Self-assembly of designed precursors: A route to crystallographically aligned new materials with controlled nanoarchitecture

Abstract

Modulated elemental reactants is a method by which new and complex intergrowth compounds can be synthesized by the self-assembly of designed precursors prepared by physical vapor deposition. Careful calibration of the composition and thickness of the precursors ensures the formation of the desired product by precise control of local composition and diffusion lengths. Superstructures of increasing complexity can be realized using binary and ternary systems as starting points. The synthesis of systems based on three different binary compounds, either alloyed together or separated into distinct layers, expands the number of possible superstructures that can be formed using this technique, but provides analytical challenges. The synthesis of [(SnSe)1.15]1([TaxV1-x]Se2)1[(SnSe)1.15]1([VyTa1-y]Se2)1 compound is used to illustrate the preparation of precursors and the challenges in both measuring and limiting the interdiffusion of layers during self-assembly. Systematic changes in the electrical properties of (SnSe)1+δ(TaxV1-x)Se2 alloys are observed as x is varied. The electrical resistivity of [(SnSe)1.15]1([TaxV1-x]Se2)1[(SnSe)1.15]1([VyTa1-y]Se2)1 can be modeled as the two constituent layers in parallel.