Interactions of hydrogen molecules with bond-centered interstitial oxygen and another defect center in silicon

Infrared spectra obtained from Czochralski (CZ) silicon heated in the range 1100<~T<~1300^∘C in H₂, D₂, or mixtures of the two gases, show vibrational absorption at 1075cm^-1 due to perturbed bond-centered interstitial oxygen atoms Oᵢ. Deconvolutions of these absorption profiles imply that the observed perturbations to the Oᵢ atom are due to adjacent defects incorporating two H atoms. This interpretation is confirmed by detection of modes ν₁ (ν1HH,ν1HD,ν1DD) with ν1HH=3789cm^-1 and ν₂ (ν2HH,ν2HD,ν2DD) with ν2HH=3731cm^-1, that both correlate in strength with that of the 1075cm^-1 absorption. A third set of modes ν₃ (ν3HH,ν3HD,ν3DD), with ν3HH=3618cm^-1 detected in heat-treated CZ and float zone silicon and not related to the absorption at 1075cm^-1, must be due to H-H pair defects trapped at an unknown impurity or lattice defect. The frequencies of the ν1HD, ν2HD, and ν3HD modes imply that the three defects are H₂ molecules with weakened bonds and small dipole moments resulting from interactions with either adjacent oxygen atoms (ν₁,ν₂) or a second type of trap (ν₃). Annealing treatments imply that isolated Oᵢ-H₂ complexes can dissociate for T>~70^∘C allowing interstitial H₂ molecules to diffuse away but they can be retrapped during a subsequent anneal at T<~50^∘C.