Lattice vibrations and electrical transport in (Bi1−xInx)2Se3 films

Abstract

We present Raman, terahertz transmission, and transport measurements on (Bi1−xInx)2Se3 films to study the evolution of phonon modes and resistivity with an increasing indium content across the metal-insulator phase transition. The frequencies of two Raman-active modes Eg2 and A1g2 as well as an infrared-active mode Eu increase with an increasing indium content due to the smaller atomic weight of indium compared to bismuth. Terahertz data are fitted by a Drude-Lorentz model. Drude scattering rates increase from 47 to 75 cm−1 with an increasing indium content from 0% to 16% due to stronger impurity scattering. The carrier concentration drops significantly for x = 24%. The temperature dependence of the resistivity switches from metallic at x = 16% to insulating at x = 24%, indicating a metal-insulator transition in between.

Photoexcited Free Carrier Dynamics in Bi2Se3, (Bi0.75In0.25)2Se3, and (Bi0.50In0.50)2Se3: From Topological to Band Insulator

“…This phonon mode broadens, with Γ α /2π increasing from ∼0.25 to ∼0.55 THz for x = 25%. It also shifts to the higher energy due to lower atomic weight of In compared to Bi, appearing at ∼2.3 THz for x = 25%, in agreement with the previous observations. , For x = 50% it shifts out of our probe bandwidth, appearing only as a broad positive real and negative imaginary conductance components, slowly increasing over the experimental spectral window.…”

“…Establishing an important benchmark, authors showed that the mobility of carriers in the QWS is more than 50 times lower than that in the SS (54 cm 2 /(V·s) versus 2880 cm 2 /(V·s)). THz TDS studies have also mapped out the evolution of the optical conductivity in (Bi 1– x In x ) 2 Se 3 over the sequential phase transitions from TI state to metallic and finally, trivial BI state as a function of In content from 0% to 25%. ,, …”

“…THz TDS studies have also mapped out the evolution of the optical conductivity in (Bi 1−x In x ) 2 Se 3 over the sequential phase transitions from TI state to metallic and finally, trivial BI state as a function of In content from 0% to 25%. 15,30,31 Finally, time-resolved techniques such as time-resolved ARPES, optical pump-optical probe spectroscopy with probe in the visible to mid-infrared range, time-resolved second harmonic generation (SHG), THz emission spectroscopy, as well as time-resolved THz spectroscopy (TRTS) have been used to uncover various aspects of optically excited carrier dynamics. 30,32−42 Of these techniques, optical pump-optical probe measurements are invaluable for probing interband processes, and time-resolved ARPES, time-resolved SHG and THz emission probe exclusively processes that occur at the surface.…”

Local structural analysis of In‐doped Bi2Se3 topological insulator using X‐ray fluorescence holography

“…Such a broad tunability of the electronic states is a unique feature of this system and favorable to the applications as electronic devices. Thus, extensive works have been performed for understanding the variation in the physical properties as a function of x .…”

“…Thus, extensive works have been performed for understanding the variation in the physical properties as a function of x. [7][8][9][10] However, the effect of the doping on the electronic states has not been clearly understood so far. In the ARPES study of (In x Bi 1−x ) 2 Se 3 , 6 ARPES spectra were systematically measured at several concentrations of x = 0.02, 0.04, 0.08, 0.20, and 0.30, where the TI to non-TI transition was observed at about x = 0.04.…”