Photoemission studies on the electronic structures modification of two-dimensional electron systems

  • 陳 至瑋

Student thesis: Doctoral Thesis


The two-dimensional electron system has been wildly developed and applied into quantum electronic devices The LAO/STO heterooxide and graphene are very classical examples To understand conduction property of two-dimensional electron systems it is quite essential to characterize and measure the electronic structure directly Photoemission spectroscopy provides non-destructive measurement which lead us to understand the intrinsic electronic structure in both of real-space and reciprocal space This is better than the conventional metal probe measurement The photoemission techniques used to study the two-dimensional can be classified into three techniques (i e XPS SPEM and ARPES) These techniques feature in different characterization XPS owns the deepest probing depth which is suitable for heterostructure measurement SPEM owns the best spatial-resolution which is suitable for micro-structure measurement ARPES owns the best energy-resolution which is suitable for electronic structure measurement In this thesis the electronic structure of low-dimensional electron system has been systematically studied by photoemission techniques Chapter 1 introduces the research background for LAO/STO and graphene Chapter 2 describes the principle of photoemission spectroscopy and angle-resolved photoemission spectroscopy In Chapter 3 we introduce an ARPES work station for in-situ ARPES measurement and further characterization for graphene systems In order to characterize the graphene a single-crystalline graphene has been characterized by LEED XPS and in-housed ARPES The high-energy resolution ARPES results are displayed in Chapter 6 Chapter 4 represents the electronic structures of LAO/STO measured by XPS with respect to Pup and Pdown polarization This enables us to understand polarization influence Two distinct ferroelectric patterns are created and assisted by large-area scanning probe station In Chapter 5 the metal-contact induced doping in graphene electronic structure has been characterized by SPEM The high-spatial resolution SPEM enables us to study the doping effect inside exfoliated graphene and their core-level information In Chapter 6 we measure the changes of electronic structures (Dirac cone) by small amount of Ti deposited onto graphene The dz2 orbital of Ti is strongly hybridized with pz orbital of C atom which resulting in the high doping efficiency Chapter 7 summarizes the conclusion and suggests the future research topics
Date of Award2015 Dec 29
Original languageEnglish
SupervisorYi-Chun Chen (Supervisor)

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