Review Reports - Towards Investigating Surface Quality of Single-Crystal Silicon Optics Polished with Different Processes

Round 1

Reviewer 1 Report

1. The authors performed a series of cleaning and etching experiments, that utilized an organic solvent or weak alkali solutions, on single crystal silicon optics polished using various processes. Additionally, the surface morphology and roughness of the samples were measured by a white-light interferometer to evaluate the surface quality of the silicon optics.
2. The results showed that the organic solvent cleaning process could successfully eliminate the surface contamination resulting from the environment as well as the near-surface polishing-introduced impurities. However, the fractured defects in the subsurface layer of the optics could not be removed.
3. The corresponding methodology of cleaning and characterization is capable of serving as a predictive tool to evaluate the level of polishing and the laser damage resistance of single crystal silicon optics.
4. The manuscript has 12 pages; the length of the manuscript should be increased.
1. Tables 1, 2, and 3 should be demonstrated in detail.
For example, in Table1, it is described that all the cleaning procedures were conducted in a seven-frequency (40 kHz, 80 kHz, 120 kHz, 140 kHz, 170 kHz, 220 kHz, and 270 kHz) ultrasonic cleaning machine. It need to discussed some conditions in the cleaning and drying processes.
1. Figure 1 should be demonstrated in detail. Figure 1 is the original picture of your laboratory, or is from a reference, it needs to be explained clearly. In addition, the paper should describe and discuss how to minimize these damage precursors to produce high-quality single crystal silicon optics.
2. The comparison and discussion between Figure 8 and Figure 9 require further description. Although vendor B is consistent, Vendor A, E and F are not. The author needs to discuss it carefully.
3. Please revise and enhance the English writing to increase readability.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript describes the effects of chemical cleaning on silicon with specific observations on subsurface defects. The paper is fairly well written with well-presented figures and concepts. The conclusions of the paper could greatly benefit from applying the same analysis to all methods applied, e.i. ToF-SIMS to the alki cleaned samples.

Figure 2 could be improved please see the attached PDF for more comments.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The manuscript by Sun et al. reported characterization of single-crystal silicon surface after various polishing processes followed by cleaning and etching tests using laser-induced scattering (SC) and photothermal weak absorption imaging together with white light interferometry to evaluate the surface quality. These results are of scientific interest. However, several problems were found in the text and must be clarified to improve the paper’s quality.

1) The most critical question is the novelty of the work. Well-known measuring techniques are used to investigate the subsurface damage after the cleaning process of silicon. Authors need to improve the motivation of their study at introduction significantly.

2) There are many wet-chemical etch recipes known for etching silicon. The authors need to explain the usage of these two specified techniques (organic and weak alkali solvents). The value of etching speed is expected as well.

3) A self-developed laser-induced SC microscopy system was employed to perform the study; however, its description is minimal without any references or scheme of the experimental setup. The same is true for a photothermal weak absorption imaging system.

4) “… the SC features obtained by laser-induced SC imaging could initially exhibit the polishing quality of the single crystal silicon optics.” This sentence seems to be too obvious. Another question here is, what are the benefits of SC imaging compared to dark-field microscopy, which is a cheaper technique?

5) Reporting a surface roughness, various parameters (such as arithmetical mean deviation R_a, root mean squared R_q …), and different lengths of assessed profile. Therefore, authors need to specify it.

6) More concrete conclusions about the connection between polishing processes and surface quality are expected.

7) Some minor problems are found through the text:

Figure 1 caption includes the value of laser intensity, not fluence;
Figure 2 does not contain any scale bar;
“For the vender F polished sample …”, should be vendorж
The scales in Figure 7 are too small.

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

Thanks for this opportunity to review this manuscript entitled “Towards Investigating Surface Quality of Single Crystal Silicon Optics Polished With Different Processes”. Authors have well discussed the single crystal surface polishing methodologies using different techniques. This manuscript is well designed for publication in Coatings. However, some of the following modifications need to be carried out before publication.

Authors should summarize the possible methodology for surface polishing process with clear advantageous.
Should discuss the corrosion/fracture development and their low impact during the polishing.
The recent findings should be discussed with valuable points in the introduction section.