The manufacturing of a metallic nano-cluster at a tip apex for field-sensitive microscopy applications.

Using a conductive atomic force microscopic setup, a metallic nano-cluster at a tip apex was successfully manufactured by an electrochemical redox process from an anodic aluminum oxide template. The diameter of the metallic nano-clusters ranged from 15 nm to 200 nm. The diameters of the nano-clusters could be well-controlled by adjusting the pore size of the templates. The formation of a variety of metallic nano-clusters at the tip apex was accomplished by preparing the electrolyte solution from different metallic salts. The formation mechanism for the nano-cluster is outlined and discussed. Moreover, we were able to enhance the performance of the nano-cluster tips for field-sensitive scanning probe microscopy, including electrostatic force microscopy and scanning Kelvin probe microscopy by laser annealing. Our experimental results indicated that for applications in field-sensitive scanning probe microscopy the stray field effect was significantly suppressed by the nano-cluster tip and hence the spatial resolution was improved.

Nanoscale of biomimetic moth eye structures exhibiting inverse polarization phenomena at the Brewster angle.

The unique functionalities of nanoscale structures in the natural world are an inspiration to the development of new nano-manufacturing techniques. For example, the cornea of the moth's eye features a sub-wavelength natural antireflective architecture. To date, almost all optical research into moth eye structures has been focused on their antireflective properties. No studies of inverse polarization phenomena at the Brewster angle have been reported, especially in biomimetic structures. For the first time, we discovered a unique inverse polarization phenomenon on moth eye structures that arises from TM-polarized light having a higher reflectance than TE-polarized light on moth eye structures at angles of incidence near the Brewster angle, unlike the behavior of polarized light on flat interfaces. Herein, we report a one-step colloidal lithography process that allows the fabrication of several kinds of moth eye structures. We characterized these moth eye structures experimentally and through rigorous coupled-wave analysis to understand the mechanism underlying this inverse polarization phenomenon in both visible and near infrared ray (NIR) regimes. Controlling the structural height and degree of non-close-packing of the moth eye structures had a dramatic effect on the extent of inverse polarization. This study is potentially important for various polarization-dependent devices and measurements.