The modification of Si nanocrystallites embedded in a dielectric matrix by high energy ion irradiation
We have followed the effects of heavy ion irradiation on the structural, electrical, and photoluminescence properties of ensembles of silicon nanocrystallites embedded in a dielectric (SiO2) matrix. This was done as a function of the irradiation dose and the content of the Si phase. The results obtained can be accounted for self-consistently assuming that a relatively small dose of the irradiation enhances the crystallization while for higher doses the irradiation enhances the amorphization. The corresponding processes suggest that tuning of the above properties can be achieved by swift heavy ion irradiation.
Swift heavy ion induced growth of nanocrystalline silicon in silicon oxide
Recystallization of nanocrystalline silicon in silicon oxide has been initiated with swift heavy ion irradiation. 100 MeV Ni ions from pelletron were used for irradiating the thin films of silicon oxide (SiOx) at fluences varying from 1×1012 to 5×1013 ions/cm2. Phase separation between silicon and silicon oxide is seen to be responsible for the photoluminescence spectrum peaking around 350 and 610 nm. This spectral nature is understood on the basis of defects and interface states in SiOx matrix and silicon nanocrystals, respectively. The formation of silicon nanocrystals resulting from the phase separation has been confirmed from the complimentary evidence of change in the refractive index, Fourier transform infrared spectroscopy, and energy despersive x-ray analysis. High electronic loss associated with the 100 MeV Ni ions is thought to be responsible for the recrystallization, and rearrangement of silicon.
Strong ultraviolet photoluminescence from silicon oxide films prepared by magnetron sputtering
Intense ultraviolet photoluminescence centered at 370 nm was observed from magnetron-sputtered silicon oxide films after they were annealed at about 1000 °C in N2 atmosphere. This photoluminescence is found to be associated with the formation of nanocrystal silicon particles in the specially structured SiO2, which highly resembles the oxide layer of porous silicon. The luminescence centers at the interface between the nanocrystal silicon particles and the SiO2 matrix are responsible for the strong ultraviolet luminescence.