In this thesis, two series of self-assembled GaN and AlxGa1-xN nanorods are grown by plasma-assisted molecular beam epitaxy (PAMBE) on Si(111) wafer. The Al contents in AlxGa1-xN nanorods is varied from 6% to 75% by changing the Al cell beam flux (BFM). Second, the GaN/AlGaN multiple quantum wells (MQWs) with variation thickness are grown on the GaN nanorods with a p-GaN layer on the top. Al concentration is determined by electron probe x-ray micro-analysis (EPMA) and x-ray diffraction (XRD). The reflection high-energy electron diffraction (RHEED) and scanning electron microscopy (SEM) images show that the height, density and morphology of nanorods depend on the Al content. The (micro-)PL, CL and Raman spectra also show the variation of the characterization from those of GaN to AlN. The transmission electron microscopy (TEM) images show that the GaN/AlGaN MQWs structures with well widths of 1, 2, 3, 4, 6, 8 and 16 c-LC (Lattice constant on c-direction) were successful grown on the nanorods. The (micro-)PL and CL spectra show red-shift of the peak position with the decrease of Mg-doped concentration. When the well thickness is less then 4 c-LC, the CL spectra show blue-shift of the peak position with the decrease of the well thickness due to the Quantum-confined effect and the polarization effect in MQWS.

Abstract¡G Scalar coupled mode theory predicts that the output powers at two nonlaunch fibers are identical for the equilateral 3x3 fiber couplers due to the geometrical symmetry, but several experimental results demonstrate that they are not equal. In this work, a power coupling model with considering the polarization property of input power is proposed for the equilateral 3x3 fiber couplers. Consistent with the measurement results, the model shows that when a polarized light is launched into one of the three fibers the output powers at the other two nonlaunch fibers are unequal.

Uma condutividade evanescente, dependente do tempo, tem sido detectada nos filmes de PVDF da BembergFolien. Após muitos ciclos de polarização e despolarização, a corrente de absorção torna-se fortemente reduzida, para o mesmo nível das correntes de despolarização. Esta condutividade é facilmente observada, aparecendo na corrente de polarização pela aplicação de altos campos. É observada recuperação em amostras deixadas em atmosfera úmida. Nós interpretamos estas observações como sendo uma limpeza, pelo campo elétrico, dos íons gerados por uma acentuação da dissociação de moléculas de água absorvida no volume, pela ação deste campo. / A time dependent evanescent conductivity has been detected in BembergFoliem PVDF films. After many polarization-depolarization cycles, the absorption current became strongly reduced, to the same level as the depolarization one. It is easily seen at higher fields by a bump appearing in the polarization current Recovering is observed in samples left in humid atmosphere. We have interpreted these observations as an electric field ion cleaning of an electric field enhanced dissociation of bulk absorbed water molecules.

Uma condutividade evanescente, dependente do tempo, tem sido detectada nos filmes de PVDF da BembergFolien. Após muitos ciclos de polarização e despolarização, a corrente de absorção torna-se fortemente reduzida, para o mesmo nível das correntes de despolarização. Esta condutividade é facilmente observada, aparecendo na corrente de polarização pela aplicação de altos campos. É observada recuperação em amostras deixadas em atmosfera úmida. Nós interpretamos estas observações como sendo uma limpeza, pelo campo elétrico, dos íons gerados por uma acentuação da dissociação de moléculas de água absorvida no volume, pela ação deste campo. / A time dependent evanescent conductivity has been detected in BembergFoliem PVDF films. After many polarization-depolarization cycles, the absorption current became strongly reduced, to the same level as the depolarization one. It is easily seen at higher fields by a bump appearing in the polarization current Recovering is observed in samples left in humid atmosphere. We have interpreted these observations as an electric field ion cleaning of an electric field enhanced dissociation of bulk absorbed water molecules.

The submitted thesis describes characteristics and use of ferroelectric materials which find their utilization in electrotechnical and electronics industry. The thesis is mainly aimed at their behaviour in the electrical field at various intensity. The method using an osciloscope is selected for measuring. For the main measuring in part of this thesis was produced experimental wafer with five samples which were subsequently mesuared. The VEE PRO program was used for creating of collecting datas for histeresis loop and it’s functionality was checked on wafer with five examples in measuring. During this measuring was also measured electric tension dependence of components of complex permittivity.