Influence of Alloying
on the Optical Properties of
IV–VI Nanorods
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Abstract
The synthesis and structural and optical characterization
of PbSe<sub><i>x</i></sub>S<sub>1–<i>x</i></sub> and
PbSe/PbSe<sub><i>x</i></sub>S<sub>1–<i>x</i></sub> nanorods with a diameter between 2 and 4.5 nm and a length
of 10 to 38 nm is reported. The energy band gap of the nanorods exhibits
a pronounced variation upon the change in diameter and composition,
with a minor influence on lengths beyond 10 nm. The photoluminescence
spectrum of the nanorods is composed of a dominant band, accompanied
by a satellite band at elevated temperatures. The dominant band shows
an exceptionally small band gap temperature coefficient and negligible
extension of the radiative lifetime at cryogenic temperatures compared
with the photoluminescence processes in PbSe nanorods and in PbSe<sub><i>x</i></sub>S<sub>1–<i>x</i></sub> quantum
dots with similar band gap energy. A theoretical model suggests the
occurrence of independent transitions from a pair of band-edge valleys,
located at the L points of Brillouin zone, related to the dominant
and satellite emission processes. Each valley is four-fold degenerate
and possesses a relatively small electron–hole exchange interaction