Figure 6 .

Fabrication of 3D woodpile structures. (a) Range of protons in silicon as a function of proton energy from SRIM calculation. (b) Regions with high defect density at four different depths using four energies with accurate alignment (dashed line demonstrates the silicon wires of the fourth layer is located half of period with respect to the second layer). (c) SEM image of the initial result on a two-layer structure.