The Annealing Kinetics of Defects in CVD Diamond Irradiated by Xe Ions
, Vladimir N. Kuzovkov 1, Aleksandr Lushchik 2, Anatoli I. Popov 1, Evgeni Shablonin 2, Theo Scherer 3 and Evgeni Vasil’chenko 2Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsDear authors,
Sorry, the whole idea of the manuscript is wrong. The ion-irradiated layer is extremely non-uniform in terms of the defect composition and the defect concentration. It is especially critical for heavy ion irradiation with energies which you use (about 1 MeV/amu). The mechanisms of the defect production change from almost totally electronic (ionization) at the surface to almost totally nuclear (atomic collisions). It is highly incorrect to apply the diffusion models developed for uniform media to the very non-uniform objects like ion-irradiated layers. There is no such a thing like “average defect concentration” in ion irradiated layers. Besides, the mechanical stress in the diamond layers implanted with high energy heavy ions are very non-uniform, may reach a value of a few GPa. Moreover, the stress may even change its sign, that is it may vary from compression to expansion, through the depth. The stress of this magnitude would affect the diffusion strongly. This fact is well known from the diffusion of nitrogen in diamond. Sorry, although you show sort of “convincing” match between the experiment and the theory, the presented description is highly speculative and does not correspond to the reality.
Below, please see some specific comments.
1. Most of the diamond properties reviewed in Introduction has no relevance to the research presented in the manuscript. Please, review only the relevant information.
2. “…while narrow bands around 2.5 eV (see also Figure 4 for details) are related to radiation-induced vacancies located nearby substitutional nitrogen atoms (tentatively, H3 and H4 centers”
Comment: The lines 2.46 eV and 2.53 eV are not H3 and N4 centers. 2.46 eV line is ZPL and 2.53 eV is the first vibrational replica of the well-known intrinsic 3H center which relates to carbon interstitials. The annealing behavior of these lines shown in Fig. 5 in your manuscript is very common for 3H center.
3. “…by moving the reactor with the sample out of the furnace…”
Comment: reactor???
4. “There is obvious transformation with temperature of substitutional N atoms connected with the radiation-induced vacancy.”
Comment: There are no any nitrogen-related centers in your spectra. In order to create H3 center in the irradiated well nitrogen-doped CVD diamond annealing must be at temperature at least 1400C. In regular CVD diamonds which are not intentionally doped with nitrogen the intensity of H3 center is not enough to be seen in absorption. It can be detected in luminescence only. H4 center does not form in CVD diamonds.
5. “Figure 6 shows the difference spectra that represent the decrease of RIOA due to the preheating of the irradiated CVD diamond (1013 Xe/cm2) from T1 to T2.”
Comment: I do not understand what you mean by the preheating from temperature T1 to temperature T2. How is it different from regular annealing at temperatures T1 and T2.
6. “(vacancy-interstitial, denoted here as F and H centers”
Comment: Are F and H defects different? Vacancies and interstitials?
7. “As is well known, the mobility of interstitials is orders of magnitude greater than that of vacancies”
Comment: Please, give the reference.
8. “D0 = 10-3 cm2 s-1 (a typical estimate used for standard diffusion in solids)”
Comment: Diamond is very different from all other solids in terms of diffusion. Please compare the chosen value of diffusion constant with the values known for diamond: e.g. diffusion of vacancies, interstitials and nitrogen. I am sure Do is much smaller.
9. “defect concentration n0 = 1017 cm-3 (estimated in the saturation region)”
Comment: Why 1e17 cm-3? Where did you get the value from? What is the saturation region?
10. “We proceed from the assumed (mainly in order of magnitude) parameter values: R = 10-7 cm (a value on the order of the lattice constant);”
Comment: What is R? What is the physical meaning of R? Why it should be comparable with the lattice constant? Why lattice constant is a parameter of diffusion?
11. What is the physical meaning of the X parameter?
12. The activation energies of vacancies and interstitials in diamond have been studied rather well. The diffusion of vacancies in diamond has been studied intensively too. Please compare your data with those already published.
13. Why did you use polycrystalline samples? Why not a regular single crystal? Since the samples are polycrystalline, you have to discuss the possible contribution of the surface diffusion.
Comments on the Quality of English LanguageQuality of English is acceptable.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe paper reports on the study of defect kinematics in fast heavy ion irradiated polycrystalline diamond. Optical absorption spectra recorded at different temperatures were used to identify and quantify radiation-induced defects and their migration energies.
