Paderborn, Universiẗat, Diss., 2003.

Recently, ZnO is more and more popular in years because ZnO which is the same with GaN is a wide bandgap semiconductor. Moreover, ZnO can be made as UV region photonic devices and it is transparent. In this article, the main discussion is the Photoreflectance spectroscopy and contactless electroreflectance spectroscopy of ZnO. The next step is that measures contactless electroreflectance spectroscopy at different temperatures. After experiments, using Lorentzian profile fits the experiment data. And observing the transition type of ZnO.

Using contactless Electroreflectance spectroscopy to determine the face terminate of GaN.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

There are different polarization fields on the Zn face and O face along the c-axis of the ZnO single crystal due to the influence of the spontaneous polarization. In this work we will determine the internal field directions of both faces of the 0.5mm thick ZnO single crystal by photoreflectance and contactless electroreflectance techniques. We found that Zn face has inversion phase line shape, which means its internal field directs outward; O face has same phase line shape, which means its internal field directs inward.

The contactless electroreflectance¡]CER¡^ spectra of ZnO bulk has been measured at 300K. It was observed the difference between the CER spectra by using the polarization E of probe light perpendicular ( E¡æc) and parallel ( E¡üc) to the c-axis of the m-plane ZnO. In addition, a mercury lamp was focused on the sample to reduce its strength of electric field. It was observed that the CER spectrum was blue-shifted with Hg lamp being on. Hence, the observed features were attributed to excitonic transitions. The experimental spectra were fitted by Lorentzian lineshapes. The energies of the A ( B¡^, B¡]A¡^, and C excitonic transitions were determined as 3.329eV, 3.343eV and 3.387eV, respectively.

Konstanz, Univ., Diplomarb., 1999.

Techn. Universiẗat, Diss., 2004--Darmstadt.

Made available in DSpace on 2014-06-11T19:25:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-01-13Bitstream added on 2014-06-13T19:12:24Z : No. of bitstreams: 1 zagato_ef_me_ilha.pdf: 261736 bytes, checksum: d0251ba5867a2a4a3e37c5f78ca9c4ee (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Desde 1993, o mineral trioxide aggregate tem sido amplamente investigado e os resultados confirmam que ele possui excelentes propriedades físicas, químicas e biológicas. Apesar do sucesso e uso deste cimento, duas dificuldades têm sido apontadas pelos profissionais: o difícil manuseio e tempo de presa muito longo. Recentemente, um novo cimento endodôntico, intitulado CER, foi desenvolvido no laboratório do grupo Vidros e Cerâmicas. A inclusão de uma emulsão em sua composição deu ao cimento uma extraordinária consistência de trabalho e uma acentuada redução no tempo de presa. O primeiro estudo com o material mostrou que o CER tem a mesma habilidade de liberar íons que o mineral trioxide aggregate. Como continuidade na caracterização do CER, este trabalho apresenta resultados obtidos com o estudo do efeito do tamanho de partículas do pó de cimento no tempo de presa e na expansão térmica, e um estudo comparativo de infiltração marginal entre o CER e o MTA-Angelus. / Since 1993, the mineral trioxide aggregate has been widely investigated and the results confirm that it has excellent physical, chemical, and biologic properties. In spite of this, one of the difficulties reported by clinicians when using MTA is its poor handling characteristic and lengthy setting time. Recently, a novel endodontic cements, entitled CER, it was developed in the laboratory of the Glasses and Ceramic group. The inclusion of an emulsion in its composition gave to it an extraordinary handling and one accentuated reduction in the setting time as compared to MTA. The first study with the material showed that CER has the same ability to release ions than the mineral trioxide aggregate. This work presents results obtained from study of effects of particle size of the CER cement powder on setting time and thermal expansion, and from a comparative study of sealing ability between CER and MTA-Angelus.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.