No abstract

We studied local leakage currents induced in stressed gate SiO2 films and their time dependence by conductive atomic force microscopy (C-AFM). The current-voltage characteristics of the leakage currents detected in the C-AFM observations indicate Fowler-Nordheim tunneling currents enhanced by holes trapped in the stressed SiO2 films. By repeated C-AFM observations at the same area, it was found that individual spot currents decrease at different rates. This result indicates hole detrapping with different time constants from the stress-induced defects that have different features.

We have demonstrated the detection of nanometer-scale current-leakage sites in electrically stressed gate SiO2 films using a conductive atomic force microscope (C-AFM). Prior to C-AFM observations, the gate SiO2 films in metal-oxide-semiconductor capacitors were subjected to constant-current Fowler-Nordheim (FN) stress. Details of image contrasts and the relationship between the surface topography and the current image of the SiO2 films were examined. Two types of contrast were clearly observed in the current image: a sharp bright spot reflecting local current leakage were caused by hole trapping at stress-induced defects and a fuzzy bright contrasts originating from the SiO2 thickness fluctuation. The dependence of C-AFM images on the electron injection direction during FN stress application and the SiO2 film thickness clearly reveals that the stress-induced defects are distributed in the region within 2.6 nm from the SiO2/Si substrate interface.

We show the existence of a new class of astrophysical objects where the self-gravity of the dust is balanced by the force arising from shielded electric fields on the charged dust. The problem of equilibrium dust clouds is formulated in terms of an equation of hydrostatic force balance together with an equation of state. Because of the dust charge reduction at high dust density, the adiabatic index reduces from two to zero. This gives rise to a mass limit M AS for the maximum dust mass that can be supported against gravitational collapse by these fields. If the total mass M D of the dust in the interstellar cloud exceeds M AS , the dust collapses, while in the case M D < M AS , equilibrium may be achieved. The physics of the mass limit is similar to the Chandrasekhar's mass limit for compact objects, such as white dwarfs and neutron stars.

ABSTR4CT. It is assumed that surfaces showing low gloss consist of small elementary facets which may be set at any angle to the mean surface. These facets may be of two types, one diffusing a proportion of the incident flux according to Lambert's law, and the other reflecting, at the specular angle, a proportion s of the incident flux, where s is determined by Fresnel's equation and is dependent on the refractive index of the material. On these assumptions formulae are obtained whereby the emergent flux E can be resolved into its diffuse and specular components R and M and from which the proportional areas B of the mirror facets, set at different angles to the mean surface, can be calculated. The use of the equations is illustrated by analysing two families of curves obtained by means of an apparatus which is described and relating to light scattered from a surface of Bristol board and from a surface of magnesium-oxide smoke deposited on plane glass.