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The mathematical model of surface erosion during ion bombardment is considered, which is reduced into a non-linear wave equation. The solutions obtained by characteristic methods describe a wide class of erosion phenomena, such as the development of arbitrary surfaces, including spherical particles, formation of edges, competition of modes showing up during the uptake of smaller inhomogeneities, and so on. Lateral views of spherical particles and sine waves for various amplitude/wavelength ratios and angles of bombardment are calculated to demonstrate applications of obtained solutions and their extrapolations onto real systems. Calculations are carried out for the Si - N 2 + system, using the experimental dependence of the sputtering yield on the angle of bombardment as approximated by the Yamamura formula. The obtained results revealing good agreement with literature and original experimental data may find use in SIMS depth profiling and micro-technology. [ABSTRACT FROM AUTHOR]

A self-forming nanostructure—a wave-ordered structure with a controllable period (20–180 nm)—results from the off-normal bombardment of amorphous silicon layers by low-energy (~ 1–10 keV) nitrogen ions. The nanostructure has been modified by reactive-ion etching in plasma to form a periodic nanomask on the surface of the channel region of a metal–oxide–semiconductor field-effect transistor (MOSFET). Implantation of arsenic ions through the nanomask followed by the technological steps completing the fabrication of the MOSFET resulted in a periodically doped channel field-effect transistor (PDCFET), which can be considered as a chain of short-channel MOSFETs with a common gate. Having worse subthreshold characteristics, PDCFETs show greater drain current and transconductance than to MOSFETs without a periodically doped channel. This improvement in device performance is attributed to the fact that the channel length is cut by the length of high-conductivity doped areas in the channel and that the voltage is distributed between the areas, depressing the scaling rules for short-channel MOSFETs and allowing the channel to be less doped between the areas, thus keeping drift mobility high. [ABSTRACT FROM AUTHOR]

The strong influence of oxygen to the positive secondary ion yield determines the problems of SIMS depth profiling of shallow boron implants in silicon, related to surface oxide and formation of modified layer. High value (4 eV) of electron affinity of BO2 molecule responds for the high yield of BO2− negative secondary ions, its small sensitivity to the variation of emission properties of the sample surface and relatively weak dependence on oxygen concentration. The features of using of named ions for shallow boron profiling was studied with a magnetic sector SIMS instrument in a high mass resolution mode under O2− and NO2− primary ion bombardment. The refuse from oxygen flooding allowed to avoid the initial significant change of sputter rate. The studied approach provides simplification of transient phenomena while still keeping sufficient sensitivity. [Copyright &y& Elsevier]

Wavy nanostructures are formed on the ion-bombarded surface of single-crystal and amorphous silicon films prepared by various methods. The period and depth of this structure have been determined as functions of the angle of incidence and the energy of nitrogen ions used for the surface sputtering. A comparative analysis of SEM images of the wavy surface nanostructures on various silicon films has been performed using a two-dimensional Fourier transform. The films of amorphous silicon obtained by electron beam deposition and magnetron sputtering techniques are closest to single-crystal silicon films with respect to the wavy surface nanostructure formation. © 2003 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The terms of primary and secondary resistance to nicotine replacement therapy in tobacco dependent patients are defined. It is shown that treatment resistance is a result of a constellation of special clinical features of tobacco dependence, tolerance to nicotine, personality traits of the patients, family history of smoking, comorbid affective disorders and somatic diseases.

In order to formulate a biosocial conception of tobacco dependence essential for fundamental grounding of smoking prevention, the authors examined 1106 subjects with smoking habits, smoking dependence and nonsmokers. A combination of internal and external factors is determined underlying the onset and maintenance of tobacco dependence. Risk factors responsible for consolidation of tobacco addiction are listed.