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The method of Rutherford backscattering spectrometry in combination with channeling is used to study the accumulation of structural defects in silicon at room temperature as a result of irradiation with P+ and F+ atomic ions and also with cluster PF ions ( n = 1, ..., 4) with the energy of 2.1 keV/amu and with identical generation rate of primary defects. The conditions for correct comparison of the results of bombardment with atomic and cluster ions composed of atoms of various types are suggested. It is found that the characteristics of accumulation of structural defects in silicon in the case of bombardment with PF cluster ions differ widely from those under irradiation with both atomic ions that are involved in the cluster ion (P+ and F+) and with atomic heavy ions that have atomic mass close to that of the mass of a PF cluster. It is shown that, with irradiation conditions being the same, cluster ions produce much more radiation defects in the surface region than do atomic ions; i.e., a molecular effect is observed. Plausible mechanisms of this phenomenon are considered. [ABSTRACT FROM AUTHOR]

The results of numerical simulation of electrical characteristics of silicon-on-insulator MOSFET nanotransistors with two independent gates are reported. The cases of grounded and floating bases with the surface recombination of charge carriers either disregarded or taken into account are considered. It is shown that, at specified design parameters (gate length 50–100 nm, thickness of silicon layer 25–50 nm), one can vary the transistor’s threshold voltage by 0.45 V, reduce the transistor current in the off state by seven orders of magnitude, and decrease the subthreshold slope of the gate characteristics to 60 mV/decade by varying the voltage applied to the second gate. Suppression of the short-channel effects in the transistors under consideration depends on a number of parameters (listed in order of decreasing effect): the gate material, the lifetime of charge carriers (for floating or grounded base), the thickness of the top silicon layer, the voltage applied to the additional gate, and the channel length. [ABSTRACT FROM AUTHOR]

The surface morphology and optical properties of the (In,Ga)As/GaAs(100) multilayer structures with self-organized quantum dots and quantum wires, which were grown by molecular-beam epitaxy, are investigated. It is found that the ordered arrangement of quantum dots in the heterointerface plane starts to form during the growth of the first periods of the multilayer structure. As the number of periods increases, quantum dots line up in series and form wires along the $$[0\bar 11]$$ direction. An increase in the lateral ordering of the structures under consideration correlates with an increase in the optical emission anisotropy governed by relaxation anisotropy of elastic strains and by the shape of nano-objects. A possible mechanism of lateral ordering of quantum dots and wires in multilayer structures, which includes both anisotropy effects of the strain fields and adatom diffusion, as well as the elastic interaction of neighboring quantum dots, is discussed. [ABSTRACT FROM AUTHOR]

Second-harmonic generation in a double-quantum-well nanostructure is analyzed. Optimization of the structure design from the viewpoint of attaining the highest intensity of the second-harmonic wave at the output is considered. Relationships between the quantum-well parameters in a structure satisfying the double-resonance condition are established. The dependence of the optical characteristics of the system on the quantum-well parameters is studied and the problem of optimization of the second-harmonic intensity is solved. It is demonstrated that the highest conversion efficiency is attained under the conditions where the second-harmonic generation coefficient is maximum. [ABSTRACT FROM AUTHOR]

The method of the charge-density functional in the tight-binding approximation is used to study the effect of different types of wall atomic defects in the MoS2 nanotubes on their structural and electronic properties. It is shown that the atomic defects in the walls of the MoS2 nanotubes can be responsible for the semiconductor-metal transitions. [ABSTRACT FROM AUTHOR]