Defect structure of Ge(111)/cubic Pr2O3(111)/Si(111) heterostructures: Thickness and annealing dependence

Abstract

The defect structure of Ge(111) epilayers grown by molecular beam epitaxy on cubic Pr2O3(111)/Si(111) support systems was investigated by means of transmission electron microscopy and laboratory-based x-ray diffraction techniques. Three main types of defects were identified, namely, rotation twins, microtwins, and stacking faults, and studied as a function of Ge film thickness and after annealing at 825 °C in ultrahigh vacuum. Rotation twins were found to be localized at the Ge(111)/cubic Pr2O3(111) interface and their amount could be lowered by the thermal treatment. Microtwins across {111¯} were detected only in closed Ge films, after Ge island coalescence. The fraction of Ge film volume affected by microtwinning is constant within the thickness range of ∼20–260 nm. Beyond 260 nm, the density of microtwins is clearly reduced, resulting in thick layers with a top part of higher crystalline quality. Microtwins resulted insensitive to the postdeposition annealing. Instead, the density of stacking faults across {111¯} planes decreases with the thermal treatment. In conclusion, the defect density was proved to diminish with increasing Ge thickness and after annealing. Moreover, it is noteworthy that the annealing generates a tetragonal distortion in the Ge films, which get in-plane tensely strained, probably due to thermal mismatch between Ge and Si.

The Anthelmintic Activity of the Cyclotides: Natural Variants with Enhanced Activity

“…The other two reflections are labeled with a “ t ” apex, as they originate from twins in the film's matrix, that is to say, domains rotated by 180° around the surface normal 34. It is noted that the formation of twin defects is common in face‐centered cubic (fcc) related heterostructures 35, 36, including tellurides on Si(111) 23, 37, 38. Using the out‐of‐plane lattice parameter inferred from the analysis of the symmetric rod and, for instance, the d‐spacing of the asymmetric α‐GeTe(0 1 ${\bar {1}}$ 8) net‐planes, it is possible to estimate the in‐plane lattice constant of α‐GeTe, which turns out to be 4.170 Å, a value ∼0.2% larger than the bulk 4.162 Å.…”

Wafer-scale all-epitaxial GeSn-on-insulator on Si(1 1 1) by molecular beam epitaxy

“…It is easy to notice that the latter triad can be obtained by a 180 azimuthal rotation of the former. This indicates the coexistence of both type-A (solid yellow) and type-B (dotted yellow) stacked domains in the GeSn epilayer [32]. By calculating the ratio of the peak-areas in θ-2θ diffractograms, corresponding to the spots at  1 = 71.5, ϕ = 36.2° and  1 = 71.5, ϕ = 96.…”

“…2°, the volume fraction of the GeSn in the type-B domains is estimated to be only ~ 1.2%.The triad of reflections at  3 = 38.9, marked by solid white circles correspond to reflection microtwins of the (111) planes in type-A domains, which are reflected about the three {1 ̅ 11} planes. The pairs of reflections at  2 = 54.5, (marked by red, purple, and orange circles) represent the triads whose third apices lie outside the detection range ( = 109.5)[32]. These triads are symmetric equivalents of the triad at  3 = 38.9, and hence correspond to the same reflection microtwins (i.e.…”

Solid-phase epitaxy of amorphous silicon films by in situ postannealing using RPCVD

“…Due to stacking faults the crystal orientation of the defective epi-Si is switching between substrate orientation (type A) and another orientation (type B). These two different orientations are better known as stacking twins or microtwins [15]. They are rotated by 180°around a {1 1 1} axis, what implied that no clear statement about the orientation of the crystallized SPE region to the Si (1 0 0) substrate can be made at lower annealing temperatures.…”