Optical, Electrical and Structural Properties of ITO/IZO and IZO/ITO Multilayer Transparent Conductive Oxide Films Deposited via Radiofrequency Magnetron Sputtering
Round 1
Reviewer 1 Report
Referee Report
On the paper “ Optical, electrical and structural properties of ITO/IZO and IZO/ITO multilayer transparent conductive oxide films deposited by RF-magnetron sputtering “ (coatings-2597910) by the authors Ayse Seyhan and Emre Kartal submitted to the Coatings
This is interesting and useful paper. It reports the preparation and investigation of the structure, electrical, optical, and morphological properties of the multilayer transparent conductive oxides structures in form of the Indium Tin Oxide and Indium Zinc Oxide thin films, to overcome high cost, limited transmittance in infrared wavelengths, and elevated sheet resistance. The results showed that the multilayer deposited at 200°C achieved the best sheet resistance of 18.5 Ohm/sq and high optical transmittance of over 90% at 550 nm. A power conversion efficiency of 17.46 % was obtained for the silicon heterojunction solar cell fabricated using the multilayer structure as a front. The obtained experimental results are reliable without any doubts. However, I have some questions and additions. I would like to note a few points to improve the paper before it can be published:
1. All the motivation should be deleted from the Abstract.
2. The authors should give in 1. Introduction and 2. Materials and Methods examples of the formation of the thin films:
(1). A.Z. Tuleushev, F.E. Harrison, A.L. Kozlovskiy, M.V. Zdorovets, Evolution of the absorption edge of PET films irradiated with Kr ions after thermal annealing and ageing, Optical Mater. 119 (2021) 111348. https://doi.org/10.1016/j.optmat.2021.111348.
(2). M.I. Panasyuk, T.I. Zubar, T.I. Usovich, D.I. Tishkevich, O.D. Kanafyev, V.A. Fedkin, A.N. Kotelnikova, S.V. Trukhanov, D. Michels, D. Lyakhov, T.N. Vershinina, V.M. Fedosyuk, A.V. Trukhanov, Mechanism of bubbles formation and anomalous phase separation in the CoNiP system, Sci. Rep. 13 (2023) 5829. https://doi.org/10.1038/s41598-023-33146-7.
3. I fully agree with the authors that: “ Transparent conductive oxide (TCO) films have been utilized in various optoelec- tronic applications due to their exceptional optical transmittance (>80 %) in the visible wavelength range (380-700nm) and favorable electrical properties (resistivity of <10-4 Ω.cm). ”. The authors should mention in 1. Introduction some results of the preparation and investigation of other substituted oxides promising for practical applications:
(3). S.V. Trukhanov, Peculiarities of the magnetic state in the system La0.70Sr0.30MnO3-γ (0 ≤ γ ≤ 0.25), J. Exp. Theor. Phys. 100 (2005) 95-105. https://doi.org/10.1134/1.1866202.
(4). M.V. Zdorovets, A.L. Kozlovskiy, D.B. Borgekov, D.I. Shlimas, Influence of irradiation with heavy Kr15+ ions on the structural, optical and strength properties of BeO ceramic, J. Mater. Sci.: Mater. Electron. 32 (2021) 15375-15385. https://doi.org/10.1007/s10854-021-06087-y.
4. I fully agree with the authors that: “ This characteristic has been the subject of recent research, where various application examples of multilayer TCO structures such as TCO/Metal/TCO or TCO/TCO have been demonstrated [28-33]. ”. It is well known that the combination of different compounds which have excellent electronic properties leads to new composite materials which have earned great technological interest in recent years. The addition of a second phase can significantly improve the electronic properties of the resulting composite material:
(5). A.L. Kozlovskiy, D.I. Shlimas, M.V. Zdorovets, Synthesis, structural properties and shielding efficiency of glasses based on TeO2-(1-x)ZnO-xSm2O3, J. Mater. Sci.: Mater. Electron. 32 (2021) 12111-12120. https://doi.org/10.1007/s10854-021-05839-0.
