Surface ionic conductivity, lattice disorder, and space charge region in thin silver bromide layers

Abstract

Carefully controlled conditions of evaporation allow the preparation of epitaxial layers of pure AgBr. The temperature dependence of the conductivity of layers with varying thickness is measured. This in principle makes possible the splitting of the conductance into surface and bulk components. The bulk conductivity of the layers is found to be practically identical with that of pure large single crystals of AgBr, which until now has not been observed. For the first time considerable surface conductance is directly observed not only for {111} but for {200} layers too. All parameters characterizing the Frenkel disorder in the subsurface region are evaluated from 150 °C down to room temperature.

Ionic field effect in epitaxial AgBr layers

“…Besides, using a probe of electrolytically sharpened silver point, it was found that the voltage varied linearly between the electrodes. Using Ohmic contacts, the values of the conductance obtained here f row dc measurements are similar to those from ac short pulses as described in [14]. Thus it can he concluded that a t the specified conditions the flow of charge is connected with nearly reversible electrode processes a t a negligible electrode polarization.…”

“…First, etching substantially decreases the density of surface states which in accordance with theoretical expectations [27] leads to a decrease in the surface potential. A comparison of the density of negatively charged surface states 1.4 x 1013 cn1-2 found in [14] corresponding to the value evaluated in the present work indicates a decrease by two orders of magnitude. Second, the enhanced concentration of majority carriers in the non-stoichiometric material studied involves in turn a reduced SC region, hence a lower surface potential.…”

“…The epitaxial (111) AgBr layers were prepared and annealed as described in [14]. Sufficiently good Ohmic current electrodes were obtained by vacuum deposition of silver on the substrate prior to the evaporation of AgBr.…”

Space‐Charge at the Lithium‐Lithium Chloride Interface

“…[11] and [12] are used. Such a variation of densities may have a decisive influence on the conductivity of a thin crystal layer (12)(13)(14)(15)(16)20). The value of q~ for a particular interface is not known.…”

“…The unexpected results of measurements have been explained by morphology and the polycrystalline structure of the layer (8,9). The conductivity of such layers is strongly affected by the type of parent substrate (12)(13)(14), or by the electrolyte into which the layer is immersed (15,16), i.e., the mobile carrier density is essentially influenced by the interface between the crystal and the surrounding medium. This paper shows that the electrical properties of the passive layer can be explained by using results obtained in the field of solid-state batteries and thin crystal layers, e.g., silver and alkali halides.…”