Electrodeposition of a Functional Solid State Memory Material: Germanium Antimony Telluride from a Non-Aqueous Plating Bath

The electrodeposition of germanium antimony telluride (GST) alloys from a single non-aqueous plating bath based on tetrabutylammonium chlorometallate precursors is presented. The system provides a case-study for plating bath optimization in order to produce complex functional materials. GST deposits in the amorphous phase and the film composition and morphology can be readily adjusted by tuning the three precursor concentrations and the electrodeposition potential. Adjustment of the precursor concentrations allows the preparation of deposits ranging from the binaries (GeSb, GeTe, Sb2Te3) to ternaries with a wide range of compositions, including the standard Ge2Sb2Te5 composition – more commonly known as GST-225 – which is widely used in the solid state memory industry. In this paper we present a detailed study discussing the complex interplay between the deposition of germanium, antimony and tellurium and how adjusting the concentrations of their chlorometallates allows control over the composition and also the morphology of the deposits. We also highlight the benefits that arise from the wide separation in the deposition potentials for the three precursors, and in particular the ability to control the composition through modulation of the deposition potential.