Selective electroless plating of silver nanograting patterns with no lateral growth for the fabrication of polarizers

Metal patterning has been useful for fabricating many optical and electronic devices. Among all the patterning methods, selective electroless plating in combination with micro-contact printing (μCP) is a simple process compatible with roll-to-roll processing. However, this process suffers from the difficulty to avoid lateral growth during the electroless plating of metal. That will place a limitation on the fabrication of nanoscale patterns, such as the metal wire grid polarizer. In this study, we launch a new approach to restrict the lateral growth of metal by depositing metal selectively in the grooves of a three-dimensional template. The template was first treated with a self-assembled monolayer (SAM) of octadecyltrichlorosilane (OTS) only on the protrusion surface using μCP, and then treated in SnCl2 solution to activate the surface of the trenches for the selective electroless plating (ELP) of silver inside the trenches. A wire-grid polarizer was thus fabricated by selectively depositing 70 nm-thick silver in the trenches of a nanograting template with a trench width of 100 nm and a pitch of 180 nm. The maximum extinction ratio of the polarizer thus obtained was about 130 in the wavelength range of 635–650 nm.