[en] The mass, charge and energy spectra of aluminium and copper ions in dependence of laser radiation frequency are presented. It was shown that with frequency growth the intensities of Al⁺are changed nonlinearly and intensities of multicharged ions Al,Cu (Z>1) were increased because of additional thermal and ionization processes at target surface as well as growth of 'tempering' effect of ionization state in plasma. (author)

[en] Short communication. 4 refs

[en] We study the deposition and the very first steps of nucleation and growth of Ag on Pd(100) with thermal energy atom scattering. This technique is a very sensitive and nonperturbing probe to surface point defects, which permits an in situ and in-time monitoring of the deposition. The intention of this paper is to give a detailed description of the approach used in our work. The form of the specularly reflected helium signal as a function of coverage and surface temperature is compared to a theoretical curve, which is computed by solving a system of rate equations that describe the formation and destruction of clusters during the deposition process. The analysis of the experimental data gives two main results. The diffusion parameters (activation barrier E_d=0.37±0.03 eV and preexponential factor ν₀=8x10⁹ s^-1) have been extracted for the system Ag on Pd(100). We find furthermore that all silver atoms impinging on a zone of 6.1 A around an adatom on the surface are captured by it at surface temperatures well below the onset of thermally activated mobility. The origin of this phenomenon is discussed and tentatively assigned to a combined effect of transient and neighbor driven mobility. copyright 1996 The American Physical Society

[en] The transient (n=1) to (n=2) intersubband absorption of a pure electron plasma in n-type Ga_0.48In_0.53As/Al_0.48In_0.52As quantum wells is studied in femtosecond pump-probe experiments. The ultrafast dynamics of nonlinear absorption shows strong changes when tuning the midinfrared pulses over the intersubband absorption line. The nonlinear optical response is determined by both intersubband relaxation with a time constant of 1.3 ps and the intraband dynamics of (n=1) electrons, which are monitored in an independent experiment. copyright 1996 The American Physical Society

[en] Soft X-ray conversion efficiencies from 0.35 μm laser-irradiated Au disk and C, Al, Cu foils at different laser intensity on the 'Xingguang II' high-intensity laser facility (energy 5-90 J, focal spot ∼200 μm, FWHM 400-800 ps) were obtained. A simple model was given to explain soft X-ray conversion efficiency from 0.35 μm laser-Al plasma interaction. In this model, because of heat conduction from the laser-heated spot, the conversion was very small at some low irradiance limit, while at some high irradiance limit it was bounded by the energy lost in plasma blow off. Consequently, at laser intensity (2 +- 0.5) x 10¹⁴ W/cm², the X-ray conversion efficiency reaches a maximum

No abstract available

[en] The diagnostics of the process of plasma chemical etching (PCE) of silicon and its oxide is carried out in most cases using spectroscopic methods which make it possible to determine the plasma parameters with a high spatial resolution. Important results were obtained when examining the process of PCE on the basis of relative intensities of radiation I of the lines of the atoms and molecules excited in the plasma. However, the relationship of the parameter I with the kinetics of the etching process is not always unambiguous. The aim of these investigations was to develop a method of the diagnostics of the carbon fluoride plasma in etching of Si/SiO₂ structures on the basis of the parameters directly linked with the kinetics of the PCE process. One of these parameters - gas temperature T₈ determines the heat flow to the processed surface, its heating and, consequently, the rate of the PCE V_T. The use of the spectroscopic method for the diagnostics of the PCE process requires detailed examination of the spectral composition and spatial-time characteristics of plasma radiation. (author)

[en] The recent discovery of electro luminescent organic materials opens new perspectives for the preparation of light emitter diodes, screens and thin profile monitors. The basic unity of these devices is a light emitter diode made on thin films, which can be deposited using relatively simple techniques over a large variety of substrates. These new electro luminescent materials exist as conjugated polymers (electric charge conductors) or as small molecules, evanescent oligomers, constituted by one or more chemical unites. Research on these materials is a field of productive, attractive and interdisciplinary work that require the close collaboration between physicists and chemists, in the theoretical as well as in the experimental level. Some cases of diodes and other electro luminescent elements made of organic materials are presented in this paper. In the same way, some measurements of the electronic levels using a tunnel effect microscope are shown. In the use of this instrument, the sharpness of the microscope can be as a cathode of an electro luminescent diode, characteristic that allows to measure the spectra of the electro luminescent emission in regions of nanoscopic ranges. (Author)

[en] The magnetic interactions in superlattices formed by alternating layers of magnetic and nonmagnetic semiconductors with common anions were studied theoretically. Within a one-dimensional tight-binding model by minimising the total electric energy we show the existence of an efficient long range mechanism of magnetic correlations between neighbouring magnetic layers in such superlattices. The cases of magnetic ions in the barriers (e.g., EuTe/PbTe) and in the wells, with the order within the magnetic layers being either ferromagnetic or antiferromagnetic, have been considered and compared with the paramagnetic case. In case of antiferromagnetic ordering within magnetic layers we have found that for even and odd numbers of magnetic monolayers different magnetic superlattices are energetically favourable. (author)

[en] Recently we completed the very first and detailed perturbed angular correlation investigation on MBE-grown very thin film multilayers. The present paper aims to show that otherwise rather unaccessible but unique information on the (interface) magnetism could be obtained. For the Fe/Cr (100) multilayer system we observe, below a critical Cr thickness of 0.5 nm, a collapse of the spin-density-wave ordering in chromium. While the magnetization in the Fe-layer is in-plane, the Cr magnetization in thicker layers is out-of-plane. In Fe/Co (1-10) system, the observation of transferred magnetic hyperfine field satellites and their temperature dependence leads to the determination of an oscillating magnetic moment profile at the Fe/Co interface as well as a structure model of superlattice. (author)