Fabrication And Optical Property Study Of Ordered Ge/Si Nanostructures Grown On Silicon Based Pit-patterned Substrates

Under the use of nanosphere lithography (NSL) and ion beam sputtering deposition (IBSD) technique, the paper focused on fabricating of ordered Ge/Si nanostructures on Si pit-patterned substrate. SEM and AFM are used to analysis the surface morphologies of the samples, Raman spectrometer is used to study the crystallinity of samples. Optical properties of ordered Ge/Si nanostructures are studied by PL spectrum and fluorospectro photometer.Based on the primary LB technique study, operations in experiments are optimized, such as new volume ratio of PS colloid, ethyl alcohol and deionized water, deionized water and ethyl alcohol, pre-treatment of samples with SDS et.al. The promoted steps can help to push particles self-organizing on deionized water more effectively. Ultraphonic environment is added to the silicon substrate anisotropic etching process in KOH solution, which can decrease the presence of unartificial factors to the experiment process.Ordered silicon nanoclusters are fabricated on patterned substrate by IBSD and their growth mechanisms are analyzed by kinetic theory. The chemical potential variations on different pit-patterned substrate surface positions are the main reason to make silicon atoms transform from higher potential positions to lower ones. Visible photoluminescence spectra of ordered Si nanoclusters, which origins from the high-density radiative recombination silicon and oxygen defect states in the forbidden band and the quantum confine effect of Si clusters.Ordered Ge/Si QDs are fabricated on patterned substrate by IBSD. The statistic sizes of ordered Ge/Si QDs are smaller than that on flat substrate which have good consistence with prediction of the theory. Growth mechanism of ordered Ge/Si QDs is analyzed by thermodynamics, which shows that nucleating position is determined by the competition between surface energy and strained energy due to the adding of strained layer (Ge wetting layer). Low temperature photoluminescence spectra are used to characterize ordered Ge/Si QDs and blue shift of peak position is found during the spectra test, which is relative to the quantum confinement of QDs.