Di-interstitial defect in silicon revisited

Infrared spectroscopy was used to study the defect spectrum of Cz-Si samples following fast neutron irradiation. We mainly focus on the band at 533 cm-1, which disappears from the spectra at ∼170 °C, exhibiting similar thermal stability with the Si-P6 electron paramagnetic resonance (EPR) spectrum previously correlated with the di-interstitial defect. The suggested structural model of this defect comprises of two self-interstitial atoms located symmetrically around a lattice site Si atom. The band anneals out following a first-order kinetics with an activation energy of 0.88 ± 0.3 eV. This value does not deviate considerably from previously quoted experimental and theoretical values for the di-interstitial defect. The present results indicate that the 533 cm-1 IR band originates from the same structure as that of the Si-P6 EPR spectrum. © 2013 AIP Publishing LLC

Infrared signals correlated with self-interstitial clusters in neutron-irradiated silicon

Using infrared spectroscopy we have investigated the defect spectrum of neutron-irradiated Czochralski-silicon (Cz-Si). The study was focused on three weak signals, mainly on a band at 533 cm-1, as well as on two other bands at 582 and 592 cm-1. The band at 533 cm-1 disappears from the spectra at ~170 C exhibiting similar thermal stability with the Si-P6 electron paramagnetic resonance spectrum, previously correlated with a di-interstitial defect. The suggested model for the latter defect, comprising two self-interstitials placed symmetrically a lattice site Si atom, is very similar with that of the allene molecule. This allowed the calculation of the vibrational frequency of the suggested di-interstitial structure giving a value close to the 533 cm-1, in further support of the above assignment. The band at 582 cm-1 is stable up to 550 C. The possible correlation of its origin to large self-interstitial clusters is examined. Also, the origin of the 592 cm-1 band, which is stable up to 200 C is discussed, with indications tentatively pointing to a CV pair. © 2013 Springer Science+Business Media New York

Localised vibrational mode spectroscopy studies of self-interstitial clusters in neutron irradiated silicon

The evolution of self-interstitial clusters in silicon (Si), produced by fast neutron irradiation of silicon crystals followed by anneals up to 750 degrees C, is investigated using localised vibrational mode spectroscopy. A band at 582 cm(-1) appears after irradiation and is stable up to 550 degrees C was attributed to small self-interstitial clusters (I-n, n <= 4), with the most probable candidate the I-4 structure. Two bands at 713 and 758 cm(-1) arising in the spectra upon annealing of the 582 cm(-1) band and surviving up to similar to 750 degrees C were correlated with larger interstitial clusters (I-n, 5 <= n <= 8), with the most probable candidate the I-8 structure or/and with chainlike defects which are precursors of the 311 extended defects. The results illustrate the presence of different interstitial clusters I-n, at the various temperature intervals of the material, in the course of an isochronal anneal sequence. As the annealing temperature increases, they evolve from first-order structures with a small number of self-interstitials (I-n, n <= 4) for the temperatures 50 < T < 550 degrees C, to second order structures (I-n, 5 <= n <= 8) with a larger number of interstitials, for the temperatures 550 < T < 750 degrees C. (C) 2013 AIP Publishing LLC

Experimental and theoretical study of the C4 defect in neutron irradiated silicon

This work reports infrared spectroscopy studies in neutron irradiated Cz-Si containing carbon. The material was thermally treated at high temperature prior to irradiation. The aim was to investigate the production and annealing of the CiOi(SiI) defect, well-known as C4 center. Besides the two standard localized vibrational modes (LVMs) at 934 and 1018 cm-1 detected always in room temperature measurements, another band was also detected at 760 cm-1. The latter band has the same annealing behavior as the 934 and 1018 cm-1 bands. Its existence has been predicted by theoretical calculations previously, but it has not been reported definitely so far experimentally. The present study verifies unambiguously its presence. Upon annealing the above three bands begin to decay in the spectra at ∼140 °C and disappear at ∼200 °C. No other bands appear to arise in the spectra upon the disappearance of the above bands. Semi-empirical calculations of the LVM frequencies of the C4 complex verify the correlation of the 760 cm-1 band with this center. The annealing kinetics of the bands was investigated, and it was found that their decay follows a second order reaction with an average activation energy of E ∼ 0.50 ± 0.02 eV. © 2018 Author(s)

The COV defect in neutron irradiated silicon: An infrared spectroscopy study

We report infrared (IR) spectroscopy studies on defects in carbon containing neutron irradiated Czochralski grown silicon (Cz-Si). Prior to irradiation the material was subjected to high temperature treatments (HT) at 1000 °C. Two weak bands at 842 and 852 cm−1 were mainly investigated. It was found that their intensity depends on the oxygen and carbon content of Si. Additionally, the bands exhibit an annealing behavior similar to that of the 3942 cm−1 optical band of the carbon-oxygen-vacancy (COV) complex, previously reported in electron irradiated Si. Semi-empirical calculations of the local vibration mode (LVM) frequencies of a proposed structure of the COV complex are in very good agreement with our experimental data. These findings led us to assign the pair of bands at 842 and 852 cm−1 to the COV defect. © 2017 Elsevier Lt

The Ci(SiI)n defect in neutron-irradiated silicon

We report experimental results in neutron-irradiated silicon containing carbon. Initially, carbon interstitial (Ci) defects form and readily associate with self-interstitials in the course of irradiation leading to the production of Ci(SiI) defects and upon annealing to the sequential formation of Ci(SiI)n complexes. Infrared spectroscopy measurements report the detection of two localized vibrational bands at 953 and 960 cm−1 related to the Ci(SiI) defect. The thermal stability and annealing kinetics of the defect are discussed. The decay out of the two bands occurs in the temperature range of 130–200 °C. They follow second-order kinetics with an activation energy of 0.93 eV. No other bands were detected to grow in the spectra upon their annealing. Density functional theory calculations were used to investigate the structure and the energetics of the Ci(SiI) and the Ci(SiI)2 defects. © 2019, Springer Science+Business Media, LLC, part of Springer Nature