With laser interference lithography it is easily possible to reduce pore sizesa in microsieves to the nanometer regime, herewith giving birth to "nanosieves" . A known technique to pattern surfaces on a substrate is to evaporate a material through a thin membrane (shadow mask) with well-defined openings  (see Figs. 42 and 43). It is also well known to use such shadow masks as a poor man's technique to make patterns on a substrate if photolacquer patterned layers are too elaborate or not wanted. Shadow masks with nanosized perforations may therefore be used in applications such as ion beam etching , electron beam patterning, near field optics, etc. Reactive ion etching through a shadow mask can be used for direct etching  of a (nano)pattern in a substrate (for example metal or polymeric foils).
Self-assembly (Nano)mask Preparation The micro/ nanopattern may for instance be formed by using particles with a uniform size, for example a silica dispersion or a latex suspension, with particle sizes ranging from 5 nm to 5 /m.
This suspensions may directly be formed on a substrate with use of a spin coating or evaporation technique. A more or less ordered distribution of particles will then be found in the pattern forming layer on the support. After the evaporation of the solvent of the suspension a very thin metal layer (e.g., a 10 nm chromium layer) may be deposited (e.g., by means of vapor deposition, i.e., sputtering or evaporation) on the substrate and on top of the particles, for example silica particles with a diameter of 30 nm. The silica particles are then solved in a buffered HF solution and a perforated chromium layer remains with perforations of approximately 20-30 nm in diameter depending on the chromium deposition conditions (correction for shadow effect of deposition). The chromium layer may be used as a membrane layer or alternatively as a mask layer for the (dry) etching of a membrane layer underneath the chromium layer (see Fig. 41).
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