times to 1200 ohm please explain it.
Answer: Thanks for the question. The absence of a change in current after laser modification may be due to an excess of free electrons in the system. Therefore, the concentration of charge carriers is approximately constant and their mobility is absent.
[Physical quantities, Handbook, Grigoriev I.S., Meilikhov E.Z., 1991.]
Author Response File: Author Response.docx
Reviewer 3 Report
This article presents an interesting way to investigate laser-irradiation effects on PbSe. The transport and optical properties were probed, which are important for device development. In particular the laser induced band gap shrinkage is interesting. Would this effect be more prominent for pulsed lasers? A comparative study on pulsed vs. cw laser could also be interesting. The article has been written well, the figures and references are correct and appropriate.
Author Response
We thank the reviewers for a thorough review of the manuscript, as well as for the comments and suggestions provided, which made it possible to qualitatively improve the text of the work and make the material presented more accessible to the general reader!
Reply to review #3:
This article presents an interesting way to investigate laser-irradiation effects on PbSe. The transport and optical properties were probed, which are important for device development. In particular the laser induced band gap shrinkage is interesting. Would this effect be more prominent for pulsed lasers? A comparative study on pulsed vs. cw laser could also be interesting. The article has been written well, the figures and references are correct and appropriate.
Answer: Thank you for your comment. In the future, we plan to prepare a comparative review of two methods of films laser modification.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The revised manuscript can be accepted. The authors have replied the queries and modified them accordingly.
