The effect of substrates on the materials properties of topological insulator films
K. H. M. Chen1*, H. Y. Lin1, C. K. Cheng2, C. Y. Wang1, X. Q. Zhang3, Y. H. Lee3, C. M. Cheng4, M. Hong2, J. Kwo1
1Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
2Department of Physics, National Taiwan University, Taipei, Taiwan
3Department of Material Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan
4National Synchrotron Radiation Research Center, Hsinchu, Taiwan
* presenting author:陳可璇, email:ykhw1436@yahoo.com.tw
Topological insulators (TIs), a new state of quantum matter, display a rich variety of extraordinary physical phenomena. High quality 3-D TI films of Bi2Se3 and Bi2Te3 have been obtained by van der Waals epitaxy on variety of crystalline substrates such as Al2O3, and Si. To further reduce the high level of defect density common of the TI films, we have extended the investigation to utilize 2D layered materials of hexagonal symmetry as the substrates, such as epitaxial graphene grown on SiC, and large area CVD MoS2 monolayer grown on Al2O3. Sharp and streaky RHHED patterns were observed during the TI growth. Surface morphologies were characterized by atomic force microscope, and the size of triangular shaped domains varies considerably among different substrates. For example, the largest domain size of Bi2Te3 up to 3μm was observed for the growth on MoS2 monolayer, substantially bigger than those on crystalline Al2O3. Normal scans of a 4-circle x-ray diffraction indicated that the c-axis of the epitaxial Bi2Te3 film grown on crystalline Al2O3, epitaxial graphene and MoS2 substrates were full strain relaxed with a FWHM varying from 0.02° to 0.04°, suggesting a very high degree of crystallinity. Sharp surface state and Dirac point were observed by angle-resolved photoemission spectroscopy (ARPES) with synchrotron radiation. Studies of transport properties such as mobility, carrier concentration are now underway.


Keywords: topological insulator