Investigating and Engineering the Electronic Structure at Organic-Inorganic Interfaces

• Main Authors: Hung-Hsiang Yang, 楊鈜翔
• Other Authors: 林敏聰
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/97421977361406402292

博士 === 國立臺灣大學 === 物理研究所 === 103 === Organic/inorganic interfaces strongly a ect the functions of organic devices. Thus, skills of engineering the organic-inorganic hybrids hold the keys for designing molecular electronic devices. Organic-inorganic systems with controllable fabrications are studied by scanning tunneling microscopy (STM) which is a powerful tool to study the interplay between structural and electronics properties with high spatial and energy resolution. In this thesis, the prototype molecule PTCDA (perylene- 3,4,9,10-tetracarboxylic dianhydride) and the coordination with iron atoms on various substrates [Au(111), Cu(111) and Bi2Se3] are investigated. Physisorption of PTCDA/Au(111) is identi ed while well-ordered metal-organic nanostructures chains and networks form in Fe-PTCDA/Au(111). Such nanostructures provide di erent metal-organic coordination for molecules and disparities in the degree of charge transfer. Digitized frontier orbital shifts are addressed in the Fe-PTCDA hybridization system, which implies the speci c coordination a ects the magnitude of charge transfer onto each PTCDA. On the other hand, chemisorption is found with PTCDA/Cu(111), in which the molecule-substrate coupling is strong yet can be attenuated by incorporating Fe adatoms. These ndings show that the formation of the metal-organic complex o ers a unique way to engineer the degree of hybridization of involved molecules as well as tune the molecule-substrate coupling. Fabricating smooth interfaces and isolations between topological insulator (TI) surfaces and electrodes are key issues for conserving the spin-momentum locked metallic surface states in TI devices. An alternative using organic molecules as a tunneling barrier is demonstrated to possess a smooth interface and the ability to prevent disturbances in the topological surface state (TSS) upon metal deposition. Utilizing the weak interaction between PTCDA molecules and Bi2Se3 surfaces, the TSS of Bi2Se3 is conserved on top of the well-ordered PTCDA assembly layer. By forming Fe-PTCDA hybrids, in uences, such as doping e ect and Coulomb scattering, of Fe atoms on the Bi2Se3 surface state are eliminated.