skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Growth and stability of oxidation resistant Si nanocrystals formed by decomposition of alkyl silanes

Abstract

The synthesis and characterization of 1-10 nm Si nanocrystals highly resistant to oxidation is described. The nanocrystals were prepared by thermal decomposition of tetramethylsilane at 680 C, or in a gold- induced catalytic process at lower temperatures down to 400-450 C using trioctylamine as an initial solvent. Transmission electron microscopic analysis of samples obtained in the presence of gold show that the nanocrystals form via solid-phase epitaxial attachment of Si to the gold crystal lattice. The results of computational modeling performed using first principles density functional theory (DFT) calculations predict that the enhanced stability of nanocrystals to oxidation is due to the presence of N or N-containing groups on the surface of nanocrystals.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
940468
Report Number(s):
UCRL-JRNL-227339
TRN: US0807136
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry - C, vol. 112, no. 10, February 19, 2008, pp. 3585-3590; Journal Volume: 112; Journal Issue: 10
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CRYSTAL LATTICES; ELECTRONS; FUNCTIONALS; GOLD; OXIDATION; PYROLYSIS; SILANES; SIMULATION; STABILITY; SYNTHESIS; TRIOCTYLAMINE

Citation Formats

Zaitseva, N, Hamel, S, Dai, Z R, Saw, C, Williamson, A J, and Galli, G. Growth and stability of oxidation resistant Si nanocrystals formed by decomposition of alkyl silanes. United States: N. p., 2007. Web.
Zaitseva, N, Hamel, S, Dai, Z R, Saw, C, Williamson, A J, & Galli, G. Growth and stability of oxidation resistant Si nanocrystals formed by decomposition of alkyl silanes. United States.
Zaitseva, N, Hamel, S, Dai, Z R, Saw, C, Williamson, A J, and Galli, G. Fri . "Growth and stability of oxidation resistant Si nanocrystals formed by decomposition of alkyl silanes". United States. doi:. https://www.osti.gov/servlets/purl/940468.
@article{osti_940468,
title = {Growth and stability of oxidation resistant Si nanocrystals formed by decomposition of alkyl silanes},
author = {Zaitseva, N and Hamel, S and Dai, Z R and Saw, C and Williamson, A J and Galli, G},
abstractNote = {The synthesis and characterization of 1-10 nm Si nanocrystals highly resistant to oxidation is described. The nanocrystals were prepared by thermal decomposition of tetramethylsilane at 680 C, or in a gold- induced catalytic process at lower temperatures down to 400-450 C using trioctylamine as an initial solvent. Transmission electron microscopic analysis of samples obtained in the presence of gold show that the nanocrystals form via solid-phase epitaxial attachment of Si to the gold crystal lattice. The results of computational modeling performed using first principles density functional theory (DFT) calculations predict that the enhanced stability of nanocrystals to oxidation is due to the presence of N or N-containing groups on the surface of nanocrystals.},
doi = {},
journal = {Journal of Physical Chemistry - C, vol. 112, no. 10, February 19, 2008, pp. 3585-3590},
number = 10,
volume = 112,
place = {United States},
year = {Fri Jan 12 00:00:00 EST 2007},
month = {Fri Jan 12 00:00:00 EST 2007}
}
  • No abstract prepared.
  • No abstract prepared.
  • Anisotropic II–VI semiconductor nanostructures are important photoactive materials for various energy conversion and optical applications. However, aside from the many available surface chemistry studies and from their ubiquitous photodegradation under continuous illumination, the general chemical reactivity and thermal stability (phase and shape transformations) of these materials are poorly understood. Using CdSe and CdS nanorods as model systems, we have investigated the behavior of II–VI semiconductor nanorods against various conditions of extreme chemical and physical stress (acids, bases, oxidants, reductants, and heat). CdSe nanorods react rapidly with acids, becoming oxidized to Se or SeO2. In contrast, CdSe nanorods remain mostly unreactivemore » when treated with bases or strong oxidants, although bases do partially etch the tips of the nanorods (along their axis). Roasting (heating in air) of CdSe nanorods results in rock-salt CdO, but neither CdSe nor CdO is easily reduced by hydrogen (H2). Another reductant, n-BuLi, reduces CdSe nanorods to metallic Cd. Variable temperature X-ray diffraction experiments show that axial annealing and selective axial melting of the nanorods precede particle coalescence. Furthermore, thermal analysis shows that the axial melting of II–VI nanorods is a ligand-dependent process. In agreement with chemical reactivity and thermal stability observations, silica-coating experiments show that the sharpest (most curved) II–VI surfaces are most active against heterogeneous nucleation of a silica shell. These results provide valuable insights into the fate and possible ways to enhance the stability and improve the use of II–VI semiconductor nanostructures in the fields of optics, magnetism, and energy conversion.« less
  • The recently discovered family of metal-carbon clusters, designated metallo-carbohedrenes or [open quotes]met-cars[close quotes] by Castleman and co-workers, are reinvestigated with a focus on titanium and vanadium systems. In addition to the stable M[sub 8]C[sub 12][sup +] clusters reported previously, a family of larger metal-carbon systems are observed. Mass spectroscopy and mass-selected laser photodissociation measurements are used to investigate the structures and stabilities of these systems, which contain up to 60 atoms in the cluster framework. The larger metal-carbon species exhibit 1/1 M/C stoichiometries characteristics of cubic lattice structures and are therefore designated as [open quotes]nanocrystals[close quotes]. The species Ti[sub 14]C[submore » 13][sup +] and V[sub 14]C[sub 13][sup +], which are proposed to have the 3 X 3 X 3 cubic structure, are especially abundant and are believed to have stabilities comparable to those of the M[sub 8]C[sub 12] species. Photodissociation of larger nanocrystals produces both the 8/12 and 14/13 stoichiometries as abundant photofragments. Evidence is also presented for the formation of endohedral met-car clusters containing a central carbon atom, which are formed as photodissociation products from larger systems. 37 refs., 5 figs., 1 tab.« less
  • In the equilibrium immiscible Hf-Nb system characterized by a positive heat of formation, five Hf-Nb metallic glasses with overall compositions of Hf{sub 84}Nb{sub 16}, Hf{sub 65}Nb{sub 35}, Hf{sub 45}Nb{sub 55}, Hf{sub 38}Nb{sub 62}, and Hf{sub 20}Nb{sub 80} are obtained by ion beam mixing with properly designed Hf-Nb multilayered films, suggesting a glass-forming composition range of 16-80 at. % of Nb. For the special case of Hf{sub 45}Nb{sub 55} located at the ridge point on the convex free energy curve, dual-glass phases are formed at a dose of 2x10{sup 15} Xe{sup +}/cm{sup 2}, which results from a spinodal decomposition of themore » expected Hf{sub 45}Nb{sub 55} amorphous phase. With increasing irradiation dose, fractal growth of nanocrystals (around 20 nm) appears in the major glass phase and the dimension is determined to be from 1.70 to 1.84 within a dose range of (4-7)x10{sup 15} Xe{sup +}/cm{sup 2}. In atomistic modeling, a n-body Hf-Nb potential is first constructed with the aid of ab initio calculations. Applying the constructed potential, molecular dynamics simulations using the hcp and bcc solid solution models, reveals an intrinsic glass-forming range to be within 15-83 at. % of Nb, which is compatible with the ion beam mixing experiments. Moreover, the formation of the metallic glasses and the fractal growth in association with the amorphous spinodal decomposition are also discussed in terms of the atomic collision theory and cluster-diffusion-limited-aggregation model.« less