Fabrication of Radially Symmetric Graded Porous Silicon using a Novel Cell Design

A contactless method using a novel design of the experimental cell for formation of porous silicon with morphological gradient is reported. Fabricated porous silicon layers show a large distribution in porosity, pore size and depth along the radius of the samples. Symmetrical arrangements of morphology gradient were successfully formulated radially on porous films and the formation was attributed to decreasing current density radially inward on the silicon surface exposed to Triton(®) X-100 containing HF based etchant solution. Increasing the surfactant concentration increases the pore depth gradient but has a reverse effect on the pore size distribution. Interestingly, when dimethyl sulfoxide was used instead of Triton(®) X-100 in the etchant solution, no such morphological gradients were observed and a homogeneous porous film was formed.