Growth, characterization, and transport properties of ternary (Bi1−xSbx)2Te3 topological insulator layers

• Published in: Journal of physics. Condensed matter 2016-10, Vol.28 (49), p.495501-495501
• Main Authors: Weyrich, C, Drögeler, M, Kampmeier, J, Eschbach, M, Mussler, G, Merzenich, T, Stoica, T, Batov, I E, Schubert, J, Plucinski, L, Beschoten, B, Schneider, C M, Stampfer, C, Grützmacher, D, Schäpers, Th
• Format: Article
• Language: English
• Subjects: angular resolved photoemission spectroscopy; low temperature; magnetotransport; molecular beam epitaxy; Raman spectroscopy; topological insulators
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/28/49/495501

Ternary (Bi1−xSbx)2Te3 films with an Sb content between 0 and 100% were deposited on a Si(1 1 1) substrate by means of molecular beam epitaxy. X-ray diffraction measurements confirm single crystal growth in all cases. The Sb content is determined by x-ray photoelectron spectroscopy. Consistent values of the Sb content are obtained from Raman spectroscopy. Scanning Raman spectroscopy reveals that the (Bi1−xSbx)2Te3 layers with an intermediate Sb content show spatial composition inhomogeneities. The observed spectra broadening in angular-resolved photoemission spectroscopy (ARPES) is also attributed to this phenomena. Upon increasing the Sb content from x  =  0 to 1 the ARPES measurements show a shift of the Fermi level from the conduction band to the valence band. This shift is also confirmed by corresponding magnetotransport measurements where the conductance changes from n- to p-type. In this transition region, an increase of the resistivity is found, indicating a location of the Fermi level within the band gap region. More detailed measurements in the transition region reveals that the transport takes place in two independent channels. By means of a gate electrode the transport can be changed from n- to p-type, thus allowing a tuning of the Fermi level within the topologically protected surface states.