From random to order: Colloidal crystals on non-flat surfaces

This paper introduces the possibility to produce 1-2 cm2 and tens of layers colloidal crystals on different non-flat surfaces by means of electrospray deposition. Two different types of crystalline silicon surfaces were tested: nanostructured “black silicon” and random pyramids. Several trenches were drilled by SEM-FIB to assess the morphology of the samples. The results of these measurements show that an ordered and consistent structure can be obtained on both cases after some disordered layers. The relative aspect ratio between the features on the silicon surface and the nanoparticle defines whether the order/disorder interface follows the surface profile. Apart from checking the internal structure, the quality of the structures has been assessed by measuring the reflectance spectra showing a consistent reflection peak of 80% at 950 nm, as expected from the size and structure on the nanoparticles.