Electron spin resonance dangling bond

Global AMI.5 sun illumination of intensity 100 mW/cm ). The DOS (or defect) is found to be low with a dangling bond (DB) density, as measured by electron spin resonance (esr) of - 10 cm . The inherent disorder possessed by these materials manifests itself as band tails which emanate from the conduction and valence bands and are characterized by exponential tails with an energy of 25 and 45 meV, respectively the broader tail from the valence band provides for dispersive transport (shallow defect controlled) for holes with alow drift mobiUty of 10 cm /(s-V), whereas electrons exhibit nondispersive transport behavior with a higher mobiUty of - 1 cm /(s-V). Hence the material exhibits poor minority (hole) carrier transport with a diffusion length <0.5 //m, which puts a design limitation on electronic devices such as solar cells. 

X-Ray irradiation of quartz or silica particles induces an electron-trap lattice defect accompanied by a parallel increase in cytotoxicity (Davies, 1968). Aluminosilicate zeolites and clays (Laszlo, 1987) have been shown by electron spin resonance (e.s.r.) studies to involve free-radical intermediates in their catalytic activity. Generation of free radicals in solids may also occur by physical scission of chemical bonds and the consequent formation of dangling bonds , as exemplified by the freshly fractured theory of silicosis (Wright, 1950 Fubini et al., 1991). The entrapment of long-lived metastable free radicals has been shown to occur in the tar of cigarette smoke (Pryor, 1987). 

The role of the second plasma treatment by HFE or Ar seems to be the removal of type B plasma polymer of TMS from the top surface region or possibly converting the type B plasma polymer to type A plasma polymer. Electron spin resonance (ESR) data (described in Chapter 6) indicate that the number of Si-based dangling bonds decreases by these second plasma treatments. The weight loss observed with some plasma polymers and the ESR data for TMS film suggest that type B plasma polymer in the top surface region of an LCVD film could be up to nearly 30% of the... 

Fig. 18. The dashed curves represent the axially-symmetric powder pattern for the dangling bond observed at Si-SiOj interfaces (Caplan et al 1979) for several values of isotropic broadening W. The solid curve is the ESR spectrum in a-Si H. [Reprinted by permission of the publisher from Electron spin resonance studies of amorphous silicon, by D.K. Biegelsen, Proceedings of the Electron Resonance Society Symposium, Vol. 3, pp. 85 - 94. Copyright 1981 by Elsevier Science Publishing Co., Inc.]...

Recently, both polycrystalline and microcrystalline ( 200 A crystallite size) Si films have been investigated by ESR (Hasegawa ft a/., 1981b, 1983b). A dangling bond resonance in microcrystalline silicon films is observed at g = 2.0049. The spin density of this resonance is typically between 10 and 10 spins cm. In P-doped samples a conduction-electron spin-resonance signal is observed at = 1.997. 

In the first demonstration of HWCVD PTFE [18], the predominance of the -CF2-bonding environment in the films was shown by X-ray photoelectron spectroscopy (XPS). The FTIR spectra of HWCVD PTFE films are dominated by the CF2 symmetric (1155 cm ) and asymmetric stretches (1215 cm" ), which are also observed for conventionally synthesized bulk PTFE. Additionally, electron spin resonance (ESR) results found the dangling bond density 10 spins/cm for HWCVD PTFE, which is... 

In tetrahedrally coordinated amorphous alloys the theraputic role of hydrogen in passivating "dangling bonds" is well known. In amorphous silicon without hydrogen (a-Si) the densities of silicon "dangling bonds" as measi ged by electron spin resonance (ESR) are almost always greater than 10 spins cm. With thj addition o hydrogen the spin densities in a-Si H can be as low as 10 spins cm... 

Biegelsen, Electron Spin Resonance Studies of Amorphous Silicon, Proc. Electron Resonance Symp. 3 85 (1981). dler and and F.R. Shapiro, Effective Correlation Energy of the Dangling Bond in Amorphous Silicon, Physica 117B and 118B 932 (1983). ... 

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