published_or_final_version / Physics / Master / Master of Philosophy

An STM head based on the design of Besocke was designed and constructed to have superior vibrational and thermal stability in order to produce very high resolution images. The vibrational properties and thermal properties of the head design are quantitatively analyzed and compared to the actual performance achieved. With this new STM head, we were able to implement spectroscopic dI/dV imaging techniques (conductance imaging) to observe electronic features on surfaces. Using this conductance imaging, benzene and chlorobenzene on the Si(111)7x7 surface were studied. We also present the first solid evidence that confirms that the rest atom is involved in the bonding of benzene to this surface. We show that conductance imaging does indeed show variations in the electronic structure of the surface with adsorbates, illustrating that this technique has strong potential for assigning binding sites. / xiv, 155 leaves ; 29 cm.

No description available.

Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 59-60) Also available in print.

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 106-114).

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 249-269).

Molecular order in surfaces is probed for several different repeat unit Spectroscopy (XPS) is chemistries. X-ray Photoelectron used, particularly with angular dependence, to obtain the compositional gradient information from the top 6 run of the surface. It is found that all materials investigated present some kind of preferential and reproducible ordering effect. The ordering ef feet can be present in different forms, such as preferential segregation of a crystalline block to the surface, segregation of a component of different crystalline structure to the surface or orientation of a backbone segment of the polymer towards the surface of the specimen. Polyethylene terephthalate shows an increasing amount of crystalline cyclic oligomer at the surface as the degree of crystallinity of the matrix increases. Block copolyesters unsaturated blocks present containing saturated and the saturated blocks preferentially segregated toward the surface. Crystalline ethylene/chlorotrifluoroethylene alternating copolymer shows the preferential orientation of ethylene groups closer to the surface. The linear polyurethanes studied reveal the surfaces enriched with soft segments, whereas no enrichment was observed for a crosslinked polyurethane. / Master of Science

published_or_final_version / Physics / Master / Master of Philosophy

Zhao, Lei = 介孔材料的光學應用和表面等離子體-熒光分子之間相互作用 / 趙磊. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Zhao, Lei = Jie kong cai liao de guang xue ying yong he biao mian deng li zi ti - ying guang fen zi zhi jian xiang hu zuo yong / Zhao Lei.

The interest in two-dimensional materials and materials physics has grown dramatically over the past decade. The family of two-dimensional materials, which includes graphene, transition metal dichalcogenides, phosphorene, hexagonal boron nitride, etc., can be fabricated into atomically thin films since the intralayer bonding arises from their strong covalent character, while the interlayer interaction is mediated by weak van der Waals forces. Among them, molybdenum disulfide (MoS₂) has attracted much interest for its potential applications in opto-electronic and valleytronics devices. Previously, much of the experimental studies have concentrated on optical and transport measurements while neglecting direct experimental determination of the electronic structure of MoS₂, which is crucial to the full understanding of its distinctive properties. In particular, like other atomically thin materials, the interactions with substrate impact the surface structure and morphology of MoS₂, and as a result, its structural and physical properties can be affected. In this dissertation, the electronic structure and surface structure of MoS₂ are directly investigated using angle-resolved photoemission spectroscopy and cathode lens microscopy. Local-probe angle-resolved photoemission spectroscopy measurements of monolayer, bilayer, trilayer, and bulk MoS₂ directly demonstrate the indirect-to-direct bandgap transition due to quantum confinement as the MoS₂ thickness is decreased from multilayer to monolayer. The evolution of the interlayer coupling in this transition is also investigated using density functional theory calculations. Also, the thickness-dependent surface roughness is characterized using selected-area low energy electron diffraction (LEED) and the surface structural relaxation is investigated using LEED I-V measurements combined with dynamical LEED calculations. Finally, bandgap engineering is demonstrated via tuning of the interlayer interactions in van der Waals interfaces by twisting the relative orientation in bilayer-MoS₂ and graphene-MoS₂-heterostructure systems.