Semiconductor Nanostructures Activities
The goal of this subproject is to develop experimental techniques that can be used to produce nanoscale materials that possess calculated properties (through the methods described above) that are of scientific or technological interest. Ultrafast pulsed laser deposition (UPLD) is a technique that can be used to produce nanostructures from virtually any material. Experimental studies on the effect of experimental parameters, including laser fluence, laser pulse width and substrate location on the size of semiconductor QDs produced by UPLD were performed to determine optimum parameters for obtaining specific QD sizes and narrow size distributions. Studies of the impact of the structure of ultrafast pulses used for target ablation on the efficiency of QD production and the size of QDs were also initiated. A liquid crystal spatial light modulator based pulse shaper and a frequency resolved optical gating apparatus were constructed to control and characterize the shape of the ultrafast laser pulses for these studies. Finally, a nanowire fabrication system that combines chemical vapor deposition (CVD) and PLD capabilities has been designed and is now undergoing initial testing. Nanowire growth in this system, which is based on a three zone tube furnace, occurs through vapor – liquid – solid or vapor – solid – solid processes that involve exposure of nanoparticle seeded substrates to vapor generated by thermal evaporation, PLD or gas inputs.