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| <sup>{{fn|1}}</sup> Measured by Eric Jensen from DTU-Nanotech, October 2013. | | <sup>{{fn|1}}</sup> Measured by Eric Jensen from DTU-Nanotech, October 2013. |
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| ===Definition of structures===
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| Due to the almost inert (111)-planes it is possible by KOH etching to realize high aspect ratio structures in sigle crytalline silicon using the (111)-planes as sidewalls. In Si(100) these sidewalls are inclined - 54.7<sup>o</sup> with respect to the (100) surface - whereas in Si(110) the sidewalls are vertical (see figures below).
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| <gallery caption="Anisotropic wet silicon etch: dependency on crystal orientation" widths="380px" heights="150px" perrow="2">
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| Image:KOH_Anisotropy.jpg|Etched profile when etching Si(100).
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| Image:KOH_Anisotropy(110).jpg|Etched profile when etching Si(110).
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| </gallery>
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| For Si(100), the relation between the width of the bottom of the etched groove (W<sub>b</sub>) and the width of the opening (W<sub>o</sub>) at the wafer surface in a groove etched to the depth l is given by:
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| <math>W_b = W_o - 2lcot(54.7^o) = W_o - \sqrt{2} l</math>
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