Fabrication of micron-sized tetrahedra by Si〈1 1 1〉 micromachining and retraction edge lithography

A new method is proposed to prepare micron-sized anisotropic-shaped particles: tetrahedral structures bounded by 〈1 1 1〉 faces. It is based on the micromachining of 〈1 1 1〉-oriented silicon wafers and retraction edge lithography (REL). The size of these Si structures is tunable but limited: roughly from 20 to 2000 nm. The importance of this method is that the fabricated structure resembles almost perfectly the mathematical tetrahedron. Furthermore, the technique offers room to change the anisotropic property of the particle by selective modification of the faces using self-aligned lithography. (Some figures may appear in colour only in the online journal)