From Black Silicon to Pink Silicon

MIT Technology Review reports that Harvard University researchers who first discovered black silicon are now studying a modified form of the material that has no cones but exhibits the same unique optoelectronic properties. One of black silicon's key characteristics is a forest of microscopic cones that form on its surface and give the material its black color. But the cones that cover the surface of black silicon, which are created during the high-intensity, short-pulse femtosecond laser restructuring of silicon, can cause problems - for example, by foiling bulk fabrication attempts.

SiOnyx company was founded to turn black silicon's potential into commercial devices, including high-sensitivity image sensors based on photoconductive gain. While the company's process doesn't use completely flat silicon, the SiOnyx researchers cut down the cone height from microns to about 200 nanometers to help the fabrication process and have recently demonstrated the prototype sensors.

Harvard University Prof. Mazur's lab has now added a new twist to the black-silicon production process, taking advantage of the absorption and high-gain properties of black silicon but keeping the material completely flat. That could help overcome fabrication challenges and allow for more detailed study of the material. The new material is nicknamed pink silicon.