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Ultrafast laser spectroscopy of semiconductor nanostructures
Neudert, Karel ; Trojánek, František (advisor) ; Nikl, Martin (referee) ; Herynková, Kateřina (referee)
This doctoral thesis deals with analysis of carrier dynamics in semiconductor nanocrystals and nanostructures by methods of ultrafast laser spectroscopy. In three chapters silicon, InAs/GaAs, InAs/AlAs and CdSSe materials are studied. Silicon nanocrystals prepared by sol-gel method were measured by time-resolved luminescence method with various time resolutions, two-photon absorption and Z-scan method. A model describing findings was suggested. InAs was well measured by upconversion method and gained knowledge appeared to be fully consistent with quantum model. CdSe material was examined in two basic forms - thin films of nanocrystals prepared by chemical deposition and nanocrystals in comercial filters. In both cases all questions regarding influencing optical properties of nanocrystals by modification of their growth were answered.
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Time-resolved laser spectroscopy of nanomaterials
Kozák, Martin ; Trojánek, František (advisor) ; Šimurda, Miroslav (referee)
This diploma thesis is oriented to study of nonlinear properties of semiconductor nanocrystals using ultrashort femtosecond pulses. There is a detailed description of theory and experimental setup of the z-scan method, which can be used to measure the nonlinear refractive index and the two-photon absorption coefficient. In theoretical part we describe the influence the quality of laser beam, quality and thickness of the sample on measurements. There are numerical simulations of the measurements influenced by these parameters. This theory is used for processing of the measured dates by a program, which is attached to this thesis on CD. In experimental part we measured nonlinear refractive indeces of diamond nanocrystals fabricated by the PECVD method, silicon and CdS nanocrystals in glass matrices. One part of this thesis deals with the preparation and optimalization of the experimental setup and increasing the signal/noise ratio.
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