On the epitaxy of germanium telluride thin films on silicon substrates

Abstract

The growth by molecular beam epitaxy of GeTe thin films on highly lattice‐mismatched Si(111) substrates is reported. In situ reflection high‐energy electron diffraction and quadrupole mass spectrometry were employed to monitor the growth process in real time and tune the deposition conditions. Epitaxy was achieved in a window of substrate temperatures between 220 and 270 °C, using a Ge/Te flux ratio of ∼0.4. Extensive ex situ X‐ray diffraction characterization showed that the epitaxial layers crystallize in the rhombohedrally distorted rocksalt structure α‐GeTe, with orientation relationships to the substrate α‐GeTe[0001] ‖ Si[111] and α‐GeTe〈10${\bar {1}}$0〉 ‖ Si〈$11{\bar {2}}$〉. ω‐scans of the α‐GeTe(000n) reflections (n = 3, 6, 9) exhibit a full width at half maximum between 10 and 20 arcsec, indicating small mosaicity. However, a large twist is observed (∼14°), pointing to the presence of rotational domains. In addition, the layer matrix is affected by twinning. The epitaxial films exhibit a slight tensile in‐plane strain, which might be due to the difference in thermal expansion coefficients between α‐GeTe and Si, and/or small deviation from stoichiometric composition, i.e., vacancies in the Ge sub‐lattice.

Rashba-Dresselhaus spin-splitting in the bulk ferroelectric oxideBiAlO3

“…In fact, whereas ferroelectric displacements have been clearly observed with many experimental techniques, 20 GeTe shows a high tendency to form Ge vacancies. 21,22 This in turn leads to a p-degenerate semiconducting behavior, calling into question the possibility to switch the ferroelectric state in such a "conducting material", therefore hindering the control of spintexture via an electric field (it is worth noticing that FE switching has been, however, recently reported in epitaxial GeTe films). 23 The search for new FERSC materials is hence essential to achieve better properties and performances.…”

Ferroelectric switching in epitaxial GeTe films

“…Experimental details regarding the growth procedure and structural characterization can be found elsewhere. 17 The ferroelectric switching behavior of the GeTe films has been studied using PFM local spectroscopy and imaging modes. 18 DFT-based computer simulations have been performed to investigate the possible structural changes associated with polarization reversal.…”

Laser-driven switching dynamics in phase change materials investigated by time-resolved X-ray absorption spectroscopy

“…This is in good agreement with the bulk lattice constant of 10.666 A and previous results grown on normal Si(111) substrates. [15] From the thickness fringes surrounding the a-GeTe(00.3) peak, Figure 1(b), a thickness of 32 nm is determined. Based on the HRXRD data, it is concluded that the crystalline GeTe layer grown on the Si(111) membrane has a fairly good structural quality.…”

“…More details about the growth conditions can be found elsewhere. [15,16] The samples were capped with Si x N y by in situ radio-frequency magnetron sputtering.…”