Optical and Structural Properties of Bismuth Doped ZnO Thin Films by Sol-Gel Method: Urbach Rule as a Function of Crystal Defects

Abstract

Bismuth (Bi) doped zinc oxide (ZnO:Bi) thin lms were prepared on glass substrates by solgel spin coating technique using homogeneous precursor solutions, and eects of Bi doping on the structural and optical properties of ZnO were investigated. The crystalline of ZnO lms shifted from polycrystalline nature to amorphous nature with Bi doping. The plane stresses (σ) for hexagonal ZnO and ZnO:Bi crystals were calculated according to the biaxial strain model. The Urbach rule was studied as a function of non-thermal component to the disorder (defects in crystal structures) which is especially observed in the case of non-crystal semiconductors. The calculated Urbach energies and steepness parameters of undoped ZnO and ZnO:Bi lms varied between 44.33 meV and 442.67 meV, and 58.3 × 10 −2 and 5.8 × 10 −2 , respectively. The Urbach energies of the lms increased with an increase in the Bi doping concentration and a great dierence was observed for 7.0 mol.% doping. The band gap values of the lms exhibited a uctuated behavior as a result of doping eect.

Influence of cobalt-doping on the optical properties of zinc tris–thiourea sulfate (ZTS) single crystal

“…On the other hand, the steepness parameter (σ) decreases with increasing Co 2+ concentration. The behavior of E U and σ is reasonable and it is in good agreement with those reported in the literatures for other materials [48]. Doping ZTS crystals with cobalt leads to increasing the defects and forming localized states.…”

“…The Urbach tail energy (E U ) is proportional to temperature (Temp.) by the following relation [48]:…”

“…Therefore, a band tail will appear for the crystals [49]. The absorption edge broadening leads to increasing E U and decreasing σ with dopant concentration increase [48].…”

Electrochemical and Structural Behavior of Bi Doped ZnO Materials Obtained with Solvothermal Synthesis Method

“…Similarly, it was observed that the FWHM values of the (100) and (002) diffraction peaks increased with the increase in the doping ratio. These results also verify that Bi atoms are successfully doped into the ZnO lattice and cause lattice expansions in the ZnO crystals [19,24]. The crystallite size of the samples was determined by the Debye-Scherer formula given in Eq.…”

Toward a Raman/FORS discrimination between Art Nouveau and contemporary stained glasses from CdSxSe1 − x nanoparticles signatures

“…The exponential absorption tails for photon energies of sub‐band gap of both crystalline and amorphous materials have been widely studied, and the E u , which is related to the steepness of the tails (the so‐called Urbach's tails), has been defined as a function of the temperature ( T ) and the degree of crystal disorder of the material. As shown in previous works, the non‐thermal component to the disorder, clearly observed especially in the case of non‐crystal semiconductors, could be extracted from the optical absorption coefficient equation obtaining a value related to the absorption edge energy width.…”