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J. Eur. Opt. Society-Rapid Publ. 22, 51( 2026)
Figure
2. Approach of calculating theoretical surface topographies with progressive etching given for simplified 2D-plots:( A) Surface normal direction( blue arrows) as a function of the initial profile resulting in the new profile after isotropic removal and( B) development of a V-shaped groove for increasing removal depths.
Figure 3. Flow chart.
Figure 4. Initial topography measurement of indentation of Sample # 1showing its lateral extent and depth. measurement, is determined. Previous studies have shown that the maximum SSD occurs where the first derivative of this determining variable, plotted over the etching depth, shows a sign change [ 22 ]. Consequently, after each etching step, the slope S VV is calculated using equation( 4), where VV is the void volume and d the etching depth.
S VV ¼ VV PJE n
� VV PJEn�1 ð4Þ d PJEn � d PJEn�1
The SSD depth is given where the slope S VV of the void volume is at its maximum. The determination of the SSD depth given in equation( 5) is finally based on maximum Sv and etching depth d.
SSD ½ lm
Š ¼ Svðmax ðS VV ÞÞþd ðmax ðS VV ÞÞ ð5Þ
We postulate that isotropic etching occurs when there is no longer any SSD, or conversely as long as anisotropic etching is present, SSD still exists. The disturbed bulk behaves like an impure material that undergoes anisotropic etching using PJE. Figures 5A – 5D exemplarily show the case of a fully isotropic removal, where the measurement is nearly identical to the calculated topography( see Figs. 5B and 5C). In the case of anisotropic removal shown as a representative example in Figures 5E – 5H, a discrepancy between experimental results and the calculated topography is