Growth of Topological Insulator Bi₂Te₃ Ultrathin Films on Si(111) Investigated by Low-Energy Electron Microscopy

Abstract

The molecular beam epitaxy growth of topological insulator Bi 2 Te 3 thin films on Si(111) substrates has been investigated in situ by low-energy electron microscopy. The crystal structure and surface morphology during growth were directly revealed, which enables us to identify the optimal growth conditions for single crystalline Bi 2 Te 3 films. The formation of thin films is preceded by several surface structures, including a wetting layer and a Te/Bi-terminated Si(111)-1Â1 reconstruction. Raman scattering spectra and AFM measurements indicate that, under Te-rich conditions, single crystalline films of Bi 2 Te 3 grow along the [111] direction in a layer-by-layer mode. Transport measurements prove the insulating behavior of the films grown in this way.

MBE growth optimization of topological insulator Bi2Te3 films

“…The Bi 2 Te 3 crystal orientation along the main axis of the Si(1 1 1) substrate indicates that the hexagonal atoms arrangement of the Si(1 1 1) surface is the driving force on the impinging Bi and Te adatoms to form the Bi 2 Te 3 single-crystal epilayer with (0 0 1) orientation. The crystalline structure of the Bi 2 Te 3 film is found to be completely relaxed, in spite of a large lattice misfit of 14% with respect to Si(1 1 1) substrate [9]. A very thin amorphous layer observed at the interface with the substrate (TEM results not shown here) helps to obtain a rapid relaxation of the strain.…”

“…The narrow gap semiconductor Bi 2 Te 3 has been traditionally considered for thermoelectricity applications [5][6][7]. Very recently, however, TI behavior has also been reported for this material system [8][9][10][11][12]. The TI behavior in Bi 2 Te 3 is based on the crystalline structure which includes a sequence of five atomic layers Te(1)-Bi-Te(2)-Bi-Te(1), so called quintuple layer (QL).…”

“…Besides facilitating the study of fundamental TI properties of Bi 2 Te 3 , the realization of Bi 2 Te 3 epilayers on low-cost substrates, such as silicon, is beneficial for device applications. Only a few studies on MBE growth of the TI Bi 2 Te 3 on Si(1 1 1) have been carried out so far [9,10], presenting scanning tunneling microscopy (STM), atomic force microscopy (AFM), and angular-resolved photoelectron spectroscopy (ARPES) measurements, and some important growth studies.…”

Topological Insulator Film Growth by Molecular Beam Epitaxy: A Review

“…Unlike the case of Bi 2 Se 3 , most growths of Bi 2 Te 3 have been conducted on Si (111) substrates [83,[96][97][98][99][100]. As discussed in Section 2.1.4, silicon substrates have dangling bonds which must be satisfied before growth can occur.…”

High-quality ultra-flat BiSbTe3 films grown by MBE

“…Benefiting from their layered structure and weak van der Waals (vdW) bonding between the neighboring Te-Te layers, high-quality single crystal (Bi 1-x Sb x ) 2 Te 3 films have been successfully obtained on different substrates, such as Si (1 1 1) [12][13][14], GaAs (1 1 1) [15], sapphire (0001) [6], and SrTiO 3 (1 1 1) [8,16]. For instance, a 20-nm thick film of (Bi 1-x Sb x ) 2 Te 3 grown on SrTiO 3 (1 1 1) [16] showed very large terraces (possibly as large as 500 nm), but it also had large terrace steps indicating a rough surface.…”