Electron paramagnetic resonance calculations for hydrogenated Si surfaces

Electron paramagnetic resonance (EPR) signatures, more specifically the elements of the electronic g tensor, are calculated within density functional theory for hydrogenated Si(111), Si(001), Si(113), Si(114), Si(112), and Si(110) surfaces. Thereby both perturbation theory and a more sophisticated Berry phase technique are applied. Specific defects on different surface orientations are shown to reproduce the resonances at (g) over bar = 2.0043 and (g) over bar = 2.0052 measured for hydrogenated microcrystalline silicon: The latter value is argued here to originate from regions with low hydrogen coverage; the resonance at (g) over bar= 2.0043 is shown to appear in positions with dihydride environment, where an H atom is directly bound to the silicon dangling-bond atoms. A third group of EPR signals with considerably larger (g) over bar values between 2.006 and 2.009 is predicted for highly symmetric dangling bonds resembling single dangling-bond defects in silicon bulk material. As the exact value depends strongly on local strain, this type of defect can explain a less intense signal with large g strain observed in microcrystalline as well as in amorphous material.