(6). A.M. Henaish, M.A. Darwish, O.M. Hemeda, I.A. Weinstein, T.S. Soliman, A.V. Trukhanov, S.V. Trukhanov, D. Zhou, A.M. Dorgham, Structure and optoelectronic properties of ferroelectric PVA-PZT nanocomposites, Opt. Mater. 138 (2023) 113402. https://doi.org/10.1016/j.optmat.2022.113402.
This issue should be mentioned and discussed in 1. Introduction.
5. The proposed 6 papers should be inserted in References.
The paper should be sent to me for the second analysis after the major revisions.
Minor editing of English language required
Author Response
We would like to express our gratitude to the reviewers for their valuable input.
1. The motivation section has been removed from the abstract, and the abstract has been revised accordingly.
2. 3. and 4. We have incorporated some of the suggested articles as references in the introduction section of the article.
- The second article has been cited as a reference in the section concerning the formation of thin films.
- For the practical applications, the fourth article has been included as a reference.
- The combination of various compounds, the fifth and sixth articles have been cited as references.
Reviewer 2 Report
In this paper，multilayer TCO films are fabricated by RF magnetron sputtering. The multilayer TCO structure presented lower sheet resistance, higher transmittances than those of single-layer films. Furthermore, as the deposition temperature rise, the optical bandgap and the figure-of-merit of the multilayer conductive films also increase. These indications suggest that multilayer TCO films are promising to replace single-layer conductive films in the application of effective TCO layers in solar cells. This work is of great significance to reduce the application limitations of TCO films. I recommend this paper can be published after the following issues are fully addressed.
1. I noticed that the article mentioned that the optical and electrical properties of single-layer and multilayer conductive films become better with increasing temperature, but only two temperature points, room temperature and 200 degree Celsius, which is not convincing.
2. Why the presence of an IZO interlayer in the multilayer ITO/IZO thin film deposited at 200 °C caused new XRD diffraction peaks while ITO intercalation did not. Please explain it.
3. Line 217 has an incorrect temperature scale regarding Celsius and needs to be changed.
4. The images of SEM and AFM look slightly rough, please improve it.
5. In Figure 5, at a deposition temperature of 200 degrees Celsius, the light transmittance of ITO films is much better than that of IZO films. However, on this basis, the light transmittance of multilayer films has not been improved, does it mean that the optical properties of TCO films can be improved by simply increasing the temperature without multilayer films? Please provide a more convincing argument.
Author Response
For research article
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Response to Reviewer 2 Comments
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1. Summary |
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Thank you very much for taking the time to review this manuscript. Thank you very much for the valuable revisions provided by the referees. These contributions have significantly improved the functionality of our paper and enhanced the quality of our work. We deeply appreciate the meticulous reviews and suggestions from the referees, which have helped us present a stronger study. Your insightful feedback has allowed us to submit a better version of our research. Please find the detailed responses below and the corresponding revisions in the re-submitted manuscript.
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2. Questions for General Evaluation |
Reviewer’s Evaluation |
Response and Revisions |
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Does the introduction provide sufficient background and include all relevant references? |
Yes |
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Are all the cited references relevant to the research? |
Yes |
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Is the research design appropriate? |
Yes |
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Are the methods adequately described? |
Yes |
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Are the results clearly presented? |
Can be improved |
improved |
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Are the conclusions supported by the results? |
Can be improved |
improved |
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In this paper, multilayer TCO films are fabricated by RF magnetron sputtering. The multilayer TCO structure presented lower sheet resistance, higher transmittances than those of single-layer films. Furthermore, as the deposition temperature rise, the optical bandgap and the figure-of-merit of the multilayer conductive films also increase. These indications suggest that multilayer TCO films are promising to replace single-layer conductive films in the application of effective TCO layers in solar cells. This work is of great significance to reduce the application limitations of TCO films. I recommend this paper can be published after the following issues are fully addressed.
