Rich p-type-doping phenomena in boron-substituted silicene systems

The essential properties of monolayer silicene greatly enriched by boron substitutions are thoroughly explored through first-principles calculations. Delicate analyses are conducted on the highly non-uniform Moire superlattices, atom-dominated band structures, charge density distributions and atom- and orbital-decomposed van Hove singularities. The hybridized 2pz–3pz and [2s, 2px, 2py]–[3s, 3px, 3py] bondings, with orthogonal relations, are obtained from the developed theoretical framework. The red-shifted Fermi level and the modified Dirac cones/π bands/σ bands are clearly identified under various concentrations and configurations of boron-guest atoms. Our results demonstrate that the charge transfer leads to the non-uniform chemical environment that creates diverse electronic properties.

(0.001 eV). I suggested the authors correct this value accordingly and compare their results with previously reported results. 2. 100x100x1 k-points are taken which will be computationally very expensive. Authors need to comment on the same. 3. In Table 1, it is not clear that the Δ symbol represents which physical or chemical parameter? Please clarify. 4. Authors have inconsistently used the Brillouin zone and BZ throughout the manuscript. I suggest the authors introduce the abbreviation BZ in the starting and then follow it consistently. 5. Authors have mentioned about the buckling but it is not mentioned in the manuscript that how it varies with different B-concentrations in Silicene? 6. In literature, there is already a study on Silicene nano-ribbons with B/N doping, "Wang et al., J. Phys. Chem. C 2013, 117, 26, 13620-13626". Authors need to comment on how their study is different from the previous report. Also, I suggest the authors compare their results with the previous studies on this topic and should highlight their novel findings. 7. There is inconsistency in naming the 'B-atom', at few places it mentioned as a 'guest atom' but it's not clear that authors are taking about 'B atoms'. I suggest the authors clarify the confusion in the manuscript. 8. I suggest authors go through the manuscript more carefully as there are some writing issues such as spelling mistakes (e.g. Dirac coin). Also, authors have used "very interesting" throughout the manuscript more than 10 times which is not going well the flow of the manuscript.

Decision letter (RSOS-200723.R0)
We hope you are keeping well at this difficult and unusual time. We continue to value your support of the journal in these challenging circumstances. If Royal Society Open Science can assist you at all, please don't hesitate to let us know at the email address below.
Dear Professor Lin: Title: Rich p-type-doping phenomena in boron-substituted silicene systems Manuscript ID: RSOS-200723 Thank you for your submission to Royal Society Open Science. The chemistry content of Royal Society Open Science is published in collaboration with the Royal Society of Chemistry. I apologise it has taken longer than usual to send you this decision.
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Once again, thank you for submitting your manuscript to Royal Society Open Science and I look forward to receiving your revision. If you have any questions at all, please do not hesitate to get in touch. ********************************************** RSC Associate Editor: Comments to the Author: Major Revision RSC Subject Editor: Comments to the Author: (There are no comments.) ********************************************** Reviewers' Comments to Author: Reviewer: 1 Comments to the Author(s) This manuscript presents a valuable systematic investigation on the stability and electronic properties of B-Si monolayer alloy phases. The calculation method is reliable and some general trends can be summarized. The work is helpful to the understanding of the bonding in this system, for examples the B-Si bond length, buckling and charge density distributions. Some structures, for example the 1:1 honeycomb structure presents interesting electronic structure which is worth of further experimental and theoretical studies. Overall, the manuscript has a decent quality that is suitable for publication in Royal Society Open Science.
One general question is that why there is no structure with higher B density (between 50% and 100%)? As boron can itself form monolayer structure, I expect many possible structures with boron density between 50% and 100%. Especially the authors aim to present a systematic investigation on this alloy system. Can the authors fill in this gap, or at least provide their reason why they ignore this region?
Reviewer: 2 Comments to the Author(s) 1. The authors mentioned that the symbol of charge transfer from silicon to boron is due to the higher carrier density. What is the fundamental mechanism? 2. The authors did calculations of band structures of different percentages of Boron atoms in silicene. However, the percentage of B atoms is as large as 33.3%. Is this a reasonable percentage of dopant for two-dimensional materials?
Reviewer: 3 Comments to the Author(s) Authors have presented a study of two-dimensional Silicene with Boron doping. Authors have used the first-principles study to understand the effect of Boron doping on electronic structure of Silicene with varied concentrations. Authors also mentioned about the highly non-uniform Moire super-lattices, atom-dominated band structures, charge density distributions and atom-& orbitaldecomposed van Hove singularities. This study is important and will facilitate experimental investigation of electronic devices based on B-doped Silicene structures. Nevertheless, I have some concerns that should be addressed. As a summary of my report, I recommend its publication in Royal Society Open Science once the following points are taken care of.
1. The bandgap of pristine Silicene mentioned in Fig 2 (a) (0.01 eV) is not consistent with the value reported in Table 1 (0.001 eV). I suggested the authors correct this value accordingly and compare their results with previously reported results. 2. 100x100x1 k-points are taken which will be computationally very expensive. Authors need to comment on the same. 3. In Table 1, it is not clear that the Δ symbol represents which physical or chemical parameter? Please clarify. 4. Authors have inconsistently used the Brillouin zone and BZ throughout the manuscript. I suggest the authors introduce the abbreviation BZ in the starting and then follow it consistently. 5. Authors have mentioned about the buckling but it is not mentioned in the manuscript that how it varies with different B-concentrations in Silicene? 6. In literature, there is already a study on Silicene nano-ribbons with B/N doping, "Wang et al., J. Phys. Chem. C 2013, 117, 26, 13620-13626". Authors need to comment on how their study is different from the previous report. Also, I suggest the authors compare their results with the previous studies on this topic and should highlight their novel findings. 7. There is inconsistency in naming the 'B-atom', at few places it mentioned as a 'guest atom' but it's not clear that authors are taking about 'B atoms'. I suggest the authors clarify the confusion in the manuscript. 8. I suggest authors go through the manuscript more carefully as there are some writing issues such as spelling mistakes (e.g. Dirac coin). Also, authors have used "very interesting" throughout the manuscript more than 10 times which is not going well the flow of the manuscript.

