Round 1

Reviewer 1 Report

The manuscript titled “Mesostructure and magnetic properties of SiO2(Co) granular film on silicon substrate” by Natalia A. Grigoryeva et. al. Its interesting piece of experimental results. But completely lack scientific writing, presentation and analysis. In addition, there are serious English mistakes majority part of the work. At this stage, the manuscript need to submitted after major revision.

1.       The author using symbol for Cobalt nanoparticle in the matrix of SiO2 is confusing. In title, it need to mentioned specifically in writing not SiO2(Co).

2.       In abstract, no mention about motivation of the work.

3.       Flaw in the sentence grammatically and technically need to be written “to find a reason for this difference in IMR coefficient”

4.       In abstract GF is not defined,  “GF and Si substrate”

5.       Unable to read due to poor scientific writing and English mistakes: It is shown that the interface layer between the GF and Si substrate reveals non-magnetic but metallic properties and eliminates the GIMR effect. This interface layer is associated with the Si diffusion to Co nanoparticles and formation of the metallic cobalt silicides.

6.       How can you define something for granular film in more general way? “Granular films (GF) are nanocomposites that consist of metallic magnetic nanoparticles incorporated in an insulating matrix.”

7.       Lacks basic introduction, motivaton and elaboration about granular film. Hard to read it.

8.       Are you writing thesis or journal paper? The paper is organized in the following way. Chapter 2 gives details of the sample preparation and experimental results supplied by different methods to reveal structural and magnetic properties. Chapter 3 provides discussion and interpretation of the combined results.

9.       What peculiarities?  “All peculiarities of the sputtering method and choice of components are described in Ref. [12]”

1.    What is the resolution of SEM? In figure 1, you seem to show high resolution or artifacts.

1.    The whole manuscript need to be rewritten without flawless English mistakes with scientific writing style.

Comments for author File: Comments.pdf

Author Response

Open Review

(x) I would not like to sign my review report
( ) I would like to sign my review report

English language and style

(x) Extensive editing of English language and style required
( ) Moderate English changes required
( ) English language and style are fine/minor spell check required
( ) I don't feel qualified to judge about the English language and style

	Yes	Can be improved	Must be improved	Not applicable
Does the introduction provide sufficient background and include all relevant references?	( )	( )	(x)	( )
Are all the cited references relevant to the research?	( )	( )	(x)	( )
Is the research design appropriate?	(x)	( )	( )	( )
Are the methods adequately described?	(x)	( )	( )	( )
Are the results clearly presented?	( )	( )	(x)	( )
Are the conclusions supported by the results?	( )	( )	(x)	( )

Comments and Suggestions for Authors

The manuscript titled “Mesostructure and magnetic properties of SiO2(Co) granular film on silicon substrate” by Natalia A. Grigoryeva et. al. Its interesting piece of experimental results. But completely lack scientific writing, presentation and analysis. In addition, there are serious English mistakes majority part of the work. At this stage, the manuscript need to submitted after major revision.

1. Referee question: The author using symbol for Cobalt nanoparticle in the matrix of SiO2 is confusing. In title, it need to mentioned specifically in writing not SiO2(Co).

Author's answer: High value of the IMR effect in SiO2(Co)/GaAs heterostructures (GIMR) was observed and explained by the theoretical model in Ref. 8 and 9 by L.V. Lutsev. Symbol "SiO2(Co)" for Cobalt nanoparticle in the matrix of SiO2 was introduced in these articles since 2005.

