PbS _x Se_1−x thin films from the thermal decomposition of lead(II) dodecylxanthate and bis(N,N-diethyl-N′-naphthoylselenoureato)lead(II) precursors

Thin films of PbS _x Se_(1−x) (0 ≤ x ≤ 1) have been deposited by spin coating of bis(dodecylxanthato)lead(II) (1) and/or bis(N,N-diethyl-N′-naphthoylselenoureato)lead(II) (2) complexes onto glass substrates followed by heating. The mole fraction of the selenium precursor in the coating mixture was varied from 0 to 1 by mixing the S and Se precursors. The as-prepared thin films were then heated at temperatures ranging from 250 to 400 °C. Powder X-ray diffraction showed all films were of the halite structure with preferred orientation along (200) plane. The PbS films showed a closely packed network of nanorods, each comprised of smaller nanoparticles. The nanorods were about 500 nm in length and 25 nm in width; the adhered particles had ca. 30 nm sides. The PbSe nanoparticles were also cubic. The alloys showed an intermediate morphology between the rods and cubes depending on the precursor ratio in the coating mixture. The band gaps estimated from Tauc plots for the films heated at 250 °C for 30 min were 1.03 and 0.79 eV for PbS and PbSe, respectively. The alloyed PbS _x Se_(1−x) thin films exhibited band gaps between those of PbS and PbSe. The band gaps and lattice parameters of the alloys varied in a Vegardian manner and could be closely correlated with the composition of the precursor mixture.