Toward Truly Single Crystalline GeTe Films: The Relevance of the Substrate Surface

Abstract

The growth of GeTe thin films on a Si(111)-(√3 × √3)R30°-Sb surface is reported. At growth onset, the rapid formation of fully relaxed crystalline GeTe(0001)-(1 × 1) is observed. During growth, a GeTe(0001)-(√3 × √3)R30° surface reconstruction is also detected. Indeed, density functional theory (DFT) simulations indicate that the reconstructed GeTe(0001)-(√3 × √3)R30° structure is energetically competing with the GeTe(0001)-(1 × 1) reconstruction. The out-of-plane α-GeTe<0001>||Si<111> and in-plane α-GeTe<−1010>||Si<−211> epitaxial relationships are confirmed by X-ray diffraction (XRD). Suppression of rotational twist and reduction of twinned domains are achieved. The formation of rotational domains in GeTe grown on Si(111)-(7 × 7) is explained by domain matched coincidence lattice formation with the Si(111)-(1 × 1) surface. Atomic force microscopy (AFM) images show the coalescence of well-oriented islands with subnanometer roughness on their top part. van der Pauw measurements are performed to verify the electric properties of the films. The quality of epitaxial GeTe thin film is discussed and related to the crystalline structure of GeTe and its rhombohedrally distorted resonant bonds.

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

“…1(c). After the preparation of this seed layer the GeTe/Sb 2 Te 3 superlattice can be grown using standard deposition parameters for GeTe 22 and Sb 2 Te 3 12 and described in detail in ref. 6.…”

Improved structural and electrical properties in native Sb2Te3/GexSb2Te3+x van der Waals superlattices due to intermixing mitigation

“…10,12,13 The repeating unit of the GST-SL investigated in this work consists of 2 quintuple layers (QLs) of Sb 2 Te 3 and a Ge 2 Sb 2 Te 5 (GST225) block, giving a bilayer thickness of ∼3.7 nm, as shown schematically in Figure 1(a). The GST225 features mixed occupation of Sb and Ge layers, as found in MBE grown Sb 2 Te 3 /GeTe SLs.…”

Operando Imaging of All-Electric Spin Texture Manipulation in Ferroelectric and Multiferroic Rashba Semiconductors

“…An important issue for switching of the polarization is that, due to the fourfold degeneracy of the rhombohedral lattice distortion, eight different domains with individual polarization vectors pointing along different h111i directions may be present. This multidomain structure is independent of the substrate epitaxial registry because thin films grown on BaF 2 or Si(111) develop the same major and secondary FE domains [4,9,10,16]. In such a multidomain structure, polarization reversal may involve intermediate steps via oblique [111] domains [purple arrow in Fig.…”