Fabrication and the third-order nonlinear optical property of hybrid thin films consist of Bismuth iodide / n-alkylammonium

@ We fabricated a hybrid thin film that consisted of bismuth triiodide Bil₃ and n-alkylammonium iodide C_nH_2n+1NH₃I, expecting to form a two-dimensional quantum well structure that shows large optical nonlinearity. Orange colored crystalline compound obtained from Bil₃ and stearylammonium iodide C₁₈H₃₇NH₃I has the composition of (C_l8H₃₇NH₃)₃Bi₂I₉, suggesting to form a corrugated layer structure of (Bi₂I₉^3-)_x. X-ray diffraction pattern of its spin-coated film on a quartz substrate showed that the inorganic layer was sandwiched between organic layers by the molecular fastener effect and that the layered structure has a parallel orientation to the substrate. A UV-Vis spectrum of the film showed the increment of the excitonic band originated from quasi-two-dimensional quantum well structure of (Bi₂I₉^3-)_x. The third order nonlinear property of the thin film was estimated by the third harmonic generation (THG) measurements. Strong THG signals were observed from the hybrid film of Bil₃ and C₁₈H₃₇NH₃I. Third-order nonlinear susceptibilities were found to be 10^-11 esu order even though they were under the non-resonant condition.