National Repository of Grey Literature 3 records found  Search took 0.01 seconds. 
Time-resolved spectroscopy of wide-bandgap semiconductors
Martínek, Miroslav ; Trojánek, František (advisor)
In this thesis experimental samples of multiple quantum wells in the InGaN/GaN structures will be compared using methods of laser spectroscopy. In particular, the optical properties of the samples will be investigated. The samples were prepared under different conditions; therefore one of the aims is to compare them. The knowledge of the influence of preparation enables utilization not only for fundamental research, but also for the construction of radiation sources or scintillation detectors. Measurements of absorption and photoluminescence will be carried out and their dynamic properties will be measured as well. There will be examined the effect of different excitation power and different excitation wavelength on the intensity of photoluminescence. From dynamic properties there will be examined the effect of different excitation wavelength on the lifetime of the absorption and how does temperature influence the lifetime of the photoluminescence. Individual quantities will be compared amongst samples and their suitability for further applications will be discussed.
Time-resolved spectroscopy of wide-bandgap semiconductors
Martínek, Miroslav ; Trojánek, František (advisor) ; Žídek, Karel (referee)
In this thesis experimental samples of multiple quantum wells in the InGaN/GaN structures will be compared using methods of laser spectroscopy. In particular, the optical properties of the samples will be investigated. The samples were prepared under different conditions; therefore one of the aims is to compare them. The knowledge of the influence of preparation enables utilization not only for fundamental research, but also for the construction of radiation sources or scintillation detectors. Measurements of absorption and photoluminescence will be carried out and their dynamic properties will be measured as well. There will be examined the effect of different excitation power and different excitation wavelength on the intensity of photoluminescence. From dynamic properties there will be examined the effect of different excitation wavelength on the lifetime of the absorption and how does temperature influence the lifetime of the photoluminescence. Individual quantities will be compared amongst samples and their suitability for further applications will be discussed.
Multiparametric fluorescence spectroscopy
Lacko, Kata ; Venerová, Tereza (referee) ; Mravec, Filip (advisor)
This diploma thesis deals with the possibilities of multiparametric fluorescence spectroscopy, since the main objective of this experiment was to evaluate the possibilities of multiparametric measurements in the fluorescence spectroscopy laboratory. A suitable fluorescence probe was proposed for this type of experiment that shows high sensitivity for pH changes in the environment, SNARF-4F AM, based on a literature research. The fluorophore was dissolved in solutions of different pH and this system was examined using a time-resolved spectrofluorimeter. The method named TRES (time-resolved emission spectra) was used to obtain the emission spectra of the probe and to find the emission maximum. Fluorescence intensity decay measurements as a function of wavelengths allowed to create deconvolution of the emission spectra, which provided information about the fluorescent lifetime and the relative representation of the states of probes in the solution. Later, the probe was dissolved in solutions of different density and pH - this system served for anisotropic measurements, during which the individual correlation-rotational times of the fluorophore were obtained. The obtained results were then used as the basis for multiparametric analysis, which was performed by using a fluorescence correlation microscope and a spectrograph. This combination allows to measure the necessary fluorescence parameters in one step. A standard operating procedure was created for the spectrograph’s control. On the basis of the obtained information the suitability, accuracy and sensitivity of the multiparametric analysis were qualified.