Determination of complex dielectric functions of ion implanted and implanted-annealed amorphous silicon by spectroscopic ellipsometry
نویسندگان
چکیده
Measuring with a spectroscopic ellipsometer (SE) in the 1.845 eV photon energy region we determined the complex dielectric function (E = e1 + ieZ> of different kinds of amorphous silicon prepared by self-implantation and thermal relaxation (500 “C, 3 h) . These measurements show that the complex dielectric function (and thus the complex refractive index) of implanted a-Si (i-a-Si) differs from that of relaxed (annealed) a-Si (r-a-Si) . Moreover, its E differs from the E of evaporated a-Si (e-a-Si) found in the handbooks as E for a-Si. If we use this E to evaluate SE measurements of ion implanted silicon then the fit is very poor. We deduced the optical band gap of these materials using the Davis-Mott plot based on the relation: (E&‘>~‘~ (E E8). The results are: 0.85 eV (i-a-Si), 1.12 eV (e-a-Si), 1.30 eV (r-a-Si) . We attribute the optical change to annihilation of point defects.
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