The Preparation of Crystalline NbSe2/TiSe2 Superlattices from Modulated Elemental Reactants

Abstract

ABSTRACTThree new crystalline NbSe2/TiSe2 superlattice compounds with 43.472±0.005A, 80.66±0.03A and 117.9±0.1Å unit cells in thec direction were prepared through controlled crystallization of Ti/Se/Nb/Se superlattice reactants with different compositional layer thicknesses. Theta-theta and rocking curve data were collected using a theta-theta diffractometer to study the evolution of the initially layered reactants into the crystalline superlattices as a function of temperature. Low angle diffraction data demonstrates that the initial layered reactant contracts in the c-axis direction upon initial annealing and suggests that the interfaces become smoother during this initial interdiffusion. High angle rocking curve diffraction data shows the development of caxis oriented NbSe2fTiSe2 crystal growth perpendicular to the substrate surface. Theta-theta scans show a gradual decrease of the (001) diffraction linewidths of the growing compound as a function of annealing time and temperature indicating an increase in the c-axis domain size. High quality caxis oriented TiSe2/NbSe2 crystalline superlattices result from annealing at the relatively low temperature of 500ºC. The rational synthesis of intergrowth compounds from superlattice reactants as described herein will permit the tailoring of physical properties as a function of compositional layer thicknesses and nativeproperties of the parent compounds.