@article{karoui_karoui_2010, title={A density functional theory study of the atomic structure, formation energy, and vibrational properties of nitrogen-vacancy-oxygen defects in silicon}, volume={108}, ISSN={["1089-7550"]}, DOI={10.1063/1.3387912}, abstractNote={The atomic structure, energy, stability, vibrational spectra, and infrared absorption intensities of major intrinsic nitrogen-related defects in nitrogen doped silicon crystals have been investigated using ab initio density functional theory and semi-empirical quantum mechanics methods. The defects that are of interest are nitrogen-vacancy-oxygen complexes which are believed to affect oxygen precipitation and void formation as well as nitrogen concentration measurement in nitrogen-doped silicon. Several chemical reactions involving nitrogen, Si vacancies and oxygen interstitial have been studied. After relaxation, the local vibrational modes of each complex are calculated within the harmonic oscillator approximation and the infrared absorption intensities are evaluated from the dipole moment derivatives. By cross correlating the stability and the infrared active lines of the defect, and taking into consideration the symmetry group of each complex, we were able to emphasize which nitrogen related complexes are likely to control the oxygen precipitation and voids formation and to assert a new calibration relationship for nitrogen concentration measurement in nitrogen doped Czochralski and float zone silicon wafers.}, number={3}, journal={JOURNAL OF APPLIED PHYSICS}, author={Karoui, F. Sahtout and Karoui, A.}, year={2010}, month={Aug} }
 @article{karoui_karoui_rozgonyi_hourai_sueoka_2004, title={Characterization of nucleation sites in nitrogen doped czochralski silicon by density functional theory and molecular mechanics}, volume={95-96}, DOI={10.4028/www.scientific.net/ssp.95-96.99}, abstractNote={Extended defect nucleation and growth in nitrogen doped Czochralski silicon crystals are investigated in terms of trapping vacancy and oxygen atoms by ni trogen-pairs using molecular mechanics. The results have been correlated to the formation ener gy and stability of nitrogen-vacancyoxygen complexes obtained by ab-initio density functional theory. We found that N2 in a split interstitial position and V2N2 when formed from VN2 are very stable and have a strong affinity for oxygen, whereas the interaction energy between these defects and vacanc ies is weak. VN2 can only be weakly coupled to oxygen atoms, whereas it reconstructs into stable V 2N2 by trapping a vacancy. These results are in agreement with the degree of stability of nitrogen-vacancy-ox ygen complexes and indicate that N 2 and V2N2 are nucleation centers for oxygen precipitation rather than for void formation.}, number={2004}, journal={Diffusion and Defect Data. [Pt. B], Solid State Phenomena}, author={Karoui, F. S. and Karoui, A. and Rozgonyi, G. A. and Hourai, M. and Sueoka, K.}, year={2004}, pages={99–104} }
 @article{karoui_karoui_rozgonyi_yang_2004, title={Oxygen precipitation in nitrogen doped Czochralski silicon wafers. I. Formation mechanisms of near-surface and bulk defects}, volume={96}, ISSN={["1089-7550"]}, DOI={10.1063/1.1773921}, abstractNote={Defect size distributions in nitrogen-doped Czochralski (N-CZ) silicon wafers were obtained using an oxygen precipitate profiler and Wright-Jenkins etching. These showed unique depth dependence in low-high and high-low-high cycled N-CZ wafers. Unique phenomena observed include a high defect concentration at the subsurface that decreases within the top 2μm of the so-called denuded zone. In contrast to N-free CZ Si for which the first high step annealing dissolves the grown-in defects, these appeared to be stable in N-CZ Si. As a result, the defect size distribution in the bulk was found to be independent of the annealing cycle. It was also found that the depth dependent defect concentration correlates well with oxygen and strongly with nitrogen secondary ion mass spectroscopy profiles, suggesting that nitrogen is the leading impurity in the defect formation processes even though introduced at very low concentration. Nitrogen appeared to effectively modify the nucleation regime by a drastic increase of the nuclei density. At low temperature under external stress, nitrogen and oxygen cosegregate to the surface where the stress is applied; such a phenomenon is largely increased at high temperature.}, number={6}, journal={JOURNAL OF APPLIED PHYSICS}, author={Karoui, A and Karoui, FS and Rozgonyi, GA and Yang, D}, year={2004}, month={Sep}, pages={3255–3263} }
 @article{karoui_karoui_rozgonyi_hourai_sueoka_2003, title={Structure, energetics, and thermal stability of nitrogen-vacancy-related defects in nitrogen doped silicon}, volume={150}, ISSN={["1945-7111"]}, DOI={10.1149/1.1621418}, abstractNote={The electronic structure, formation energy, and thermal stability of nitrogen-vacancy related complexes in silicon have been investigated using density functional theory and semi-empirical Hartree-Fock calculations. The calculated energies of formation in the ground state showed that VN 2 was not stable, whereas V 2 N 2 when formed from VN 2 was the most stable, followed by N 2 and V 2 N 2 formed from a divacancy. The calculated free energy changes of the considered chemical reactions confirmed the low stability of VN 2 compared to V 2 N 2 . The latter can form during crystal growth from VN 2 , whereas reactions between N 2 and divacancy can also occur upon wafer heating. At low nitrogen concentration (∼5 X 10 13 cm -3 ), only about 10% of vacancy concentration was converted into VN 2 , while at a high nitrogen concentration (∼10 16 cm -3 ) about 75% of vacancies are trapped by nitrogen. V 2 N 2 appeared to create a potential well of -2.4 eV for oxygen and about -0.3 eV for vacancies, suggesting that the stable V 2 N 2 is a nucleus for oxygen precipitation while it is a weak trapping center for vacancies.}, number={12}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Karoui, A and Karoui, FS and Rozgonyi, GA and Hourai, M and Sueoka, K}, year={2003}, month={Dec}, pages={G771–G777} }