Low temperature formation of copper rich silicides

The reactions of copper and amorphous silicon were studied by in-situ transmission electron microscopy up to 500 degrees C. Only the Cu76Si24-eta phase and the Cu82Si18-delta phase formed at this temperature. The crystal structure of the dominating Cu76Si24 changed, by the elapsed time after heating. The Cu-Si ordering resulted in different supercells, built up by topologically identical subcells with different site occupancies and arrangement. Two modulated crystal structures were solved based on diffraction data and HRTEM images

Encapsulation of the Graphene Nanoribbon Precursor 1,2,4-trichlorobenzene in Boron Nitride Nanotubes at Room Temperature

Graphene nanoribbons are prepared inside boron nitride nanotubes by liquid phase encapsulation and subsequent annealing of 1,2,4-trichlorobenzene. The product is imaged with high resolution transmission electron microscopy, and characterized by optical absorption and Raman spectroscopy. Carbon-containing material is detected inside the boron nitride nanotubes with energy-dispersive x-ray spectroscopy (EDS) and scanning transmission electron microscopy (STEM). The observed structures twist under the electron beam and the characteristic features of nanoribbons appear in the Raman spectra.Comment: 8 pages, 4 figure

In situ TEM Study of Ni-Silicides Formation Up to 973K

Low-temperature solid-state reactions between Ni and Si were studied using in situ transmission electron microscopy (TEM). In the experiments thin amorphous silicon (a-Si) films were laid on Ni micro-grids and heated up to 973 K. In our approach the supporting Ni-grid serves as an unlimited source of nickel to successively form the whole range of Ni-silicide phases while diffusing into amorphous silicon. Unlike other thin film experiments where Ni and Si are layered on top of each other, our arrangement enables lateral diffusion of Ni along the Si layer and therefore enables the formation and study of successive Ni-Si phases side by side. That allowed us to observe in situ α-NiSi2 as the first reaction product, in contrast to most studies that had reported either δ-Ni2Si or θ-Ni2Si as the first phase to form. α-NiSi2 was continuously present at the reaction front propagating into the a-Si film. The phase sequence followed the increasing Ni concentration from a-Si towards the Ni-grid: α-NiSi2, NiSi, Ni3Si2, δ-Ni2Si, γ-Ni31Si12 and Ni3Si. Almost all known Ni-silicide phases were found to form at relatively low temperatures except the θ-Ni2Si, β-NiSi2 and β3-Ni3Si. The dominant phase was γ-Ni31Si12 which appeared in three structural modifications, differing in lattice periodicity along the c-axis. The periodicity of the basic γ-Ni31Si12 structure along the c-axis is ~12 Å (c0 = 12.288 Å) and that of the other two modifications were ~18 Å and ~36 Å, denoted by S12, S18 and S36 respectively. Of the three, only S12 has a structural model, S18 had been previously observed by Chen, but S36 had not been documented in previous works. During our in situ heating experiments, in addition to the Ni-silicide layer formation a new phenomenon was observed, namely the appearance, growth and transformation of Ni-silicide whiskers which was attributed to the accumulation of compressive stress in the thin layer

Peack frequency and linewidth of the optical bands of F_2 and F+_3 centers in LiF

Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Encapsulation of the Graphene Nanoribbon Precursor 1, 2, 4‐trichlorobenzene in Boron Nitride Nanotubes at Room Temperature

Graphene nanoribbons are prepared inside boron nitride nanotubes by liquid phase encapsulation and subsequent annealing of 1,2,4-trichlorobenzene. The product is imaged with high resolution transmission electron microscopy, and characterized by optical absorption and Raman spectroscopy. Carbon-containing material is detected inside the boron nitride nanotubes with energy-dispersive x-ray spectroscopy (EDS) and scanning transmission electron microscopy (STEM). The observed structures twist under the electron beam and the characteristic features of nanoribbons appear in the Raman spectra.Comment: 8 pages, 4 figure