Author's Response to Decision Letter for (RSOS-200723.R0)
See Appendix A.

Decision letter (RSOS-200723.R1)
We hope you are keeping well at this difficult and unusual time. We continue to value your support of the journal in these challenging circumstances. If Royal Society Open Science can assist you at all, please don't hesitate to let us know at the email address below. This manuscript presents a valuable systematic investigation on the stability and electronic properties of B-Si monolayer alloy phases. The calculation method is reliable and some general trends can be summarized. The work is helpful to the understanding of the bonding in this system, for examples the B-Si bond length, buckling and charge density distributions. Some structures, for example the 1:1 honeycomb structure presents interesting electronic structure which is worth of further experimental and theoretical studies. Overall, the manuscript has a decent quality that is suitable for publication in Royal Society Open Science.
One general question is that why there is no structure with higher B density (between 50% and 100%)? As boron can itself form monolayer structure, I expect many possible structures with boron density between 50% and 100%. Especially the authors aim to present a systematic investigation on this alloy system. Can the authors fill in this gap, or at least provide their reason why they ignore this region?
Reply: Thanks for your comments. Regarding the issue raised by the reviewer, we would like to explain as follows: 1. In fact, we are able to compute configurations at high concentrations as suggested by the reviewers. However, based on the results calculated in 12 cases, we can Appendix A easily predict the properties of the configurations between 50% and 100% Bsubstituted concentration. The red-shift Fermi level and modified Dirac cone might clearly be identified. Boron and silicon atoms, respectively, possess three and four valence electrons that will lead the p-type doping and create plenty of free hole near the Fermi level. The pi and sigma energy bands due to [2pz-3pz] and [2s, 2px, 2py -3s, 3px, 3py] might well-separated and are able define the pi and sigma bandwidths. This feature implies that we can simulate first-principle results by the tight-binding model and when it succeeds, the varied fundamental properties could be explored fully in future studies, such as the rich and unique magnetic quantization phenomena, the quantum spin Hall effect, Coulomb excitation, and optical properties [1,2]. That is also the importance of this study.
2. In the experimental side, in recent studies on chemical absorption and substitution of Nitrogen on graphene [3], the highest guest-atom concentration that can be reached is 26% wt. Apparently, synthesizing structures at high concentrations such as 50%, 100% seems to be very challenged. However, our research is a theoretical study, we need to set many concentrations and configurations whether one of them is ideal. This also implies that in practice, we should focus our attention on configurations with low concentrations instead of high ones.

Reviewer: 2
Comments to the Author(s) 1. The authors mentioned that the symbol of charge transfer from silicon to boron is due to the higher carrier density. What is the fundamental mechanism?
Reply: The charge transfer from silicon atom to boron atom can be realized by many features. The observable red area is located around the boron-guest atom. The increase of Si-Si bond lengths after substitution. For example, the longer Si-Si bond length in substitution systems compare with the pristine case implies that charges from Silicone atom transfer to Boron one and make the binding between Si-Si becomes weaker, therefore, these bond lengths become longer. These features of charge transfer might be closely related to the strong affinity of the boron atoms.
2. The authors did calculations of band structures of different percentages of Boron atoms in silicene. However, the percentage of B atoms is as large as 33.3%. Is this a reasonable percentage of dopant for two-dimensional materials? Reply: In fact, the emergence of recent synthetic experiments shown that few-layer graphene systems can be produced by various methods, e.g., mechanical exfoliation and molecular vapor deposition. However, 2D silicene systems can be generated only with the molecular beam epitaxy (MBE). Moreover, in recent studies on chemical absorption and substitution of N on graphene [3], the highest guest-atom concentration that can be reached is 26% wt. Nevertheless, our research is a theoretical study, we need to set many concentrations and configurations whether one of them is ideal.

Reviewer: 3
Comments to the Author(s) Authors have presented a study of two-dimensional Silicene with Boron doping. Authors have used the first-principles study to understand the effect of Boron doping on electronic structure of Silicene with varied concentrations. Authors also mentioned about the highly non-uniform Moire super-lattices, atom-dominated band structures, charge density distributions and atom-& orbital-decomposed van Hove singularities. This study is important and will facilitate experimental investigation of electronic devices based on Bdoped Silicene structures. Nevertheless, I have some concerns that should be addressed. As a summary of my report, I recommend its publication in Royal Society Open Science once the following points are taken care of.
1. The bandgap of pristine Silicene mentioned in Fig 2 (a) (0.01 eV) is not consistent with the value reported in Table 1 (0.001 eV). I suggested the authors correct this value accordingly and compare their results with previously reported results.