Evidence for cubic phase in deposited germanium nanocrystals

Abstract

Germanium nanocrystals with sizes ranging from 1 to 5 nm are condensed out of the gas phase in helium or argon buffer-gas atmospheres and subsequently deposited. The generated particle sizes are found to depend on the buffer gas, with helium yielding a narrower size distribution than argon and argon exhibiting a stronger pressure dependence of the produced particle sizes. Structural analysis of nanoparticles with average sizes around 5 nm reveals the bulklike cubic (diamond) phase—in contrast to recent experiments which suggest the tetragonal phase for similar-sized particles. These results are explained in terms of particle formation dynamics.

Solution Synthesis of Germanium Nanocrystals: Success and Open Challenges

“…For every assynthesized powder, qualitative energy-dispersive X-ray (EDX) analysis of such large aggregates indicates the presence of only Ge and C. X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra of the powders at the Ge L and K edges, respectively, ( Figure 5) exhibit bulk-like behavior, as it was observed for pure Ge clusters larger than ∼5 nm. 8 The EXAFS oscillations are the same as those of bulk Ge, but differ markedly from those of commercial Ge powder whose surface is oxidized. Similarly, the absorption onset and slope of the XANES spectra almost overlap.…”

Probing the Electronic Density of States of Germanium Nanoparticles: A Method for Determining Atomic Structure

“…We analyze the electronic density of states (DOS) in the valence band yielding insight into the bonding configuration of the investigated structures. As a test system, we choose to study germanium nanoparticles, synthesized using gas aggregation techniques [17]. In addition to the technological importance of germanium nanoparticles these nanoparticles are of interest as the structure of the nanoparticles is not fully resolved, and two different phases have been reported: Sato et al [18] used cluster beam techniques to synthesize particles in the 4 -5 nm size range.…”

Microstructure and dielectric functions of Ge nanocrystals embedded between amorphous Al2O3films: study of confinement and disorder

“…The clusters thus formed are subsequently deposited on the hot substrates kept at 550 K facilitating in situ growth of Ge-NCs. The growth of Ge-NCs occurs through accumulation of atoms and molecules captured from the supersaturated Ge vapours [16]. We presumably assume that the growing Ge-NCs contain a small amount of Ge in disordered or amorphous form, co-deposited during the nanocrystal growth experiment.…”