PbSe films were chemically deposited with a range of controlled
microstructures, from nanocrystalline to monocrystalline films. The crystal
size in the nanocrystalline films was controlled in a range 7 to 25 nm with
a fairly narrow size distribution, which allowed fine-tuning of the PbSe
energy gap. The optical properties of the films were investigated using
infrared (IR) transmission and IR photoluminescence measurements. The
nanocrystalline PbSe films showed single bandgap values in the
technologically important near-IR region. Two bandgap values, corresponding
to both bulk and confined nanocrystals, were obtained for films with mixed
microstructure. Strong blue shifts in both the absorption and emission peaks
of the nanocrystalline layers were obtained. The bandgaps of the PbSe films
were found to be in good agreement with theoretical calculations. The
results point out the potential of these films for nanoscale optical device
applications operating in the near-IR range.