Paper TF+SE-TuM12
Structural, Optical and Electrical Properties of Fe-doped BiOCl

Tuesday, November 11, 2014, 11:40 am, Room 305

BiOCl is an attractive p-type semiconductor with a wide band-gap of 3.4 eV. It has a unique layered structure of alternating [Bi₂O₂]²⁺ layers, interleaved by double slabs of Cl^- ions. The ionic layering guides the growth of BiOCl along the c-axis to form a 2D nanosheet morphology, favoring rapid and efficient electron/hole separation. Thus, BiOCl nanosheets can be naturally exploited as a photoactive material in applications such as solar harvesting, photocatalysis and sensing. However, given the large band-gap of BiOCl strategies to sensitize the BiOCl to the visible spectrum must be made. Substitutional doping of transition metal ions is an attractive approach given that many of the transition metal oxides are earth-abundant and have their band-gaps in the visible spectrum.

In this study, we demonstrate the effect of Fe doping on the structural, optical and electrical properties BiOCl nanosheets. Fe-doped BiOCl were synthesized by a facile hydrolysis process. Next, the samples are subjected to various annealing temperatures. We show that anneal temperatures >200 ^oC can initiate successful Fe incorporation in BiOCl crystal lattice. X-ray diffraction (XRD) shows a higher angle shift after thermal annealing, corresponding to decrease in the lattice constant as a result of Fe³⁺ substitution of the Bi³⁺ ions. Raman spectroscopy shows the E_g stretching mode of the Bi–Cl bond has lower frequency shift, which is consistent with the XRD analysis of Fe³⁺ substitution. Electrical property measurements including IV characteristics show a linear behavior with a resistance of (2.5x10¹¹, 9.8x10¹⁰ and 9.32 x 10¹⁰ Ω) for samples annealed at 200, 300 and 400^oC respectively.

Finally, we demonstrate a highly sensitive O₂ sensor using Fe-doped BiOCl nanosheets, operating at room temperature. The interaction of vacancies and O₂ is explored in the context of the Fe-doping in BiOCl.