Development and properties of single-crystal silver selenide layers

Abstract

The development of Ag 2Se was studied by transmission electron microscopy (TEM) on thin samples prepared by successive deposition of (100) silver films and selenium onto NaCl. The formation of Ag 2Se takes place by a topotactic reaction and the nucleation, grain growth and coalescence of the compound phase was revealed during the first stage of selenium condensation. Ag 2Se domains were found grwoing initially by nucleation with tetragonal symmetry. Fully selenized layers proved to have both single-crystal and mosaic structure, consisting of slightly misoriented domains depending on the preparation conditions. Orthorhombic symmetry of low-temperature silver selenide was found in layers prepared at temperatures both above and below the transition temperature (133 °C). A reversible phase transition between low- and high-temperature Ag 2Se phases could be generated by changing the intensity of the electron beam during TEM investigation.