Efficient N-Type Doping in Epitaxial Graphene Through Strong Lateral Orbital Hybridization of Ti Adsorbate
Jhih-Wei Chen1*, Camilla Coletti2, Cheng-Maw Cheng3, Ming-Fa Lin1, Stefan Heun4, Forest Shih-Sen Chien5, Yi-Chun Chen1, Chia-Hao Chen3, Chung-Lin Wu1
1Department of Physics, National Cheng Kung University, Tainan, Taiwan
2Center for Nanotechnology Innovation@NIST, Istituto Italiano di Tecnologia, Pisa, Italy
3National Synchrotron Radiation Research Center, NSRRC, HsinChu, Taiwan
4NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore, Pisa, Italy
5Department of Physics, Tunghai University, Taichung, Taiwan
* presenting author:Jhih-Wei Chen, email:paul005paul005@gmail.com
Recently, various doping methods for epitaxial graphene have been demonstrated through atom substitution and adsorption. Here we observe by angle-resolved photoemission spectroscopy (ARPES) a coupling-induced Dirac cone renormalization when depositing small amounts of Ti onto epitaxial graphene on SiC. We obtain a remarkably high doping efficiency and a readily tunable carrier velocity simply by changing the amount of deposited Ti. First-principles theoretical calculations show that a strong lateral (non-vertical) orbital coupling leads to an efficient n-type doping of graphene by hybridizing the 2pz orbital of graphene and the 3d orbitals of the Ti adsorbate, which attached on graphene without creating any trap/scattering states. This Ti-induced hybridization is adsorbate-specific and has major consequences for efficient doping as well as applications towards adsorbate-induced modification of carrier transport in graphene.

Keywords: Epitaxial graphene, Angle-resolved photoemission spectroscopy (ARPES), High doping efficiency