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
Peter Grünberg Institute (PGI-9) and JARA-Fundamentals of Future Information Technology, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Helmholtz Virtual Institute for Topological Insulators (VITI), Forschungszentrum Jülich, 52425 Jülich, Germany.
J Phys Condens Matter. 2016 Dec 14;28(49):495501. doi: 10.1088/0953-8984/28/49/495501. Epub 2016 Oct 17.
Ternary (Bi Sb )Te 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 (Bi Sb )Te 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.
通过分子束外延法在Si(1 1 1)衬底上沉积了Sb含量在0%至100%之间的三元(Bi Sb )Te薄膜。X射线衍射测量证实所有情况下均为单晶生长。Sb含量通过X射线光电子能谱确定。从拉曼光谱获得了一致的Sb含量值。扫描拉曼光谱表明，Sb含量处于中间值的(Bi Sb )Te层存在空间成分不均匀性。角分辨光电子能谱(ARPES)中观察到的光谱展宽也归因于这种现象。随着Sb含量从x = 0增加到1，ARPES测量显示费米能级从导带向价带移动。相应的磁输运测量也证实了这种移动，其中电导从n型变为p型。在这个过渡区域，发现电阻率增加，表明费米能级位于带隙区域内。在过渡区域进行的更详细测量表明，输运发生在两个独立的通道中。通过栅电极，输运可以从n型变为p型，从而允许在拓扑保护的表面态内调节费米能级。
