Study of controlled quantum dot formation on focused ion beam patterned GaAs substrates

In this project, we combine focused ion beam patterning (FIB) and self-assembly of quantum dots, in order to produce regular quantum dot arrays. Quantum dots are expected to nucleate at specific locations, where the ion beam has formed a patterned array. Different ion beam patterning parameters were used, including accelerating voltage, probe current, dwell time and pitch. Secondary electron (SEI) imaging in the scanning electronic microscopy (SEM) and atomic force microscopy (AFM) have been performed between patterning and overgrowth and also after overgrowth. By comparing images before and after overgrowth, we can understand how patterning parameters influence quantum dot nucleation. Quantum dots are more likely formed at patterns made with low acceleration voltage and ion dose. Also, the relationship between patterning parameters and site of quantum dots has been studied.