Incubation of PbSe Thin Films in a Tin(II) Salt Aqueous Solution: Modification and Ion-Exchange Reactions

Topochemical ion-exchange reactions between solid micro- and nanostructured metal chalcogenides and aqueous salt solutions are generally used for formation of composite structures based on initial metal chalcogenides and products of their ion-exchange transformation. However, ion exchange has promises as a route to obtaining both composites and solid solutions based on the initial and the end chalcogenide phases. With the help of the ion-exchange technique, single-phase films of Pb1–xSnxSe substitutional solid solutions with a tin content up to ∼2 at.%, which are promising for mid- and long-wavelength infrared radiation (IR) optoelectronics, have been obtained at the interface between PbSe polycrystalline thin films and SnCl2 aqueous solutions containing sodium citrate. It has been shown that the pH value and temperature of the reaction system play an important role in the ion-exchange process. Incubation of lead selenide (PbSe) films in a tin(II) salt aqueous solution also leads to their modification with oxygen-containing tin compounds to a depth of ∼3 nm. Differences in the film structure, such as changes in the coherent scattering region sizes and orientation of crystallites along the [220] direction, which arise during the contact with citrate-containing SnCl2 solutions, have also been revealed. For the first time, an idea of the existence of a relatively wide reaction zone of an intragranular topochemical ion-exchange reaction in an aqueous solution, within which substitutional solid solutions can form in micro- and nanostructured systems, has been set forth.