The Ge Stranski-Krastanov growth mode on Si(001) (2 × 1) tested by X-ray photoelectron and Auger electron diffraction

• Published in: Surface science 1993-07, Vol.291 (1), p.110-116
• Main Authors: Diani, M., Aubel, D., Bischoff, J.L., Kubler, L., Bolmont, D.
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Physics; Solid surfaces and solid-solid interfaces; Surface and interface dynamics and vibrations; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/0039-6028(93)91482-5

X-ray photoelectron and Auger electron diffractions have been used here for the first time to identify growth morphology in the earliest stages (0–10 monolayers) of Ge epitaxy on Si(001)(2 × 1) surfaces held at room temperature (RT) and at 400°C. The Ge atomic arrangement in the (1 1 0) plane is examined by performing polar angle distribution of the Ge LMM intensities and by comparison with the corresponding Si2p substrate pattern. A detailed plot as a function of the Ge coverage of the forward scattering peak contrasts in the [111] and [001] directions, which correspond to the 1st and 3rd atomic neighbour rows, respectively, yields informations about the layer number distribution and the growth mode. Contrarily to the nearly two-dimensional (2D) growth taking place at RT, we obtain a 3D island formation at 400°C for a critical thickness exceeding 5 ML. Nevertheless, in the coverage domain between 2 and 5 ML for which layer-by-layer growth is normally expected, the observation of a significant up to 4 ML roughness across the surface prefigurates the islanding process and confirms very recent STM reports. Photoelectron scattering results are only consistent with pure 2D formation during the first 2 ML growth.