3. Point-by-point response to Comments and Suggestions for Authors |
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Comments 1: I noticed that the article mentioned that the optical and electrical properties of single-layer and multilayer conductive films become better with increasing temperature, but only two temperature points, room temperature and 200 degree Celsius, which is not convincing. |
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Response 1: Thank you for pointing this out. We agree with this comment. Therefore, we have explained as follow: SHJ (Silicon Heterojunction) solar cells have a distinct structure when compared to traditional single-crystal silicon (c-Si) solar cells. The fundamental design of SHJ solar cells is based on a specialized architecture that offers advantages such as higher efficiency and lower costs. These silicon heterojunction solar cells consist of an n-type c-Si absorber encased by layers of intrinsic (i), phosphine-doped (n), and boron-doped (p) hydrogenated amorphous silicon (a-Si). This arrangement forms a stack of (p) a-Si:H / (i) a-Si:H / n-type c-Si / (i) a-Si:H / (n) a-Si:H.The a-Si:H layers within the cell structure begin to transition from an amorphous to a crystalline structure at temperatures exceeding 200 degrees Celsius. However, crystalline formation is undesired at the interfaces, which is why all these processes are carried out at 200 degrees Celsius to preserve the amorphous structure. The TCO (Transparent Conductive Oxide) structures used in SHJ solar cells are also deposited at 200 degrees Celsius. Therefore, in our study, a temperature of 200 degrees Celsius was selected. Room temperature was also included in the research to compare the optical and electrical properties of TCOs based on temperature dependence. TCO layers used in SHJ solar cells are typically deposited at 200 degrees Celsius to avoid disrupting the structure of amorphous Si layers within the SHJ solar cell configuration. Therefore, only two temperature values were selected. This explanation summarized as follows “In order to preserve the amorphous structure of a-Si:H layers within SHJ solar cells, a deposition temperature of 200 °C was selected for the TCO structures. Additionally, room temperature (RT) was included to facilitate the comparison of the electrical and optical properties of these TCO structures according to temperature. This change can be found – page number (4), and line (129-132). |
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Comments 2: Why the presence of an IZO interlayer in the multilayer ITO/IZO thin film deposited at 200 °C caused new XRD diffraction peaks while ITO intercalation did not. Please explain it. |
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Response 2: The ITO/IZO (multilayer TCO-II) and IZO/ITO (multilayer TCO-IV) structures are deposited as ITO(50nm)/IZO(5nm)/ITO(50nm)/IZO(5nm)/ITO(50nm), and IZO(50nm)/ITO (5nm)/IZO(50nm)/ITO(5nm)/IZO(50nm), respectively. The thickness of the intermediate layers are very small in both TCO structures. In the structure where IZO is used as an intermediate layer, many of the diffraction peaks of In2O3 were observed due to both ITO being thicker and its crystallization being higher compared to IZO at 200°C. At RT, the IZO film appears amorphous, with a broad peak observed in the 20°–35° range. However, as the deposition temperature increases, particularly at 200 °C, the (222) broad peak of the IZO film gradually becomes more pronounced, indicating an improvement in the film's crystallinity. Typically, the crystallization of IZO becomes clearly visible after 350°C. This phenomenon is studied in the paper titled [ZnO-Doped In2O3 Front Transparent Contact Enables >24.0% Silicon Heterojunction Solar Cells]. In our study, the structure where ITO is used as an intermediate layer, the IZO structure is thicker, and its crystallization is lower, resulting in only a few diffraction patterns of In2O3 being observed. The higher intensity of In2O3 diffraction peaks, compared to the single-layer IZO structure produced at 200°C, is due to the presence of the thin but highly crystalline ITO interlayer. Additionally, according to our XRD results and analyses, the crystal size of IZO is smaller than that of ITO, which supports our interpretation (see Table 2). In TCO/TCO structures, it is notable that the layer with a greater thickness and the layer that initially interacts with X-ray radiation exhibit a more dominant XRD diffraction pattern. We observe same features in our result like discussed in the following paper [Characteristics of IZO/AZO and AZO/IZO Bi-layer Transparent Conducting Thin Films Prepared by Using PLD]. In situations where X-rays cover a longer path length within the material, more atoms contribute to the X-ray scattering, leading to an elevation in the peak height or intensity of the diffraction pattern. This increase in peak height makes the diffraction peaks more distinct and easily identifiable. This change can be found – page number (6), and line (178-214). |
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Comment 3. Line 217 has an incorrect temperature scale regarding Celsius and needs to be changed. Response 3: We have made the necessary corrections to the temperature scale in the line related to Celsius. This change can be found – page number (9), and line (265).
