Problem: Silicon has limitations as an optical material. While devices from digital cameras to x-ray detectors take advantage of its ability to absorb electromagnetic radiation, longer wavelengths of light fly right through it. If engineers could make silicon light detectors that “see” more thoroughly into the visible and infrared spectra, relatively inexpensive silicon could replace the costlier, more exotic materials often used in optoelectronics.
Solution: As a graduate student at Harvard, James Carey made thin, super-sensitive light detectors out of “black silicon”–a material discovered accidentally when his colleagues fired a laser at a silicon wafer in the presence of a sulfur-containing gas. Carey demonstrated that the process did more than turn silicon black: it also gave the material the ability to absorb the longer wavelengths of visible and infrared light that thin layers of traditional silicon can’t. What’s more, it absorbed every wavelength more efficiently than conventional silicon does.
Carey cofounded SiOnyx in Beverly, MA, to manufacture black-silicon chips for devices such as inexpensive night-vision equipment and infrared surveillance systems. Other potential applications include better cell-phone cameras and cheaper, more sensitive detectors that could lower the x-ray dose needed for advanced medical imaging. –Anne-Marie Corley