Ternary (Bi 1−x Sb x ) 2 Te 3 films with an Sb content between 0 and 100% were deposited on a Si(111) 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 1−x Sb x ) 2 Te 3 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.

We report on the Shubnikov-de Haas oscillations in the longitudinal resistance of thin films of three-dimensional topological insulator Sb 2 Te 3 grown by means of molecular beam epitaxy. The oscillations persist up to the temperatures of 30 K, and the measurements at various tilt angles reveal that they originate from a two-dimensional system. Using a top gate, we further study the change of oscillation amplitude and frequency, which in combination with the standard Hall measurements suggest the origin of oscillations to be at the interface between the film and the Si substrate.