Comment 4. The images of SEM and AFM look slightly rough, please improve it. Response 4: The SEM and AFM image quality has been meticulously improved within the limitations of the SEM and AFM system's software, without affecting the results. This change can be found – page number (8-9, 10-11), and line (264-265, 298-301). |
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Comment 5. In Figure 5, at a deposition temperature of 200 degrees Celsius, the light transmittance of ITO films is much better than that of IZO films. However, on this basis, the light transmittance of multilayer films has not been improved, does it mean that the optical properties of TCO films can be improved by simply increasing the temperature without multilayer films? Please provide a more convincing argument. Response 5: No multilayer effect has been observed in the light transmittance of all thin films; instead, the influence of temperature is clearly evident. This indicates that the changes in the optical properties of these films are primarily attributed to temperature variations rather than the presence of multiple layers. All thin films demonstrate excellent transparency in the visible and near-infrared (NIR) spectrum, ranging from 80% to 85% (glass+thin film). This makes them viable candidates for use as transparent windows in optoelectronic devices. This change can be found – page number (11-12), and line (303-329).
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Reviewer 3 Report
The paper is based on the study of optical, electrical and structural properties of ITO/IZO and IZO/ITO multilayer oxide films. The films were prepared by RF-magnetron sputtering method. The authors have done the experimental characterizations by XRD, SEM, AFM, Ellipsometer and electrical study. The paper is interesting one, but some major modifications are required before it’s acceptance for publication. So, my recommendation is Major Revision of the manuscript.
Comments:
1. The first two sentences of abstract is not required. It may be placed in Introduction section.
2. In the multilayer structure how many layers of ITO and IZO are there? Do the authors have studied the bilayer structure only? Means one ITO and on top of that IZO.
3. In room temperature, the films showed amorphous one and at 200 degree celcius, the films showed crystallinity. What is the mechanism behind this?
4. The structural parameters obtained from XRD peaks needs more discussion with Williamson-Hall plot. Refer- https://doi.org/10.1021/acsaom.2c00002; Scientific Reports 11 (21518), 1-13 (2021)
5. The scaling in Fig.3 is not visible.
6. “Generally, the multi-layer films showed lower roughness values than the single-layer films”. How do the author justify this? The change in roughness needs more elaboration-Refer ACS Applied Electronic Materials 4 (2), 856-868 (2022); Applied Physics A 126 (3), 203 (2020).
7. The roughness value variation should also corelated with the surface morphology.
8. For fig.5, the transmittance curve is very close to each other. So, the authors should put an enlarge view for a particular wavelength region to see the changes.
9. The authors have calculated the bandgap for the films which are very close to each other and same. Then the related discussion should be there for such same values.
10. The I-V discussion is to be improved further as the main focus is to study the electrical response towards solar cells. Refer- Sensors and Actuators: A. Physical 349, 114065 (2023), Physica Scripta 97 (6), 065814 (2022)
Author Response
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Author Response.docx
Reviewer 4 Report
The recommendations are enclosed here.
Comments for author File: 
Comments.pdf
Author Response
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Reviewer 5 Report
The paper presents the characterization of optical and electric performances for Indium Tin Oxide (ITO)-Indium Zinc Oxide (IZO) bilayer structures in comparison with single ITO and IZO layers commonly used as transparent conductive oxides in various optoelectronic devices, particularly in solar cells. The obtained results demonstrate that the considered approach is promising to improve the combination of optical transmission in an extended wavelength range and low electrical resistance. However, the paper lacks a consistent discussion on the following issues required to be acceptable for publication:
1. The effect of surface roughness according to Fig. 4 on the target properties should be clarified more exactly. Particularly, in Fig. 4 the roughness of layers obtained at room temperature seems lower compare to those prepared at 200°C which contradicts to the discussion regarding the improvement of the optoelectronic efficiency with the decrease of roughness and better performances for the films obtained at elevated temperature.
