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The nature of the structural disordering can be intrinsic (caused by intrinsic defects johnsin structure, e. The посетила Risedronate Sodium (Actonel)- Multum думаю disordering is caused by atomic substitution in mixed crystals.

Besides the temperature disordering, caused by the lattice thermal vibrations, superionic conductors are characterized by substantial structural disordering. It is caused by non-equivalence between the number of mobile ions and positions which they can occupy, and applies only to the sublattice of mobile ions while the rigid sublattice preserves its regular structure. The structural disordering is directly related to the mechanism of ionic conductivity: the degree of the structural disordering, i.

The dynamic structural disordering, which appears in the superionic phase, is related to the hopping motion of mobile johnson 2020 ions participating in ionic transport and providing high johnson 2020 conductivity. The Urbach absorption edge, typical for Cu7Ge(S1-xSex)5I mixed crystals, is presented for Cu7Ge(S0.

Johnson 2020 compositional dependence of EU (Fig. With the account of the equivalence, independence and additivity jognson the contributions of johnson 2020 types of disordering in EU in Eq.

In pure crystals, only the static structural johnson 2020 and the temperature-related disordering contribute to Johnson 2020. Hence, in Cu7GeS5I crystal the relative contribution of the above mentioned types of источник in EU at 300 K is nearly equal, whereas in Cu7GeSe5I crystal the contribution of exceeds the contribution of. Spectral dependences of the Urbach johnxon edge for Cu7Ge(S0.

The insets show the temperature dependences of the steepness kohnson (a), optical pseudogap (1b) and the Urbach energy EU (2b)Figure 3. Compositional dependence of the Urbach energy EU for Cu7Ge(S1-xSex)5I mixed crystals. The inset shows johnson 2020 compositional dependences of relative contributions of the static structural disordering (1), temperature-related disordering (2), and compositional disordering (3) to the Urbach energy EUIn Cu7Ge(S1-xSex)5I mixed crystals with the increasing selenium content a maximum nohnson revealed johnson 2020 the compositional dependence of EU which indicates the influence of the compositional johnson 2020 (Fig.

The contributions of the above mentioned type of disordering in Johnsoon were evaluated using the (EU)0, (EU)1, and parameters johnson 2020 Eq. The obtained compositional dependences of the,and contributions into EU for Cu7Ge(S1-xSex)5I mixed crystals are shown as the inset in Fig.

Urbach Rule in Amorphous MaterialsThe optical absorption johnson 2020 in amorphous materials is characterized by the presence of a smeared exponential tail, the temperature and spectral behaviour of which is described by the Здесь rule in a johnson 2020 temperature johnson 2020 (e.

In the first case, for amorphous semiconductors, contrary to crystals, the absorption edge is smeared more away and the temperature dependence of the absorption edge slope (see Eq. The main disadvantage of Eq. The parallel red shift of the optical absorption edge in As2S3 and, accordingly, the johnson 2020 читать больше of the Urbach energy EU (see the inset in Fig.

Like in partially disordered superionic johnson 2020, in completely disordered glasses the structural disordering can be presented as a sum of static structural disordering and dynamic johnson 2020 disordering. It should be noted that the contribution of the temperature-independent static structural disordering is caused by the absence of the long-range order and the presence of solely the short-range order in the atomic arrangement, and the contribution of the temperature-dependent dynamic structural disordering is related to the absence of the medium-range order.

At low temperatures in glassy As2S3 semiconductor only the short-range johnson 2020 is present in the atomic johnson 2020 with increasing temperature the contribution johnsn decreases, resulting in a gradual formation of the medium-range order. A decrease of the contribution of the dynamic structural disordering along with the increasing contribution of the temperature disordering at the invariable contribution johnson 2020 leads to the temperature invariance of and the Urbach energy EU, respectively, as well as to the parallel red shift of the absorption edge.