We suppose, that most readers may not be aware of this, so we propose changing the Тitle:

“Mesostructure and magnetic properties of SiO$_2$-Co granular film on silicon substrate”

 

We attach the following references in confirmation of wide using "SiO2 -- Co":

1. Xiaoli Li, Yanchun Li, Yana Shi, Fanfan Du, Yuhao Bai, Zhiyong Quan, Xiaohong Xu. (2017) Electrically-controlled resistance and magnetoresistance in a SiO₂-Co film. Materials Letters 194, 227-230. Online publication date: 1-May-2017.
2. Fanfan Du, Yanchun Li, Xiaoli Li, Jie Yang, Yuhao Bai, Zhiyong Quan, Chunli Liu, Xiaohong Xu. (2019) Resistive switching and its modulating ferromagnetism and magnetoresistance of a ZnO-Co/SiO₂-Co film. Journal of Magnetism and Magnetic Materials 489, 165445.
   Online publication date: 1-Nov-2019.
3. Kravets, V.G., Poperenko, L.V. Magnetooptical properties of Co-SiO2granular films. Opt. Spectrosc. 104, 610–614 (2008). https://doi.org/10.1134/S0030400X08040206

4. S. Honda and Y. Yamamoto Tunneling magnetoresistance in ultrathin Co–SiO₂ granular films Journal of Applied Physics 93, 7936 (2003); https://doi.org/10.1063/1.1555832

 

2.Referee question: In abstract, no mention about motivation of the work.

Author's answer: The abstract is re-written:

Granular films SiO$_2$(Co) exhibit unusual magnetic and magnetotransport properties which are strongly dependent on the composition of the film and material of a substrate. For example, the injection magnetoresistance (IMR) coefficient reaches a giant (GIMR) value of 10$^5$\% at the room temperature in SiO$_2$(Co) films on n-GaAs substrate. However, the IMR effect is negligible in the case of a similar granular film deposited on the n-Si substrate.  In this report the structural and magnetic properties of granular film SiO$_2$(Co) on Si substrate are studied with the aim to understand the cause of difference in IMR coefficients for SiO$_2$(Co) thin film deposited on n-GaAs and on n-Si substrates. Investigations were carried out using complementary methods of Polarized Neutron Reflectometry, Grazing Incidence Small-Angle X-ray Scattering, X-Ray Reflectometry, Scanning Electron Microscope, and SQUID magnetometry. It is shown that the interface layer between the granular film and Si substrate exhibits metallic rather than magnetic properties and eliminates the GIMR effect. This interface layer is associated with the Si diffusion to Co nanoparticles and formation of the metallic cobalt silicides.

3.Referee question: Flaw in the sentence grammatically and technically need to be written “to find a reason for this difference in IMR coefficient”

Author's answer: Appropriate changes have been made to the abstract.

4.Referee question: In abstract GF is not defined,  “GF and Si substrate”

Author's answer: Appropriate changes have been made to the abstract.

5.Referee question: Unable to read due to poor scientific writing and English mistakes: It is shown that the interface layer between the GF and Si substrate reveals non-magnetic but metallic properties and eliminates the GIMR effect. This interface layer is associated with the Si diffusion to Co nanoparticles and formation of the metallic cobalt silicides.

Author's answer: We agree with the referee's remark. Appropriate changes have been made to the article:

It is shown that the interface layer between the granular film and Si substrate exhibits metallic rather than magnetic properties and eliminates the GIMR effect. This interface layer is associated with the Si diffusion to Co nanoparticles and formation of the metallic cobalt silicides.

6.Referee question: How can you define something for granular film in more general way? “Granular films (GF) are nanocomposites that consist of metallic magnetic nanoparticles incorporated in an insulating matrix.”

Author's answer: It seems redundant to add more references. But if the referee sees fit, we can add the following:

