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Dielectric matrix

Stella A ef al 1996 Comparative study of thermodynamic properties of metallic and semiconducting nanoparticles in a dielectric matrix Mater. Res. Soc. Symp. Proc. 400 161... [Pg.2923]

One uses a simple CG model of the linear responses (n= 1) of a molecule in a uniform electric field E in order to illustrate the physical meaning of the screened electric field and of the bare and screened polarizabilities. The screened nonlocal CG polarizability is analogous to the exact screened Kohn-Sham response function x (Equation 24.74). Similarly, the bare CG polarizability can be deduced from the nonlocal polarizability kernel xi (Equation 24.4). In DFT, xi and Xs are related to each other through another potential response function (PRF) (Equation 24.36). The latter is represented by a dielectric matrix in the CG model. [Pg.341]

In addition to the amount of filler content, the shape, size and size distribution, surface wettability, interface bonding, and compatibility with the matrix resin of the filler can all influence electrical conductivity, mechanical properties, and other performance characteristics of the composite plates. As mentioned previously, to achieve higher electrical conductivity, the conductive graphite or carbon fillers must form an interconnected or percolated network in the dielectrical matrix like that in GrafTech plates. The interface bonding and compatibility between... [Pg.324]

The absorption spectrum is proportional to the imaginary part of the macroscopic dielectric function. Adopting the same level of approximation that we have introduced to obtain GW quasiparticle energies, i.e. neglecting the vertex correction by putting T = 55, we get the so called random phase approximation (RPA) for the dielectric matrix. Within this approximation, neglecting local field effects, the response to a longitudinal field, for q 0, is ... [Pg.214]

Chapter 10 deals with composite films synthesized by the physical vapor deposition method. These films consist of dielectric matrix containing metal or semiconductor (M/SC) nanoparticles. The film structure is considered and discussed in relation to the mechanism of their formation. Some models of nucleation and growth of M/SC nanoparticles in dielectric matrix are presented. The properties of films including dark and photo-induced conductivity, conductometric sensor properties, dielectric characteristics, and catalytic activity as well as their dependence on film structure are discussed. There is special focus on the physical and chemical effects caused by the interaction of M/SC nanoparticles with the environment and charge transfer between nanoparticles in the matrix. [Pg.7]

Vapor Deposited Composite Films Consisting of Dielectric Matrix with Metal/Semiconductor Nanoparticles... [Pg.523]

M/SC nanoparticles in size from 1 to 10 nm are of greatest interest because their electronic structure depends markedly on the particle size [4-6]. There are now a lot of methods for a deposition of M/SC and dielectric on solid substrates from liquid or gaseous phase to produce composite films containing M/SC nanoparticles inside or on a surface of a dielectric matrix. Liquid-phase technique uses colloidal solutions of M/SC nanoparticles. Such solutions are formed by chemical reactions of various precursors in the presence of stabilizers, which are adsorbed on the surface of nanoparticles and preclude their aggregation. But it is necessary to take into account, that... [Pg.524]

R [15]. For particles Ag with R = 5nm this correction lifts Fermi level to 0.22 eV in comparison with level for bulk metal [15]. The surface-determined size effect for Fermi energy of metal nanoparticles results in mutual charging of nanoparticles of different sizes by the tunnel electron transfer between nanoparticles. Such charging processes, as it will be shown below (Subsection 4.4), greatly influence catalytic reactions induced by assembly of metal nanoparticles with size distribution immobilized in solid dielectric matrix. [Pg.528]

Optical absorption in M nanocrystals embedded in dielectric matrix depends on characteristics of matrix and interface between matrix and nanocrystals. In the classical model of Mie only macroscopical dielectric permeability of environment e 2 is taken into account [16]. In this model charges at the M nanocrystal surface are determined by s2 and so frequency coa corresponding to a peak of resonant absorption is defined from a relation [18]. [Pg.530]

The considered classical model allows the explanation of the basic features of optical absorption for M nanocrystal in dielectric matrix at low nanocrystals content [18]. In particular, half-width (A 1/2) of the plasmon... [Pg.530]

It is believed that surface localized electron-hole pairs produced under light in SC nanoparticles participate in photo-induced processes of charge transfer between nanoparticles. These processes most probably of quantum tunnel type determine photoconductivity of composite films containing SC nanoparticles in a dielectric matrix. The photocurrent response time in this case should correspond to the lifetime ip of such pairs, which is of the order nanosecond and even more [6]. This rather long ip makes photo-induced tunnel current in composite film possible. [Pg.535]

For synthesis of composite films with M/SC nanoparticles distributed in the volume of a dielectric matrix, method PVD is used as co-deposition of M/ SC and dielectric material vapors. A comparison of films produced by codeposition and layer-by-layer deposition PVD methods has been made on the example of BN-Fe nanocomposite films [57]. Unlike the above considered film from alternating layers of Fe and BN, which has ordered structure, co-deposited BN-Fe nanocomposite films consist of amorphous completely disorder matrix BN containing a chaotic system of immobilized Fe nanoparticles. At the same time, these particles in contrast to those of layered film have much smaller size (d — 2.3 nm) since in this case the metal atoms are inside a matrix which slowdowns the diffusion process of atoms aggregation. [Pg.544]

If the arising dielectric matrix is very rigid, the deposition process gives a film of solid M/SC solution in dielectric material. Such solution is formed, in particular, by co-deposition of CdS and SiC, sputtered under the action of ionic plasma [61]. Semiconducting crystals of CdS in amorphous matrix... [Pg.544]

At the co-deposition of nanocomposite components formation of M/SC particles proceeds simultaneously with formation of a dielectric matrix, and the relationship between these processes determines the nanocomposite structure. This problem has been in detail investigated for the case of M/SC nanoparticles formation in polymer matrices. Synthesis of nanocomposite films by simultaneous PVD of polytetrafluoroethylene (PTFE) and Au has been carried out in works [62-64], Polymer and metal were sputtered under action of Ar ions and then the obtained vapors were deposited on substrates (quartz, glass, silica, mica, etc.) at various temperatures. Here, it is necessary to note that polymer sputtering cannot be considered as only physical process PFTE polymer chains destruct under action of high-energy ions, and formed chemically active low-molecular fragments are then deposited and polymerized on a substrate surface. [Pg.545]

Thus, the size effects for catalytic reactions of metal atom clusters in a gas phase are manifested only in very small, essentially quantum clusters, which are in essence nonmetal particles. Another situation takes place in films, containing a set of nanoparticles immobilized at a surface or inside of a dielectric matrix. In this case the influence of M nanoparticle size on catalytic activity and structure of products formed is observed for considerably larger already classical particles of sizes from 2 ( 150 atoms) to 20-30 nm ( 105 atoms) [113, 114]. It is necessary to note that catalytic properties of M nanoparticles in composite systems are determined substantially by their interaction with a matrix, which depends on the size of particles. [Pg.567]


See other pages where Dielectric matrix is mentioned: [Pg.2209]    [Pg.311]    [Pg.288]    [Pg.41]    [Pg.44]    [Pg.2351]    [Pg.525]    [Pg.531]    [Pg.535]    [Pg.566]   
See also in sourсe #XX -- [ Pg.43 ]

See also in sourсe #XX -- [ Pg.19 , Pg.26 , Pg.34 , Pg.72 , Pg.85 , Pg.91 , Pg.92 , Pg.97 , Pg.133 , Pg.160 , Pg.184 , Pg.195 , Pg.227 , Pg.299 , Pg.304 ]

See also in sourсe #XX -- [ Pg.1261 ]




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