Structural, optical and electrical properties of chemically grown Pb1−xFexSe nanoparticle thin films

Single phase Pb1−xFexSe (0.00≤x≤0.070.00≤x≤0.07) thin films, with typical rocksalt structure, are grown by the chemical bath deposition method. An additional segregated phase of Fe2O3 is observed in the x≥0.08x≥0.08 films. The average grain size in the films grown at a fixed bath temperature (Tb)(Tb) is observed to remain constant with increase in Fe concentration from x=0.00x=0.00 to x=0.07x=0.07. A decrease in TbTb, for fixed x, results in a decrease in grain size in the films. The TbTb induced decrease in grain size is seen to result in an increase of direct optical band gap (Eg)(Eg) in films with the same xx. In the typical case of x=0.06x=0.06 films, decrease in grain size from 9 nm to 3 nm due to change in TbTb from 85 to 55 ∘C, results in an increase in EgEg from 2.09 eV to 2.89 eV. The blue shift is attributed to enhanced quantum confinement in the nanograins. However, at a fixed TbTb, while grain size remains constant with increase in xx, EgEg is observed to decrease. EgEg is seen to decrease from 2.20 to 1.84 eV with change in xx from 0.02 to 0.07 in TbTb of 85 ∘C films. This decrease is attributed to tailoring of EgEg due to alloying between PbSe (Egbulk=0.28eV) and FeSe (Egbulk=0.14eV) in the single-phase nanoparticle films of Pb1−xFexSe. Resistivity decreases while Hall mobility increases with the increase in xx (0.00≤x≤0.060.00≤x≤0.06) in the films.