Stabilizing the surface of porous silicon opens application avenues

March 1, 1998

Purdue University (West Lafayette, IN) researchers have developed a novel approach to producing highly stable porous-silicon surfaces using Lewis acid-catalyzed hydrosilylation. Porous silicon has a micron-thick porous surface layer that can be made to emit light--stabilizing this surface is important because it opens u¥the possibility of developing silicon-based chemical sensors, electroluminescent displays, photodetectors, and a matrix for photopumped tunable lasers.

Jillian Buriak and Matthew Allen report a mild and general approach for covalent modification of the surface through ethyl aluminum dichloride mediated hydrosilylation of alkynes and alkenes. This yields surface-bound vinyl and alkyl groups, respectively. In other words, the process creates a greasy coating that protects the surface and allows the porous silicon to maintain its photoluminescent properties. The method is tolerant of a wide variety of functional groups, as demonstrated by the formation of nitrile-, hydroxy-, and ester-terminated surfaces. The researchers showed that porous silicon functionalized with hydrophobic groups was able to withstand boiling aerated water and potassium hydroxide with a pH of 10. No oxidation and only minor changes in the surface infrared spectra were noted, whereas unfunctionalized porous silicon would have been dissolved.