Strain Relaxation in “2D/2D and 2D/3D Systems”: Highly Textured Mica/Bi₂Te₃, Sb₂Te₃/Bi₂Te₃, and Bi₂Te₃/GeTe Heterostructures

Abstract

Strain engineering as a method to control functional properties has seen in the last decades a surge of interest. Heterostructures comprising 2D-materials and containing van der Waals(-like) gaps were considered unsuitable for strain engineering. However, recent work on heterostructures based on Bi 2 Te 3 , Sb 2 Te 3 , and GeTe showed the potential of a different type of strain engineering due to long-range mutual straining. Still, a comprehensive understanding of the strain relaxation mechanism in these telluride heterostructures is lacking due to limitations of the earlier analyses performed. Here, we present a detailed study of strain in two-dimensional (2D/2D) and mixed dimensional (2D/3D) systems derived from mica/Bi 2 Te 3 , Sb 2 Te 3 /Bi 2 Te 3 , and Bi 2 Te 3 /GeTe heterostructures, respectively. We first clearly show the fast relaxation process in the mica/Bi 2 Te 3 system where the strain was generally transferred and confined up to the second or third van der Waals block and then abruptly relaxed. Then we show, using three independent techniques, that the long-range exponentially decaying strain in GeTe and Sb 2 Te 3 grown on the relaxed Bi 2 Te 3 and Bi 2 Te 3 on relaxed Sb 2 Te 3 as directly observed at the growth surface is still present within these three different top layers a long time after growth. The observed behavior points at immediate strain relaxation by plastic deformation without any later relaxation and rules out an elastic (energy minimization) model as was proposed recently. Our work advances the understanding of strain tuning in textured heterostructures or superlattices governed by anisotropic bonding.

Effects of Intermixing in Sb2Te3/Ge1+xTe Multilayers on the Thermoelectric Power Factor

“…The corresponding targets were obtained from KTECH with a purity of 99.999%. The substrate cleaning method is described elsewhere . For the single layers of Sb 2 Te 3 and GeTe, first, a “seed” layer of 200 pulses (∼3 nm) film was grown at RT, followed by heating to 210 °C with a heating rate of 10 °C min –1 .…”

Te and Ge solid-state reaction: comparison between the 2D and 3D growth of α-GeTe

“…[12][13][14] For all these applications, it is important to understand the GeTe growth mechanisms. Several studies have shown and studied the possibility to grow high quality epitaxial GeTe using either molecular beam epitaxy or pulsed laser deposition techniques, enabling to grow ultrathin (down to 1 nm) epilayers for ferroelectricity applications 15,16 or strain engineering 17 for example. However, most studies that seek to investigate GeTe focus on the crystallization of an amorphous homogeneous stoichiometric, or near-stoichiometric, thin film.…”

Controlling Strain Relaxation by Interface Design in Highly Lattice-Mismatched Heterostructure

“…Among the factors of strain engineering, the one with a high priority is how strain relaxes and behaves in thin films, which significantly affects the strain state of thin films. According to the bond hierarchy, the strain relaxation falls into two main strategies . (i) The strain gradually decays with the increase of film thickness, forming a strain gradient inside the thin film.…”