1. B. Dieny, S. Sankar, M.R. McCartney, D.J. Smith, P. Bayle-Guillemaud, A.E. Berkowitz, Spin-dependent tunneling in discontinuous metal/insulator multilayers, Journal of Magnetism and Magnetic Materials, 185(3),1998, 283-292. doi.org/10.1016/S0304-8853(98)00028-6},
2. Lutsev, L.V., Kalinin, Y.E., Sitnikov, A.V. et al. Electron transport in granular amorphous silicon dioxide films with ferromagnetic nanoparticles placed in a magnetic field. Phys. Solid State 44, 1889–1897 (2002). https://doi.org/10.1134/1.1514778
3. Aronzon, B.A., Kovalev, D.Y., Varfolomeev, A.E. et al. Conductivity, magnetoresistance, and the Hall effect in granular Fe/SiO2 films. Phys. Solid State 41, 857–863 (1999). https://doi.org/10.1134/1.1130891
4. Varfolomeev, A.E., Sedova, M.V. Large positive magnetoresistance effect in metal-insulator nanocomposites in weak magnetic fields. Phys. Solid State 45, 529–533 (2003). https://doi.org/10.1134/1.1562242
5. S. Mitani, K. Takanashi, K. Yakushiji, and H. Fujimori, Anomalous behavior of temperature and bias-voltage dependence of tunnel-type giant magnetoresistance in insulating granular systems, Journal of Applied Physics, 83, 6524 (1998). doi.org/10.1063/1.367649
6. K. Yakushiji, S. Mitani, K. Takanashi, J.-G. Ha, H. Fujimori, Composition dependence of particle size distribution and giant magnetoresistance in Co-Al-O granular films, 212(1), 75-81 (2000). https://doi.org/10.1016/S0304-8853(99)00813-6.

7.Referee question: Lacks basic introduction, motivaton and elaboration about granular film. Hard to read it.

Author's answer: For a better understanding of the motivaton, the necessary accents and references have been added to the article.

The references about granular film elaboration are also given.

We understand that neutron and synchrotron methods are much more challenging to understand than electron microscopy methods, for example.

8.Referee question: Are you writing thesis or journal paper? The paper is organized in the following way. Chapter 2 gives details of the sample preparation and experimental results supplied by different methods to reveal structural and magnetic properties. Chapter 3 provides discussion and interpretation of the combined results.

Author's answer: We agree with the referee's remark. Appropriate changes have been made to the article:

“The paper is organized in the following way. Section 2 gives details of the sample preparation and experimental results obtained by different methods to reveal structural and magnetic properties. Section 3 provides a discussion and interpretation of the results combined. A combination of different methods makes it possible to build a model explaining the negligible value of GIMR effect, providing that almost all structural and magnetic properties of GF are practically the same for the films disposed on GaAs and Si substrates. It is shown that the interface layer between the GF and Si substrate shows metallic rather than magnetic properties and eliminates the GIMR effect. This interface layer is associated with the Si diffusion to Co nanoparticles and the formation of metallic cobalt silicides. Section 4 is the conclusion.“

9.Referee question: What peculiarities?  “All peculiarities of the sputtering method and choice of components are described in Ref. [12]”

Author's answer: We agree with the referee's remark. Appropriate changes have been made to the article:

“The sputtering method and choice of components are described in Ref. [12]» (Line   73-74)

10. Referee question: What is the resolution of SEM? In figure 1, you seem to show high resolution or artifacts.

Author's answer: The next changes have been made to the article: “Field Emission SEM (FE-SEM) Zeiss Leo 1530 capable of 2.5 nanometer resolution equipped with In-Lens secondary electron detector has been used.” (Line   93-95)

11. Referee question: The whole manuscript need to be rewritten without flawless English mistakes with scientific writing style.

Author's answer: We are grateful for carefully reading the article by referee. We hope that our additional work on the text was fruitful.

 

 

 

 

Reviewer 2 Report

1-     Line 52: Chapter 2 in this paper? Possibly part 2

2-     Line 54: Chapter 3? Part 3

3-     In SEM image (figure 1), it would be better that authors address the type of detector (Secondary or Backscatter).

4-     Line 68: authors mentioned that the concentration of cobalt set by the ratio of cobalt and target area. This kind of measurements is not accurate enough to be rely on. EDS measurements is necessary.

5-     The SEM image is located in experiment part. While it is necessary to place in results.

6-     Authors should explain which type of SEM instrument has been used for measurements and do EDX for presence of Si and Co.

7-     Line 89: there isn’t any cross-section of cobalt in the paper

8-     Line 207: Authors mentioned particle size by SEM is clearly visible. However, it is not.

9-     There isn’t any strong evidence to support authors statement on formation of thin film on Si.

Looking at the cross- section using SEM or TEM will help

10-  The conclusion should be re-written.