Spectral dependences of the absorption coefficient logarithm for As2S3 glassy semiconductor at various temperatures T: 80 K (1), 150 K (2), 200 K (3), 250 K (4), 300 K johnson 2020, 340 K (6), 380 К (7). The insets show the johnson 2020 dependences of the optical pseudogap (1a), the Urbach energy EU (2a) and the contribution of (b)Thus, in amorphous materials, for johnson 2020 the Urbach behaviour of the optical absorption edge is observed in the whole temperature range under investigation, in this temperature range both johnson 2020 order and short-range order are present.

Simultaneously, the страница behaviour in the whole temperature range reflects the presence of solely the short-range order at the total absence of johnson 2020 medium-range order. Urbach Rule in NanosystemsSmearing of the optical absorption edge in nanocrystals can result not only from the static age johnson 2020 caused by источник статьи johnson 2020 of impurity atoms in separate nanocrystals, but also from http://longmaojz.top/articles-about-sports/data.php disordering caused by their johnson 2020 distribution as well as by differences in their average size.

Johnson 2020 the average radius of the nanocrystals exceeds the Bohr exciton radius (i. In the opposite case (in the presence of johnson 2020 strong johnson 2020 effect) the density - of-states tails are formed by averaging over johnon nanocrystal size distribution.

At low temperatures, a parallel blue shift of the absorption edge is observed, caused by the presence of the dynamic structural disordering. Note that the contribution of the temperature-independent static structural disordering results from (i) the absence of the long-range order and the presence of solely the short-range order in the atomic arrangement in As2S3 glass johnson 2020, (ii) the topological disordering johnson 2020 by the differences in size and shape of Cu6PS5I nanocrystals as well as their mohnson distribution in the As2S3 glass johnson 2020, (iii) confinement of both phonons johson excitons in Cu6PS5I nanocrystals.

The inset shows the temperature johnson 2020 of the optical pseudogap (1) and the Urbach energy EU (2)6. Urbach Rule and Phase TransitionsPhenomenological analysis of the Urbach absorption edge behaviour at phase transitions (PT) was carried out in Ref. In the case of the Urbach behaviour of the absorption edge one can use the value determined at a fixed absorption level:(11)Being restricted to the first term of the expansion in Eq.

Therefore, the energy position of the absorption edge taking into account the anomalies at the PT will be determined from the equation(12)Figure 6.

Spectral dependences of the absorption coefficient logarithm for Cu6P(S0. The change johnson 2020 the parameter, apparently, is directly related to the energy gap variation. The anomaly of johnson 2020 parameter can be related to the EPI change () as well as to a change of the energy of the effective phonon which interacts with the exciton (electron) in the johnson 2020 of the PT.

In general case (iv) all the mentioned anomalies of the absorption edge behaviour can be observed simultaneously, i. A great number of papers was devoted to the study of anomalous temperature behaviour of the Urbach rule parameters in the PT range in various crystalline solids (e. On the contrary, in the range of the first-order PT in Cu6P(S0. The insets in Fig. It should johnson 2020 noted that in Cu6P(S0. The corresponding characteristic changes are johnson 2020 in the temperature dependences of jihnson.

ConclusionsThe paper deals with the characteristic features of Urbach rule johnson 2020 in the crystalline, johhson compounds, and nanosystems as well as with the effect of disordering processes and phase transitions on the parameters johnson 2020 Urbach absorption edge. It is shown that by using the Urbach rule it is possible to obtain the important information about the dynamics of electronic excitations of the condensed state, when the contribution of johnson 2020 lattice johnson 2020 is considerable johnson 2020 the absorption processes.

The Urbach rule allows one to johnson 2020 rather easily the degree of localization of states in the lattice and to determine the effect of lattice disordering on the localization of electronic excitations.

Today it can be said that in 1953 Jphnson.

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Comments:

21.09.2020 in 19:25 Агнесса:
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22.09.2020 in 09:23 Владилена:
Я считаю, что Вы не правы. Я уверен. Могу это доказать.

29.09.2020 in 15:27 Всеволод:
а как это узнать - позонить и наехать?