ELECTRON-PARAMAGNETIC RESONANCE OBSERVATION OF TRIGONALLY SYMMETRICAL SI DANGLING BONDS IN POROUS SILICON LAYERS - EVIDENCE FOR CRYSTALLINE SI PHASE

In photoluminescent porous Si layers is observed a dominant intrinsic EPR signal of trigonal symmetry with g(parallel-to) = 2.0023+/-0.0003 and g(perpendicular-to) = 2.0086+/-0.0003 as principal g values. This EPR signal can be identified with Si dangling bonds by its symmetry and characteristic g values. The rotation pattern of the EPR signal indicates that the axial directions of the dangling bonds are distributed in all the four [111] crystal axes of the original silicon lattice. These results can be exclusively explained by the existence of the crystalline Si phase with retention of the original crystal orientation in porous Si. The dangling bond formation is found to be closely related to the surface oxidation.