Accession Number : ADA295968

Title :   The Synthesis of Crystalline Superlattices by Controlled Crystallization of Modulated Reactants.

Descriptive Note : Technical rept. Jun 94-Jun 95,

Corporate Author : OREGON UNIV EUGENE DEPT OF CHEMISTRY

Personal Author(s) : Noh, Myungkeum ; Thiel, James ; Johnson, David C.

PDF Url : ADA295968

Report Date : 16 JUN 1995

Pagination or Media Count : 20

Abstract : A series of new crystalline superlattice compounds containing an integral number of inter grown dichalcogenide layers were prepared through controlled crystallization of Ti/Se/Nb/Se superlattice reactants. Discussed in this paper are two members of this series containing seven dichalcogenide layers (3 NbSe2, 3 TiSe2 and one mixed layer) and twelve dichalcogenide layers (6 NbSe2 and 6 TiSe2 layers) oriented with the dichalcogenide layers parallel to the substrate surface. The synthesis of these new compounds begins with the design and preparation of an elementally modulated reactant. The component elemental layer thicknesses and annealing sequence are chosen to favor interfacial nucleation of the component binary compounds. The evolution of the initially layered reactants into the crystalline superlattices was monitored as a function of temperature using x-ray diffraction. The layered reactants contract in the c-axis direction during an initial low temperature anneal as NbSe2 and TiSe2 crystallites nucleate and grow along the interfaces, kinetically trapping the desired superlattice structure. ... jg p. 3

Descriptors :   *SUPERLATTICES, *CRYSTALLIZATION, *CRYSTALS, *MODULATION, *REACTANTS(CHEMISTRY), ANNEALING, LOW TEMPERATURE, CRYSTAL STRUCTURE, SYNTHESIS, INTERFACES, LAYERS, CRYSTAL LATTICES, X RAY DIFFRACTION, SUBSTRATES, NUCLEATION, SEQUENCES, SURFACES, NIOBIUM, TITANIUM, MIXING, KINETICS, SELENIUM, BINARY COMPOUNDS.

Subject Categories : Inorganic Chemistry
      Physical Chemistry
      Crystallography
      Thermodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE