metallic surface states makes controlling the spin signal through currents possible. In addition, electron transport through three-dimensional (3D) TIs generates a fully spin-polarized current inside the bulk bad gap. To minimize the influences on the TSS, such as electron doping and scattering, a buffer layer that forms smooth interfaces and prevents interactions between electrodes is required during fabrication processes. We propose and demonstrate a new approach (Figure 1) that exploits an organic monolayer as a buffer layer to fabricate smooth interfaces and to prevent disturbances in the TSS during metal deposition [1]. In our study, we use the organic molecule perylene-3,4,9,10-tetracarboxylic-dianhydride (PTCDA) to form the buffer layer on the 3D TI Bi2Se3 with Fe atoms as surface dopants that represent the disturbance of electrodes. Scanning tunneling microscopy and spectroscopy (STM and STS) are used to investigate the PTCDA/Bi2Se3 and Fe deposited PTCDA/Bi2Se3 systems. In the PTCDA/Bi2Se3 system (Figure 2), due to the weak interactions between the PTCDA molecules and the Bi2Se3, the Bi2Se3 TSS is conserved on top of the well-ordered PTCDA assembly layers. By depositing Fe atoms on the Bi2Se3, the electron doping effect and Coulomb scattering between the TSS and the Fe atoms are addressed in the STS results. After introducing a PTCDA monolayer between the Fe and the Bi2Se3, the abovementioned effects are eliminated. Our results indicate that in the presence of the PTCDA buffer layer, the Fe atoms hybridized with the PTCDA molecules instead of interacting with the Bi2Se3. Accordingly, the TSS is protected from the Fe deposition. Our findings provide a new approach for the construction of a buffer layer that exhibits a smooth interface and prevents interactions between dopants and TI surfaces. The text was prepared by Dr. Huang-Hsiang Yang and Prof. Minn-Tsong Lin.   Reference [1] Hung-Hsiang Yang, Yu-Hsun Chu, Chun-I Lu, Christopher John Butler, Raman Sankar, Fang-Cheng Chou and Minn-Tsong Lin, Organic Monolayer Protected Topological Surface State, Nano Lett., 2015, 15 (10), pp 6896–6900. DOI: 10.1021/acs.nanolett.5b02811 Professor Minn-Tsong Lin Department of Physics mtlin@phys.ntu.edu.tw Reference Hung-Hsiang Yang, Yu-Hsun Chu, Chun-I Lu, Christopher John Butler, Raman Sankar, Fang-Cheng Chou and Minn-Tsong Lin. (2015). Organic Monolayer Protected Topological Surface State, Nano Letters, 15(10), 6896-6900. DOI: 10.1021/acs. nanolett.5b02811 Professor Minn-Tsong Lin Department of Physics mtlin@phys.ntu.edu.tw Hung-Hsiang Yang Department of Physics f99222012@ntu.edu.tw