Silicon translational energy

As earlier discussed, the dominant factor in the near-surface region is the particle detection system. For a typical silicon surface barrier detector (15-keV FWHM resolution for Fle ions), this translates to a few hundred A for protons and 100— 150 A for Fle in most targets. When y rays induced by incident heavy ions are the detected species (as in FI profiling), resolutions in the near-surface region may be on order of tens of A. The exact value for depth resolution in a particular material depends on the rate of energy loss of incident ions in that material and therefore upon its composition and density. 

From an optical viewpoint, on the other hand, the difference between semiconductors and insulators lies in the value of Eg. The admitted boundary is usually set at 3 eV (see Appendix A for the energy units) and materials with Eg below this value are categorized as semiconductors, but crystals considered as semiconductors like the wurtzite forms of silicon carbide and gallium nitride have band gaps larger than 3 eV, and this value is somewhat arbitrary. The translation into the electrical resistivity domain depends on the value of Eg, and also on the effective mass of the electrons and holes, and on their mobilities. The solution is not unique moreover, the boundary is not clearly defined. Semi-insulating silicon carbide 4H polytype samples with reported room temperature resistivities of the order of 1010flcm could constitute the... 

The Si nanocrystals exhibit photoluminescence upon irradiation with UV light at 230 nm. The MPL spectrum is shown in Figure 10. The spectrum is similar to that reported for 4 nm Si nanocrystals upon excitation with 350 nm at 20 K and also to that PL spectrum of Porous Silicon (49). In these systems the red luminescence is interpreted as a consequence of quantum crystallites which exhibit size-dependent, discrete excited electronic states due to a quantum effect (6,50,51). This quantum confinement shifts the luminescence to higher energy than the bulk crystalline Si (1.1 eV) band gap. This indirect gap transition is dipole forbidden in the infinite preferred crystal due to translational symmetry. By relaxing this symmetry in finite crystallite, the transition can become dipole allowed. As pointed out by Brus (49), the quantum size effect in Si nanocrystals is primarily kinetic mainly due to the isolation of electron-hole pairs from each other. 

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