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Crystal and electronic structure of PbTe/CdTe nanostructures.

Bukała M, Sankowski P, Buczko R, Kacman P - Nanoscale Res Lett (2011)

Bottom Line: 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 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Physics PAS, Al, Lotnikow 32/46, 02-668 Warsaw, Poland. bukala@ifpan.edu.pl.

ABSTRACT
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.

No MeSH data available.


(Color online) The DOS near the Fermi level for PbTe wires in CdTe matrix with not-relaxed atomic positions. The wire diameters are 5 nm (a) and 9 nm (b).
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Figure 4: (Color online) The DOS near the Fermi level for PbTe wires in CdTe matrix with not-relaxed atomic positions. The wire diameters are 5 nm (a) and 9 nm (b).

Mentions: In Figure 3, the difference in DOS for PbTe NWs of diameter about 3.6 nm with relaxed and not-relaxed atomic positions is presented. It can be observed that, for such a small structure, the relaxation changes DOS but its qualitative character remains the same. As the ab initio computations are highly time consuming, the DOS for structures containing more than 500 atoms, has been calculated without relaxation of the atomic positions. The role of the relaxation, which proceeds mainly at interfaces, should diminish with the size of the structure. The long-range stress relaxation is omitted in the tight-binding calculations, due to the very good match of the PbTe and CdTe lattice constants. In Figure 4 the calculated DOS of PbTe NWs in CdTe matrix with not relaxed atomic positions for larger diameters is presented. In both Figures 3 and 4, it can be noticed that quantum confinement of PbTe wires leads to 1 D sub-bands and abrupt changes of the carrier DOS with energy. Thus, the derivative of the DOS at the Fermi level depends strongly on its position, i.e. on carrier concentration--small changes of the latter can lead even to a sign change in the derivative. As the energy spacing between the 1 D sub-bands depends on the confinement potential, the DOS depends strongly on the diameter of the NWs, as shown in the figures.


Crystal and electronic structure of PbTe/CdTe nanostructures.

Bukała M, Sankowski P, Buczko R, Kacman P - Nanoscale Res Lett (2011)

(Color online) The DOS near the Fermi level for PbTe wires in CdTe matrix with not-relaxed atomic positions. The wire diameters are 5 nm (a) and 9 nm (b).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211172&req=5

Figure 4: (Color online) The DOS near the Fermi level for PbTe wires in CdTe matrix with not-relaxed atomic positions. The wire diameters are 5 nm (a) and 9 nm (b).
Mentions: In Figure 3, the difference in DOS for PbTe NWs of diameter about 3.6 nm with relaxed and not-relaxed atomic positions is presented. It can be observed that, for such a small structure, the relaxation changes DOS but its qualitative character remains the same. As the ab initio computations are highly time consuming, the DOS for structures containing more than 500 atoms, has been calculated without relaxation of the atomic positions. The role of the relaxation, which proceeds mainly at interfaces, should diminish with the size of the structure. The long-range stress relaxation is omitted in the tight-binding calculations, due to the very good match of the PbTe and CdTe lattice constants. In Figure 4 the calculated DOS of PbTe NWs in CdTe matrix with not relaxed atomic positions for larger diameters is presented. In both Figures 3 and 4, it can be noticed that quantum confinement of PbTe wires leads to 1 D sub-bands and abrupt changes of the carrier DOS with energy. Thus, the derivative of the DOS at the Fermi level depends strongly on its position, i.e. on carrier concentration--small changes of the latter can lead even to a sign change in the derivative. As the energy spacing between the 1 D sub-bands depends on the confinement potential, the DOS depends strongly on the diameter of the NWs, as shown in the figures.

Bottom Line: 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 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Physics PAS, Al, Lotnikow 32/46, 02-668 Warsaw, Poland. bukala@ifpan.edu.pl.

ABSTRACT
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.

No MeSH data available.