In this thesis, we combined inductively coupled plasma reactive ion etching (ICP-RIE) and SiO2 sputtering to enhance quantum well intermixing (QWI). The samples used in this study were grown by molecular beam epitaxy (MBE) and metal organic chemical vapor deposition (MOCVD) on InP substrates. MBE sample consists of three In0.53Ga0.47As quantum wells, and the other consists of three In0.77Ga0.23As0.79P0.21 quantum wells. Ar+ bombardment by ICP-RIE was the first process step, and then a 300 nm SiO2 capping layer was sputtered upon the samples. The processed samples were subject to rapid thermal annealing. The properties of quantum wells after annealing were determined by photoluminescence (PL) measurement. The In0.53Ga0.47As/In0.53Ga0.26Al0.21As structure was used to design a series of experiments. First, we observed that the amount of blueshift increased with ICP-RIE time increased. ICP-RIE for 8 minutes was the optimum resulting in a bandgap blueshift of 60 nm, leaving a distance of about 200 nm between QWs and the SiO2 interface. The PL blueshift was directly ascribed to QWI caused by compositional interdiffusion between QWs and barriers. To determine how ICP-RIE affects QWI, we used H3PO4 solution to etch samples to the depth that was around 200 nm away from the QWs, and then coated by a sputtered SiO2 layer. Under 700¢J annealing, it gave rise to a blueshift of only 18 nm. And we also proved that the sputtered SiO2 capping layer provided an extra amount of bandgap blueshift. After the mechanism of QWI combining ICP-RIE and SiO2 sputtering was established, we applied this QWI process in In0.77Ga0.23As0.79P0.21/In0.57Ga0.43As0.64P0.36 material system, and we obtained a maximum amount of blueshift of 90 nm in this study.

This diploma thesis was focused on studying the interaction of humic substances with ionic organic xenobiotics and its structural aspects. The method was chosen from my bachelor thesis, steady-state fluorescence spectroscopy, which is suitable for substances with weak fluorescence. The results showed that the interaction between humic acids and representatives of ionic organic xenobiotics (Septonex) was reflected in fluorescence quenching of humic acids and the shift of emission maximum to lower wavelength, hypsochromic (blue) shift. From the measurement results, we can assume that the interaction that is formed between the aromatic structures in humic acids and Septonex could be -cation interaction.

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