Absence of island–island interaction during formation of isolated Ge islands in small windows

Abstract

Isolated Ge islands, i.e., islands not connected by a wetting layer can be obtained by selective epitaxial growth in voids of ultrathin oxides of thickness 1-2 nm. Voids of 30-600 nm size were created before epitaxy during a high temperature anneal of the ultrathin oxide. The formation of one island per window was investigated at 700°C as a function of Ge thickness and void size. Islands nucleate mainly at the edge of the void and for this reason they have an anisotropic shape. In voids smaller than 300 nm only one island is nucleated. Islands form only in voids greater than a critical size ͑30-80 nm͒ which depends on the total amount of Ge deposited. We observe that height, width, and aspect ratio of isolated islands increase with void size for a given Ge thickness. A metastable state of Ge in small windows was observed. Moreover, the Si interdiffusion is strongly reduced with decreasing island size ͑i.e., with void size͒ reaching only ϳ10% in comparison with ϳ50% in islands on large areas.

Two-dimensional arrays of self-organized Ge islands obtained by chemical vapor deposition on pre-patterned silicon substrates

“…Ge islands along rims of microscopic mesa structures [7][8][9][10], or on 2D arrays of e-beam and focused ion beam patterned substrates [11,12] has been achieved.…”

Assembly of Ge nanocrystals on SiO2via a stress-induced dewetting process

“…Introduction of Si or Ge nanocrystals into the oxide has been attempted by different techniques, including ion implantation and subsequent annealing, laser ablation, etc [4,5]. Nevertheless, control over the density of nanocrystals and their size distribution remains challenging to achieve, and methods for the positioning of Ge dots, for example via growth in 2D arrays of nanometre-scale windows in a thermal SiO 2 layer on Si, have been proposed only recently [6,7]. The formation of Si nanocrystals on a SiO 2 layer has been achieved by thermally induced dewetting of ultrathin Si-on-insulator (SOI) during annealing at temperatures above 800 • C [8,9].…”

Two-dimensional arrays of nanometre scale holes and nano-V-grooves in oxidized Si wafers for the selective growth of Ge dots or Ge/Si hetero-nanocrystals

“…For the deposition temperature of 700 • C used in the present experiments a critical window size about 270 nm was found, below which one island per window was grown. The formation mechanism of isolated Ge islands in small windows in SiO 2 was investigated in detail in [7] and [8]. Figure 5(b) shows an example of Ge growth in windows of about 270 nm.…”

“…By selective epitaxy, either Ge or complex heterostructures of Ge/Si islands were grown in SiO 2 holes [6] and in Si nano-V-grooves. The number and the characteristics of the nucleated Ge or Ge/Si islands, both in the case of Si nano-V-grooves and in the case of simple holes in SiO 2 , were found to depend on hole size and the amount of the deposited Ge [7,8].…”