Physikingenieurwesen (PHY)
Redistribution of deep selenium and sulfur impurities in silicon upon surface doping with phosphorus
(2009)
The study is concerned with the effect of short-term high-temperature heating on Si:Se and Si:S samples, whose surface layers are doped with phosphorus to high concentrations. It is found that the resistivity of the wafers substantially increases deep in the bulk within up to similar to 10 mu m. The experimental data suggest that this effect is due to enhanced diffusion of chalcogen in the presence of the phosphorus-doped surface region. The mechanism of the effect is the injection of nonequilibrium interstitial silicon atoms from the layer heavily doped with phosphorus to the bulk of the sample. This results in a shift of the equilibrium between the concentrations of substitutional and interstitial impurity atoms towards higher concentrations of interstitials and, as a consequence, towards the increase in the relative content of the fast-diffusing interstitial component of the impurity.
The production of free-standing large aspect ratio metal nanofilms by femtosecond laser separation
(2009)
We demonstrate a new method for the production of free-standing metal films of thickness down to several tens of nanometres. Films of different metals as well as multilayer structures have been produced by means of femtosecond laser-induced separation of evaporated layers from a plane glass surface. This technology enables the production of large-area films with different properties for optical or nanotechnological applications. We study the properties of the film and demonstrate the possibility of high-pass filtering of electrons with an energy of several keV by means of the free-standing films. The physical mechanisms leading to the film separation under femtosecond laser radiation are discussed.
In this paper a novel concept of ablation cell for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is presented. Suppression of the turbulence in the flush gas flow in the ablation region reduces the wash-out time of the ablation cell considerably. An ablation chamber which enables ICP-MS pulse duration down to several ten milliseconds has been designed. Dependence of the ICP-MS peak amplitude, width, and shape on the gas flow parameters is studied experimentally for aerosol ablated under laminar and turbulent conditions. Experiments demonstrate that the ICP-MS peak becomes sharper and the amplitude of the signal grows as the turbulence in the ablation cell is suppressed. Furthermore, the possibility of the LA-ICP-MS analysis with a sampling rate of more than 10 Hz has been demonstrated. Express in-depth profiling in the new ablation cell is demonstrated on examples of an Al -Zn multilayer structure and an industrial Mg -Zn coating.
Self-sustained current oscillations in a Townsend discharge that is excited in a short plane discharge gap and is uniform along the electrode surface are investigated experimentally. A thin semiconductor plane serves as a discharge cathode, a ballast resistor, and an additional capacitor in the dc power supply circuit. The domain of existence and the frequency and waveform, of oscillations are determined over a wide pressure range.
Analytical features of particle counting sensor based on plasmon assisted microscopy of nano objects
(2011)
The dewetting of liquid filaments in linear grooves of a triangular cross section is studied experimentally and theoretically. Homogeneous filaments of glassy polystyrene (PS) are prepared in triangular grooves in a nonequilibrium state. At elevated temperatures, the molten PS restores its material contact angle with the substrate. Liquid filaments with a convex liquid-vapor interface decay into isolated droplets with a characteristic spacing depending on the wedge geometry, wettability, and filament width. This instability is driven by the interplay of local filament width and Laplace pressure and constitutes a wide class of ID instabilities that also include the Rayleigh -Plateau instability as a special case. Our results show an accurately exponential buildup of the instability, suggesting that fluctuations have a minor influence in our system.