Tese
Estudo das propriedades estruturais, eletrônicas e termoelétricas de nanofios de PbSe e PbTe
Fecha
2013-04-29Registro en:
WRASSE, Ernesto Osvaldo. Study of the structural, electronic and thermoelectric properties of PbSe and PbTe nanowires. 2013. 204 f. Tese (Doutorado em Física) - Universidade Federal de Santa Maria, Santa Maria, 2013.
Autor
Wrasse, Ernesto Osvaldo
Institución
Resumen
In this work we study simultaneously the structural, electronic and thermoelectric
properties of PbSe and PbTe nanowires, analyzing the quantum confinement effects, the
dependence with the planar stoichiometry and the spin-orbit interactions. We also study
these nanowires in the presence of intrinsic defects (vacancies and antisites) and doped
with group III (Al, Ga, In, and Tl) impurity. We use first principles calculations within
the formalism of the density functional theory (DFT). We observed that the nanowires are
more stable in the rock salt structure and aligned along the (001) direction. The electronic
properties of nanowires are in
uenced by three effects: the quantum confinement, spinorbit
interactions and the planar stoichiometry. The quantum confinement increases the
thermoelectric efficiency of the PbSe and PbTe nanowires when compared to the system in
the bulk phase, reaching an increase up to two orders in the magnitude, leading the PbSe
and PbTe nanowires with great potential to be used in thermoelectric devices. We studied
the in
uence of intrinsic defects and group III impurity doping in the main properties of
PbSe and PbTe, we show that these defects give rise to different electronic properties in the
nanowires as compared to the bulk one. Intrinsic defects and group III impurities, which
modify the electronic density of states (DOS) near to the top of the valence band or near to
the bottom of the conduction band increase the thermoelectric efficiency of the PbSe and PbTe nanowires. However, defects that introduce electronic levels in energy band gap are
shown to cause and degradation in the thermoelectric efficiency. The increase (decrease)
in thermoelectric efficiency is associated with a lower (higher) value of electronic part of
the thermal conductivity. In summary, we show that PbSe and PbTe nanowires are very
promising materials to be used in thermoelectric, electronic and optical devices.