Vacancy and vacancy-hydrogen complexes in silicon

Abstract

The neutral vacancy (V) snd the (V,H") (n = 1, . . . , 4) complexes in silicon are studied in various molecular clusters at the approximate ab initio and ab initio Hartree-Fock levels, with post-HartreeFock corrections in electron correlation. The quantities calculated are the equilibrium con6gurations and electronic structures, dissociation energies, diffusion paths, and activation energies. The dissociation energies are compared to those of other traps for H calculated at the same level of theory, such as substitutional C, interstitial Ti, or the (B,H) pair. The calculations predict that the (V,Hq) pair in Si should be mobile above room temperature. A part of the barrier for diffusion of (V,Hq) is lower than that of V, due to a mechanism analogous to the H-enhanced diffusion of interstitial 0 in Si. Another part of this barrier is higher than that for V. The consequences of this process include the possibility of enhanced diffusion of H in polycrystalline versus crystalline Si and leads us to propose a mechanism for the nucleation of platelets in the subsurface region of plasma-exposed Si.

Nucleation and growth of platelets in hydrogen-ion-implanted silicon

“…Silicon vacancies are extremely mobile during the 380°C anneal 16 and calculations suggest that the VH 1 defect may be mobile in silicon but with a higher activation energy than the pure vacancy. 17 With the flux of these defects being biased by strain and the vacancy hydrogenation processes being exothermic, one expects that vacancy-hydrogen defects will plate out in the region of high stress. The dipole tensile field should ultimately lead to the growth of platelets on planes that are perpendicular to the out-of-plane strain direction.…”

Evidence for ion irradiation induced dissociation and reconstruction of Si–H bonds in hydrogen-implanted silicon

“…The bonding energy of H to Si in the form of H 2 ‫ء‬ is about 1.65 eV. 22 Robertson and Estreicher 23 calculated the binding energies for the different VH n complexes with the energy decreasing from 3.6 to 3.0 eV with n increasing from 1 to 4. Estimates of the electronic energy deposited during proton irradiation show that there is sufficient energy for Si-H bond breaking; 6,24 the actual bonding state after ion irradiation depends on the competition between bond dissociation and recombination.…”

Sampling the diffusion paths of a neutral vacancy in silicon with quantum mechanical calculations

“…For example, in silicon, antimony impurities are vacancy diffusers and phosphorus are interstitial diffusers 1 . Therefore, self-diffusion in Si has been extensively investigated by experiments 1,2,3,4,5 and simulations 6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33 .…”