Mechanism of Surface Hydroxylation Acceleration and Laser-Induced Damage Threshold Reduction during Ion Beam Sputtering of Fused Silica
Round 1
Reviewer 1 Report
Comments and Suggestions for Authorsline 104: what do you mean by "no obvious brittle scratches." in ductile material we use ploughing.
Line 112: Both the two surfaces of sample 1# - should be: Both surfaces of sample one
Also, is sample 1# a single sample on to which multiple tests were conducted or a series of samples? If the latter is the case, you should write samples 1#
The data in table 2 needs to be explained properly. For instance, which results pertain to samples 2# and which partial to samples 1#. What do you mean by “LIDT of non-megasonic cleaning (J/cm2)” in the procedure section all samples were described to be subjected to megasonic cleaning. You need to better explain the procedure followed and the results.
Comments on the Quality of English Language
Lines 190 -193: what you are describing is the surface energy of the material due to unused chemical bonds. Its best to use these terms instead of force fields which are not appropriate for this description.
Plasma surface activation of solids is a well-known phenomena which is used in manufacture and surface engineering of components for a long time. I suggest to use more appropriate terminology.
Author Response
The author's response to the review report can be found in the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors describe an interesting method of treating fused silica based an ion beam sputtering (IBS) and HF acid etching to make it more resistant to laser damage. It is therefore worthy of publication; however, there are some indications that must be addressed to the manuscript.
Questions:
Fused silica is a very interesting material because it has high transmittance in the UV electromagnetic spectrum and low coefficient of thermal expansion. But I consider that the authors should expand the state of the art a little more with studies carried out to highlight the resistance to laser damage or abrasion resistance such as metal coatings, as DLC (Carbon like diamond), or DLC/Si films.
1. In line 36, authors say: “many scholars internationally are committed to researching the processing methods for …” Maybe would be better to add the references at the end of the sentence, because it´s talking about the conclusions of the mentioned researchers.
2. In line 51, authors say: When IBS is used to remove a certain depth (<1000nm) of HF acid etched surface, it can reduce the concentration of ODC, NBOHC and OH- groups on… The authors should define the acronyms used in the text.
3. In line 94-98, Authors say; ..”Therefore, it is necessary to strictly control the content of OH- groups inside fused silica to improve its optical uniformity and increase its LIDT under 351 nm ultraviolet laser irradiation”. Authors should add a reference.
4. In line 112-120, Authors say; “Both the two surfaces of sample 1# were sputtered with the same removal depth of 900nm, 1500nm and 2000nm respectively before damage performance test”…. Explanation of methodology is not clear, needs to be redrafted.
5. In line 140, authors say: Infrared spectroscopy is the main means to study the structure characteristics of OH- group in fused silica, which has an absorption peak near 3660 cm in infrared spectra. Authors should add a reference.
6. In line 166, authors say: As a nondestructive test method, the photothermal weak absorption detection is directly related to the damage precursors, and reflects the damage resistance performance of optics. Authors should add a reference.
7. In line 223, authors say: “which can be expressed as:” Authors should rewrite the chemical reaction.
Author Response
The author's response to the review report can be found in the attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe reviewed manuscript is devoted to the study of the mechanism of combined process of ion beam sputtering and fluoric acid etching on the chemical structure defects of the fusуd silica and its laser damage resistance performance. Manuscript is of interest for the scientists amnd engineers working with the materials used in the different lasaer systems and can be published in the "Applied Sciences" but only after some corrections in it.
1. Some missing spaces between words etc. should be installed (for example, "12-16J/cm2" (line 40, page 1), "processes[4-8] (line 46, page 2)", "defects[9-12]" (lines 55-56, page 2) etc.).
2. All the abbreviations should be described at the first appearance in the text (ODC, NBOHC (line 52, page 2) etc. (for example, VUV, CCD)).
3. It seems, it would be better (and shorter) instead "1000 nm" write "1 mcm" etc.
4. In the end of Introduction (the last paragraph) authors shoud reference their manuscripts in which the earlier results obtained by their team were published.
5. Sentence "The absorption effect of individual defects is equivalent o that of Ce element" (lines 95-96, page 2) should be commented and explained in detail.
6. When authors described ions, they should mark their charges (F-, not F etc.).
7. What is the equipment was used for the preparation of the samples of fused silica studied in the manuscript (polishing, ultrasonic etching etc.)? Which "absolute alcohol" authors used for the drying of the samples? Note, that equipment used for studiyng of the samples, should be described in the part of Experimental Method, not in the other parts of manuscript (FTIR is described in the part of Measurement of OH- groups, photothermal weak absorption detection did not described at all).
8. Equations (1-4) should be presented in the readable form. When (2) is equation, the stoichiometry in it should be established.
9. On the Fig.5 absent the some symbols (one "O" for Si2O5- and Si2O3+, and one Si for Si2O3+). The space arrangement of atoms (ions) the structure elements of silica surface are not understandable (interatomic distances, angles etc.).
10. It should be stated from which source the information given in the lines 197-202 (page 6) was taken.
Author Response
The author's response to the review report can be found in the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThank you for improving the script and congratulation for a work well done.
In reply to your comment:
'Actually, the ion beam sputtering with ultra-low energy Ar+ is different from the plasma surface activation in use and application.'
When using IBS at 900eV, ions penetrate a few atomic layer before their impact cross section becomes large enough to create appreciable transfer of kinetic energy with the target atoms. This results in sub surface structural changes, however backscattered ions and target atoms knocked out from their lattice sites on their way out of the surface will in turn interact with the surface molecules in an analogous way of low energy ions hitting the surface. Added to this effect, is the sputter amplification of any impurity heavy atom which might be present in their path. So high energy interactions will create both surface near surface defects in the chemistry and structure.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe revised version of manuscript can be published in "Applied Sciences".
Some missing spaces between words etc. should be installed (see pages 1,2,3,5,6).
