Transient Photoinduced Absorption in Ultrathin As-grown Nanocrystalline Silicon Films
1 Department of Physics, Research Center of Ultrafast Science, University of Cyprus, P.O. Box 20537, Nicosia, 1678, Cyprus
2 Solid State Physics Section, Department of Physics, Aristotle University of Thessaloniki, Thessaloniki, 541 24, Greece
Nanoscale Research Letters 2007, 3:1-5 doi:10.1007/s11671-007-9105-1Published: 27 November 2007
We have studied ultrafast carrier dynamics in nanocrystalline silicon films with thickness of a few nanometers where boundary-related states and quantum confinement play an important role. Transient non-degenerated photoinduced absorption measurements have been employed to investigate the effects of grain boundaries and quantum confinement on the relaxation dynamics of photogenerated carriers. An observed long initial rise of the photoinduced absorption for the thicker films agrees well with the existence of boundary-related states acting as fast traps. With decreasing the thickness of material, the relaxation dynamics become faster since the density of boundary-related states increases. Furthermore, probing with longer wavelengths we are able to time-resolve optical paths with faster relaxations. This fact is strongly correlated with probing in different points of the first Brillouin zone of the band structure of these materials.