'Buried' etched moth-eye gratings enhance properties of optoelectronics

A method for engraving a structured metal coating into an optically-active semiconductor allows more light through while preventing reflections and allowing electrical charge to flow

A novel method for creating a structured surface on metal is the key to a transparent yet electrically-conducting coating that could improve the performance of electronic devices that convert light into current and vice-versa. Called MacEtch, the process has helped researchers from the University of Illinois at Urbana-Champaign to create a surface that allows 90 per cent of incident light through; around 20 per cent more than the bare surface of ther component.

The film is in fact an anti-reflection coating, which allows light through without impeding the flow of current to and from the underlying optoelectronic component. Team leader Daniel Wasserman explained that the patterning of the film’s surface takes the form of an array of microscopic pillars similar to those found on the surface of as moth’s eye. This pattern had previously been found to ‘beat’ a mathematical function called the Fresnel Equation, which governs how light is reflected from and refracted and transmitted through the interface between transparent and opaque materials. “these tiny nanopillars can ‘beat’ the Fresnel equations at certain wavelengths and angles. tiny nanopillars which can ‘beat’ the Fresnel equations at certain wavelengths and angles,’ Wasserman said.