Size hydrogenated silicon cluster

Theoretical investigations of AEV and AEC have indicated that the ratio AEV/AEC is greater than 1 [Zh2, Vo2, Ne2] and may be as high as 3 for the case of hydrogenated silicon clusters [Re3], In a similar calculation for thin silicon films, even-odd oscillations of A v according to the number of Si monolayers have been found [Zh2], For the latter case the ratio AEy/AEc showed values between 1 and 2. The results of a study [Wa5] including the decrease in the static dielectric constant with size are close to the experimentally [Bu2] observed values of about 2 for the ratio AEy/AEc, as shown in Fig. 7.16. In this work [Wa5], it is concluded that the electron-hole pair is confined by the physical dimension of the quantum dot, not by Coulomb attraction. 

Size-Dependent Oxidation of Hydrogenated Silicon Clusters... 

The optical band gap of silicon clusters increases with decreasing cluster size and all surface atoms with dangling bonds contribute to mid-gap electronic states (defects) which are assumed to quench photoluminescence. Saturation of the surface dangling bonds with hydrogen is the simplest way to eliminate defects, and therefore theoretical studies of the electronic structure of silicon clusters without defects are most easily performed on hydrogenated silicon clusters. The thermodynamic stability of these species is also of interest, because hydrogenated silicon clusters are formed in thermal and plasma CVD of silane. ... 

Compared to the situation described in earlier reviews, the scope of applications has noticeably widened. In particular, more mixed clusters are now being studied (albeit only binary ones). Also, a few papers have appeared that treat clusters other than bare clusters in a vacuum hydrogen-passivated silicon clusters and ligand-coated gold clusters have been investigated, as well as clusters on supporting surfaces. Studies of molecular clusters, however, which were attempted at the very beginning of the development described earlier, are still quite rare, and are limited to comparatively small cluster sizes. This bears testimony to the additional difficulty of this task, and perhaps also to the lack of reliable intermolecular potentials. 

Clusters of small and intermediate size play an important role in the explanation of the chemical and physical properties of matter on the way from molecules to solids. The great interest in silicon clusters stems from the importance of silicon in solid-state physics and from the photoluminescence properties of porous silicon. In Chapter 20, A. F. Sax presents theoretical models to describe bare and hydrogenated small silicon clusters and discusses... 

Puzder A, Williamson AJ, Grossman JC, Galli G (2002b) Surface control of optical properties in silicon nanoclusters. J ChemPhys 117 6721-6729 Ren SY Dow JD (1992) Hydrogenated Si clusters band formation with increasing size. Phys Rev B 45(12) 6492-6496... 

The ion-molecule reactions that occur in mixtures of SiH4 and PH3 have recently been described As in the aforementioned cases, the main reaction channels for the formation of larger-sized clusters from SiH " cations (n = 0-3) and PH3, and from the reactions of PH t+ cations (n = 0-3) with SiH4, correspond to the addition of the neutral molecule and dissipation of the excess energy via loss of a hydrogen molecule. It was concluded in this study that the nucleation of mixed silicon-phosphorous ions was favored upon ionization of mixtures that contain a large excess of SiH4. 

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