Growth Mechanism and Surface Structure of Ge Nanocrystals Prepared by Thermal Annealing of Cosputtered GeSiO Ternary Precursor

Abstract

Ge nanocrystals (Ge-ncs) embedded in a SiO2superlattice structure were prepared by magnetron cosputtering and postdeposition annealing. The formation of spherical nanocrystals was confirmed by transmission electron microscopy and their growth process was studied by a combination of spectroscopic techniques. The crystallinity volume fraction of Ge component was found to increase with crystallite size, but its overall low values indicated a coexistence of crystalline and noncrystalline phases. A reduction of Ge-O species was observed in the superlattice during thermal annealing, accompanied by a transition from oxygen-deficient silicon oxide to silicon dioxide. A growth mechanism involving phase separation of Ge suboxides (GeOx) was then proposed to explain these findings and supplement the existing growth models for Ge-ncs in SiO2films. Further analysis of the bonding structure of Ge atoms suggested that Ge-ncs are likely to have a core-shell structure with an amorphous-like surface layer, which is composed of GeSiO ternary complex. The surface layer thickness was extracted to be a few angstroms and equivalent to several atomic layer thicknesses.

The Effects of Ge Substrate Surface States and Au Catalyst Layer Thickness on the Growth of Different Ge_xO_y Nanomaterials and Nanocrystals Configurations Using Vapor-Liquid-Solid Method with two Steps Temperature Mode

“…So far although there were a series of investigations done, there were also many vital features of the OAG (Oxide Assisted Growth) mechanism that still need to be fully understood, and a unified model for the growth mechanism of NWs still needs to be investigated [26][27][28][29][30][31][32].…”

“…The applications of semiconductor nanocrystals promise to play a significant role in several new technologies, which gives rise to their potential use in the fields of nonlinear optics, luminescence, electronics, catalysis, solar energy conversion, and optoelectronics, as well as other areas [29,30]. So far many works are studying the different aspects of Ge nanocrystalline, nanocrystals concerning the synthesis methods [31][32][33][34][35][36][37][38][39][40]. Based on these definitions with their properties and the basis of the grown experiment results of the multifacial and spheres configurations as shown in Figures 8,12,15,and 18, in addition to the obtained results of TEM investigations being on Figures 8, 16 we could say that the grown multifacical and spheres configurations, in this case, are the nanocrystals configurations.…”

Ge Quantum Dots Coated with Metal Shells (Al, Ta, and Ti) Embedded in Alumina Thin Films for Solar Energy Conversion

“…Germanium (Ge) QDs embedded in oxide matrices were extensively studied both theoretically and experimentally due to their strong confinement effects and compatibility with the modern nanotechnology. − The production of more complex Ge-based QDs having Ge-core Si-shell internal structure and their properties recently intrigued researchers. − The core–shell geometry with a size of only a few nanometers causes specific confinement effects in semiconductors, resulting in charge separation in space, significant reduction of recombination rates, strong enhancement of absorption, and tunability of the absorption curve. Very recent theoretical studies have shown a great potential of Ge-core Al-shell nanoparticles .…”