Radiation-induced paramagnetic defects in porous silicon under He and Ar ion irradiation

Abstract

A study of damage and the concentration of radiation-induced paramagnetic defects by He+ and Ar+ ion beam irradiation in porous silicon is presented. Porous silicon layers were fabricated and irradiated with beams of noble gases ions. The shift in a crystalline phase line in Raman spectra was used to estimate the size of nanocrystallites in the structure of porous silicon at different irradiation fluences. Electron paramagnetic resonance measurements were conducted to obtain the fluence dependence of the spin concentration in the porous structure after ion implantation. The concentration of paramagnetic defects (dangling bonds) in porous silicon was found to be monotonically dependent on ion irradiation fluence and reached the value of 1021 cm−3. A comparison of the defect formation rate in bulk and porous silicon is shown, the extreme spin concentration in porous silicon is estimated. The potential application of ion beam irradiations to enhance the efficiency of porous silicon-based contrasts agents in magnetic resonance imaging is discussed.