Charge spectroscopy of SiO2 layers with embedded silicon nanocrystals modified by irradiation with high-energy ions

Abstract

The method of charge deep-level transient spectroscopy (Q-DLTS) is used to study and compare the ejection of charge carriers from silicon nanocrystals (NCs) located in an ordered or random way in the SiO2 matrix. It is shown that, in all cases, this ejection is a thermally activated process. The parameters of energy barriers characterizing the processes of ejection of charge carriers from the levels of nanocrystals in the layers NCs:SiO2 before (random distribution) and after their modification by irradiation with high-energy ions (ordered distribution of nanocrystals) are determined. It is found that the activation energies for ejection of charge carriers from nanocrystals and the size of nanocrystals estimated from the difference between energies of two levels observed by the Q-DLTS method decrease as the ion fluence is increased. The density of nanocrystals observed by the Q-DLTS method decreases by approximately an order of magnitude as a result of irradiation with fluence of 1012–1013 cm−2 in comparison with an initial unirradiated structure; this decrease is due to formation of conducting chains of nanocrystals in tracks.