 

11-  There are a plenty of typo mistake in paper for example:284- Fo, 355: studed 

Author Response

Open Review

( ) I would not like to sign my review report
(x) I would like to sign my review report

English language and style

( ) Extensive editing of English language and style required
( ) Moderate English changes required
(x) English language and style are fine/minor spell check required
( ) I don't feel qualified to judge about the English language and style

	Yes	Can be improved	Must be improved	Not applicable
Does the introduction provide sufficient background and include all relevant references?	( )	(x)	( )	( )
Are all the cited references relevant to the research?	( )	(x)	( )	( )
Is the research design appropriate?	( )	( )	(x)	( )
Are the methods adequately described?	( )	(x)	( )	( )
Are the results clearly presented?	( )	( )	(x)	( )
Are the conclusions supported by the results?	( )	( )	(x)	( )

Comments and Suggestions for Authors

1- Referee question: Line 52: Chapter 2 in this paper? Possibly part 2

Author's answer: We agree with the referee's remark. Appropriate changes have been made to the article.

2-Referee question: Line 54: Chapter 3? Part 3

Author's answer:  We agree with the referee's remark. Appropriate changes have been made to the article.

3-Referee question: In SEM image (figure 1), it would be better that authors address the type of detector (Secondary or Backscatter).

Author's answer:  The next changes have been made to the article: “Field Emission SEM (FE-SEM) Zeiss Leo 1530 capable of 2.5 nanometer resolution equipped with In-Lens secondary electron detector has been used.” (Line   93-95)

4-Referee question: Line 68: authors mentioned that the concentration of cobalt set by the ratio of cobalt and target area. This kind of measurements is not accurate enough to be rely on. EDS measurements is necessary.

Author's answer:  We agree with the referee's that EDS method defined concentration of cobalt more accurate. However, this is not essential for achieving the aim of the article, since all studied concentrations of ferromagnetic cobalt granules in a diamagnetic silicon oxide matrix correspond to samples with mixed conductivity. When the electrical conductivity is due to percolation along the metallic maze and electron tunneling between isolated metal particles.

The next changes have been made to the article :

“A detailed description of the characteristics of granular films is given in Ref. [8].” (Line   74-75)

5-Referee question: The SEM image is located in experiment part. While it is necessary to place in results.

Author's answer:  The SEM images are located in Experiment part cause images are done on purpose to attestate the geometric characteristics of the object of study. It confirms the objects under study belong to the class of GFs demonstrating  semiconductor-like (intermediate) properties as metal particles with increase in x becomes interconnected to form a maze structure.

Whereas the purpose of the article is to study the structural and magnetic properties of granular films. What are the Results part about. We suggest leaving the SEM images in the Experimental part.

6-Referee question: Authors should explain which type of SEM instrument has been used for measurements and do EDX for presence of Si and Co.

Author's answer:  EDX measurement for the presence of Si and Co is outside the scope of this article. A description of the characteristics of the samples can be found in Ref. L.V. Lutsev, A.I. Stognij, N.N. Novitskii, Giant magnetoresistance in semiconductor/granular film heterostructures with cobalt nanoparticles. Physical Review B, v. 80, 2009, 184423.

The next changes have been made to the article:

“Field Emission SEM (FE-SEM) Zeiss Leo 1530 capable of 2.5 nanometer resolution equipped with In-Lens secondary electron detector has been used.” (Line     93-95)

“The more characteristics of granular films is given in Ref. [8].” (Line  74-75)

 

7-Referee question: Line 89: there isn’t any cross-section of cobalt in the paper

Author's answer: The average cross-section of cobalt nanoparticles is determined by SEM (Fig.1).

The next changes have been made to the article:

“ The average size of cobalt nanoparticles has been obtained from a set of linear measurements using ImageJ software and equals about 75 $\pm $ 15 \AA. The microscope achieves a resolution of approx. 1 nm.” (Line  95-97)

 

8-Referee question: Line 207: Authors mentioned particle size by SEM is clearly visible. However, it is not.

