O. N. Nashchekina

Quantum size effects in PbSe quantum wells

In PbSe epitaxial thin films grown by thermal evaporation on KCl(001) substrates and covered with an EuS protective layer, oscillatory dependences of the galvanomagnetic and thermoelectric properties (electrical conductivity σ, the Hall coefficient RH, charge carrier mobility μ, and the Seebeck coefficient S) on the PbSe layer thickness d (3<d<200 nm) were observed at room temperature. Oscillations of the transport properties are associated with quantum size effects due to electron confinement in the PbSe quantum wells.

Effect of oxidation on the thermoelectric properties of PbTe and PbS epitaxial films

We report on the thickness d dependences of the Seebeck coefficient, electrical conductivity, and Hall coefficient of PbTe and PbS epitaxial thin films (d=5–200 nm), prepared by thermal evaporation in vacuum and deposition on (001) KCl substrates. The oxidation of the films in air at 300 K leads to a sign inversion of the carrier type from n to p in films with d⩽125 and 110 nm for PbTe and PbS, respectively. The observed d dependences are interpreted in terms of compensating acceptor states created by oxygen on the film surface.

Quantum size effects in n-PbTe∕p-SnTe∕n-PbTe heterostructures

The dependencies of the thermoelectric properties of n-PbTe∕p-SnTe∕n-PbTe heterostructures on the SnTe quantum well width (dSnTe=0.5–6.0nm) at fixed PbTe barrier layers thicknesses were studied. It was established that the thickness dependencies of the Seebeck coefficient, electrical conductivity, the Hall coefficient, charge carrier mobility, and the thermoelectric power factor are distinctly nonmonotonic. The observed effect is attributed to the size quantization of the energy spectrum of the hole gas in a SnTe quantum well.

Quantum-size effects in n-type bismuth thin films

Oscillatory thickness dependences of the electrical conductivity, Hall coefficient, charge carrier mobility, and Seebeck coefficient were obtained at room temperature for n-type thin Bi films (d=3–300 nm) fabricated by the thermal evaporation of a bismuth crystal in a vacuum and deposition on mica substrates at 380 K. We attribute this oscillatory behavior to quantum-size effects, which are observable when the electron mean-free path and Fermi wave length exceed the film thickness d.

Oscillatory behaviour of the transport properties in PbTe quantum wells

Oscillatory behaviour was detected in the dependences of the transport properties (electrical conductivity, Hall coefficient, charge carrier mobility, Seebeck coefficient and thermoelectric power factor) on the PbTe layer thickness d (d = 2–200 nm) in (001) KCl/PbTe/EuS quantum well (QW) structures at room temperature. The non-monotonic character of these dependences is attributed to quantum size effects, which manifest themselves in PbTe QWs at sufficiently small values of d. The positions of the extrema in the thickness dependences of the transport properties shift with changing electron concentration in PbTe QWs.

Effect of thickness on the thermoelectric properties of PbS thin films

Abstract A non-monotonic dependence of the thermoelectric properties of PbS epitaxial films grown on (001)KCl substrates and covered with an EuS protective layer on the PbS layer thickness (d=2–200 nm) was detected at room temperature. The complex character of the dependence on d is attributed to a competition between percolation phenomena and size quantization. Within the framework of percolation theory on the basis of experimental data, the critical exponent for the electrical conductivity was determined. Oscillations in the thickness dependence of the kinetic coefficients are attributed to quantum size effects occurring in thin layers.

Quantum size effects in IV–VI quantum wells

For IV–VI (PbS, PbSe, PbTe) epitaxial thin films grown by thermal evaporation on KCl (001) substrates and covered with a EuS protective layer, oscillatory dependences of the galvanomagnetic and thermoelectric properties on the IV–VI layer thickness d were observed at room temperature. The oscillations of the transport properties are believed to be associated with quantum size effects due to the electron confinement in IV–VI quantum wells.

Percolation transition of thermoelectric properties in PbTe thin films

Extrema were observed in the film thickness d dependence of various thermoelectric parameters (Seebeck coefficient S, electrical conductivity σ, Hall coefficient RH, charge carrier mobility μ, and power factor P) of epitaxial PbTe/(001) KCl thin films prepared by thermal evaporation in vacuum and protected from oxidation by an EuS layer. We attribute the observed extrema in properties and the high values of μ and P at d≈50 nm to the percolation transition from an island-like to a continuous film and to the self-organization of the islands, which can occur not only in quantum dot superlattices but also in an individual layer.

Influence of oxidation on the transport properties of IV–VI-thin films

Abstract The effect of oxidation at room temperature on the thickness dependences of transport properties of IV–VI (PbS, PbSe, PbTe) thin films was studied. The effect of charge carrier concentration on the character of these dependences in n-PbTe thin films was detected. The regularities in the behavior of IV–VI thin films exposed to air were established. The experimental results are interpreted within the framework of models taking into consideration the presence of compensating acceptor states created by oxygen on the film surface.

Effect of non-stoichiometry on oxidation processes in n-type PbTe thin films

Abstract The dependences of the galvanomagnetic and thermoelectric properties on the thicknesses d (5–200 nm) of PbTe thin films prepared by the thermal evaporation of non-stoichiometric PbTe with 2 at.% excess lead were studied, with measurements conducted in air at room temperature on freshly grown films. It was established that with decreasing film thicknesses, an inversion of the dominant charge carrier sign from n to p takes place at d ∼40 nm. A comparison of the results obtained in this work with those for PbTe films prepared from stoichiometric PbTe showed that the increase in n-type charge carrier concentration results in a shift of the inversion point to smaller d values. The observed effect is attributed to oxidation processes taking place in PbTe thin films at room temperature in air, and the effect is interpreted in terms of compensating acceptor states created by oxygen on the film surface.