Silicon study with Raman

Complementary studies based on measurements of US-velocity changes and Raman spectroscopy were performed on bulk single-crystalline silicon irradiated with high doses of fast neutrons and compared with the non-irradiated material this revealed the presence of tunnelling states in highly coordinated bulk silicon [59],... 

The molecular structure of sila-heterocycles is reviewed <98MI649>. The Raman and infrared spectra of 1-chloro-l-methylsilabutane have been studied in detail <99MI399>. The first allenic coompoimds with both silicon and phosphorus doubly bonded (ArP C Si(Ph)Tip, Tip = 2,4,6-triisopropylphenyl) have been prepared and dimerised to give 38 and 39 in the ratio of 3 2 <99MI774>. 

Optical absorption measurements give band-gap data for cubic silicon carbide as 2.2 eV and for the CC-form as 2.86 eV at 300 K (55). In the region of low absorption coefficients, optical transitions are indirect whereas direct transitions predominate for quantum energies above 6 eV. The electron affinity is about 4 eV. The electronic bonding in silicon carbide is considered to be predominantly covalent in nature, but with some ionic character (55). In a Raman scattering study of valley-orbit transitions in 6H-silicon carbide, three electron transitions were observed, one for each of the inequivalent nitrogen donor sites in the silicon carbide lattice (56). The donor ionization energy for the three sites had values of 0.105, 0.140, and 0.143 eV (57). 

One further finding with the —lIRNMeR — pyrolysis studies comes from Raman studies of the ceramic product. The NMR data show no traces of Si—C bonds, nor does the Raman spectrum. However, the Raman spectrum does show the presence of C—N bonds up to 1200 °C (the highest temperature studied). This suggests that the silicon nitride nanoparticles interact with the carbon matrix through C—N bonds. One might speculate that the interface looks somewhat like C3N4. 

The energy changes observed in the Raman effect have to do with vibrations and rotations of the molecule under study or vibrations of the crystal lattice. Raman spectra can be used to identify particular molecules, or polyhedra in solids or polyhedral linkages (e.g., particular silicon-oxygen units in silicate glasses)... 

Micro-Raman spectroscopy was used to characterise 4H-SiC layers grown from a variety of precursor systems.381 FTIR data were able to characterise hydrogenated amorphous silicon nitride films with embedded nanoparticles. Oxidation leads to the appearance of an Si O feature at 1070 cm 1,382 Raman spectra were used to determine the degree of micro-crystallinity of pc Si I I layers, using the intensity ratio of bands at 520 cm-1 and 480 cm-1.383 IR and Raman spectra were used to determine the effects of neutron irradiation on a-SiC H films.384 A range of a-SiCx I I and a-SiCxNy H films were studied using IR spectroscopy 385 similar experiments were carried out on a-Si i xGcx Il,F films.386... 

General discussion of intra- and intermolecular interactions 3 van der Waals interactions 3 Coulombic interactions 5 Medium effects on conformational equilibria 5 Quantum mechanical interpretations of intramolecular interactions 7 Methods of study 8 Introduction 8 Nmr and esr spectroscopy 8 Microwave spectroscopy (MW) 12 Gas-phase electron diffraction (ED) 12 X-ray crystallographic methods 13 Circular-dichroism spectroscopy and optical rotation 14 Infrared and Raman spectroscopy 18 Supersonic molecular jet technique 20 Ultrasonic relaxation 22 Dipole moments and Kerr constants 22 Molecular mechanic calculations 23 Quantum mechanical calculations 25 Conformations with respect to rotation about sp —sp bonds 27 Carbon-carbon and carbon-silicon bonds 28 Carbon-nitrogen and carbon-phosphorus bonds 42 Carbon-oxygen and carbon-sulphur bonds 48 Conformations with respect to rotation about sp —sp bonds Alkenes and carbonyl derivatives 53 Aromatic and heteroaromatic compounds 60 Amides, thioamides and analogues 75 Conclusions 83 References 84... 

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