Nano Lett. 12, 4200–4205 (2012)

The origin of photoluminescence from silicon nanocrystals has been a controversial topic for many years. In an attempt to gain a better understanding of the mechanisms involved, Daniel Hannah and coworkers in the United States have now performed a series of experiments to investigate the part that pressure plays. Samples of alkane-terminated, plasma-synthesized silicon nanocrystals (2.6 or 4.6 nm in diameter) were placed into a diamond anvil cell and both X-ray diffraction and photoluminescence data were collected as functions of pressure up to 73 GPa. The data suggest that the bright emission from the nanocrystals originates from an Xconduction-to-Γvalence transition associated with silicon's bulk properties rather than from defects, as has been postulated previously. The researchers also comment that the transition remains highly indirect despite quantum confinement effects.