Phase transformation from PbS to PbSe:S in hot-wall deposition of nanocomposite thin film with evaporation sources of PbS and ZnSe

Simultaneous evaporation of PbS and ZnSe using hot-wall deposition was investigated to prepare nanocomposite thin films. X-ray diffraction patterns indicated that the films formed a phase mixture of ZnSe and PbSe, suggesting that an evaporation source of PbS phase-transformed to PbSe during a film deposition. Wavelength-dispersive spectroscopy indicated that the composite contains a small amount of S below 1 at.%. High-angle annular dark-field scanning transmission electron microscopy and line scan analysis in electron energy-loss spectroscopy indicated that PbSe nanocrystals were dispersed in a ZnSe, while S tended to segregate in ZnSe matrix. Photocurrent spectra indicated that peak position at approximately 460 nm shifted toward a shorter wavelength as Pb concentration increased.