Design and characterization of Bi2O3/ZnPc optical interfaces رسالة ماجستير

Abstract

In this thesis heterojunction devices made by stacking layers of Bi2O3 and zinc phthalocyanine (ZnPc) are studied. The Films are coated by the thermal evaporation technique under a vacuum pressure of 10-4 mbar. The produced Bi2O3, ZnPc and Bi2O3/ZnPc are structurally and optically characterized. It was observed that coating of ZnPc onto polycrystalline Bi2O3 induces the crystallinity of ZnPc. Both of the stacked layers are of polycrystalline nature. The induced crystallization of ZnPc is attributed to the atomic substitutions and completed bonding mechanisms. In general, ZnPc layer decreased the Strain and defect density in Bi2O3 leading to larger crystallite sizes. The behavior is probably due lower ionic radii of Zn+2 as compared to Bi+3 .On the other hand, optical studies have shown that formation of two stacked layers is accompanied with pronounced free carrier absorption and pronounced interband transition, it is also noted that increasing the thickness of Bi2O3 substrate results in indirect allowed photonic transitions at the Bi2O3 /ZnPc interfaces. In addition, although both of Bi2O3 and ZnPc show the same energy band gaps (2.9 eV), the Bi2O3/ZnPc interface displayed narrower band gap (2.15 eV). Bi2O3/ZnPc heterojunction devices are also observed showing symmetrical condition and valance band of sets of 1.46 eV and 1.40 eV, respectively. Moreover, the dielectric dispersion studies on the proposed heterojunction devices have shown that Bi2O3/ZnPc film can perform as dielectric resonators with critical energies centered at 2.48, 1.73, 2.97 and 3.28 eV. Drude –Lorentz modeling on the imaginary part of the dielectric spectra revealed optical conductivity parameters that show the suitably of devices for optoelectronic application.