2. A detailed comparison of target properties between multilayer structures ITO-IZO-ITO-IZO-ITO and IZO-ITO-IZO-ITO-IZO should be provided.
3. Certain advantages (or at least comparative data) of ITO/IZO bilayer structures over the conventional ITO should be provided in respect to solar cells which characteristics are only shown for the ITO/IZO system.
4. The effect of bandgap (Eg) values on the target properties should be discussed in more detail.
Author Response
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Round 2
Reviewer 1 Report
Referee Report
On the paper “ Optical, electrical and structural properties of ITO/IZO and IZO/ITO multilayer transparent conductive oxide films deposited by RF-magnetron sputtering “ (coatings-2597910-v2) by the authors Ayse Seyhan and Emre Kartal submitted to the Coatings
Although some changes have been implemented, significant additional efforts are still needed to improve the article. Authors should be more attentive and scrupulous to the reviewer’s suggestions and additions in order to achieve the desired result quickly:
1. The authors should give in 1. Introduction and 2. Materials and Methods examples of the formation of the thin films:
(1). A.Z. Tuleushev, F.E. Harrison, A.L. Kozlovskiy, M.V. Zdorovets, Evolution of the absorption edge of PET films irradiated with Kr ions after thermal annealing and ageing, Optical Mater. 119 (2021) 111348. https://doi.org/10.1016/j.optmat.2021.111348.
2. I fully agree with the authors that: “ Transparent conductive oxide (TCO) films have been utilized in various optoelec- tronic applications due to their exceptional optical transmittance (>80 %) in the visible wavelength range (380-700nm) and favorable electrical properties (resistivity of <10-4 Ω.cm). ”. The authors should mention in 1. Introduction some results of the preparation and investigation of other substituted oxides promising for practical applications:
(2). S.V. Trukhanov, Peculiarities of the magnetic state in the system La0.70Sr0.30MnO3-γ (0 ≤ γ ≤ 0.25), J. Exp. Theor. Phys. 100 (2005) 95-105. https://doi.org/10.1134/1.1866202.
3. The proposed 2 papers should be inserted in References.
The paper should be sent to me for the third analysis after the major revisions.
Minor editing of English language required
Author Response
Please see the attachment
Author Response File: Author Response.docx
Reviewer 3 Report
The authors addressed the comments. So I would recommend the acceptance of the manuscript for publication.
Author Response
We appreciate your time and effort in reviewing this manuscript. We express our thanks for the valuable contribution provided through the comments and for accepting the publication of the paper.
Reviewer 5 Report
The authors significantly revised the paper, addressed most of the comments and demonstrated a certain increase in the efficiency of the suggested multilayer ITO-IZO-ITO-IZO-ITO structures compared to the conventional single ITO counterparts in solar cells. However, the following issues still require an improvement or clarification:
The manuscript should be properly formatted. Particularly, Table 2 is almost not readable now. The indication of all the samples in the figures captions and tables should be similar, i.e. either only TCO-I, TCO-II, etc. or only ITO, ITO-IZO-ITO-IZO-ITO, etc.
There is a contradiction in lines 521-523 “In addition, although the multilayer films seem to show higher RSH values than the single-layer films, the multilayer TCO-II_200°C film showed the highest RSH value among all films and was determined as the TCO film with the best electrical properties”. However, the best target performances must correspond to the LOWEST sheet resistance RSH providing the highest conductivity.
It is not clear why wider bandgaps are preferable for the considered applications. On the contrary, the reduction of a semiconductor bandgap provides an extension of the part of solar radiation spectrum promoting the solar cell activation.
The conclusion should be more concise.
Some minor corrections are desirable.
Author Response
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Author Response File: Author Response.docx
