Properties of three-dimensional structures prepared by Ge dewetting from Si(111) at high temperatures

Abstract

The formation of three-dimensional (3D) structures during Ge deposition on Si(111) at about 800 °C is studied with scanning tunneling, Kelvin probe and electron microscopies, and scanning tunneling and Raman spectroscopies. The observed surface morphology is formed by dewetting of Ge from Si(111), since it occurs mainly by means of minimization of surface and interfacial energies. The dewetting proceeds through massive Si eroding around growing 3D structures, providing them to be composed of SiGe with about a 30% Ge content, and leads to the significant reduction of the SiGe/Si interface area. It is found that the SiGe top component of 3D structures forms sharp interfaces with the underlying Si. The minimization of interfacial and strain energies occurs on the way that the 3D structures appear to get the dendrite-like shape. The Ge distribution in the 3D SiGe structures is inhomogeneous in the lateral dimension with a higher Ge concentration in their central areas and Ge segregation on their surface.

Raman and photoluminescence spectroscopy of SiGe layer evolution on Si(100) induced by dewetting

“…It is widely used for the formation of various metal layer surface morphologies. [1][2][3] The dewetting of SiGe layers was observed recently on both Si(111) 4 and Si(100) 5,6 substrates. A detailed investigation of the dewetting process would be thus highly desirable both from the scientific and applied viewpoints.…”

“…This shift may be caused by the lattice strain. Using the relation e S ¼ Àðx SS À 520:6Þ 830 (4) derived from Eq. (1a) with x ¼ 0, we obtain a compressive stress in the Si substrate below the continuous film.…”

“…It leads to the formation of different surface morphologies depending on the surface crystallographic orientation. The appearance of structures such as the net of ridges was observed on Si(111), 4 whereas compact individual islands were formed on Si(100). 16 In the other approach, about 30-100 nm thick Ge layers, initially deposited on Si(100) or Si(111) surfaces at relatively low temperatures ($400 C), were subsequently annealed at higher temperatures.…”

“…On Si(111), it leads to the formation of ridgelike structures, and it occurs suddenly on the whole surface. 4 On Si(100), a continuous film formation is observed at the initial stage of high temperature annealing, and then, it slowly transforms into a porous film. The transformation occurs through a slow movement of the boundary between the continuous and porous film areas.…”

Surface Morphology Transformation Under High-Temperature Annealing of Ge Layers Deposited on Si(100)

“…As suggested here, the porous SiGe layer formation is the result of surface melting which is significantly facilitated by the strong stain caused by the Si-Ge lattice mismatch. It can also be suggested that the same reason is responsible for the porous SiGe layer formation on Si(111) [ 16 , 22 ]. Under annealing at temperatures in the range from 700 to 900 °C, two processes compete with each other.…”