Ionic semiconductor

AU these features—low values of a, a strong temperature dependence, and the effect of impurities—are reminiscent of the behavior of p- and n-type semiconductors. By analogy, we can consider these compounds as ionic semiconductors with intrinsic or impurity-type conduction. As a rule (although not always), ionic semiconductors have unipolar conduction, due to ions of one sign. Thus, in compounds AgBr, PbCl2, and others, the cation transport number is close to unity. In the mixed oxide ZrOj-nYjOj, pure 0 anion conduction t = 1) is observed. 

Finally, we point out that there is a close relation in description of ion electro-diffusion and the phenomenological theory of the electron and hole transport in semiconductors. In order to facilitate the reading we present below a brief ionics-semiconductor vocabulary. ... 

Covalent semiconductors, such as Si or GaAs, have a large density of surface states in the band gap, causing pinning of the barrier [83]. On the other hand, ionic semiconductors, such as ZnO, have low density of surface states in the band gap, and the barrier height does indeed depend on the work function difference between the metal and the semiconductor. It has been shown that for strongly ionic semiconductors the barrier height will indeed be equal to or proportional to the... 

All these features low values of u, a strong temperature dependence, and the effect of impurities, are reminiscent of the behavior of p-type and n-type semiconductors. By analogy, we can consider these compounds as ionic semiconductors with intrinsic or impurity-type conduction. 

As a rule (though not always), ionic semiconductors have unipolar conduction because of ions of one sign. Thus, in compounds AgBr, PbCl2, and others the cation transport number is close to unity. In the mixed oxide Zr02 nY20 pure anion conduction = 1) is observed. 

Although strong dependence of the barrier height, b> with the metal work function, 4>m, is observed in some ionic semiconductors, the majority of metal/inorganic semiconductor contacts do not appear to obey Schottk/s rule. In many semiconductors, the barrier is a less sensitive function of < m than given by Equation 19.4 and Equation 19.5 and, in some cases, it is independent of 4>m-... 

The concept was elaborated as the expansion of the theory of liquid semiconductors [30] applied to the problem of electrochemical decomposition of liquid chalcogen-ide compounds [26, 31]. In particular, basic components of namral metal ores, non-oxidised metal sulphides, exhibit the properties of PFC in the fused state. According to Velikanov, the PFC is an idealised complex ion-electron conductor where several electron transport mechanisms (ionic, semiconductor, metallic) of different physical nature contribute to the overall conductivity, and each of these contributions exhibits its own temperature dependency of the conductivity [26,31]. 

To show that our scheme is not hmited to describing monoatomic semiconductors, I generated a potential for bcc iron, a metal, and for gallium nitride, an ionic semiconductor. Our preliminary tests, which were the comparison of the phonon dispersion and the elastic moduli with Density Functional Theory values, demonstrate that GAP models can easily be built for different kinds of materials. I also suggest that the Gaussian Approximation Potentials can be generated on the fly and used as auxiliary tools for example, in structure search applications. 

For rather ionic semiconductors, it appears that oxygen uptake is predominantly by electron transfer adsorption in which the electronic charge participating in the adsorption bond comprises electrons from the semiconductor conduction band. The principal evidence for this is the frequent observation that the kinetics for this tyipe of gas-solid interaction are governed by an Elovich rate law typical of a reaction whose rate is limited by the diffusion of electronic majority carriers through a Schottky-type barrierSemiconductivity modulation has also been observed to accompany this type of gas-solid interaction. 

In sp -bonded crystals, the energy associated with the angles between the bonds is rather small. In contrast, the energy associated with the length of the bonds is large. Accordingly, reconstruction of covalent (or moderately ionic) semiconductors occurs through dis-... 

---