Picosecond dynamics of photoexcited carriers in silicon nanocrystal/Si3N4 superlattices: Presence of K centers

Abstract

We report in detail on the picosecond dynamics of photoexcited charge carriers in size-controlled silicon nanocrystals in silicon nanocrystal/Si3N4 superlattices. The samples were prepared using plasma enhanced chemical vapor deposition and subsequent thermally induced phase separation. The pump and probe transmission technique was used to monitor directly the initial (picosecond) carrier dynamics. The transient transmission signal (decay time about 2 ps) was found to be independent of the nanocrystal size, pump pulse intensity and wavelength from the interval 400 to 700 nm. The signal is attributed to the dynamics of photoexcited carriers captured on the K0 centers in Si3N4.

The effect of oxide shell thickness on the structural, electronic, and optical properties of Si-SiO2 core-shell nano-crystals: A (time dependent)density functional theory study

“…1 Furthermore, the possibility of the band-gap engineering in the strong confinement regime (r < a Bohr ) 2-5 renders silicon NC as a promising candidate for photovoltaics and optoelectronics. [6][7][8][9] Quantum confinement effects on the optical properties of silicon NCs have been studied for the first time with intense visible-light emission from porous silicon. 10 However, because of numerous inter-related parameters including interfacial stress, 11,12 defects, 13,14 suboxide species, [15][16][17] and the chemistry, [18][19][20] and geometry [21][22][23] of the NC's surface, the electronic and optical properties are still a subject of debate.…”