The paper is well-structured and the results are presented clearly. The authors have provided an appropriate theoretical background for the analysis of "annealing curves" as well as a sound discussion about the main results. I suggest several points that should be considered before the paper is accepted for publication.
1. In the introduction, the authors mention examples (solar cells - lines 68-71, larger macromolecular structures - lines 79-81) that are not supported by references. Please add appropriate references.
2. In the last paragraph of the introduction authors claim that "only effects of the high energy electron irradiation were discussed". It is not clear what effects they refer to, as several radiation damage studies are reported in diamond crystals and devices, including fast heavy ions. Please expand on this paragraph, by clarifying the original statement and providing additional references if needed.
3. On line 159 it is stated that the sample is heated to a high temperature in steps lasting 5 minutes. This annealing time is quite low, as many previous works indicated that annealing processes should last on the order of hours to be effective. Authors should comment on this important point, and provide additional context for a reader in the main text about annealing time.
4. On lines 173-175 authors state that "obvious transformation" of substitutional N with radiation-induced vacancies occurs. Do you feel that it is appropriate to provide additional comments and/or references to the reader to support this statement?
5. Table 1 reports on the results of the fitting to the data in annealing curves. Relevant values, especially migration energy must be given with uncertainties! Appropriate comments on the uncertainty values should be added also. This is the most important point that needs improvement.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript by Kotomin et al. covers the experimental work and theoretical modelling on the annealing kinetics of defects in CVD diamond after irradiation by xenon ions. The results presented in the manuscript are novel and fascinating, however some improvements must be made before the acceptance for publication. Here are several points for authors to consider:
Line 35: For a better framing of authors work they might consider expanding on the technology of “electronic cyclotron heating system”, since it seems to be the prime application of the CVD diamond disks. What temperatures and fluence are the diamond disks supposed to withstand? Are there any recent reports of them being tested in fusion reactors? What technologies are currently used for this purpose in fusion reactor prototypes?
Lines 44 – 48: Please consider providing references for recent synthesis advances. Here are several suggestions: doi.org/10.1016/j.carbon.2024.118839, https://doi.org/10.1016/j.diamond.2024.111169,
Lines 65 – 67: Please consider adding references for boron-doped diamonds used as biomedical agents. Here are some articles to choose from: doi.org/10.3390/nano13243124, doi/10.1002/adom.202200631, doi.org/10.3390/ma16175942.
Line 117: Is the in Figure 1 really that necessary? Maybe just mention that absorption of low energy photons is due to defects produced during the fabrication stage? Authors also might want to trim the energy axis to 5.5 eV in order to demonstrate the difference in “background absorption” of the studied samples more clearly.
Line 162: Are absorption spectra measured during or after the preheating? If spectral measurements are conducted during the heating authors may consider presenting the apparatus for such procedure.
Line 191: The statement on loss of optical transparency in lines 191 - 193 should be cited. The manuscript suggests that optical density of the sample is in inverse ratio with preheating temperature, hence the statement does not seem natural.
Line 194: Authors may want to expand on degradation of specimen. Is it the graphitization of the crystal struture? Or are there more complex reasons to it?
Line 215: Please consider aligning the formulas to the center of the page. Also, it would be best to retype the calculations in specified software (i.e. LaTeX or EndNote).
Line 287: Diamond lattice constant is reported to be an order of magnitude higher. [DOI: 10.1107/S0021889875010965]
Line 288: Authors may consider citing the information on standard diffusion in solids.
Line 289: Please consider expanding on the estimation of defects concentration.
Line 293: Please consider providing some statistical proof for the statement ‘works quite well’. In order to do that authors may want to provide data points with error bars.
Lines 299 – 301: The temperature interval is indeed not large enough. As far as can be understood from the manuscript, the reason for that is samples degradation. Authors might consider proposing a way to overcome that issue and the reasons for it.
Lines 312 – 313: What could be the reason for this anomalous diffusion? Could it be the fact that authors do not consider D_H parameter? Thus, two-component diffusion is described by a single component model.
Overall, I suggest accepting the manuscript after major revision. Good luck!
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe changes made make the manuscript acceptable for publication in its present state.
Comments on the Quality of English LanguageEnglish is acceptable.
