Growth of nanostructured materials from the hexagonal crystal class

Abstract

This thesis examines the growth of nanostructured materials from the hexagonal crystal class such as molybdenum sulfide and boron nitride. We report for the first time a low-temperature, cheap, convenient way of producing oriented MoS2 two-dimensional nanosheets from the one-step thermal evaporation of a single source precursor tetrakis(diethylaminodithiocarbomato) molybdate(IV). By designing the appropriate heterogeneous chemistry routes, different morphological types ranging from nanosheets to nanocups, as well as different materials such as MoGe2, MoSi2 or carbon microwhiskers can be prepared using the very versatile precursor. The surface chemistry of the precursor has been investigated using in situ XPS and TPD techniques. In order to evaluate the chemical reactivity of the basal planes and edges, the surface chemistry of MoS2 nanosheets has been studied by laser trimming, electrochemical and chemical vapor deposition methods.Nickel-encapsulated hexagonal boron nitride nanodots array on silicon have been fabricated by plasma-assisted chemical vapor deposition using borazine as precursor. The BN overcoat prevents the oxidation of the inner ferromagnetic metal nanoclusters, offering important technological application in ferromagnetism and quantum devices. Silicon oxide (SiOx) nanowires have been successfully grown by MPCVD on catalytically-patterned silicon substrate without using any gaseous silicon-containing precursors. Ultra-long, high density, multiple branching SiOx nanowires could be synthesized with a high growth rate.