Scanning Tunneling Microscopy Study on Emergent Materials
Minn-Tsong Lin1,2*
1Department of Physics, National Taiwan University, Taipei, Taiwan
2Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
* presenting author:Minn-Tsong Lin,
We present here the study of scanning tunneling microscopy (STM) on emergent materials. It often requests information not only on morphology, but also the local electronic structure. Scanning tunneling spectroscopy (STS) is almost the only approach to monitor the local electronic structure in nanometer scale for material surface, and with help of a magnetic tip, can be spin-sensitive, becoming spin-polarized STM.
Two examples will be given in this talk. The first one is the 2-D network of Fe-PTCDA (perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride) grown on Au(111) [1]. In this case, the STS study indicates that the frontier orbital shifts of the PTCDA molecules are correlated with the metal-organic coordination number, which affects the magnitude of charge transfer onto each PTCDA in the Fe-PTCDA hybridization system. SP-STM also provides the spin-response of the organic molecules when they are deposited on magnetic Co islands.
Another system is the Rashba Semiconductor BiTeI [2], which is of great interest for use in spintronic devices exploiting the Rashba effect. Using spatially resolved tunnelling spectroscopy across the lateral boundary between the two terminations, a previously speculated on p-n junction-like discontinuity in electronic structure at the lateral boundary is confirmed experimentally. These findings realize an important step towards the exploitation of the unique behavior of the Rashba semiconductor BiTeI for new device concepts in spintronics.

[1] H. H. Yang, Y. H. Chu, C. I. Lu, T. H. Yang, K. J. Yang, C. C. Kaun, G. Hoffmann, and Minn-Tsong Lin, ACS Nano 7, 2814-2819 (2013).
[2] Christopher J. Butler, H.-H. Yang, J.-Y. Hong, S.-H. Hsu, R. Sankar, C.-I. Lu, H.-Y. Lu, K.-H. Ou Yang, H.-W. Shiu, C.-H. Chen, C.-C. Kaun, G.-J. Shu, F.-C. Chou, and Minn-Tsong Lin, Nat. Commun. 5:4066 doi: 10.1038/ncomms5066 (2014).

Keywords: Scanning Tunneling Microscopy , Rashba Semiconductor, Spin-Polarized Scanning Tunneling Microscopy , Organic Molecules, BiTeI