Robust surface electronic properties of topological insulators: Bi2Te3 films grown by molecular beam epitaxy

The surface electronic properties of the important topological insulator Bi2Te3 are shown to be robust under an extended surface preparation procedure which includes exposure to atmosphere and subsequent cleaning and recrystallization by an optimized in-situ sputter-anneal procedure under ultra high vacuum conditions. Clear Dirac-cone features are displayed in high-resolution angle-resolved photoemission spectra from the resulting samples, indicating remarkable insensitivity of the topological surface state to cleaning-induced surface roughness.Comment: 3 pages, 3 figure

Spin-polarization limit in Bi2Te3Bi_{2}Te_{3} Dirac cone studied by angle- and spin-resolved photoemission experiments and ab initio calculations

The magnitude of electron spin polarization in topologically protected surface states is an important parameter with respect to spintronics applications. In order to analyze the warped spin texture in Bi2Te3 thin films, we combine angle- and spin-resolved photoemission experiments with theoretical ab initio calculations. We find an in-plane spin polarization of up to ∼45% in the topologically protected Dirac cone states near the Fermi level. The Fermi surface of the Dirac cone state is warped and shows an out-of-plane spin polarization of ∼15%. These findings are in quantitative agreement with dedicated simulations which find electron density of the Dirac cone delocalized over the first quintuple layer with spin reversal occurring in the surface atomic layer

MBE growth optimization of topological insulator Bi2Te3 films

We investigated the growth of the topological insulator Bi2Te3 on Si(1 1 1) substrates by means of molecular-beam epitaxy (MBE). The substrate temperature as well as the Bi and Te beam-equivalent pressure (BEP) was varied in a large range. The structure and morphology of the layers were studied using X-ray diffraction (XRD), X-ray reflectivity (XRR) and atomic force microscopy (AFM). The layer-by-layer growth mode with quintuple layer (QL) as an unit is accomplished on large plateaus if the MBE growth takes place in a Te overpressure. At carefully optimized MBE growth parameters, we obtained atomically smooth, single-crystal Bi2Te3 with large area single QL covering about 75% of the layer surface. Angular-resolved photoelectron spectroscopy reveals a linear energy dispersion of charge carriers at the surface, evidencing topologically insulating properties of the Bi2Te3 epilayers. (C) 2011 Elsevier B.V. All rights reserved