S. M. Solov’ev

Emf induced by a change in the samarium ion valence as a result of a phase transition in SmS single crystals

The mechanism of the emf appearing in a semiconductor under heating in the absence of external temperature gradients, an effect revealed by the present authors, is considered. The experiments were performed on samarium sulfide (SmS) single crystals. It is shown that the emf is generated by an abrupt change in the samarium ion valence, which results from the ion screening by the electrons activated into the conduction band. We succeeded in obtaining emf pulses 1.3 s long with an amplitude of up to 2.5 V at T ∼ 460 K, as well as CW emf generation within the 375-to 405-K temperature interval with a maximum value of ∼50 mV.

Initial stages of the growth and magnetic properties of cobalt films on the Si(100)2 × 1 surface

The initial stages of the growth of cobalt films on the Si(100)2 × 1 surface and the dynamics of variation in their phase composition, electronic structure, and magnetic properties with a coverage increasing in the range 1–20 Å resolution photoelectron spectroscopy with synchrotron radiation and magnetic linear dichroism in Co 3p electron photoemission. It has been shown that a film of metallic cobalt starts to grow at a coverage of ∼7 Å. This process is preceded by the stages involving the formation of the interface cobalt silicide and the Co-Si solid solution. It has also been demonstrated that, at coverages below 15 Å, the sample surface is coated by segregated silicon. The ferromagnetic ordering of the film in the surface plane has been found to follow a threshold character and set in at a coverage of ∼6 Å. A further increase in the coverage in the range 8–16 Å is accompanied by a slower increase in the remanence of the film.

Anomalous thermal electromotive force in samarium monosulfide

The thermal emf in samarium monosulfide was investigated at temperatures between 300 and 530 K. At T=435–455 K, an anomalous increase in the emf was found. This effect is explained by a noncoherent change in the valency of samarium ions.

Electrical conductivity and band structure of thin polycrystalline EuS films

A study of the electrical resistance of thin polycrystalline EuS films (0.4–0.8 μm thick) in the temperature range 120–480 K has provided the basis for a model of the band structure of this substance. It has been shown that the main impurity levels in thin polycrystalline EuS films are those related with localized states near the conduction band bottom, as well as the Ei donor levels of Eu ions outside regular lattice sites. The “tail” of the localized states extends in energy up to at least −0.45 eV.

Formation and magnetic properties of the silicon-cobalt interface

Formation of the Si/Co interface and its magnetic properties have been studied by high-resolution photoelectron spectroscopy with synchrotron radiation. The experiments have been performed in situ in superhigh vacuum (5 × 10−10 Torr) with coating thicknesses up to 2 nm. It has been found that, in the initial stage of silicon deposition on the surface of polycrystalline cobalt maintained at room temperature, ultrathin layers of the Co3Si, Co2Si, CoSi, and CoSi2 silicides are formed. The three last phases are nonmagnetic, and their formation gives rise to fast decay of magnetic linear dichroism in photoemission of Co 3p electrons. At deposition doses in excess of ∼0.4 nm Si, a film of amorphous silicon grows on the sample surface. It has been established that the Si/Co interphase boundary is stable at temperatures up to ∼250°C and that further heating of the sample brings about escape of amorphous silicon from the sample surface and initiates processes involving silicide formation.

Interaction of iron atoms with the Si(100)-2 × 1 surface

Interaction of iron atoms with the Si(100)-2 × 1 surface at room temperature is studied by core-level photoelectron spectroscopy using synchrotron radiation for Fe coverages ranging from a fraction of a monolayer to six monolayers. It is shown that the Fe/Si(100)-2 × 1 interface is chemically active: the Fe-Si solid solution forms early in deposition of iron on silicon. When the Fe coverage reaches four to five monolayers, the state of the system is changed and Fe3Si silicide arises.

Thermovoltaic effect in samarium sulfide-based Sm1 − xEuxS heterostructures

The thermovoltaic effect in samarium sulfide-based Sm1 − xEuxS bulk heterostructures in the temperature interval 300–520 K is considered. It is shown that this effect is due to an artificially produced samarium ion concentration gradient, rather than to an external temperature gradient.

Thermovoltaic effect in polycrystalline samarium sulfide

A thermovoltaic effect has been observed for the first time in a polycrystalline sample of samarium sulfide (SmS) with artificially created concentration gradient of excess (overstoichiometric) samarium ions, in which an electric voltage of 12–22.5 mV was generated in a temperature interval of 370–485 K. It is shown that the specific voltage generation in SmS due to the thermovoltaic effect can be observed in a temperature range of 100–1800 K.

Temperature dependence of the SmS lattice parameter

The behavior of the lattice parameter of single-crystal SmS with temperature was studied by x-ray diffractometry in the range 100–700 K. The observed features are assigned to a temperature-induced variation in the filling of the Sm2+f-shell ground-state multiplet levels. The temperature dependence of the thermal expansion coefficient of SmS was measured. It is shown that the lattice constant behavior in samples that exhibit a pronounced emf generation effect under heating is influenced by the transition of defect samarium ions from the divalent to trivalent state and that the effect itself derives from phase transitions in SmS.

Electromotive force generation in homogeneously heated semiconducting samarium monosulfide

The emf generated in samarium monosulfide (SmS) single crystals heated in the absence of external temperature gradients was measured for the first time in a broad temperature range (from room temperature to 712 K). The phenomena of self-heating (up to T=866 K) and the emf generation were observed in the SmS samples after termination of the external heating. A high level of the emf (0.4–0.6 V) generated for 12 min (including 10 min without external heating) suggests that these effects can be used for the conversion of thermal energy into electricity.