Submicrometer Surface Patterning Using Interfacial Colloidal Particle Self-Assembly

Hexagonal noncontiguously packed (HNCP) arrays of submicrometer-sized particles trapped at an air-water interface are successfully transferred to solid substrates. The long-range order of the hexagonal arrays at the interface can be improved by compression-relaxation cycles. The interparticle distance (i.e., the periodicity of the hexagonal array) can be controlled by varying the degree of compression of the particle film. The critical characteristics of the substrate surface are hydrophobicity (advancing water contact angle of > 70 degrees) and a charge complementary to the surface of the particles. Suitable silicon and glass substrates are easily prepared by treatment with commercially available organosilicon compounds. Two transfer processes have been developed. When the parallel transfer process is used, the HNCP arrays are deposited oil the solid substrates with minimal pattern distortion. The vertical dipping transfer distorts the pattern and renders a sense of directionality perpendicular to the dipping direction. This surface patterning technique is applied to fabrication Of subwavelength grating for antireflection in the visible region. Antireflective HNCP arrays comprising varied particle diameters and pattern periodicities are fabricated on glass substrates to demonstrate the effects of these parameters on the antireflection performance.