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

Single phase Ph1-xFexSe (0.00 <= x <= 0.07) thin films, with typical rocksalt structure, are grown by the chemical hath deposition method. An additional segregated phase of Fe2O3 is observed in the x >= 0.08 films. The average grain size in the films grown at a fixed bath temperature (T-b) is observed to remain constant with increase in Fe concentration from x = 0.00 to x = 0.07. A decrease in T-b, for fixed x, results in a decrease in grain size in the films. The T-b induced decrease in grain size is seen to result in an increase of direct optical band gap (E-g) in films with the saine x. In the typical case of x = 0.06 films, decrease in grain size from 9 nm to 3 nm due to change in T-b from 85 to 55 degrees C, results in an increase in E-g from 2.09 eV to 2.89 eV. The blue shift is attributed to enhanced quantum confinement in the nanograins. However, at a fixed T-b, while grain size remains constant with increase in x, E-g is observed to decrease. E-g is seen to decrease from 2.20 to 1.84 eV with change in x from 0.02 to 0.07 in T-b, of 85 degrees C films. This decrease is attributed to tailoring of E-g due to alloying between PbSe (E-g (bulk) 0.28 eV) and FeSe (E-gbulk = 0.14 eV) in the single-phase nanoparticle films of Pb1-xFexSe. Resistivity decreases while Hall mobility increases with the increase in x (0.00 <= x <= 0.06) in the films. (c) 2008 Elsevier Ltd. All rights reserved.