RESUMO
Many new materials emerging are strictly two dimensional (2D), often only one or two monolayers thick. They include transition metal dichalcogenides, such as MoS2 , and graphene. Graphene in particular appears to have many potential applications. Typically the crystalline film without contamination is of interest. Therefore, a reliable method is needed to routinely evaluate the quality of the synthesized samples. Here, we present one such candidate method that utilizes standard electron diffraction and low/medium magnification imaging in a rudimentary transmission electron microscope. The electron irradiation dose is very low thus reducing electron irradiation damage of the investigated samples. As an example, the method was applied to the evaluation of as-grown graphene sample quality and a study on heating-induced change in graphene. It can be used to evaluate the volume and areal ratio of crystalline to noncrystalline component. The method is amiable to automated film quality evaluation.
RESUMO
Titanium oxide (TiO(x)) nanowires of various compositions were synthesized using a vapour-liquid-solid growth process without the need of a titanium-based support layer. The process utilized liquid gold droplets, evaporated titanium vapours, and an argon-5% oxygen gas mixture at 1100 degrees C. A thin layer of thermally grown silicon oxide was used as the support layer. The resulting nanowires were 80-100 nm in diameter with lengths varying from 0.5 to 10 microm. Nanowires of TiO, as opposed to TiO(2), were formed in low pressures of argon-oxygen. Environmental pressure was found to greatly affect nanowire quality. Surface abrasion did not contribute to or inhibit the overall growth process. X-ray photon spectroscopy and Auger electron spectroscopy confirmed the presence of titanium. X-ray diffraction and transmission electron microscopy electron diffraction analysis confirmed the presence of rutile and face centred cubic crystal structures in both materials.