Fabrication Of Colloidal Crystals By Using Polystyrenemicrospheres And Their Application

Ordered micro/nano structures show unique properties in the optical, electrical, magnetic, thermal, etc, thushaving a wide range of applications for optoelectronic devices, bio-sensing, magnetic storage materials, surface-enhanced Raman scattering, phonon diffraction gratings and other high-tech fields. Self-assembly plays an important role in the preparation of colloidal crystals due to its simplicity, flexibility, and low cost. This thesis focuses on the fabrication of colloidal crystals by means of self-assembly of polystyrene (PS) microspheres. Two kinds of application of PS colloidal crystals are demonstrated. One is to use a PS colloidal monolayer as a template. The other one is to construct photonic crystal heterostructure by using multilayer PS colloidal crystals. The main contents include the following three parts:1. Ordered ZnO nanorods array with dense accumulation pattern was fabricated by using a colloidal monolayer template. Field emission measurement results show enhanced field emission properties of the patterned ZnO arrays, which was attributed to the decreased screening effect that resulted from the interval between neighboring ZnO nanorods.2. Highly ordered titanium (Ti)-doped ZnO nanorod arrays were preparted utilizing a facile hydrothermal method and a PS microsphere monolayer mask. The crystalline phase and morphology of as-prepared samples were investigated systematically. The field emission (FE) properties measurement results demonstrated that the Ti-doped ZnO nanorod arrays exhibited a significantly improved field enhancement factor β as well as a lowered turn-on field and a lowered threshold field. These improved FE performances were attributed to the decreased work function which resulted from the widened energy gap combined with the up-shift of Fermi level in n-type Ti-doped ZnO nanorod arrays.3. The colloidal photonic crystal heterostructures free of interface defects were realized by a combination of the saturated solvent vapor annealing approach and the flow-controlled vertical deposition self-assembly. Both structural observation and optical performance characterization confirmed the resultant heterostructure possessed a high optical quality. The optical characterization exhibited a single widen stop band for the integrated colloidal photonic crystal heterostructure.