Energy confinement

Eig. 13. Absorption between confined energy levels in a quantum well infrared photodetector (QWIP). The energy difference between the... 

Y. Ohmori, H. Kajii, T. Sawatani, H. Ueta, and K. Yoshino, Enhancement of electroluminescence utilizing confined energy transfer for red light emission, Thin Solid Films, 393 407-411 (2001). 

The large Stokes shift for confinement energies above 2.1 eV can be explained by the electronic states produced by an Si=0 double bond. 

Fig. 7.19 Influe nee of QC on the basic properties of excitons localized in Si nanocrystals. Confinement energy dependence of (a) relative strength of no-phonon and TO phonon-...

The first two terms in equation (4.8.6) have been given by Brus [115,116,131]. The first term in equation (4.8.6) with the 1/k dependence represents the quantum localization energy, and is the sum of the confinement energy for the electron and holes. The second term, with HR dependence, accounts for the coulombic interaction between the electron and hole. The third term in equation (4.8.6) was introduced by Kayanuma [126] and is a result of spatial... 

Fig. 13. Absorption between confined energy levels in a quantum well infrared photodetector (QWIP). The energy difference (E —E ) between the confined energy levels in a quantum well may be designed such that it is resonant with ir radiation. The band gap, E is much greater, therefore direct band...

Table 2 Observed Transition and Quantum Confinement Energies in M0S2 Nanoparticles...

Figure 4 Energy spectrum of the low-lying states of two electrons confined in a quasi-two-dimensional Gaussian potential for different strength of confinement. Energy levels are colored by green for singlet states and red for triplet states, respectively. The parameter vp specifies the polyad quantum number (See the text for details). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this book.)...

The different behavior (direct versus indirect band gap) of Si and Ge with respect to the film orientation can be explained in term of confinement effects on the conduction band minima (CBM) of the two semiconductors.Whereas the six equivalent ellipsoidal CBM of bulk Si occur in the (100) directions about 80% of the way to the zone boundary, in bulk Ge there are eight symmetry-related ellipsoids with long axes along the (111) directions centered on the midpoints of the hexagonal zone faces. Also the different confinement energy shifts with respect to the orientation of the layer can be interpreted in terms of the different highly anisotropic behavior of the effective masses for bulk Ge and Si [170,171]. 

Figure 5.57 Illustration of the relationship between particle size and energy levels for (a) a bulk material possessing energy bands, (b) a nanoparticle with quantum-confined energy levels, and (c) a single molecule with molecular orbitals...

A plot of ground-state confinement energies is shown in Figure 5.2 as a function of atomic number. The obvious periodicity corresponds in detail with the structure of the compact periodic table, based on number theory, Figure 4.5. 

Figure 5.2 Ground-state confinement energies Eg as a function of atomic number.

Figure 2 summarises the situation the chain has partially entered into the pore (over a length F >D). It can be pictured as a sequence of blobs, each of size D and of monomer number gD=(D/a)5/3 (theFlory law). The confinement energy per blob is of the order kT [13] and the overall confinement energy is thus kT f/D ( /D being the number of squeezed blobs. The force tending to pull the chain out of the pore is thus kT/D. 

Photoluminescence could be due to the radiative annihilation (or recombination) of excitons to produce a free exciton peak or due to recombination of an exciton bound to a donor or acceptor impurity (neutral or charged) in the semiconductor. The free exciton spectrum generally represents the product of the polariton distribution function and the transmission coefficient of polaritons at the sample surface. Bound exciton emission involves interaction between bound charges and phonons, leading to the appearance of phonon side bands. The above-mentioned electronic properties exhibit quantum size effect in the nanometric size regime when the crystallite size becomes comparable to the Bohr radius, qb- The basic physics of this effect is contained in the equation for confinement energy,... 

Explosives can also be classified by the detonation velocity at which they release the confined energy. This classification differentiates explosives as... 

The fact that the size exponent f (often called wandering exponent) is different from 1/2 has important implications in various applications, especially for flux lines in superconductors. For example, confinement of a flux line in presence of many other flux lines would lead to a steric repulsion [27] (similar to the confinement energy in Sec. 4.3.2) and the interaction of the vortices may lead to an attractive fluctuation induced (van der Waals type) interaction [28]. 

If the polymer is confined in a tube of diameter D then the dimensionless variable is Rq/D. This will appear in the form for change in entropy or in confinement energy . This is used in Sec. 4.3.2. 

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