Self-assembly of pillar structures in nanodiamond layers

The self-assembly of pillar-like structures in nanodiamond (ND) layers has been obtained for the first time by pulsed spray technique [1]. This technique has enabled to directly deposit ND layers on silicon substrate using natural nanocrystals of 250 nm. ND particles were dispersed in the apolar solvent 1, 2 - dichloroethane (DCE) by sonication for 30 minutes, then the dispersion was sprayed on the substrate. Various samples were sprayed at different number of pulses, ranging from 1 to 500. The obtained ND layers were analyzed by Raman spectroscopy, atomic force microscopy (AFM), 3D confocal microscopy, and contact angle measurements. The Raman spectroscopy allowed the measurement of the chemical and structural composition and the photoluminescent properties, the microscopic techniques measured the topography and morphology of the layers and contact angle measurements established the hydrophilic/hydrophobic nature of substrate/ND layers surfaces. A careful morphological analysis evidenced the existence of self-assembled pillar-like structures. The formation mechanisms of self-assembly, based on the so-called coffee stain effect, i.e. on the time evolution of DCE evaporation will be presented and discussed. Theoretical electrical aspects of the single pillar will also be discussed.