The growth of wurtzite GaAs and InAs nanowires with diameters of a few tens of nanometers with negligible intermixing of zinc blende stacking is reported. The suppression of the number of stacking faults was obtained by a procedure within the vapor-liquid-solid growth, which exploits the theoretical result that nanowires of small diameter ( approximately 10 nm) adopt purely wurtzite structure and are observed to thicken (via lateral growth) once the axial growth exceeds a certain length.
Using ab initio methods, we study the stability of thin (diameters up to 10 nm) GaAs and
InAs nanowires. Modelled nanowires were constructed using bulk atomic positions along six
different crystallographic directions of either zinc-blende or wurtzite structures. Taking into
account the reconstruction of the nanowire surfaces, we have found that, for diameters of
up to 50 Å, the most stable nanowires adopt the wurtzite (0001) structure—for such
diameters the free energy of zinc-blende nanowires along any crystallographic axis is
always larger than that of the wurtzite (0001) ones. To calculate the free energy in
nanowires with larger diameters, we have approximated their total energy by the sum
of congruous bulk and bulk surface energies. In these nanowires the interplay
between the wurtzite and zinc-blende structures was demonstrated. The band
structure and the density of charge in the nanowires have also been calculated.
The molecular beam epitaxial growth of PbTe nanowires on GaAs(111)B substrates is reported. The growth process was based on the Au-catalyzed vapor−liquid−solid mechanism. These nanowires grow along the [100] axis; they are perpendicular to the substrate, have tapered shapes, and have diameters of about 90 nm at the base and 60 nm at the top. High resolution transmission electron microscopy pictures reveal that the PbTe nanowires have a rock-salt structure and, in contrast to the one-dimensional structures of III−V and II−VI compound semiconductors such as GaAs, InAs, or ZnTe, are free from stacking faults. A theoretical analysis of these experimental findings, which is based on ab initio modeling of the PbTe nanowires, is also presented.
In this article, the authors reported a theoretical study of structural and electronic properties of PbTe inclusions in CdTe matrix as well as CdTe nano-clusters in PbTe matrix. The structural properties are studied by ab initio methods. A tight-binding model is constructed to calculate the electron density of states (DOS) of the systems. In contrast to the ab initio methods, the latter allows studying nanostructures with diameters comparable to the real ones. The calculations show that both kinds of inclusions lead to changes of the DOS of the carriers near the Fermi level, which may affect optical, electrical and thermoelectric properties of the material. These changes depend on the size, shape, and concentration of inclusions.
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