Current burst

From the point of view of GCE, one is interested primarily in effects averaged over long periods of time of the order of Gyr but in dwarf galaxies which may have experienced only a few star formation bursts over a Hubble time the sporadic character may have appreciable effects, especially when one bears in mind that much of the abundance data for such objects comes from H II regions which are intrinsically the result of a current burst, and there is indeed evidence for a cosmic dispersion in certain element abundance ratios such as N/O in such objects (see Chapter 11). 

Pores form due to a silicic layer on walls9 Current burst theory... 

In the late 1990 s, Foil et al.40-43 proposed the current burst theory. The basic hypothesis is that the electrochemical reactions involved in the dissolution of the silicon surface operate in microscopic units. These reaction units have a temporal and a spatial distribution in number and in the state of activity. The formation of pores is due to the synchronization of these operation units at certain time and geometrical scales. 

Pore formation due to cyclic current bursts governed by oxide dissolution and hydrogen passivation. Carsiensen et... 

Current Burst Theory. The current burst theory of Foil et 0 Tii35,ii40,ii4i... 

Current flow is always spatially and temporally inhomogeneous, that is, it occurs by local current bursts. 

Current flow induces either direct dissolution or oxide formation and dissolution which always follows a current burst. 

The rate of hydrogen termination varies with crystal orientation, is fastest on the (111) surface, and thus determines the probability of a current burst on surfaces of different orientations. 

The current burst model is potentially powerful in providing explanations for many mechanistic and morphological aspects involved in the formation of PS. However, as recognized by Foil et al. themselves, it would be extremely difficult for such a unified model to be expressed in mathematical form because it has to include all of the conditional parameters and account for all of the observed phenomena. Fundamentally, all electrochemical behavior is in nature the statistical averages of the numerous stochastic events at a microscopic scale and could in theory be described by the oscillation of the reactions on some microscopic reaction units which are temporally and spatially distributed. Ideally, a single surface atom would be the smallest dimension of such a unit and the integration of the contribution of all of the atoms in time and space would then determine a specific phenomenon. In reality, it is not possible because one does not know with any certainty the reactivity functions of each individual atoms. The difficulty for the current burst model would be the establishment of the reactivity functions of the individual reaction units. Also, some of the assumptions used in this model are questionable. For example, there is no physical and chemical foundation for the assumption that the oxide covering the reaction unit is... 

J. Carstensen, M. Christophersen, and H. Foil, Parameter dependence of pore formation in silicon within a model of local current burst, Phys. Status Solidi, (a)182, 1, p. 63, 2000. 

Fig. 7.13 Anodic polarization curve showing current bursts at potentials below the breakdown potential. Type 304 stainless steel in 200 ppm chloride ion solution at room temperature, pH = 4...

Only the semiconductor SWNT are suitable for the preparation of field-effect transistors (FET) so IBM researchers (Science, April 27. 2001) have developed a destructive technique for eliminating conducting tubes from conductor/semiconductor clumps with a current burst. The technique can also be used to remove the outer layers of multiwallcd tubes that consist of multiple concentric tubes about a common axis. Bandgaps increase as the diameter of multiwalled tubes is decreased which means that the destructive technique can be used to tailor a semiconductor tube to specific requirements. 

Figure 4. Multistate conductance shown by alamethicin on a planar bilayer membrane with applied potential of 210 mV (top) and on frog sarcolemmal membrane with — 110-mV resting potential (bottom). Current bursts begin at A and continue until B. The different levels observed are not integral multiples of unit current conductance, which implies different states of the pore. (Upper figure reproduced with permission from reference 41. Copyright 1972 Elsevier. Lower figure reproduced with permission from reference 302. Copyright 1979 Macmillan Magazines.)...

The Current Burst Model (CBM) Spatial and temporal inhomogeneity of current, hydrogen siuface passivation (Carstensen et al. 2000 Foil et al. 2002)... 

Foil H, Carstensen J, Christophersen M, Hasse G (2000) Parameter dependenee of pore formation in silieon within a model of local current bursts. Phys Stat Solid A 182 63-69 Kleimann P, Linnros J, Juhasz R (2001) Formation of three-dimensional microstructures by electrochemical etching of silicon. Appl Phys Lett 79 1727-1729 Kohler M (1999) Etching in microsystem technology. Wiley, Weinheim... 

Light emission is connected with current burst (Sibillot and Coelho, 1974 Arii and Schmidt, 1984 Denat et al., 1987) ... 

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