Number Of Mobile Ions Research Articles

Manifestations of the deneutralization of mobile charges in SiO2 in the spectroscopy of the silicon-oxide interface

The total number of mobile ions in the oxide film in a Si-based MOS structure is determined by the conventional methods of recording capacitance-voltage and dynamic current-voltage characteristics. The fraction of ions in the neutral state at the Si-SiO2 interface is determined. Spectroscopy of the interface reveals a peak of the effective density of interface states. It is shown that the number of states in this peak corresponds to the number of neutralized particles. The mechanism for neutralization of the mobile charge of ions is discussed.

A nuclear spin-lattice relaxation study of the mixed-alkali effect in glasses

The 7Li nuclear spin-lattice relaxation time has been measured as a function of temperature for a series of mixed-alkali Li-Na disilicate glasses. No evidence of a pronounced non-linear mixed-alkali effect was found for the low-temperature activation energy, ELT, of the spin-lattice relaxation (SLR) rate, nor of the ratio ELT/Eσ (where Eσ is the dc conductivity activation energy). These results can be interpreted, in terms of Elliott and Owens' diffusion-controlled relaxation model for SLR, as indicating that there is no significant change in the number of mobile ions in mixed-alkali glasses; instead, the mixed-alkali effect must be due to changes in the ionic mobility.

Conductivity and Thermally Srimulated Processes I Model Ionic Pplymers. I. Halato Telechelic Polybutadienes.

The relaxation and conductivity properties of model ioncontaining macromolecules, i. e. halato-telechelic polybutadienes with various degrees of neutralization, were investigated from 100 to 350 K by means of thermally stimulated depolarization and polarization methods, stressing the comparison of materials based on alkaline (Na, K, Li) and alkalineearth (Ba, Ca, Mg) cations. It was shown that the behavior is largely determined by the thermal stability of ionic associations and their ability to trap impurity charge carriers. With alkaline-earth cations, the associations are thermally stable at least up to 350 K (i. e. more than 150 K above the glass transition temperature), which allows to observe a conductivity level smaller than that of the precursor polymer by several orders of magnitude. An opposite result is observed with alkaline cations as a consequence of the thermal breaking of unstable ionic associations. This dissociation first gives rise to a large relaxation process involving isolated carboxylate groups and then to a rapidly growing number of mobile ions which induce an important increase in conductivity. Generally speaking, and taking into account similar results previously obtained in various ionomers, it can be concluded that introducing a few percent ionic groups in polymers can modify their conductivity by several orders of magnitude (either decrease or increase depending on the type of cation involved).

Ionic conductivity of Li4SiO4 solid solutions in the system Li2O-Al2O3-SiO2

In the system Li2O-Al2O3-SiO2, Li4SiO4 forms two limited ranges of solid solutions: Li4+x Si1−x Al x O4: 0 < x ≲ 0.4, containing interstitial Li+ ions and Li4−3y Al y SiO4: 0⩽y≲ 0.06, containing Li+ vacancies. The a.c. conductivity of polycrystalline samples of several compositions was measured over a range of frequency (2×102 to 5×104 Hz) and temperature (25 to 500°C). Both solid solutions, especially the Li+ interstitial ones, have markedly higher conductivity than has stoichiometric Li4SiO4. This is due to an increase in the number of mobile ions and a decrease in the activation energy for conduction in the solid solutions.

Study of low-frequency relaxation phenomena in thin-film capacitors

Experiments are described to determine the dispersion characteristics at low frequencies of thin-film capacitances. It is supposed that mobile positive ions are responsible for the observed relaxation phenomena. The number of mobile ions and their relaxation time are investigated in function of the applied voltage for thin films of SiO, Al2O3, Ta2O5 and polytetrafluoraethylene. Theoretical models to explain the experimental data are also given.

Interface phenomena in integrated circuit oxides : C. R. Viswanathan and S. Ogura. California Univ. School of Engineering & Applied Science, U.S.A. December (1970), pp. 71. AD-719283M.REP-70-80. TR-ECOM-0203-F. DAAB-07-68-C-0203 FR

Abstract : The instability in MIS devices, arising due to mobile positive ions in the insulator layer was investigated experimentally and theoretically. A direct measurement of the built-in voltage in the MIS structure, viz., the voltage existing across the insulator due to interface effects, was shown to be possible using the photoelectric technique. The diffusion of ions in the oxide layer was studied and the results point out to the conclusion that the mobile ions tend to be localized either near the metal interface or near the silicon interface. Of these two, the sites near the metal interface have a larger activation energy and as such, the ions stay predominately near the metal interface. Calculations of the potential in the oxide layer, in the presence of mobile ions were carried out and found to give reasonable agreement with experimental results. The role of impurities like Al and Au was also studied. Interface Characteristics and the number of mobile ions and the number of traps were also studied for a chemically grown MNS sample. A number of problem areas requiring further investigation is also pointed out. (Author)