Large plasmonic absorption enhancement effect of triangular silver nanowires in silicon

Two-dimensional finite difference time domain (FDTD) simulations were performed for evaluating optical absorption enhancement and loss effects of triangular silver (Ag) nanowires embedded in silicon (Si) thin-film photovoltaic device structures. Near-bandgap absorption enhancement in Si was much larger than the reported values of other nanostructures from similar simulations. A nanowire with equal sides of 20 nm length showed 368-fold absorption enhancement whereas only 5× and 15× values of solid spherical and two-dimensional core-shell type nanostructures, respectively. Undesirable absorption loss in the metal of the nanowire was 3.55× larger than the absorption in Si which was comparable to the value reported for the spherical nanoparticle. Interestingly, as the height of the nanowire was increased to form a sharper tip, absorption loss showed a significant drop. For a nanowire with 20 nm base and 20 nm height, absorption loss was merely 1.91× larger than the absorption in Si at the 840 nm plasmon resonance. This drop could be attributed to weaker plasmon resonance manifested by lower metallic absorption in the spatial absorption map of the nanowire. However, absorption enhancement in Si was still large due to strong plasmonic fields at the sharper and longer tip, which was effective in enhancing absorption over a larger area in Si. Our work shows that the shape of a nanostructure and its optimization can significantly affect plasmonic absorption enhancement and loss performance in photovoltaic applications.

2. The authors mentioned the absorption is related with the electric field intensity and the imaginary component of the refractive index of the material in Line 42 Page 2. References should be added here. 3. For Simulation Methodology, the excitation mode of TFST source should be added in the Fig. 1. 4. There is a redundant (a) in the lower Fig. 1, please delete it. 5. Fig. 3 is called 'Log scale spatial absorption maps of the nanowires', while the absorption is corresponded with wavelength, which is not show in this figure. And generally, the 'Log scale' is related with electric field enhancement instead of absorption. Can the authors explain your definition in Fig. 3 more clearly and deeply? 6. It is better to show a line plot of the enhancement in Fig. 3 in order to compare the different enhancement performances more easily.

13-Mar-2020
Dear Dr Sabuktgin: Title: Large Plasmonic Absorption Enhancement Effect of Triangular Silver Nanowires in Silicon Manuscript ID: RSOS-191926 Thank you for submitting the above manuscript to Royal Society Open Science. On behalf of the Editors and the Royal Society of Chemistry, I am pleased to inform you that your manuscript will be accepted for publication in Royal Society Open Science subject to minor revision in accordance with the referee suggestions. Please find the reviewers' comments at the end of this email.
The reviewers and handling editors have recommended publication, but also suggest some minor revisions to your manuscript. Therefore, I invite you to respond to the comments and revise your manuscript.
Please also include the following statements alongside the other end statements. As we cannot publish your manuscript without these end statements included, if you feel that a given heading is not relevant to your paper, please nevertheless include the heading and explicitly state that it is not relevant to your work. We have included a screenshot example of the end statements for reference.
• Acknowledgements Please acknowledge anyone who contributed to the study but did not meet the authorship criteria.
• Funding statement Please include a funding section after your main text which lists the source of funding for each author.
Because the schedule for publication is very tight, it is a condition of publication that you submit the revised version of your manuscript before 22-Mar-2020. Please note that the revision deadline will expire at 00.00am on this date. If you do not think you will be able to meet this date please let me know immediately.
To revise your manuscript, log into https://mc.manuscriptcentral.com/rsos and enter your Author Centre, where you will find your manuscript title listed under "Manuscripts with Decisions". Under "Actions," click on "Create a Revision." You will be unable to make your revisions on the originally submitted version of the manuscript. Instead, revise your manuscript and upload a new version through your Author Centre.
When submitting your revised manuscript, you will be able to respond to the comments made by the referees and upload a file "Response to Referees" in "Section 6 -File Upload". You can use this to document any changes you make to the original manuscript. In order to expedite the processing of the revised manuscript, please be as specific as possible in your response to the referees.
When uploading your revised files please make sure that you have: 1) A text file of the manuscript (tex, txt, rtf, docx or doc), references, tables (including captions) and figure captions. Do not upload a PDF as your "Main Document".
2) A separate electronic file of each figure (EPS or print-quality PDF preferred (either format should be produced directly from original creation package), or original software format) 3) Included a 100 word media summary of your paper when requested at submission. Please ensure you have entered correct contact details (email, institution and telephone) in your user account 4) Included the raw data to support the claims made in your paper. You can either include your data as electronic supplementary material or upload to a repository and include the relevant doi within your manuscript 5) All supplementary materials accompanying an accepted article will be treated as in their final form. Note that the Royal Society will neither edit nor typeset supplementary material and it will be hosted as provided. Please ensure that the supplementary material includes the paper details where possible (authors, article title, journal name).
Supplementary files will be published alongside the paper on the journal website and posted on the online figshare repository (https://figshare.com). The heading and legend provided for each supplementary file during the submission process will be used to create the figshare page, so please ensure these are accurate and informative so that your files can be found in searches. Files on figshare will be made available approximately one week before the accompanying article so that the supplementary material can be attributed a unique DOI. ********************************************** RSC Associate Editor: Comments to the Author: (There are no comments.) RSC Subject Editor: Comments to the Author: (There are no comments.) ********************************************** Reviewer comments to Author: Reviewer: 1 Comments to the Author(s) This manuscript reports plasmonic absorption enhancement of triangular silver nanowires in silicon calculated by 2D FDTD simulations. The absorption enhancement of triangular silver nanowires is much larger than solid spherical nanoparticles and core-shell nanowires. Triangular nanowire with equal edge size of 20 nm showed 368 fold absorption enhancement and 3.55 times absorption loss at 863 nm. Increasing the sharpness of the corner resulted in reduced absorption loss. This work provides useful information on the shape-related plasmonic absorption enhancement and absorption loss, and will contribute to the design of photovoltaic devices. It can be published in Royal Society Open Science after marking the sizes of the objects in Figure 1.

Reviewer: 2
Comments to the Author(s) The authors reported on the absorption enhancement and loss effects of a nanostructure composed of triangular silver nanowires embedded in silicon thin film. The calculations were finished by two dimensional FDTD simulations. Two kinds of triangular silver nanowires were employed, equilateral nanowire and bilateral nanowire, the heights of which are 17.5 nm and 20 nm, respectively. The two nanowires both show large absorption enhancement effects, while the bilateral shows lower absorption loss effect. The results may be published after minor revision according to the following points. It is a pleasure to accept your manuscript in its current form for publication in Royal Society Open Science. The chemistry content of Royal Society Open Science is published in collaboration with the Royal Society of Chemistry. I am sorry it has taken longer than usual to be able to send you this decision.
The comments of the reviewer(s) who reviewed your manuscript are included at the end of this email.
Thank you for your fine contribution. On behalf of the Editors of Royal Society Open Science and the Royal Society of Chemistry, I look forward to your continued contributions to the Journal. We sincerely apologise for any delays with the review and processing of your manuscript. However, we are happy to report that your manuscript can now be published as is.
With best regards, Tobias Hertel Associate Editor, RSOS RSC Subject Editor: Comments to the Author: (There are no comments.) ********* Reviewer(s)' Comments to Author: Reviewer: 2 Comments to the Author(s) The authors addressed all of my questions.