The processes of the formation and annealing of VnOm (n, m ≥ 2) vacancy–oxygen complexes in Czochralski silicon crystals irradiated with fast electrons and reactor neutrons have been studied by infrared absorption Fourier spectroscopy. A number of arguments are presented in favor of identification of absorption bands at 829.3 and 844.2 cm–1 as being related to local vibrational modes of V2O2 and V3O2 complexes, respectively.

AbstractThe processes of the formation and annealing of V_ n O_ m ( n , m ≥ 2) vacancy–oxygen complexes in Czochralski silicon crystals irradiated with fast electrons and reactor neutrons have been studied by infrared absorption Fourier spectroscopy. A number of arguments are presented in favor of identification of absorption bands at 829.3 and 844.2 cm^–1 as being related to local vibrational modes of V_2O_2 and V_3O_2 complexes, respectively.

In the present work, we report local vibrational mode (LVM) related absorption lines which are assigned to the complex incorporating interstitial boron and interstitial oxygen atoms (B i O i ), a possible precursor of the center responsible for light‐induced degradation (LID) in solar cells produced from boron‐doped oxygen‐rich silicon. Fourier transform infrared absorption (IR) spectroscopy was used for detection and analysis of absorption lines due to defects which were created in boron‐doped Czochralski‐grown Si samples by irradiation with 6 or 10 MeV electrons at room temperature. Changes in the IR absorption spectra upon isochronal annealing of the irradiated samples in the temperature range 75–225 °C have also been monitored. A set of previously unreported LVM lines with the same formation and elimination behavior has been studied. The most intense lines of the set are found to be at 991, 721, and 550 cm −1 . On the basis of an analysis of changes in intensity of the lines with the concentrations of impurities in the silicon and on the similarity of their annealing features with those for the DLTS signal due to the B i O i center, it is argued that the lines are related to the LVMs of this defect. The positions of the lines have been compared with the previously reported LVMs derived from ab initio modeling calculations for different configurations of the B i O i complex. A configuration having calculated LVMs close to those determined experimentally has been found and the origins of the modes are discussed.

The processes of formation and annealing of vacancy–oxygen-related V n O m complexes in Czochralski-grown silicon crystals irradiated with fast electrons have been investigated by means of low-temperature IR Fourier spectroscopy. A number of arguments are presented confirming the identification of the vibrational absorption band at 829.3 cm –1 as arising from the V 2 O 2 defect.

Various approaches are used to determine the position of the local vibrational modes (LVM) of 28 Si– 16 O s – 29 Si and 28 Si– 16 O s – 30 Si quasimolecules (O s is a substitutional oxygen atom). An analysis of published data serves as a basis for determining the geometry (internal angle α = 62°) of the Si–O s –Si quasimolecule and the interaction mass m * = 4.035 amu, and the isotopic shifts of the LVM: 1.6 cm −1 for 28 Si– 16 O s – 29 Si and 3.1 cm −1 for 28 Si– 16 O s – 30 Si relative to the basic band of 28 Si– 16 O s – 28 Si near 835.8 cm −1 . A statistical approach is used to calculate the relative intensity of the absorption bands for the different isotopic modifications of the structural unit Si–O s –Si in natural silicon. The isotopic shifts of the corresponding modes are estimated by fitting the shape of the absorption band for the vacancy-oxygen complex in irradiated Si crystals.

In the present work we have exploited different kinds of defect engineering (hydrogenation, irradiations at elevated temperatures etc) to enhance the formation of small oxygen clusters in Si crystals grown by the Czochralski technique. In these ways we manage to increase significantly the concentration of a defect giving rise to a local vibrational mode (LVM) band at 1006 cm(-1). The highest concentration of the defect is achieved in samples first enriched with the vacancy-trioxygen complex (VO3) and then electron irradiated. It is found that an interaction of the radiation-induced Si self-interstitials with VO3 occurs, so resulting in the appearance of a complex incorporating three interstitial oxygen atoms. The results obtained give strong support for the assignment of the 1006 cm(-1) band to the oxygen trimer. Three LVM bands positioned at 537, 723 and 1020 cm(-1) are found to develop in a similar way to the 1006 cm(-1) band and all of them are suggested to arise from the trimer. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

It is widely believed that the light induced degradation of crystalline silicon solar cells is due to the formation of a BsO2i recombination center created by the optically excited migration of the oxygen dimer (charge-state-driven motion). In this letter the concentration dependence of the neutral state of O2i on [Oi] in p- and n-type Cz–Si has been determined using infrared absorption. A systematic search for the absorption signature of the dimer in the doubly positively charged state has been unsuccessful. These data strongly suggest that charge-state-driven motion (Bourgoin–Corbett mechanism) of the oxygen dimer cannot occur in typical solar silicon and hence bring into question the accepted degradation mechanism.