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Content available remote Zastosowania metod ewolucyjnych w analizie TSDC
Wyniki pomiarów TSDC są superpozycją wielu procesów relaksacji. Złożone spektrum czyni analizę trudną, stąd parametry opisujące proces relaksacji są obarczone dużym błędem. Aby separować poszczególne procesy relaksacyjne i estymować odpowiadające im parametry, zastosowano algorytmy ewolucyjne. Algorytmy te efektywnie przeszukują skomplikowane przestrzenie rozwiązań, do których należy estymacja parametrów złożonego spektrum TSDC.
The result of a TSDC measurement is a superposition of several relaxation processes. The resulting complexity of the spectrum makes the analysis difficult, while the parameters describing the relaxation process carry a large error. In order to separate individual relaxation processes and estimate the corresponding parameters, the evolutionary algorithm has been used. The algorithms are durable and effective in analyzing processes in very complicated solution spaces, such as the estimation of a complex TSDC spectrum.
We present investigation of carrier traps and their transport in 4H-SiC single crystals and high energy radiation detectors. SiC detectors have been produced from bulk vanadium-compensated semi-insulating 4H-SiC single crystal. They were supplied with a nickel ohmic contact on the back surface and titanium Schottky contact on the front surface. The prevailing defect levels were revealed by means of thermally stimulated current (TSC) and thermally stimulated depolarization (TSD) methods and their advanced modification ń multiple heating technique. From I-V measurements of the samples a barrier height of ~ 1.9 eV was found. In 4H-SiC:Va, the following thermal activation values were deduced: 0.18-0.19 eV, 0.20-0.22 eV, 0.33-0.41 eV, and 0.63 eV. The maximum with activation energy of 0.33-0.41 eV appears below 125 K and most probably is caused by the thermal carrier generation from defect levels. In contrast, the first two maxima with the lowest activation energies, which nevertheless appear at higher temperatures, are likely associated with material inhomogeneities causing potential fluctuations of the band gap. The existence of different polarization sources in different temperature ranges is also demonstrated by TSD.
Content available remote Rare earth oxide films: their preparation and characterization
Summarises the results of our investigations dealing with preparation of rare earth oxide films and examinations of their physical properties. Different deposition methods have been applied for fabrication of these films and rare-earth-oxide-based thin film coatings. The main results concerning film microstructure and optical properties in the wavelength range from the UV up to the IR are presented. Electrical and dielectric studies have been carried out in the time domain and in the frequency domain (from very low frequencies up to radio frequencies) for selected rare earth oxides. MIM sandwich-type structures have been fabricated for this aim. Trapping levels in these oxides have been investigated. The complex impedance diagnostics was applied to the analysis of the volume of the R/sub 2/O/sub 3/ film and interfacial properties (metal/insulator barriers) of M/R/sub 2/O/sub 3//M thin film structures.
Content available remote Thermally stimulated currents in silica xerogels with temperature gradient.
Presents results obtained by the application of the method of thermally stimulated depolarization (TSD) to investigate dipole relaxation in SiO/sub 2/ xerogels. The presence of a strong temperature gradient in the sample has been revealed during measurements of the TSD current. The paper describes the method of determination of activation energy W, initial polarization P/sub 0/ and factor tau /sub 0/, for the dipole relaxation processes under investigation. It has been shown that the modified TSD method is a sensitive tool for the investigation of changes taking place in the peripheral molecular layer on the surface of pores in SiO/sub 2/ xerogels.
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