A Convenient Method for Preparing Alkyl-Functionalized Silicon Nanocubes

Abstract

The first solid-state synthesis of diamond structure silicon nanocube structures with edge lengths of 8-15 nm is reported. It is well-established that controlled high-temperature processing of hydrogen silsesquioxane produces exceptionally well-defined pseudospherical silicon nanocrystals. However, only a small number of accounts outlining shape-controlled synthesis have appeared. We report here that, upon prolonged annealing in an oxide matrix, nanocrystal surfaces thermodynamically self-optimize, yielding particles with cubic geometries. Surface functionalization of the resulting nanocubes is readily achieved via thermal hydrosilylation. Discussion will include description of the synthetic procedure, comprehensive material characterization, and the factors that lead to the formation of cubic structures.

Shape Evolution of Faceted Silicon Nanocrystals upon Thermal Annealing in an Oxide Matrix

“…Larger nanocubes are formed at 1400 °C and they tend to grow in the [111] direction, consistent with the samples from 1300 °C reaction [16]. In addition, hexagonal and truncatedtrigonal NCs with {111} bases and facets were found, consistent with the expected tetrahedral symmetry.…”

“…The size and crystallinity of these NCs may be tailored by defining the processing temperature [15]. Recently, we reported it is possible to exploit the relative thermodynamic stabilities of crystal faces to induce formation of silicon 890 nanocubes inside the oxide matrix and that these cubes could be liberated via HF etching [16]. In the present study, we extend the synthesis of Si-NCs to include more complex morphologies (e.g., hexagonal-shape) by tailoring the processing temperature and time.…”

Near-Unity Internal Quantum Efficiency of Luminescent Silicon Nanocrystals with Ligand Passivation

“…26 Compared to the other techniques that afford spherical and pseudospherical NCs, 27,28 size and morphology can be controlled more precisely using the chosen method via rational variation of the processing time and temperature. 29 Fourteen various samples of Si NCs prepared with different surface ligands using different passivation procedures were evaluated optically. The NCs with highest and lowest luminescence peak energy positions and decay rates (samples A and F, respectively), as well as four with intermediate emission energies and decay times (samples B, C, D, and E), were selected for a detailed study.…”

Alternative Methods of Silicon Porosification and Properties of These PSi Layers

“…It is not influenced by particle size and shape; it affords comparatively high yields and there is no need to remove trace catalyst impurities (Yang et al 2012). A commonly accepted thermal hydrosilylation mechanism requires sufficient heat (T ≥ 150°C) to homolytically cleave Si−H bonds to create silyl radicals that subsequently react with neat alkenes or alkynes (Figure 13.10).…”