AFM-Patterned 2-D Thin-Film Photonic Crystal Analyzed by Complete Angle Scatter

摘要

The purpose of this research was to use an atomic force microscope (AFM) to generate a 2-D square array of sub-wavelength surface features from a single material over a region large enough to permit optical characterization. This work is an extension of previous AFIT nano-patterning work and is in response to the small subunit sizes demanded for the production of optical metamaterials and photonic crystals. A diamond nano-indentation AFM probe was used to produce a 325-&(number sign)956;m by 200-&(number sign)956;m array of indentations in a 120-nm thick polystyrene film deposited on silicon. Indentation spacing of 400 nm produced well-defined surface features with a maximum height of 140 nm. The full size array was achieved by tiling together single arrays, limited in size by the AFM scanner range, through the use of the AFM's translation stage. A Complete Angle Scatter Instrument (CASI) was used (beam focused to 140 &(number sign)956;m) to determine scatter at incident angles ranging from 0 to 80 degrees. Two wavelengths were investigated (633 and 544 nm) at both s and p-polarization. Negative first order diffraction peaks were observed for both wavelengths and were consistent with feature spacing. This is the first demonstration of an AFM- patterned surface to behave as a 2D photonic crystal and has potential DoD applications in laser eye protection, enhanced solar cell efficiency, satellite thermal management, and anti-reflection coatings for high power laser optics.