Collective Shape Oscillations of SiGe Islands on Pit-Patterned Si(001) Substrates: A Coherent-Growth Strategy Enabled by Self-Regulated Intermixing

Abstract

The shape of coherent SiGe islands epitaxially grown on pit-patterned Si(001) substrates displays very uniform collective oscillations with increasing Ge deposition, transforming cyclically between shallower ''dome'' and steeper ''barn'' morphologies. Correspondingly, the average Ge content in the alloyed islands also displays an oscillatory behavior, superimposed on a progressive Si enrichment with increasing size. We show that such a growth mode, remarkably different from the flat-substrate case, allows the islands to keep growing in size while avoiding plastic relaxation.

Site‐controlled SiGe islands on patterned Si(001): Morphology, composition profiles, and devices

“…After the deposition of 20 ML Ge at 720 °C, a perfect site‐controlled array of barn‐shaped islands is observed. After 20 min in situ annealing, the barns have transformed into pyramids, as demonstrated by the surface orientation maps 45, 57 in the insets of Fig. 4(a) and (b).…”

“…Nanotomography, which combines selective wet chemical etching and atomic force microscopy (AFM), is a relatively simple tool to obtain quantitative 3D alloy distribution of individual SiGe islands 44. The reliability of the compositional values obtained by nanotomography was confirmed by anomalous X‐ray scattering measurements in grazing‐incidence performed at the ID01 beamline of the European Synchrotron Radiation Facility 44 and by coplanar X‐ray diffraction (XRD) measurements 45. Here, we investigate the composition profiles of site‐controlled islands by using nanotomography.…”

Epilayer thickness and strain dependence of Ge(113) surface energies

“…Here we specifically calculate net effective surface energies for {105} and {113} pyramids and estimate the net effective surface energy of the experimentally observed "dome" and "barn" nanostructures 48 shown schematically in Fig. 4.…”

Enhanced intermixing in Ge nanoprisms on groove-patterned Si(1 1 10) substrates

“…Thus, the SiGe nanoripples are simply the degenerate form of ͕105͖-terminated SiGe pyramids on a ͑1 1 10͒ plane. [19][20][21][22] The distribution of the composition was then obtained by analyzing the etched profiles with the software package XIM 1.1. 13,16,17 Besides these observations, very little is known about the morphological and compositional behavior of the nanoripples on patterned Si͑1 1 10͒ substrates, which is the topic of this letter for the case of a grove pattern.…”