The ultraviolet absorption edge of stannic oxide (SnO2)

摘要: Abstract The ultraviolet absorption edge spectrum of pure single crystal SnO 2 has been obtained at 300° K to coefficients as high 10 3 cm −1 . use polarized light revealed a large dichroism, the edges differing by ca 0.3 eV for radiation parallel and perpendicular axis. results suggest that both represent intrinsic transitions, yield estimates direct energy gaps 3.93 3.57 (∥) (⊥) c axis, respectively. Thresholds phonon coupled transitions occur approximately 3.7 3.4 eV, but indirect appear involve several lattice vibrational frequencies. Shape differences in two low arise from forbidden ∥ To account these observations, oxygen p levels are assumed split D 4 h into valence bands A u E symmetry, with upper eV. Selection rules electric dipole 1 g conduction band shown be different ⊥