Comparative Analysis of Process of Diffusion of Interstitial Oxygen Atoms and Interstitial Hydrogen Molecules in Silicon
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Comparative Analysis of Process of Diffusion of Interstitial Oxygen Atoms and Interstitial Hydrogen Molecules in Silicon and Germanium Crystals: Quantumchemical Simulation Vasilii Gusakov Theory, Joint Institute of Solid State and Semiconductor Physics, P. Brovka str. 17, Minsk, 220072, Belarus ABSTRACT A theoretical simulation and comparative analysis of the process of diffusion of the interstitial oxygen atoms and interstitial hydrogen molecules (H2) in silicon and germanium crystals at normal and hydrostatic pressure (HP) have been presented . The process of diffusion of particle with a strong interaction with a crystal lattice (interstitial oxygen atom) is a cooperative process. Three nearest Si (Ge) atoms of crystal lattice are involved in an elementary oxygen jump from a bond-center site to another bond-center site along a trajectory in the (110) plane. It is precisely their optimum position (corresponding to the local minimum of the crystal total energy) determines the value of the diffusion parameters of an interstitial oxygen atom in silicon and germanium crystals. In a sense, the diffusion process may be considered as a diffusion process of qwasiparticle - (Oi+3Si). In the case of a particle weakly interacting with a crystal lattice (interstitial hydrogen molecules) we come up against the opposite case - the diffusion of H2 is not a cooperative process. The calculated values of the activation energy and pre-exponential factor for an interstitial oxygen atom ∆E(Si) = 2.59 eV, ∆E(Ge) = 2.05 eV, D0 (Si)= 0.28 cm2 s-1, D0 (Ge)= 0.39 cm2 s-1 and interstitial hydrogen molecule ∆E(Si) = 0.79 - 0.83 eV, ∆E(Ge) = 0.58 - 0.62 eV D0 (Si)= 7.4 10-4 cm2 s-1, D0 (Ge)= 6.510-4 cm2 s-1 are in an excellent agreement with experimental ones and for the first time describe perfectly an experimental temperature dependence of an interstitial oxygen atom and hydrogen molecules diffusion constant in Si crystals. INTRODUCTION The elaboration of the theoretical methods for the calculation of atoms diffusion in crystals is of interest not only from fundamental point of view (an understanding of the microscopic process of diffusion), but also is of practical significance. The reason is that essentially all technological process of microelectronics is connected directly with diffusion of atoms (defects) in crystals. Moreover, diffusion in crystals (nanomaterials, nanostructures) goes very often under extreme conditions (fields of stress and temperatures, interfacial regions etc) and this impedes, makes expensive or even impossible experimental study of the process of diffusion. In this case, theoretical methods are of fundamental importance. However, until now there are obscure questions related to a quantitative description of a microscopic mechanism of diffusion, whenever the split of covalent bonds accompanies the migration of an atom. In this article the comparative analysis of the process of diffusion of an interstitial oxygen atom (a particle strongly interacting with a crystal lattice) and an interstitial hydrogen
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