Robust topological surface states of Bi2Se3 thin films on amorphous SiO2/Si substrate and a large ambipolar gating effect

Abstract

ABSTRACT:The recent emergence of topological insulators (TI) has spurred intensive efforts to grow TI thin films on various substrates. However, little is known about how robust the topological surface states (TSS) are against disorders and other detrimental effects originating from the substrates.Here, we report observation of a well-defined TSS on Bi 2 Se 3 films grown on amorphous SiO 2 (aSiO 2 ) substrates and a large gating effect on these films using the underneath doped-Si substrate as the back gate. The films on a-SiO 2 were composed of c-axis ordered but random

Textured Sb2Te3 films and GeTe/Sb2Te3 superlattices grown on amorphous substrates by molecular beam epitaxy

“…In order to realize (0 0 1) t (the subscript t is used to indicate that the trigonal lattice indexing is used instead of the (pseudo) cubic lattice symmetry) oriented GeTe/Sb 2 Te 3 superlattices on amorphous substrates and patterned device substrates, an approach was used that is similar to that of Bansal et al used for Bi 2 Se 3 . 17 The first Sb 2 Te 3 layer of approximately 5 nm is deposited at 50 • C, which is below the crystallization temperature of Sb 2 Te 3 and hence the layer is amorphous. Subsequently, the temperature is raised to the deposition temperature of 227 • C at a rate of 0.3 • /s.…”

“…9 The 2D nature of materials, such as Sb 2 Te 3 or Bi 2 Se 3 , makes it possible to obtain textured materials and a number of studies have indeed demonstrated the ability to grow textured 2D materials on amorphous substrates. 9,[17][18][19] Saito et al showed that the film texture can be greatly improved by using Ar + sputtering before the deposition in order to "clean" the substrate surface. 20 Moreover, they argued that a good texture is only obtained when there is a low reactivity between substrate and film.…”

Topological Insulator Film Growth by Molecular Beam Epitaxy: A Review

“…Finally, dielectric SiO 2 /Si substrates have been widely used to back gate Bi 2 Se 3 flakes [90][91][92], prompting many attempts to directly grow on these substrates [73,74,93]. Although the amorphous nature of SiO 2 /Si would hinder traditional MBE growth, Bi 2 Se 3 can still be grown by taking advantage of van der Waals epitaxy.…”

Surface and interface states of Bi2Se3 thin films investigated by optical second-harmonic generation and terahertz emission

“…Although such behavior of Ið2xÞ for the films is reminiscent of the 4 mm point group, we attribute it instead to the formation of the domains with random in-plane orientations; 17,18,[23][24][25] this can make the in-plane SH response effectively inversion-symmetric, whereas the inversion symmetry along the out-of-plane direction remains broken. In this context, it is straightforward to understand not only the isotropic SHG responses for P out geometries but also the negligible Ið2xÞ for S out geometries.…”

“…[14][15][16]18 For the film grown on Al 2 O 3 , one sample was left with Bi 2 Se 3 as a top surface, and the other sample was capped with a 20-nm-thick Al 2 O 3 layer via atomic layer deposition. In the former and latter cases, the Bi 2 Se 3 film thicknesses were about 30 and 20 nm, respectively.…”