Author's answer: In the article literally says: “As one can see, the value of $l_1$ obtained by GISAXS matches very well the particle size observed by SEM on the top surface of GF where percolation is clearly visible (Fig.1).”

We additionally specified, that "the average size of cobalt nanoparticles has been obtained from a set of linear measurements using ImageJ software." (Line   95-96)

9-Referee question: There isn’t any strong evidence to support authors statement on formation of thin film on Si.

Looking at the cross- section using SEM or TEM will help

Author's answer: The authors disagree with the referee that SEM or TEM will help in this case. Figure 1 shows that light contrast corresponds to SiO$_2$ matrix and dark areas correspond to Co nanoparticles. Diffusion of silicon atoms from the substrate into adjacent cobalt particles will only change the gray scale in the "black/white" contrast at the interface. Because not a continuous film of the metallic cobalt silicides is formed on the interface, but a mixture of the metallic cobalt silicides and SiO$_2$ matrix. For the same reason, EDS or EDX measurements will also not be informative.

Yes, there is not strong evidence to support the authors statement on formation of thin film on Si, other than the dramatic difference in IMR coefficient for SiO$_2$(Co) thin film deposited on GaAs-substrate and on Si-substrate. That in itself is a strong proof of our assumption.

 

10-Referee question: The conclusion should be re-written.

Author's answer:  We agree with the referee's remark.  The conclusion is re-written:

            In the present paper we studied the structure and magnetic properties of the maze structure with interconnected cobalt particles SiO$_2$(x at.\% Co) deposited on Si substrate at 54 at.\% $\leq $ x $\leq $ 82 at.\%).  Investigations were carried using Polarized Neutron Reflectometry, Grazing Incidence Small Angle X-ray Scattering, X-Ray Reflectometry, Scanning Electron Microscopy, and Superconducting Quantum Interference Device Magnetometry.

             The reason for the dramatic difference in IMR coefficients for SiO$_2$(x at.\% Co) heterostructures deposited on GaAs, or Si substrates was established. Despite the fact that both granular films have a very similar values of the thickness, the interparticle distances, magnetizations, as well as the additional layer of Co at the interface granular film/substrate, there is a difference  in the interface morphology for SiO$_2$(x at.\% Co)/Si.  On the interface granular film/Si substrate there is boundary interlayer diffusion of Si atoms into Co, leading to the formation of an interface of variable binary composition - cobalt silicides. The formation of cobalt silicide at the GF/Si interface leads to the conductivity of the granular film determined by the electron movement via chains "ferromagnetic granule (Co) - metal (Co -Si) - semiconductor (Si)", and not by electron tunnelling between ferromagnetic granules through the SiO$_2$ dielectric matrix into the Si semiconductor. A high value of the GIMR effect  in SiO$_2$(x at.\% Co) on GaAs \cite{Lutsev_2009,Lutsev_2017} substrate is probably related with the spin-dependent potential barrier formed in the accumulation electron layer in the semiconductor near the interface. The action of the spin-dependent potential barrier is amplified by the avalanche process and by the electron accumulation in the quantum well in the semiconductor interface region induced by the backscattering process of injected electrons on exchange-split levels \cite{Lutsev_2017}.  In the granular film SiO$_2$(x at.\% Co) on Si substrate the cobalt silicide does not allow the formation of the region  at the GF/Si interface saturated with electrons capable of polarizing in the direction of the applied magnetic field. Therefore further efforts to form a quantum well with exchange-split levels on the well top at the surface of Si are necessary to gain a high positive magnetoresistance in SiO$_2$(x at.\% Co)/Si geterostructure. For example, this can be achieved by introducing a buer layer between the granular film and substrate \cite{Fan_2012,Volkov_2013}.

11-Referee question: There are a plenty of typo mistake in paper for example:284- Fo, 355: studed 

Author's answer: We agree with the referee's remark. Appropriate changes have been made to the article.

Round 2

Reviewer 1 Report

Authors have addressed all my comments properly and sincerely. I recommend it for publication in the present form.