Identifying Native Point Defects in the Topological Insulator Bi₂Te₃

Abstract

We successfully identified native point defects that occur in Bi 2 Te 3 crystals by combining high-resolution bias-dependent scanning tunneling microscopy and density functional theory based calculations. As-grown Bi 2 Te 3 crystals contain vacancies, antisites and interstitial defects that may result in bulk conductivity and therefore may change the insulating bulk character. Here, we demonstrate the interplay between the growth conditions and the density of different types of native near-surface defects. In particular, scanning tunneling spectroscopy reveals the dependence on not only the local atomic environment, but also on the growth kinetics and the resulting sample doping from n-type towards intrinsic crystals with the Fermi level positioned inside the energy gap. Our results establish a bias-dependent STM signature of the Bi 2 Te 3 native defects and shed light on the link between the native defects and the electronic properties of Bi 2 Te 3 , which is relevant for the synthesis of topological insulator materials and the related functional properties. Keywordstopological insulators, Bi 2 Te 3 , native point defects, scanning tunneling microscopy, density functional theory Topological insulators (TIs) represent one of the most active areas of quantum technology related research in condensed matter physics the last couple of years. The intense interest in TI materials soon after their theoretical prediction and experimental confirmation is justified as they realize a new electronic phase with promising applications ranging from advanced electronic and spintronic devices to quantum computing. The topological surface states (TSSs) of a three-dimensional TI provide robust conduction on the surface while the bulk is insulating. The low-energy electronic properties of these TSSs are dominated by massless Dirac fermion excitations, where the emerging Dirac cone defines the energy dispersion relations. Furthermore, a spin-momentum locking property is acquired due to spin-orbit interaction and time reversal symmetry that is present in these materials. As a result, backscattering from non-magnetic impurities is not allowed in TIs. [1][2][3][4][5][6][7][8][9][10][11] However, these fascinating properties experience many challenges caused by intrinsic point defects that exist naturally in binary tetradymites, including Bi 2 Te 3 and Bi 2 Se 3 . 12 Bi antisite defects denoted as Bi Te , Te antisite defects denoted as Te Bi , and Te vacancies denoted as V Te , are native defects with low formation energies that dope Bi 2 Te 3 crystals, which in turn exhibit bulk conductance that overshadows the TSSs. [13][14][15][16] On the other hand, identifying and investigating the impact of such native point defects close to the surface of the Bi 2 Te 3 is critical for improving the sample quality and the TI electronic properties necessary for TI-based

Disorder-Promoted Splitting in Quasiparticle Interference at Nesting Vectors

“…This pushed us to consider a more realistic shape of the scattering potential. The STM and density functional theory calculations 35 demonstrate that in Bi 2 Te 3 Te-vacancies form a triangular defect with the side about four lattice constants (see inset in Fig. 1b).…”

“…In the present paper we study the QPI from a collection of Te-vacancies -native surface defects in Bi 2 Te 3 . Using STM we focus on large areas where hundreds of Te-vacancies 35 are present, dense enough to enable the overlap of Friedel oscillations from neighbouring scatters.…”

“…It is then straightforward to model such a potential by a sum of the three scalar point potentials located at the vertices. 32,35 The Fourier transform of this impurity potential is written as:…”

Superconducting Long-Range Proximity Effect through the Atomically Flat Interface of a Bi2Te3 Topological Insulator

“…The topographic STM image in Fig. 1(a) obtained after in-vacuum Bi 2 Te 3 cleavage reveals the atomically clean surface on which typical structural defects [52][53][54] are observed. A typical dI(V )/dV spectrum measured at the Bi 2 Te 3 surface in a large energy window around the Fermi level is presented in Fig.…”

Дефекты межслоевой поверхности и термоэлектрические свойства в слоистых пленках топологических изоляторов n-Bi-=SUB=-2-=/SUB=-Te-=SUB=-2.7-=/SUB=-Se-=SUB=-0.15-=/SUB=-S-=SUB=-0.15-=/SUB=-

“…2), что согласуется с СТМ исследованиями материалов на основе теллурида висмута различного состава [11,27]. Te 2.7 Se 0.15 S 0.15 антиструктурные дефекты Te Bi находятся на расстоянии около 4 nm, а парные антиструктурные дефекты не были обнаружены.Обычно идентификация дефектов проводится путем сравнения изображений дефектов, полученных СТМ на бинарных материалах при низких температурах, с расчетными изображениями этих дефектов[26,29]. При измерениях морфологии поверхности (0001) при комнатной температуре, характер дефектов можно оценить по величинам провалов на профилях поверхности, используя значения атомных радиусов Bi, Te, Se и S, приведенные в таблице.…”