In 1999, Harvard researchers used laser pulses to etch the surface of silicon, the most common substance used in electronic devices. By accident, they created a material that efficiently traps light. Called black silicon, it holds amazing potential for efficiently converting sunlight to electricity, for communicating by light, and for monitoring the environment for evidence of pollution and global warming. Now, a Harvard graduate student has discovered another use for black silicon. When placed in a strong electric field, the substance emits electrons with surprising efficiency. Since many electronic devices depend on beams of electrons to operate, the new discovery by James Carey, a graduate student in Harvard’s Division of Engineering and Applied Sciences, is sparking intense interest over its possible commercial applications. Such applications include ultra-thin television screens, ultra-sensitive pollution monitors, and even satellite maneuvering systems.