Photonic crystals (PCs) are a new type of artificial materials with refractive index periodically modulated on the scale of the working light wavelengths.For the proper structural parameters,electromagnetic waves may backscatter coherently,forming a photonic-bandgap (PBG) within which the propagation of wave is inhibited inside the structure.[1] Such ability has paved novel routes for single photon sources,[2] efficient lasers[3] and all-optical switches.[4] To date,high quality PCs have mostly been manufactured by using expensive and time-consuming fabrication techniques such as electron-beam lithography or focusedion-beam writing.As a cost-effective alteative,the self-assembly method has been developed to prepare large area PCs.[5] Although the self-assembly method was mostly employed to prepare three-dimensional (3D) colloidal crystals,[6-10] the optical properties of monolayers or few finite layers of hexagonally close packed (HCP) dielectric spheres have been studied for decades.